9.3 — Reference Charts
- 9.3.1 Pitch suggestion chart (flexibility vs. forward pitch)
- 9.3.2 CLT chart (lateral tilt angle vs. lateral pitch)
- 9.3.3 5/16 rule ring finger span distance chart
- 9.3.4 Insert OD chart — standard insert sizes by brand
- 9.3.5 Oval cut chart for manual (NONE mode) calculations
- 9.3.6 Glossary of all terms and abbreviations used in Spectre Cloud
9.3.1 Pitch suggestion chart (flexibility vs. forward pitch)
Pitch suggestion chart (flexibility vs. forward pitch)
9.3.1 reference
This reference chart maps the relationship between a bowler's hand flexibility and the appropriate forward pitch range for the finger holes. Forward pitch is one of the most impactful fitting decisions on a spec sheet — too much forward pitch locks the fingers in, too little (or reverse pitch) causes them to exit too early. Flexibility is the primary physical characteristic that determines where in the pitch range a bowler belongs. This chart gives you a quick starting point for the pitch conversation before measurements are taken and before auto-suggestions are generated.
📐 How to Use This Chart
Assess the bowler's hand flexibility using the simple test described below, then locate their flexibility category in the chart. The chart gives a recommended forward pitch starting range for the finger holes — not a fixed value, but a zone within which the fitting should begin. Auto-suggestions in Spectre Cloud will refine this further once measurements are entered; this chart serves as a pre-measurement orientation and a useful cross-check against those suggestions.
📌 Note: This chart covers finger hole forward pitch only. Thumb pitch, lateral pitch, and oval cut values are not addressed here — see the related sections at the bottom of this page for those references.
✋ Assessing Hand Flexibility
A quick flexibility assessment takes under thirty seconds and requires no tools beyond the bowler's hand. Ask the bowler to extend their fingers straight out, then curl them toward the palm as if gripping a ball. Observe how naturally and completely the fingers curl:
| Flexibility category | What you observe | Typical bowler profile |
|---|---|---|
| Very flexible | Fingers curl fully and easily past 90° — knuckles bend well beyond a right angle with no resistance | Younger bowlers, bowlers with naturally hypermobile joints, some women and junior bowlers |
| Flexible | Fingers curl easily to 90° and slightly beyond with minimal resistance | Most recreational and league bowlers without joint stiffness; standard adult range |
| Average | Fingers curl comfortably to approximately 90° — normal, unrestricted grip position | The majority of adult bowlers; typical starting assumption for an unknown bowler |
| Stiff | Fingers curl to approximately 90° but with noticeable effort or slight resistance | Older bowlers, bowlers with early-stage arthritis, bowlers returning after a hand injury |
| Very stiff | Fingers do not reach 90° comfortably — significant resistance before the grip position is reached | Bowlers with moderate to severe arthritis, significant joint stiffness, or restricted range of motion |
📊 Forward Pitch Starting Range by Flexibility
| Flexibility category | Fingertip — forward pitch range | Conventional — forward pitch range | Notes |
|---|---|---|---|
| Very flexible | 0 to 1/8" forward |
0 to 1/8" forward |
Very flexible bowlers often need minimal forward pitch — too much creates a locked, uncomfortable release. Zero pitch or slight forward is the common fit. |
| Flexible | 1/8" to 1/4" forward |
1/8" to 1/4" forward |
Standard range for most comfortable, unrestricted grips. Auto-suggestions typically fall here for average adult measurements. |
| Average | 1/4" to 3/8" forward |
1/4" to 3/8" forward |
Most common range for recreational and league bowlers. IBPSIA standard suggestions for typical measurements land in this range. |
| Stiff | 3/8" to 1/2" forward |
3/8" to 1/2" forward |
Higher forward pitch compensates for reduced flexibility by making the hole more accessible at the grip position. |
| Very stiff | 1/2" to 3/4" forward |
1/2" to 3/4" forward |
Significant forward pitch required for comfort. Oval holes may also be beneficial to further ease grip entry and exit. |
⚠️ Verify with Spectre team: Confirm these pitch ranges against the IBPSIA standard values used as the basis for Spectre Cloud's auto-suggestion algorithm, and update the chart if the app's reference values differ from those used here.
⚖️ Factors That Shift the Starting Range
The chart above is a starting point. Several bowler-specific factors push the appropriate pitch value toward the lower or upper end of the range — or outside it entirely:
Factors that push toward less forward pitch (lower end or below range)
- ✅ High rev rate — aggressive release bowlers often prefer less forward pitch for a cleaner, faster finger exit.
- ✅ Long fingers relative to span — fingers that extend well beyond the first knuckle in the hole may feel over-secured with standard forward pitch.
- ✅ Bowler reports fingers feel locked in — the most direct signal that forward pitch is too high for this bowler.
- ✅ Two-handed bowler — as noted in section 9.2.6, standard forward pitch values often do not apply. Start conservatively.
Factors that push toward more forward pitch (upper end or above range)
- ✅ Shorter fingers relative to span — fingers that sit more shallowly in the hole may need more forward pitch to remain secure through the swing.
- ✅ Bowler reports fingers feel loose or slide out early — a direct signal that forward pitch may need to increase.
- ✅ Arthritis or joint swelling that is not fully captured by the flexibility test — the flexibility test assesses range of motion, not pain. A bowler who can reach average flexibility but experiences pain doing so may functionally benefit from stiff-category pitch values.
- ✅ Conventional grip bowlers generally — conventional grips often sit at the higher end of the range for their flexibility category compared to fingertip bowlers with the same flexibility.
🔄 Using This Chart Alongside Auto-Suggestions
This chart and Spectre Cloud's auto-suggestion system approach pitch from different directions — the chart starts with physical observation, the auto-suggestion starts with measurements. When used together they provide a useful cross-check:
- ✅ Chart and suggestion agree — high confidence. Proceed with the suggested value.
- ✅ Chart range is lower than the suggestion — check whether the bowler has unusual flexibility for their measurements. The suggestion may be technically correct but the bowler may be more comfortable with a lower value than standard.
- ✅ Chart range is higher than the suggestion — check whether the flexibility assessment identified significant stiffness that the measurement formula does not capture directly. Consider adjusting upward toward the chart range.
- ✅ Significant disagreement between chart and suggestion — re-assess flexibility and re-verify measurements before deciding. A large discrepancy often signals either an unusual bowler profile or a measurement entry issue.
📌 Quick Reference — Pitch Starting Points by Bowler Type
| Bowler type | Typical starting forward pitch |
|---|---|
| Junior bowler (under 18, typical flexibility) | 1/8" to 1/4" forward |
| Adult recreational bowler, fingertip | 1/4" to 3/8" forward |
| Adult recreational bowler, conventional | 1/4" to 3/8" forward |
| Competitive league bowler, fingertip | 1/4" to 3/8" forward — adjust per release |
| Senior bowler (65+), average flexibility | 3/8" to 1/2" forward |
| Senior bowler with arthritis | 1/2" to 3/4" forward |
| High rev rate cranker, fingertip | 1/8" to 1/4" forward — sometimes zero |
| Two-handed bowler, no thumb | 1/8" to 1/4" forward — start conservatively |
| Bowler returning after finger injury | Start at upper end of flexibility range — adjust from bowler feedback |
🎳 A Note on Reverse Pitch
Reverse pitch — where the bottom of the hole tilts away from the palm — is not covered by this chart because it is rarely a starting point for a fitting. It typically emerges as an adjustment for specific bowlers whose release characteristics make forward pitch counterproductive. The situations where reverse finger pitch may be appropriate include:
- ✅ Very high rev rate bowlers who report their fingers catching or dragging through the release despite minimal forward pitch.
