Standard Work · SOP

Drawer Box Bottom Groove Width Tolerance

This document defines the procedure for machining the 1/4″ (6.35 mm) groove in drawer box sides to accept the bottom panel. Tolerance is ±0.15 mm on width and depth. Essential for preventing drawer racking and bottom panel binding.

Estimated Time

15 min per side

Difficulty

Intermediate

Regulation

ISO 2768‑m

Version

1.0

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Purpose

To ensure that all drawer box bottom grooves are machined consistently to a width of 6.35 mm (+0.15 mm / −0.0 mm) and a depth of 6.35 mm (±0.10 mm). A properly sized groove guarantees that the bottom panel slides in with light finger pressure yet holds without glue or fasteners, preventing racking during assembly and service life. This SOP reduces rework, material waste, and assembly labour.

Scope

This procedure applies to all drawer box sides machined in the main cabinet cell (CNC router #3 and table saw #2). It covers Baltic birch plywood, MDF, and pre‑laminated particleboard in 1/2″ (12.7 mm) nominal thickness. Any material substitution must be approved by the lead fabricator and verified with a test cut. This SOP does not cover dowel‑and‑edge joinery or dovetailed drawer construction.

Safety Precautions

LOTOPerform lockout/tagout on CNC router and table saw before changing bits or adjusting dado stack. Verify zero‑energy state.
PPEWear safety glasses, hearing protection, and cut‑resistant gloves (ANSI A3 minimum) when handling sharp tools.
KICKBTable saw: use push stick for cuts under 150 mm from the blade. Keep riving knife aligned within 3 mm of blade arbor.
DUSTConnect dust extraction to both machines; air‑borne MDF dust is a Class C combustible dust hazard. Vacuum only – never sweep.

Required Tools & Materials

Pre‑cut drawer box side panels (1/2″ nominal thickness)
Drawer bottom panel material (1/4″ nominal thickness, e.g., hardboard or plywood)
Feeler gauge set (metric, 0.05 mm increments)
Digital calipers (0.02 mm resolution, calibration current)
Sharp pencil and inspection log sheet
Shop air blowgun (clean chips from groove)
CNC router with 1/4″ spiral up‑cut bit (or table saw with dado stack set to 1/4″)
Vacuum clamp or hold‑down system
Digital angle finder (verify 90° reference)
Flashlight for visual edge inspection

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Procedure: Step-by-Step

1 Verify Material & Set Up Machine. Confirm drawer box sides are nominal 1/2″ (12.7 mm) – measure three points with calipers. For CNC: install 1/4″ spiral up‑cut bit, set spindle speed 18,000 rpm, feed 250 IPM. For table saw: install dado stack to 1/4″ width, use a test cut in scrap to confirm width 6.35 mm (+0.05 mm/−0.0). Program depth of cut to 6.35 mm from outside face.

2 Machine the Groove. Secure workpiece with vacuum clamp or jig. Run first side (inside face groove). For CNC: run full‑depth single pass; check chip evacuation. For table saw: use push stick, make multiple passes if dado stack is undersized – never force the work. After cut, blow chips and inspect visually for burn marks or tear‑out.

3 Inspect Groove Width. Using digital calipers, measure groove width at three locations: left end, center, right end. Acceptable range: 6.20 mm – 6.50 mm. Depth: measure from shoulder – acceptable 6.25 mm – 6.45 mm. Record each measurement in inspection log. If any value exceeds tolerance, reject the panel and adjust machine immediately.

4 Verify Groove Fit. Insert sample drawer bottom piece (1/4″ nominal) into the groove. It should slide in fully without binding; no more than 0.2 mm visible gap on either side. Use feeler gauge to check side clearance: maximum 0.15 mm. If too tight, rechuck and pass again with 0.05 mm offset. Loose fits require scrapping the panel.

5 Document & Sign Off. Stamp approved panels with operator initials and date (use date‑stamp or permanent marker on inside face). Complete the in‑process inspection checklist. File checklist in job folder. Reject any panel failing width or fit tolerance and tag for rework. Rework allowed only if material can be shimmed or recut – if groove is oversize, panel is scrap.

Drawer Box Bottom Groove Width Tolerance

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