Guides / Process

How Much Stock to Leave for Grinding

November 1, 2026

Grinding finishes a part to its final size. The machining step before it has to leave enough material for the grinder to clean up every surface, and not so much that grinding takes forever. That extra material is the stock allowance.

Typical allowances

Process	Soft part	After heat treatment
Surface grinding, per face	0.05 to 0.1 mm	0.15 to 0.3 mm
OD grinding, on diameter	0.1 to 0.2 mm	0.2 to 0.4 mm
ID grinding, on diameter	0.1 to 0.15 mm	0.15 to 0.3 mm
Centerless, on diameter	0.1 to 0.2 mm	0.2 to 0.3 mm

These are typical ranges. Long, thin or asymmetric parts distort more in heat treatment and need the upper end.

Why heat treatment changes everything

Hardening moves the part. Plates bow, shafts bend and bores shrink or grow. The allowance has to cover that movement, or the ground surface will not clean up and the part is scrap.

What happens when the allowance is wrong

Too little: black spots remain where the wheel never touched, and the part is out of size before it is finished.

Too much: grinding takes longer and the extra heat can burn or crack hardened surfaces.

Practical rules

1. Agree the allowance with the grinder before machining.
2. Write it on the machining drawing, not only on the final drawing.
3. Stress relieve long or welded parts before final machining.
4. Mark the datum faces so they are ground first.

Getting this right is free. Getting it wrong costs a batch.

Frequently asked questions