- ✅ Bowlers who have been on forward pitch for many years and want to experiment with a cleaner, earlier exit.
- ✅ Bowlers with unusual finger anatomy where the joint geometry is better served by a slight reverse angle.
Reverse pitch on finger holes is an advanced adjustment — it should be reached by deliberate fitting progression rather than used as a default starting point for any bowler profile.
Related Sections
- 9.1.4 — Using Auto-Suggestions effectively for faster fitting sessions
- 9.2.3 — The suggested pitch is not what I expect — is Auto-Suggestion on
- 9.2.4 — How do I switch a bowler from fingertip to conventional mid-session
- 9.2.6 — How do I document a bowler who is a two-hander (no thumb)
- 6.1.3 — Step 3: Set grip type and enter finger measurements
- 5.6.5 — Choosing EDGE vs. CENTER: which method fits which bowler
✨ Tip: Keep a laminated copy of the quick-reference table at the fitting counter. A bowler who walks in without an appointment and without a previous spec sheet can be oriented to a starting pitch range in under a minute using only the flexibility test and this chart — giving you a confident starting point for the fitting conversation before a single measurement has been taken.
9.3.2 CLT chart (lateral tilt angle vs. lateral pitch)
CLT chart (lateral tilt angle vs. lateral pitch)
9.3.2 reference
The CLT chart — Compensating Lateral Tilt — maps the relationship between a bowler's lateral axis tilt angle and the appropriate lateral pitch value for the finger holes. Where forward pitch addresses how deeply and securely the fingers seat in the ball, lateral pitch corrects for the natural angle at which the fingers approach the holes relative to the ball surface. Getting lateral pitch right produces a grip that feels neutral and natural — the fingers enter and exit without twisting, and the hand does not have to compensate for a misaligned hole during the release.
📐 What CLT Measures and Why It Matters
When a bowler's hand approaches the ball at rest, the fingers do not always come straight down perpendicular to the ball surface — most bowlers have a natural lateral tilt to the axis of the finger approach. If the holes are drilled straight (zero lateral pitch) and the bowler's natural approach angle is offset, the inside wall of the hole contacts the finger on one side while the other side has a gap. The finger compensates by twisting slightly to fill the hole — and that twist is felt at the release as friction, torque, or discomfort.
Lateral pitch corrects for this by tilting the hole axis to match the bowler's natural approach angle. When the hole and the approach angle align, the finger seats cleanly and exits cleanly without compensation. The CLT chart gives you the pitch value that produces that alignment for a measured tilt angle.
✋ Measuring the Lateral Tilt Angle
The lateral tilt angle is the angle between the bowler's finger axis and the vertical when the hand is in grip position. It is assessed with the bowler holding a ball in their natural stance or with a fitting ball:
- Ask the bowler to hold or rest their hand on a fitting ball in their natural grip position — relaxed, not forced.
- Observe the angle of the middle finger from the side — specifically whether the finger tilts toward the thumb side (inward tilt) or away from the thumb (outward tilt) relative to vertical.
- Estimate the angle of tilt in degrees. Most bowlers fall between
0°and10°— values beyond15°are uncommon and warrant verification before drilling. - Note the direction — tilt toward the thumb (toward the ring finger side for the middle finger hole) is the most common direction and typically calls for lateral pitch toward the thumb side.
📌 Note: Lateral tilt is most easily assessed with a fitting ball or a house ball in the bowler's hand rather than from observation alone. A bowler who is asked to mime their grip without a ball often holds their hand in a slightly different position from their actual delivery grip — the weight and feel of the ball reveals the natural approach angle more accurately.
📊 CLT Chart — Lateral Tilt Angle vs. Lateral Pitch
| Lateral tilt angle | Direction | Recommended lateral pitch | Notes |
|---|---|---|---|
0° |
None — fingers approach vertically | 0 (zero lateral pitch) |
Holes drilled straight. Most common in bowlers with a neutral, square grip position. |
1° – 3° |
Toward thumb (inward) | 1/16" toward thumb |
Minimal tilt — borderline for correction. Some fitters leave this at zero; others prefer to compensate even at small angles. |
4° – 6° |
Toward thumb (inward) | 1/8" toward thumb |
Most common range for right-handed fingertip bowlers. Standard lateral pitch for a typical fingertip fit. |
7° – 9° |
Toward thumb (inward) | 3/16" toward thumb |
Moderate tilt requiring meaningful correction. Verify the tilt angle before committing — this range is less common and worth re-assessing. |
10° – 12° |
Toward thumb (inward) | 1/4" toward thumb |
Significant tilt. Check for physical causes — unusual hand geometry, grip tension, or measurement technique. Use this pitch only if the angle is confirmed. |
1° – 3° |
Away from thumb (outward) | 1/16" away from thumb |
Less common direction. Occurs in some left-handed bowlers or those with an unusually open grip position. |
4° – 6° |
Away from thumb (outward) | 1/8" away from thumb |
Requires careful verification — outward tilt at this level is atypical and worth discussing with the bowler before drilling. |
Above 12° |
Either direction | Consult experienced fitter | Values above 12° are unusual. Re-measure and verify before proceeding. May indicate grip tension, an atypical physical characteristic, or a measurement technique issue. |
⚠️ Verify with Spectre team: Confirm the lateral pitch values in this chart against the CLT standard values used as the basis for Spectre Cloud's auto-suggestion algorithm. The values above are based on general IBPSIA-derived CLT guidance and should be cross-checked against the specific values the app references before publishing.
⚖️ Middle Finger vs. Ring Finger — Are They the Same?
In most fits, the middle and ring fingers have similar lateral tilt angles and receive the same lateral pitch value. However, they should always be assessed independently — assuming symmetry without checking is a common source of subtle grip discomfort that is hard to trace after drilling.
- ✅ Assess both fingers in grip position and note whether their tilt angles appear the same or different.
- ✅ For most bowlers the difference, if any, is small enough to round to the same pitch value — but note the independent assessment in the spec sheet rather than recording a single assumed value for both.
- ✅ In cases where the middle and ring finger tilt angles are noticeably different — more than one or two degrees apart — enter different lateral pitch values for each hole and note the reason.
🎳 CLT and Handedness
The direction of lateral tilt is often influenced by handedness, though it varies by individual. As a general orientation:
- ✅ Right-handed bowlers most commonly tilt toward the thumb (inward) — lateral pitch toward the thumb side is the standard correction.
