Manufacturing Process

Grinding

磨削

Holding flatness, parallelism, diameter and surface finish with abrasive wheels and belts - surface grinding, cylindrical grinding and weld dressing.

Process Steps

Datums and stock defined
Wheel or belt selected
Material removed in controlled passes
Flatness and finish checked

What grinding is used for

Direct answer: grinding removes a small amount of material with an abrasive wheel or belt to do one of three jobs — hold a face flat and parallel, hold a diameter and its roundness, or take a weld and a burr off an edge so the part is safe to handle and ready to finish. It is a finishing operation, not a way to make a part from stock.

The three jobs, and what each one holds

Operation	What it holds	Typical use
Surface grinding	Flatness and parallelism, typically within 0.01–0.02 mm on a small plate; Ra 0.4–1.6 µm	Plates, spacers, die plates, faces that have to seat against something
Cylindrical / centreless grinding	Diameter, roundness and straightness on turned parts	Shafts, pins, bushings and sleeves where the fit decides function
Weld dressing and blending	A weld brought flush without undercutting the parent metal	Visible frames, handles and any face that will be powder coated
Deburring and edge break	A radiused or chamfered edge, free of burr	Every laser-cut and blanked part, before it is handled or coated
Belt finishing (linishing)	A controlled, consistent scratch pattern	Parts where the surface is seen, and as preparation before polishing

Grinding or machining?

Both remove metal; they differ in how much and in what shape. Milling and turning are the economical way to move a part to size, and grinding is what closes the last few hundredths — or what reaches a hardness that a cutting tool will not touch. Practical rules:

Hardened material — grinding, or wire EDM where the geometry is a profile rather than a face;
A face that has to be flat and parallel — grinding, because a milled face carries a cutting-tool pattern and slight relief;
A tight tolerance on a thin part — grinding, because the cutting force is small and the part does not spring away from the tool;
Removing a lot of stock — machine it first. Grinding stock removal is slow and grinds the part's cost up with it.

Where a part needs both, the sequence is fixed at DFM stage: rough machine, heat treat where required, then grind the faces that the drawing actually calls out, so no tolerance is stacked twice.

What the drawing should carry

A flatness or parallelism callout on the face that matters, rather than a blanket general tolerance;
A surface-finish value (Ra) where the surface is functional — sealing, sliding or optical;
Any no-grind area, such as a coated face or a marked surface;
The material condition: grinding a case-hardened or heat-treated part changes nothing about the hardness, but it does change the wheel and the feed.

Where grinding sits in the workflow

Edge work comes first and cosmetic work comes last, because every later operation scratches what came before:

Cut — laser, punch or shear;
Deburr and break the edges (deburring);
Form, bend and weld;
Dress the welds and blend the joints;
Grind the faces the drawing calls out, then machine or tap where needed;
Surface finish — coating, plating or passivation runs after all of it.

Deburring and grinding run in-house; the bulk finishing steps that follow (plating, passivation, electropolishing) are carried out by audited partner companies and declared as such — see metal finishing and secondary operations.

Frequently asked

How flat can grinding hold a face?

On a part of ordinary size, a ground face holds flatness and parallelism within roughly 0.01–0.02 mm. Tighter than that starts to depend on the part's own stiffness, how it is held, and where it is measured — so it is agreed per part rather than promised generally.

Does grinding change the hardness of a part?

No — it removes material, it does not heat treat it. What it can do is burn a surface if the wheel and the feed are wrong, which is why hardened parts are ground with the right wheel and light passes.

Can a welded part be ground flush without weakening it?

Yes, provided the grinding stops at the surface and does not cut into the parent metal. Dressing a weld flush is normal where the face is visible or has to seat; grinding through the parent is a defect, and it is caught at inspection.

Should the drawing ask for grinding or for a machined finish?

Ask for the result you need — a flatness figure, a diameter with its tolerance, or an Ra value. The shop then chooses grinding, turning or milling to get there, and says so on the quotation.

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