Patch fitting layouts and the toughening drawing

Patch fittings only work if the glass is cut to the fitting maker’s pattern. That pattern goes to the glass processor as a toughening drawing with every hole, notch and cut-out dimensioned from a datum.

What the drawing must show

• Overall glass size and thickness.
• Every hole: diameter and centre position, dimensioned from two edges.
• Every notch or cut-out: shape and position, with corner radii.
• Which edges are polished and which are exposed.
• Hardware make and model, so the processor can cross-check against a known pattern.

Typical door layout

A standard patch door has a bottom patch and a top patch at the pivot edge, a top pivot patch, a lock patch at the leading bottom corner, and two holes for the pull handle. The pivot edge patches align vertically; the pivot spindle centre from the bottom patch must line up with the floor spring spindle within a couple of millimetres.

Tolerances

• Hole positions: work to ±1 mm. The processor toughens to a tolerance and you cannot adjust afterwards.
• Glass size: allow the fitting maker’s stated gap to the floor and the head — usually 8–12 mm at the bottom for the spring cover and floor level.
• Edge clearance: keep holes at least 1.5× to 2× the glass thickness from any edge, or toughening can fail at the hole.

Before you order glass

Dry-assemble the fittings on the drawing. Confirm the floor spring model and its spindle height. Send us the door schedule and we will return the patch set with a dimensioned pattern for each door.