- ✅ Left-handed bowlers follow the same physical principle but mirrored — inward tilt for a left-handed bowler also tilts toward the thumb, which is on the opposite side from a right-handed bowler.
- ✅ Confirm the direction by observation rather than assumption — a right-handed bowler with an outward tilt is unusual but not impossible.
🔄 Using CLT Values in Spectre Cloud
Once you have determined the lateral pitch value from the CLT chart, enter it in the lateral pitch field for each finger hole on the spec sheet. Spectre Cloud's auto-suggestion system may generate a lateral pitch suggestion based on the bowler's measurements — compare this against the CLT chart value as a cross-check:
- ✅ Suggestion and chart agree — accept the suggestion with confidence.
- ✅ Suggestion is zero but chart indicates correction needed — the measurement-based formula may not capture the tilt angle directly. Override with the CLT chart value and note the reason.
- ✅ Chart and suggestion differ by one increment — use fitting judgement. The chart value is based on physical observation; the suggestion is based on measurements. Both are valid inputs — the bowler's comfort after a test session is the final arbiter.
- ✅ Large discrepancy between chart and suggestion — re-assess the tilt angle and re-verify the measurements before committing. A large discrepancy usually means one of the inputs needs checking.
📌 CLT Quick Reference — Common Lateral Pitch Values
| Bowler profile | Typical lateral pitch |
|---|---|
| Most right-handed adult fingertip bowlers | 1/8" toward thumb |
| Most left-handed adult fingertip bowlers | 1/8" toward thumb (mirrored) |
| Bowler with very neutral grip position | 0 (zero) |
| Bowler with noticeable inward tilt | 3/16" to 1/4" toward thumb |
| Conventional grip bowler | 0 to 1/8" toward thumb — less lateral correction typically needed than fingertip |
| Two-handed bowler | Start at 0 — assess from delivery observation; standard CLT values less reliable |
| Junior bowler | 0 to 1/8" — start conservatively and adjust |
✨ When Lateral Pitch Needs Revisiting After Drilling
Lateral pitch is one of the fitting values most likely to need fine-tuning after a bowler has thrown the ball in competition. The following post-drill feedback signals that lateral pitch may need adjustment:
- ✅ Fingers feel like they are twisting in the hole — lateral pitch is in the wrong direction or insufficient.
- ✅ One side of the finger hole causes a pressure mark or soreness — the hole wall is contacting the finger unevenly, typically a sign of lateral pitch mismatch.
- ✅ Bowler reports the ball feeling like it wants to roll off one side of the fingers — often a lateral pitch issue, though it can also relate to the oval cut orientation.
- ✅ Release feels inconsistent side to side despite consistent swing — lateral pitch is a likely contributor when the inconsistency is specifically directional rather than general.
Related Sections
- 9.3.1 — Pitch suggestion chart (flexibility vs. forward pitch)
- 9.1.4 — Using Auto-Suggestions effectively for faster fitting sessions
- 9.2.3 — The suggested pitch is not what I expect — is Auto-Suggestion on
- 6.1.3 — Step 3: Set grip type and enter finger measurements
- 5.6.5 — Choosing EDGE vs. CENTER: which method fits which bowler
- 5.5.2 — Using the oval cut chart to determine cuts manually
✨ Tip: For a new bowler or any bowler whose lateral tilt you are assessing for the first time, take the measurement twice — once with the bowler holding a ball in their delivery grip, and once with them resting their hand flat in a natural position. The difference between the two positions is often instructive: a bowler whose hand is neutral at rest but shows significant tilt in grip position has developed a grip-specific compensation that the lateral pitch needs to accommodate. A bowler whose tilt is consistent in both positions has an anatomical characteristic that the pitch should correct.
9.3.3 5/16 rule ring finger span distance chart
5/16 rule ring finger span distance chart
9.3.3 reference
The 5/16 rule is a widely used pro shop guideline for determining the ring finger span relative to the middle finger span. Because most bowlers' ring fingers are shorter than their middle fingers, the ring finger hole is positioned closer to the thumb hole than the middle finger hole — and the 5/16 rule provides a standard offset for deriving the ring finger span from the middle finger span without measuring both fingers independently every time. This page explains the rule, when to apply it, and provides a reference chart of ring finger span distances derived from common middle finger spans.
📐 What the 5/16 Rule States
The 5/16 rule states that the ring finger span should be 5/16" shorter than the middle finger span for a standard fingertip fit on a typical adult hand. This offset accounts for the natural length difference between the middle and ring fingers and produces a grip where both fingers seat at approximately the same relative joint position in their respective holes.
- ✅ The rule applies to fingertip grip as the primary use case — both fingers should seat at the first knuckle.
- ✅ It is a starting point, not an absolute. Bowlers with an unusual difference between their middle and ring finger lengths may need a different offset.
- ✅ The same rule is applied independently of span type — whether Full Span, Cut to Cut, or Oval is used, the 5/16 offset applies to whichever span measurement convention the shop uses.
- ✅ Spectre Cloud's auto-suggestion system may apply this rule automatically when generating span suggestions from finger measurements — the chart below provides a manual reference for cross-checking those suggestions.
⚠️ Verify with Spectre team: Confirm whether Spectre Cloud's span auto-suggestion applies the 5/16 rule as described, or whether it uses a different offset formula derived from the joint measurements entered on the spec sheet. Update the introduction above if the app uses a different standard.
📊 5/16 Rule Reference Chart
Find the middle finger span in the left column. The ring finger span derived from the 5/16 rule appears in the right column. All values are in inches expressed as fractions.
| Middle finger span | Ring finger span (5/16 rule) | Difference |
|---|---|---|
3 1/4" |
2 15/16" |
5/16" |
3 5/16" |
3" |
5/16" |
3 3/8" |
3 1/16" |
5/16" |
3 7/16" |
3 1/8" |
5/16" |
3 1/2" |
3 3/16" |
5/16" |
3 9/16" |
3 1/4" |
5/16" |
3 5/8" |
3 5/16" |
5/16" |
3 11/16" |
3 3/8" |
5/16" |
3 3/4" |
3 7/16" |
5/16" |
3 13/16" |
3 1/2" |
5/16" |
3 7/8" |
3 9/16" |
5/16" |
3 15/16" |
3 5/8" |
5/16" |
4" |
3 11/16" |
5/16" |
4 1/16" |
3 3/4" |
5/16" |
4 1/8" |
3 13/16" |
5/16" |
4 3/16" |
3 7/8" |
5/16" |
4 1/4" |
3 15/16" |
5/16" |
4 5/16" |
4" |
5/16" |
4 3/8" |
4 1/16" |
5/16" |
4 7/16" |
4 1/8" |
5/16" |
4 1/2" |
4 3/16" |
5/16" |
4 9/16" |
4 1/4" |
5/16" |
4 5/8" |
4 5/16" |
5/16" |
4 11/16" |
4 3/8" |
5/16" |
4 3/4" |
4 7/16" |
5/16" |
⚖️ When to Apply the 5/16 Rule and When to Deviate
The 5/16 rule is an industry standard starting point — reliable for the majority of adult hands in the typical span range. The following circumstances call for deviation:
Measure both fingers independently when
- ✅ The bowler's ring finger appears significantly longer or shorter than their middle finger relative to the typical adult proportion — visible at a glance during measurement.
