How accurate is surface grinding?

A good surface grinder holds thickness within about ±0.005–0.01 mm (±0.0002–0.0004 inch) and flatness within a few microns over normal part sizes, with a finish around Ra 0.4 µm.

Can aluminium be surface ground?

Yes, but it is not held by a magnetic chuck, so it needs a fixture or vacuum chuck, and a suitable wheel to avoid loading.

How much material should be left for grinding?

Usually about 0.2–0.3 mm (0.0079–0.0118 inch) per face after machining, a little more if the part distorts in heat treatment.

Surface grinding job work: accuracy, finish and cost

Surface grinding makes flat faces very flat, parallel and smooth by passing the part under a spinning abrasive wheel. It is used after milling or heat treatment, for die plates, tool parts, gauges and any part whose flat faces need close thickness and a fine finish.

Quick facts

Machine: Surface grinder (horizontal spindle, reciprocating table)
Typical thickness tolerance: About ±0.005–0.01 mm (±0.0002–0.0004 inch)
Flatness and parallelism: Within about 0.005–0.01 mm (0.0002–0.0004 inch) over the part
Surface finish: About Ra 0.2–0.8 µm
Holding: Magnetic chuck for steel; fixtures or vices for others
Usually priced: Per piece or per hour

When surface grinding is needed

Faces that must be flat and parallel within a few microns
Hardened steel parts that cannot be milled to size
Die plates, punches, gauges, fixtures and tool-room parts
Parts that need a fine ground finish for sliding or sealing

How to specify it

Leave a grinding allowance, typically about 0.2–0.3 mm (0.0079–0.0118 inch) per face after machining
Give the final thickness with its tolerance, and flatness or parallelism where it matters
State the hardness if the part is ground after heat treatment
Mark the faces to be ground; others stay as machined

Limits

Non-magnetic materials (aluminium, brass, stainless 304) need clamping fixtures
Thin parts can bow; they are ground on both sides in turns
Large plates need a grinder with a big enough table

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Questions

How accurate is surface grinding?: A good surface grinder holds thickness within about ±0.005–0.01 mm (±0.0002–0.0004 inch) and flatness within a few microns over normal part sizes, with a finish around Ra 0.4 µm.
Can aluminium be surface ground?: Yes, but it is not held by a magnetic chuck, so it needs a fixture or vacuum chuck, and a suitable wheel to avoid loading.
How much material should be left for grinding?: Usually about 0.2–0.3 mm (0.0079–0.0118 inch) per face after machining, a little more if the part distorts in heat treatment.

The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 9 October 2026.