Precision Finishing
Precision finishing covers final operations such as lapping, honing and superfinishing that bring critical surfaces to specified roughness, flatness or geometry beyond what grinding gives. It is used on sealing faces, bores, valve seats and bearing surfaces.
What it is
Lapping rubs parts against a flat lap with fine abrasive to produce extremely flat, smooth sealing surfaces. Honing uses abrasive stones in a bore to correct roundness and straightness and give a controlled cross-hatch. Superfinishing uses fine stones on a rotating part to remove the damaged surface layer and reduce roughness.
These processes remove only microns, so they follow grinding or fine machining on the features that need them.
Typical applications
- Mechanical seal faces and valve seats
- Hydraulic cylinder and valve bores (honing)
- Bearing races and shaft journals
- Gauge and measuring surfaces
- Pump plungers and spools
Suitable materials
- Hardened steels
- Stainless steel
- Cast iron
- Carbide and ceramics
- Bronze
Points to consider
- Specify the parameter that matters: Ra, flatness, roundness or cross-hatch angle.
- Only a few microns are removed, so size the part accurately beforehand.
- Clean parts thoroughly after lapping to remove abrasive.
- Check requirements such as bearing ratio (Rmr) for seal faces with your seal supplier.
Frequently asked questions
What is lapping used for?
Producing extremely flat and smooth surfaces, such as mechanical seal faces, valve seats and gauge surfaces.
What is honing?
An abrasive finishing process for bores that improves roundness, straightness and finish, leaving a cross-hatch that holds oil in cylinders.
How smooth can precision finishing get?
Lapping and superfinishing can reach around Ra 0.02–0.1 µm, depending on material and process.