- ✅ The bowler has an injury, medical condition, or surgical history affecting one finger but not the other.
- ✅ A previous spec sheet for this bowler records a ring finger span that deviates from the 5/16 rule by more than
1/16"— follow the established fit rather than the formula. - ✅ The bowler is a junior with hands that are still developing — proportions change more rapidly than in adults and the 5/16 assumption is less reliable.
- ✅ The bowler reports discomfort specifically in the ring finger hole of previous drillings despite correct hole sizing.
Apply the 5/16 rule as the default when
- ✅ Both fingers appear proportionately typical for the bowler's hand size.
- ✅ The bowler is new with no previous spec sheets and no reported issues with either finger.
- ✅ You are working in a high-volume session and need a reliable starting point quickly — the rule produces a correct or near-correct span for the majority of adult hands.
- ✅ The auto-suggestion for the ring finger span matches the 5/16 rule output — convergence between the formula and the suggestion adds confidence.
🔄 Using This Chart With Spectre Cloud
After measuring the middle finger span and entering it on the spec sheet, use this chart to derive the expected ring finger span before entering it. Compare against Spectre Cloud's auto-suggestion for the ring finger:
- ✅ Chart and suggestion agree — enter the value with confidence.
- ✅ Chart and suggestion differ by
1/16"— minor variance. Confirm the middle finger span was entered correctly and choose the value that best reflects the physical measurement. - ✅ Chart and suggestion differ by
1/8"or more — investigate before entering. Check whether the joint measurements used by the suggestion algorithm differ meaningfully from what the 5/16 rule assumes, or whether a measurement entry error has skewed the suggestion.
🎳 Conventional Grip — Does the 5/16 Rule Apply?
The 5/16 rule is most reliably applied to fingertip grips where both fingers seat at the first knuckle. For conventional grips, both fingers seat at the second knuckle and the relative span difference between middle and ring fingers at the second knuckle is typically smaller than the 5/16 standard — the fingers are more equal in length at the second knuckle than at the first.
- ✅ For conventional grips, measure both fingers to the second knuckle independently rather than applying the 5/16 rule — the offset is less predictable at the conventional seating depth.
- ✅ If a conventional bowler is transitioning to fingertip, re-measure both fingers to the first knuckle — do not apply a 5/16 offset to a second-knuckle measurement.
- ✅ For semi-fingertip grips, treat the 5/16 rule as a rough guide only and confirm with independent measurement.
📌 Quick Formula for Values Not in the Chart
If the middle finger span falls between entries in the chart or outside the range shown, the ring finger span is always:
Ring finger span = Middle finger span − 5/16"
In decimal terms: Middle finger span − 0.3125"
Apply the result and round to the nearest 1/16" increment consistent with your shop's measurement precision.
Related Sections
- 9.3.1 — Pitch suggestion chart (flexibility vs. forward pitch)
- 9.3.2 — CLT chart (lateral tilt angle vs. lateral pitch)
- 6.1.3 — Step 3: Set grip type and enter finger measurements
- 9.1.4 — Using Auto-Suggestions effectively for faster fitting sessions
- 9.2.4 — How do I switch a bowler from fingertip to conventional mid-session
- 5.5.2 — Using the oval cut chart to determine cuts manually
✨ Tip: Print this chart and laminate it alongside the pitch and CLT reference charts at the fitting counter. A three-chart reference covering forward pitch, lateral pitch, and ring finger span gives any driller — experienced or new — a complete quick-reference toolkit for the most common manual calculations in a fitting session. The charts do not replace measurement or judgement, but they cut the mental arithmetic out of a routine fitting and let you focus on the bowler rather than the numbers.
9.3.4 Insert OD chart — standard insert sizes by brand
Insert OD chart — standard insert sizes by brand
9.3.4 reference
Finger inserts add a consistent, replaceable grip surface inside drilled finger holes and are used by the majority of fingertip bowlers. Each insert brand and model has a defined outer diameter (OD) — the dimension that determines how large the hole needs to be drilled to accept the insert. Drilling to the wrong OD produces a hole that is either too tight (the insert cannot seat) or too loose (the insert spins or falls out). This chart provides standard insert OD values by brand as a quick reference for the hole size field on the spec sheet.
⚠️ Verify with Spectre team and insert manufacturers: Insert OD specifications change when manufacturers update product lines. Verify all values in this chart against current manufacturer documentation before publishing, and establish a review schedule to keep the chart current. The values below represent commonly used sizes at the time of writing and should be treated as a starting reference, not a definitive specification.
📋 How to Use This Chart
Find the insert brand and model being used. The OD value in the chart is the hole diameter to drill — enter this value as the finger hole size on the spec sheet. The insert will seat at this diameter; the bowler's finger then fits inside the insert according to the insert's inner diameter (ID), which is sized separately by the fitter from the bowler's finger measurement.
- ✅ The hole size field on the spec sheet should reflect the insert OD, not the bowler's finger measurement directly.
- ✅ The bowler's finger size determines which insert ID to select — the insert OD determines the hole to drill.
- ✅ When in doubt, verify the OD with the physical insert using a micrometer or caliper before drilling — manufacturer tolerances vary and individual inserts occasionally fall outside the stated specification.
📊 Standard Insert OD by Brand
Turbo
| Insert model | Outer diameter (OD) | Notes |
|---|---|---|
| Turbo Quad | 1" |
Most common Turbo insert. Standard hole size for the majority of fingertip fits using Turbo grips. |
| Turbo Quad Jr. | 29/32" |
Smaller OD version for junior or smaller-handed bowlers. |
| Turbo Switch Grip | 1" |
Same OD as standard Quad — designed for quick change between inserts without redrilling. |
| Turbo Oval Quad | Varies by size | Oval inserts — verify OD with the specific insert before drilling. Oval OD is measured at the widest point. |
Vise
| Insert model | Outer diameter (OD) | Notes |
|---|---|---|
| Vise IT Insert | 1" |
Standard Vise insert. 1" OD is consistent across the IT line. |
| Vise Oval IT Insert | Varies by oval size | Oval inserts — measure the specific insert. Round dimension is typically 1"; oval adds length in one axis. |
| Vise Grip Tape (in-hole) | N/A — tape applied inside hole | Grip tape is applied inside an existing hole and does not change the drilled OD. No hole size change required. |
Ebonite / Storm / Roto Grip (shared insert line)
| Insert model | Outer diameter (OD) | Notes |
|---|---|---|
| Standard fingertip insert | 1" |
Shared across several brands in the same manufacturing group. Confirm with the specific insert packaging. |
| Small fingertip insert | 29/32" |
For smaller holes — junior and small-handed bowlers. |
Brunswick
| Insert model | Outer diameter (OD) | Notes |
|---|---|---|
| Brunswick Finger Insert | 1" |
Standard 1" OD. Confirm with physical insert — Brunswick has produced inserts at slightly varying ODs across different product generations. |
Master Industries
| Insert model | Outer diameter (OD) | Notes |
|---|---|---|
| Master Finger Insert | 1" |
Standard OD. Verify with physical insert before drilling. |
| Master Oval Insert | Varies by oval size | Measure individual insert — round dimension typically 1". |
📐 OD Tolerance — Why Measuring the Physical Insert Matters
Manufacturer OD specifications are nominal values — the actual insert may be slightly larger or smaller due to manufacturing tolerance. For most inserts the variance is negligible, but for a small number of older, overstocked, or off-brand inserts, tolerance differences can affect seating. A micrometer or caliper reading of the actual insert is the most reliable input for the hole size field, particularly when:
- ✅ The insert is from a brand not listed in this chart.
- ✅ The insert is from an older product line whose specifications may have changed.
- ✅ The bowler supplies their own inserts rather than using shop stock — unbranded or import inserts vary widely.
- ✅ A previous drilling using the same nominal OD resulted in an insert that was too tight or too loose.
⚖️ Fit Allowance — Drilling Slightly Larger Than OD
In practice, most pro shop operators drill the hole to a diameter slightly larger than the nominal insert OD — typically 1/64" to 1/32" over — to allow the insert to seat cleanly without forcing. The exact allowance depends on:
- ✅ Ball coverstock hardness — harder coverstocks compress less around the insert and may need a slightly larger allowance for clean seating.
- ✅ Insert material — softer inserts compress slightly on insertion; harder inserts do not. A softer insert may need less allowance than the nominal OD suggests.
- ✅ Shop standard — most experienced operators develop a consistent allowance over time. Enter this in the hole size field rather than the bare nominal OD if your shop applies a standard allowance.
📌 Note: Enter the actual hole size drilled on the spec sheet — including any fit allowance — rather than the nominal insert OD. The spec sheet should reflect what was physically drilled, not the theoretical specification. A future re-drill based on the spec sheet will produce the same result only if the recorded hole size matches what was actually in the ball.
🔌 Recording Inserts in Spectre Cloud
Spectre Cloud's spec sheet hole size field accepts the drilled diameter directly. Beyond the hole size, insert details worth capturing elsewhere in the record include:
- ✅ Insert brand and model — record in the spec sheet Notes field. A future re-drill can replicate the same insert if this information is on file.
- ✅ Insert colour — optional but useful for bowlers who have colour preferences or who use colour to identify their ball in a bag.
- ✅ Insert OD as measured — if you measured the actual insert with a caliper and it differed from the nominal value, note both in the spec sheet notes:
Turbo Quad nominal 1" — measured 63/64" — drilled 63/64". - ✅ Arsenal entry notes — for Arsenal Plus users, the insert brand and model can also be recorded in the ball's Arsenal entry notes for quick reference when the bowler returns for a re-drill or insert replacement.
🎳 Oval Inserts — Additional Considerations
Oval inserts require the hole to be drilled to the insert's oval dimensions rather than a simple round diameter. The hole must match both the round dimension and the oval extension of the insert:
- ✅ Measure the oval insert at its widest point (the oval axis) and at its round dimension before drilling.
- ✅ Confirm the oval orientation on the insert matches the oval cut direction configured in Spectre Cloud — an oval insert seated in the wrong orientation defeats the purpose of the oval cut.
- ✅ Record both the round and oval dimensions in the spec sheet hole size and oval fields respectively — do not record only the round dimension for an oval insert.
- ✅ For oval inserts where the OD varies by insert size, confirm the specific model's dimensions from the manufacturer's current product documentation rather than relying on this chart.
Related Sections
- 9.3.1 — Pitch suggestion chart (flexibility vs. forward pitch)
- 9.3.2 — CLT chart (lateral tilt angle vs. lateral pitch)
- 9.3.3 — 5/16 rule ring finger span distance chart
- 6.1.3 — Step 3: Set grip type and enter finger measurements
- 7.1.3 — Hole Depth option — setting desired depth for each hole
- 04.x — Spec Sheets: field reference and measurement guide
✨ Tip: Keep a physical sample of each insert brand and model your shop stocks, mounted on a card with the OD written beside it, at the fitting counter. When a bowler brings in their own inserts or requests a specific brand, you can confirm the OD visually in seconds rather than searching through packaging or charts. A five-minute investment in a sample card at setup saves repeated lookups across hundreds of fittings.
9.3.5 Oval cut chart for manual (NONE mode) calculations
Oval cut chart for manual (NONE mode) calculations
9.3.5 reference
When Spectre Cloud's Oval Cut Direction is set to NONE, the app does not generate directional oval cut suggestions — the fitter determines the oval cut value manually and enters it directly on the spec sheet. This reference chart provides the standard oval cut sizes mapped to forward pitch values and ball track types, giving operators working in NONE mode a quick, reliable starting point for every fit without needing to consult an external chart or rely on memory.
📋 How to Use This Chart
Locate the bowler's forward pitch value in the left column and their ball track type across the top. The cell at the intersection gives the recommended starting oval cut size. Enter this value in the Oval field on the spec sheet.
- ✅ This chart applies to finger holes only — thumb oval cuts are determined separately based on thumb anatomy and release characteristics.
- ✅ Values are expressed in inches as fractions — the same unit used in Spectre Cloud's oval field.
- ✅ The chart gives a starting point, not a fixed prescription. Adjust based on the bowler's hand anatomy, insert type, and release feedback.
- ✅ This chart is designed for use with NONE mode. If your shop uses Forward/Back or Left/Right directional mode, the Oval Calculator generates directional output automatically — see sections 5.6.1–5.6.5.
📊 Oval Cut Chart — Forward Pitch vs. Ball Track
| Forward pitch | Low track | Medium track | High track | Notes |
|---|---|---|---|---|
Reverse pitch or 0 |
0 (round) |
0 (round) |
0 to 1/8" |
Reverse or zero pitch rarely requires an oval. High track bowlers may benefit from a minimal oval for comfort even at zero forward pitch. |
1/8" forward |
0 to 1/8" |
1/8" |
1/8" |
Small oval appropriate at this pitch level. Low track bowlers may not need any oval at 1/8" forward. |
1/4" forward |
1/8" |
1/8" to 3/16" |
3/16" to 1/4" |
The most common pitch range for recreational and league bowlers. Oval size begins to have meaningful impact on feel. |
3/8" forward |
1/8" to 3/16" |
1/4" |
1/4" to 5/16" |
Standard range for average to stiff flexibility bowlers. A 1/4" oval is the most frequently used size across this pitch value. |
1/2" forward |
3/16" to 1/4" |
1/4" to 5/16" |
5/16" to 3/8" |
Higher forward pitch begins to require more meaningful oval correction. Track type has increasing influence at this level. |
5/8" forward |
1/4" |
5/16" |
3/8" |
Significant forward pitch — typically seen in bowlers with stiff hands or arthritic conditions. Larger oval essential for comfortable grip and release. |
3/4" forward |
1/4" to 5/16" |
3/8" |
3/8" to 1/2" |
Very high forward pitch. Verify the pitch value before proceeding — values at this level are uncommon and worth confirming against the bowler's history. |
⚠️ Verify with Spectre team: Confirm the oval cut values in this chart against the IBPSIA-standard reference values used internally by Spectre Cloud. The values above are based on general industry practice and should be cross-checked against the app's own reference data before publishing.
🎳 Determining Ball Track Type
Ball track type is assessed by examining the wear pattern on the ball surface from previous use, or estimated from the bowler's delivery characteristics if the ball is new.
| Track type | Wear pattern location | Delivery characteristics |
|---|---|---|
| Low track | Track runs close to the thumb and finger holes — often within an inch of the holes | Typically associated with lower axis tilt, smoother roll, earlier transition through the pins |
| Medium track | Track runs roughly midway between the holes and the ball's equator | Most common track type — the standard assumption for an unknown bowler |
| High track | Track runs near the ball's equator, well away from the holes | Associated with higher axis tilt, stronger backend reaction, more angular breakpoint |
📌 Note: For a new ball with no wear pattern yet established, estimate track type from the bowler's delivery observation or default to medium track as the starting assumption. The oval cut can be refined on a subsequent drilling once the track has developed.
⚖️ Factors That Adjust the Chart Value
The chart gives the standard starting oval for the pitch and track combination. Several bowler-specific factors push the appropriate value above or below that starting point:
Factors that suggest a larger oval than the chart value
- ✅ Very stiff flexibility — the bowler has difficulty fully gripping the ball and needs a more forgiving release path.
- ✅ Large finger holes relative to finger size — a looser fit benefits from a larger oval to maintain consistent finger contact through the swing.
- ✅ Bowler reports fingers dragging or catching after drilling to a previous smaller oval — direct feedback that the oval was insufficient.
- ✅ Arthritis or joint swelling — the grip entry and exit path needs more clearance than a standard fit.
Factors that suggest a smaller oval than the chart value
- ✅ Very flexible hand — flexible bowlers often need less oval correction because the fingers exit the ball more cleanly regardless.
- ✅ Tight insert fit — a snug insert may not require oval correction at smaller pitch values where the fit is already secure.
- ✅ Bowler prefers a firmer, more controlled feel — some experienced fingertip bowlers intentionally use a smaller oval for a more precise release.
- ✅ Previous drilling with this oval size felt too loose — reduce by one increment and re-assess.
🔄 Cross-Checking Against Spectre Cloud Auto-Suggestions
If you switch from NONE mode to a directional mode temporarily to check what the Oval Calculator would suggest for a given pitch and track combination, the directional output provides a useful cross-reference for your manual NONE mode entry:
- ✅ The total oval size component of a directional output should broadly agree with the chart value for the same pitch and track. A significant discrepancy is worth investigating before entering a value.
- ✅ Use this cross-check for unfamiliar bowler profiles or when the chart produces a value that seems unexpectedly large or small for the fit.
- ✅ Switch back to NONE mode before saving the spec sheet — running the calculator in directional mode and then saving under NONE produces a spec sheet without directional labels, which is correct for NONE mode operation but only if the switch back was completed.
📌 Quick Reference — Most Common Oval Cut Values
In practice, the majority of pro shop fittings fall within a narrow oval cut range. This condensed reference covers the most frequently encountered combinations:
| Situation | Starting oval cut |
|---|---|
Recreational bowler, standard fit, 1/4"–3/8" forward pitch |
1/4" |
League bowler, medium track, 3/8" forward pitch |
1/4" |
Senior bowler, stiff hands, 1/2"+ forward pitch |
3/8" |
Junior bowler, flexible, 1/8"–1/4" forward pitch |
1/8" |
High rev bowler, high track, 1/4" forward pitch |
1/4" |
Conventional bowler, any track, 3/8" forward pitch |
1/4" |
| Bowler with zero or reverse pitch | 0 (round hole) |
| Arthritis — significant forward pitch, any track | 3/8" to 1/2" |
✨ Entering the Value in Spectre Cloud (NONE Mode)
- Confirm Oval Cut Direction is set to NONE in Settings — see section 5.5.1.
- On the spec sheet, locate the Oval field for each finger hole.
- Enter the oval cut size determined from this chart — for example,
1/4". - Because NONE mode produces a single unlabeled value, no axis direction is required — just the size.
- Save the spec sheet. The oval value appears on the printed spec sheet as a single measurement without a directional label.
Related Sections
- 5.5.1 — Setting up: Oval Cut Direction = NONE in Settings
- 5.5.2 — Using the oval cut chart to determine cuts manually
- 5.5.3 — When NONE mode is preferable (experienced fitters, custom setups)
- 5.6.5 — Choosing EDGE vs. CENTER: which method fits which bowler
- 9.3.1 — Pitch suggestion chart (flexibility vs. forward pitch)
- 9.3.2 — CLT chart (lateral tilt angle vs. lateral pitch)
✨ Tip: Print this chart and laminate it alongside the pitch and CLT reference charts at the fitting counter and drill press. The three charts together — forward pitch by flexibility, lateral pitch by tilt angle, and oval cut by pitch and track — give any driller a complete manual reference for the most common fitting calculations without needing to open Settings, run the calculator, or leave the press. A well-maintained laminated reference at the press is one of the most practical tools in a busy shop, especially when training new staff who are building their fitting intuition alongside their technical knowledge.
9.3.6 Glossary of all terms and abbreviations used in Spectre Cloud
Glossary of all terms and abbreviations used in Spectre Cloud
9.3.6 reference
This glossary defines every term, abbreviation, and acronym used throughout Spectre Cloud and this wiki. Entries are organised alphabetically. Where a term has a dedicated wiki page covering it in depth, a cross-reference is provided. Use this page as a quick reference during fittings, when training new staff, or when a term appears in a spec sheet or setting that needs clarification.
🔤 A
- Add Pitch Thumb
- An optional setting within the Oval Calculator that includes the thumb's pitch values in the finger oval calculation. When enabled, the combined pitch geometry of the full grip — fingers and thumb — influences the oval output. See sections 5.6.3 and 5.6.4.
- Arsenal
- The per-bowler ball inventory system in Spectre Cloud. Each Arsenal entry represents one physical ball and links to all spec sheets ever created for that ball. See section 7.1.1.
- Arsenal Plus
- An optional plugin (
$5 USD/month) that adds bowlingdatabase.com integration, barcode scanning, suggested layouts, layout conversion, and 3D layout rendering to the Arsenal. See Book 07. - Auto-Suggestion
- Spectre Cloud's system for generating recommended pitch, span, and oval cut values based on the measurements entered on a spec sheet and IBPSIA-standard fitting guidelines. See section 9.1.4.
- Axis Rotation
- The angle of the bowler's axis of rotation relative to the target line at the moment of release. Expressed in degrees. Influences ball motion and is used as an input for layout suggestions in Arsenal Plus.
- Axis Tilt
- The angle of the bowler's axis of rotation relative to the horizontal at the moment of release. Expressed in degrees. A higher tilt produces a more angular backend motion; lower tilt produces a smoother, earlier roll. Used as an input for layout suggestions in Arsenal Plus.
