Lapping / Polishing Machine Guidance

Hi All,

I need to lap and polish advanced ceramic components that I'm manufacturing. I'm looking into purchasing a machine (surplus), but I'm not sure what is needed for the job in terms of equipment, tooling (wear plates, I believe they are called), and consumables (grinding grit / paste).

The largest part to be lapped / polished is 4" square. The spec given was a surface finish between 16 and 4 microns, lapped flat to 16 hlb or better, with .002" or better parallelism for top and bottom.

A 15" lapmaster looks suitable, but I've found surplus machines that may do the job for thousands less. Would something like a spitfire sp-ml-15 work for this job?

Also, any practical guides/reference books that would be a good resource on lapping and polishing?

That Spitfire looks to be a single-sided lap, for parallelism it's easiest if you use a double-sided machine. But .002" isn't that tight a spec, if you maintain good // during rough machining you should be able to hold it even working on one side.

For technique, practice, practice, etc. Cleanliness during changeover of grits is critical, as is maintaining the flatness of the plate(s). Learn how to maintain the dress of the plate, basics should be the same for most brands of machine.

Thanks for the info.

I looked through a spitfire manual and lapmaster manual searching for any mention of procedure without any luck. Any ideas on a source for this info?

.002" is very generous. A lot of lapping and polishing is done to 10 times higher. For ceramic a diamond slurry or past must be used. Lapping and polishing works best if only a minimal amount of material is to be removed. I am not sure what is the process to make your ceramic parts, but practically always grinding to close final dimensions is standard. In fact with .002" grinding should be completely adequate and no lapping needed (maybe just a touch of polishing for better surface finish). I grind ceramic parts held in toolmakers vice on jig grinder and on a surface grinder. Using diamond wheels of various grit and lots of coolant.

billzweig said:

.002" is very generous. A lot of lapping and polishing is done to 10 times higher. For ceramic a diamond slurry or past must be used. