Mechanical Seal Face Lapping
What This Process Needs To Solve
A mechanical seal has one job: hold a fluid back across a gap measured in microns, with two faces rubbing against each other for years. The faces have to be flat to within a light band, parallel to each other, and finished fine enough that the fluid film can form and stay. Every one of those properties is set at the lapping step.
We supply micron powder from W0.5 to W14 for seal face lapping, with grades selected by face material rather than by seal size.
Why flatness and finish pull in opposite directions
Lapping a seal face is not polishing a flat surface. The face has to be flat to a level that a light band test will reveal, and it has to carry a finish that lets a fluid film form without leaking. A grade that is too coarse reaches flatness quickly but leaves a scratch pattern deep enough to open a leak path. A grade that is too fine holds the finish but laps too slowly, and the plate starts to follow the existing geometry instead of correcting it. The usual answer is a two-grade sequence, not one grade run longer.
Face material sets the grade
Silicon carbide is hard and brittle, so it tolerates a coarser start but chips at an edge if the grade is too aggressive. Carbon graphite is soft and loads the lap, which means the grade has to clear the swarf rather than the material. Tungsten carbide sits between the two and takes a conventional sequence. Running one grade across all three materials is the usual reason a seal shop has one product that laps well and two that do not.
What we hold on the batch
Top cut is controlled tighter than the standard grade window, because a single oversize particle on a seal face shows up as a light-band distortion rather than as a visible scratch — and by then the ring has been lapped twice.
Where It Goes Wrong
- Light band shows distortion after the last pass. One oversize particle, not a plate fault.
- Leak path along the lapped face. Scratch pattern too deep for the fluid film to bridge.
- Lapping takes far longer than quoted. Grade too fine to correct the geometry.
- Lap loads up on carbon faces. Swarf clearance, which presents as a powder problem.
Recommended Grade By Face Material
Seal lapping is specified by face material and by the flatness target, not by seal diameter.
| Face material | Recommended grade | Micron size | Why this grade |
|---|---|---|---|
| Silicon carbide facesHard, brittle | |||
| SiC rough lap | HDY monocrystalline | W9 – W14 | Corrects geometry quickly without chipping the edge |
| SiC finish lap | HDYM fine micron | W1 – W3 | Brings the finish to the level a fluid film needs |
| Carbon graphite facesSoft, loads the lap | |||
| Carbon lap | HDYS agglomerated | W3 – W10 | Cluster structure clears swarf instead of smearing it |
| Carbon finish | HDYM fine micron | W0.5 – W1.5 | Reaches finish on a material that marks easily |
| Tungsten carbide facesIntermediate hardness | |||
| TC rough lap | HDY monocrystalline | W7 – W14 | Standard sequence, geometry correction first |
| TC finish lap | HDY, tight top cut | W1 – W3 | Oversize control keeps the light band clean |
Factory Direct Since 1990
Zhecheng Hongxiang Superhard Material Co., Ltd. is an integrated manufacturer and exporter of synthetic diamond powders since 1990, located in the Diamond Capital of China.
- Own manufacturing base in Zhengzhou, Henan — powder, coating and grading on one site.
- In-house particle size and SEM inspection on every batch before packing.
- Export packing with neutral or custom label, plus sample quantities for process trials.
What To Include
Describe your workpiece, process and target result. We will match the diamond grade from the existing product range.