🔤 B
- Balance Hole
- A non-gripping hole drilled into a bowling ball to adjust its static weight balance. Not a thumb grip hole — noted as such in the spec sheet thumb section when present. Regulations governing balance holes vary by governing body and era; confirm current rules with the relevant association before drilling.
- Barcode Scanning
- An Arsenal Plus feature that scans the barcode on a ball's box or surface to look up its specifications in the bowlingdatabase.com integration, pre-filling the Arsenal entry automatically. See section 7.2.3.
- Book
- The top-level organisational unit of this wiki. The Spectre Cloud Manual contains nine books covering Getting Started, Settings, Bowlers, Spec Sheets, Oval Calculator, Drilling Your First Ball, Arsenal, Account and Business, and Tips, Troubleshooting and Reference.
- BowlDevs
- The development company behind Spectre Cloud. Founded by Mark (Wichita State University Computer Science graduate) and Luis (competitive bowler based in Montreal). Website:
bowldevs.com. - Bowler Plus
- An optional plugin (
$5 USD/month) that adds full address storage, client consent signatures, and a hand photograph gallery to bowler profiles. See Book 03. - bowlingdatabase.com
- A third-party database of bowling ball specifications. Integrated into Spectre Cloud via Arsenal Plus to provide core specifications (RG, differential, MB differential, coverstock) for use in layout suggestions and 3D rendering.
- Bridge
- The distance between the edges of the two finger holes (middle and ring) on a drilled bowling ball. Calculated automatically by Spectre Cloud from the hole sizes and span values on the spec sheet. See section 9.2.5.
🔤 C
- CENTER method
- An Oval Calculator method that anchors pitch at the geometric centre of the oval hole rather than its leading edge. Appropriate for small ovals, low to zero pitch, and legacy record continuity. See section 5.6.2.
- CG (Centre of Gravity)
- The point on a bowling ball's surface directly above its internal centre of mass. Used as a reference point in some layout systems, particularly 2LS. The CG is marked on the ball by the manufacturer.
- CLT (Compensating Lateral Tilt)
- A fitting standard that maps the bowler's lateral finger approach angle to the appropriate lateral pitch value for the finger holes. See section 9.3.2.
- Clone
- A Spectre Cloud function that creates an exact copy of an existing spec sheet attached to the same bowler. All field values are duplicated; the clone is independent from the source. See section 9.1.2.
- Conventional grip
- A grip style in which the fingers are inserted to the second knuckle. Produces a more secure but less expressive release than fingertip. Selected as a grip type on the spec sheet.
- Coverstock
- The outer shell of a bowling ball. The coverstock material (reactive resin, urethane, plastic) and surface finish determine how the ball interacts with the lane. Relevant to layout decisions and surface maintenance notes in the Arsenal.
- Cut to Cut (C)
- A span type in which the span is measured from the near edge of the thumb hole to the near edge of the finger hole. One of three span types supported by Spectre Cloud alongside Full Span and Oval. See section 6.1.2.
🔤 D
- Differential
- A measure of a bowling ball core's track flare potential. Total differential is the difference between the ball's maximum and minimum RG values. MB differential measures the asymmetric mass bias influence. Higher differential generally produces more flare potential.
- Drilling Angle
- The rotation of the ball in the drilling jig that determines where the mass bias marker ends up relative to the VAL after drilling. Most significant for asymmetric core balls. Entered in the layout section of the spec sheet. See section 7.1.6.
🔤 E
- EDGE method
- An Oval Calculator method that anchors pitch at the leading edge of the oval hole — the point closest to the bowler's palm. Produces a delivered pitch closer to the specified pitch value than the CENTER method, particularly for larger ovals and higher forward pitch. See section 5.6.1.
🔤 F
- Fingertip grip
- A grip style in which the fingers are inserted to the first knuckle only. Produces more leverage and hook potential than conventional grip. The most common grip type for league and competitive bowlers. Selected as a grip type on the spec sheet.
- Flare Potential
- The degree to which a bowling ball's track migrates across the ball surface during a game. Determined by core differential and layout. Higher flare generates more surface contact with fresh coverstock on each shot.
- Flip V/H
- A Spectre Cloud setting that swaps the Vertical and Horizontal axis labels on oval cut outputs to match a drill press whose axis convention is the reverse of Spectre Cloud's default. A labelling correction only — does not affect calculations. See sections 5.7.1 and 5.7.2.
- Forward pitch
- Pitch in which the bottom of the hole tilts toward the bowler's palm. Expressed as a positive value in Spectre Cloud. The primary pitch variable for fingertip and conventional fits. See section 9.3.1.
- Full Span (F)
- A span type in which the span is measured from the back edge of the thumb hole to the back edge of the finger hole. The most commonly used span type for fingertip and conventional fits in North America. See section 6.1.2.
🔤 G
- Grip Centre
- The midpoint of the grip — the point equidistant between the two finger holes and the thumb hole. Used as a reference point for some layout measurements and as the span anchor for two-handed bowlers. See section 9.2.6.
- Grip type
- The classification of how deeply the fingers are inserted into the ball. Spectre Cloud supports Conventional, Fingertip, and Semi-fingertip. Grip type controls which measurement fields are active and which auto-suggestions are generated on the spec sheet.
🔤 H
- Hole Depth
- The depth, in inches, to which a finger or thumb hole is drilled — measured from the ball surface to the bottom of the hole along the drill axis. Recorded on the spec sheet for each hole. See section 7.1.3.
- Horizontal (H)
- One of the two axes used to express directional oval cut values in Spectre Cloud. Which physical direction H represents depends on your drill press orientation and the Flip V/H setting. See sections 5.7.1 and 5.7.2.
🔤 I
- IBPSIA
- International Bowling Pro Shop and Instructors Association. The professional body that establishes fitting and drilling standards for pro shop operators. Spectre Cloud's auto-suggestion system is based on IBPSIA-standard guidelines.
- Insert OD
- The outer diameter of a finger insert — the dimension used to determine the hole size to drill. See section 9.3.4.
🔤 J
- Job Board
- An optional plugin (
$15 USD/month) that provides a workshop to-do list and service history per ball for pro shops that manage a ball service queue. See Book 08.
🔤 K
- Knuckle size
- The diameter at the widest part of the finger knuckle. Entered on the spec sheet to confirm the hole can accommodate the finger at its widest point. Distinct from hole size, which is the finished diameter the finger seats in.
🔤 L
- Lateral pitch
- Pitch applied in the left or right direction relative to the grip centre, correcting for the bowler's natural lateral approach angle. Determined using the CLT chart. See section 9.3.2.
- Layout
- The geometric placement of the ball's pin and mass bias relative to the bowler's PAP. Determines ball motion characteristics. Recorded on the spec sheet using VLS, 2LS, PAL, or manual entry. See section 6.1.5.
- Layout conversion
- An Arsenal Plus feature that converts a layout recorded in one system (e.g., VLS) into the equivalent values in another system (e.g., PAL) without modifying the original record. See section 7.2.4.
🔤 M
- Mass Bias (MB)
- The preferred spin axis marker on an asymmetric bowling ball core — the point of highest mass concentration. Its position relative to the VAL line influences ball motion, particularly for high-differential asymmetric balls. See section 7.1.6.
