4.5.2 Entering thumb hole size

4.5.2   thumb

For a round thumb, the hole size is a single value entered on the spec sheet. The thumb section records both the O.D. (the drill/hole size) and, when a thumb insert or slug is used, the hole size the bowler's thumb actually sits in — the two are different values whenever an insert or slug is involved.

• ✅ Bare thumb: the O.D. is the hole drilled directly into the ball.
• ✅ Thumb slug or insert: the O.D. is the pilot hole drilled to accept the slug/insert; the hole size is the finished opening the thumb sits in. Record both — don't put the same value in both fields.
• ✅ For an oval thumb, the size is not a single value — it comes from the four oval inputs (see 4.6.1), so this single size field does not apply.

🛠️ Entering Thumb Size in Spectre Cloud

1. Confirm the thumb shape is set to Round (see 4.5.1).
2. Enter the thumb O.D. (hole/drill size).
3. If a slug or insert is used, enter the finished hole size as well.
4. Proceed to pitch and insert entry.

⚠️ Verify with your Spectre team: confirm the exact field labels for thumb O.D. vs. hole size, and the unit (fractional/decimal inches).

Related Sections

• 4.5.1 — Selecting the thumb hole shape (Round or Oval)
• 4.5.3 — Entering vertical and lateral pitch for thumb
• 4.5.4 — Thumb insert type and size
• 4.4.2 — Finger inserts
• 4.6.1 — Oval thumb inputs (for oval hole sizing)

Tip: Thumb size is the measurement most likely to change between visits — with temperature, time of day, and swelling. Don't carry a thumb size forward from an old sheet without re-checking it.