# 4.4.3 STD vs. VACU

<span style="font-family: monospace; color: #6b7280;">4.4.3</span> <span style="border: 1px solid #d1d5db; color: #4b5563; padding: 2px 8px; border-radius: 3px; font-size: 0.85em;">concept</span>

Finger inserts seat in one of two ways — **STD (Standard)** or **VACU (Vacuum)**. The insert type you record on the sheet (see 4.4.2) tells Spectre Cloud how the hole is drilled. This page explains the difference. For the OD-sizing concept, see **4.1.6**.

## 📐 STD (Standard)

Standard inserts are **press-fit**: the hole is drilled to the insert's OD, at full depth, and the insert is pressed in and held by friction against the ball's coverstock.

- ✅ Drill bit size equals the insert's published OD — a direct, one-to-one match, full depth.
- ✅ A correct STD fit presses in with firm hand pressure or a seating tool — it shouldn't drop in freely or need excessive force.
- ❌ Never undersize an STD hole — a too-tight press-fit risks cracking the ball surface.

## 📐 VACU (Vacuum)

VACU inserts are drilled in **two diameters** so the insert has room to expand:

1. Drill the **top portion** at the size shown on the spec sheet.
2. Drill that top portion **`1"` deep**.
3. Continue to the insert's **actual OD** for the rest of the depth.

The oversized top forms a **pocket** — a void where the insert doesn't touch the surrounding ball wall — giving the insert room to expand.

- ✅ The spec-sheet OD for a VACU insert is the **top-portion (pocket) size**, not the insert's body OD.
- ✅ The deeper portion is drilled to the insert's actual OD, exactly like a STD hole.
- ❌ Drilling the whole hole at one size removes the pocket entirely and defeats the VACU fit.

## 📊 STD vs. VACU

<table id="bkmrk-std-%28standard%29vacu-%28"><thead><tr><th> </th><th>STD (Standard)</th><th>VACU (Vacuum)</th></tr></thead><tbody><tr><td>**Drilling**</td><td>Single diameter at the insert OD, full depth</td><td>Oversized pocket ~1" deep, then actual OD to depth</td></tr><tr><td>**Spec-sheet OD means**</td><td>Drill size for the whole hole</td><td>Top-portion (pocket) size</td></tr><tr><td>**Why**</td><td>Friction press-fit</td><td>Void lets the insert expand</td></tr></tbody></table>

### Related Sections

- 4.4.2 — Finger inserts (recording type, size, OD)
- 4.1.6 — Insert OD concept: STD vs. VACU, insert size vs. OD
- 2.6.6 — Autofill Insert OD

**Tip:** The most common VACU error is drilling the whole hole at one size. Remember it's two cuts — the spec-sheet size for the first inch to form the pocket, then the insert's actual OD to depth.