- MB Differential
- The difference in RG between the ball's intermediate and minimum axis values. Indicates the strength of the asymmetric mass bias influence. A higher MB differential produces stronger, more predictable asymmetric motion characteristics.
🔤 N
- NONE mode
- An Oval Cut Direction setting in which Spectre Cloud does not generate directional oval labels. The fitter enters a single oval cut size manually, without F/B or L/R axis labelling. Appropriate for non-directional presses and experienced fitters who prefer manual oval determination. See sections 5.5.1–5.5.3.
🔤 O
- OD (Outer Diameter)
- The outside diameter of an insert — used to determine the hole size to drill. See section 9.3.4.
- Oval (O)
- As a span type: a span measured to the centre of the oval cut on the finger hole. As a hole type: a finger or thumb hole that is elongated along one axis rather than perfectly round. See sections 5.5.1–5.5.3 and 6.1.2.
- Oval Calculator
- The Spectre Cloud module that calculates oval cut sizes, angles, and directional values from the pitch and span values on a spec sheet. Configurable by method (EDGE/CENTER), degree increment, cut direction, and Flip V/H. See Book 05.
- Oval Cut Direction
- A Settings option that controls whether oval cut outputs include directional axis labels — NONE, Forward/Back (F/B), or Left/Right (L/R). See sections 5.5.1–5.5.3.
- Oval Degree Increment
- A Settings option that controls the angular resolution of oval cut output — either 1° or 5°. See section 5.6.6.
🔤 P
- PAL (Positive Axis Point Layout)
- A layout system in which all measurements — pin distance, pin angle, and MB angle — are expressed relative to the bowler's PAP. See section 6.1.5.
- PAP (Positive Axis Point)
- The point on the bowling ball surface that represents the bowler's axis of rotation at the moment of release. The primary reference point for all layout measurements. See sections 7.1.5 and 7.1.6.
- Pin
- The top weight marker on a bowling ball — the lightest point on the weight block axis. Its position relative to the PAP determines flare potential. Shown on the 3D layout rendering in Arsenal Plus.
- Pin to PAP distance
- The straight-line distance from the ball's pin to the bowler's PAP. The primary driver of flare potential and overall ball motion strength. See section 7.1.6.
- Pitch
- The angle at which a finger or thumb hole is drilled relative to the ball surface. Expressed in inches of forward, reverse, or lateral offset. See sections 9.3.1 and 9.3.2.
- Plugin
- An optional add-on to the core Spectre Cloud subscription that unlocks additional features. Current plugins: Bowler Plus, Arsenal Plus, and Job Board. See Book 08.
- Pro shop
- A retail and service establishment specialising in bowling ball drilling, fitting, and equipment. The primary user of Spectre Cloud.
🔤 R
- Referral code
- A unique code associated with each Spectre Cloud account that can be shared with other pro shops. When a new shop signs up using the code, both parties receive a billing benefit. See section 8.1.5.
- Reverse pitch
- Pitch in which the bottom of the hole tilts away from the bowler's palm. Expressed as a negative value in Spectre Cloud. Used for bowlers who grip tightly or whose thumb tends to hang through the release.
- RG (Radius of Gyration)
- A measure of how the mass of a bowling ball is distributed relative to its axis of rotation. Lower RG produces an earlier, smoother roll; higher RG produces a later, more angular motion. Available as a ball specification in Arsenal Plus.
🔤 S
- Semi-fingertip grip
- A grip style in which the fingers are inserted between the first and second knuckle. A compromise between conventional and fingertip. Selected as a grip type on the spec sheet.
- Slug
- A pre-drilled thumb insert installed into the thumb hole to provide a consistent, replaceable grip surface with a specific pitch bore. The slug's outer diameter is entered as the thumb hole size on the spec sheet; the slug's bore angle is entered as the thumb pitch.
- Span
- The distance between the thumb hole and a finger hole, measured according to the selected span type (Full Span, Cut to Cut, or Oval). Entered on the spec sheet for middle and ring fingers independently.
- Spec sheet
- The primary drilling record in Spectre Cloud. Contains all measurements, pitch values, span values, oval cuts, layout, and notes for one ball belonging to one bowler. See Book 04.
- Suggested Layouts
- An Arsenal Plus feature that generates data-driven layout recommendations based on the bowler's PAP, axis data, and the ball's core specifications. See section 7.1.5.
🔤 T
- 3D Layout view
- An Arsenal Plus feature that renders a rotatable three-dimensional model of the bowling ball showing pin, MB, PAP, VAL line, and hole positions based on the spec sheet's layout values. See sections 7.2.1–7.2.3.
- 2LS (Two-Layout System)
- A layout system that uses pin buffer distance and CG placement as its two primary measurements. A streamlined alternative to VLS. See section 6.1.5.
🔤 V
- VAL (Vertical Axis Line)
- The line running through the bowler's PAP from the top to the bottom of the ball, dividing it into front and back halves. The reference line from which the VAL angle is measured. Displayed on the 3D layout rendering.
- VAL Angle
- The angle between the bowler's VAL and the line from the PAP to the pin. Controls the shape and timing of the breakpoint — lower angles produce smoother, more arcing motion; higher angles produce sharper, more angular motion. See section 7.1.6.
- Vertical (V)
- One of the two axes used to express directional oval cut values in Spectre Cloud. Which physical direction V represents depends on the drill press orientation and the Flip V/H setting. See sections 5.7.1 and 5.7.2.
- VLS (Val Siebert Layout System)
- A widely used layout system defining a drilling using three measurements from the PAP: pin distance, VAL angle, and mass bias distance. Based on IBPSIA curriculum. See section 6.1.5.
🔤 W – Z
- Weight block
- The internal core of a bowling ball. Its shape, density distribution, and orientation after drilling determine the ball's motion characteristics. The pin and MB markers on the ball surface indicate the weight block's axis positions.
📌 Note: This glossary covers terms as used in Spectre Cloud and this wiki. Some terms — particularly layout and fitting terms — have slightly different definitions in other educational contexts or fitting systems. Where Spectre Cloud's usage differs from an alternative convention, the definition above reflects how the term is used within this platform specifically.
Related Sections
- 9.3.1 — Pitch suggestion chart (flexibility vs. forward pitch)
- 9.3.2 — CLT chart (lateral tilt angle vs. lateral pitch)
- 9.3.3 — 5/16 rule ring finger span distance chart
- 9.3.4 — Insert OD chart — standard insert sizes by brand
- 9.3.5 — Oval cut chart for manual (NONE mode) calculations
- 9.1.1 — Recommended Settings configuration for a new pro shop
✨ Tip: When training a new staff member, have them read this glossary before their first fitting session — not to memorise it, but to build familiarity with the vocabulary. A driller who knows what PAP, VAL, CLT, and EDGE mean before they encounter those terms on a spec sheet or in a fitting conversation starts from a much stronger position than one encountering them for the first time at the press. Return visits to the glossary during training reinforce terms as they are encountered in practice, which is far more effective than a single read-through.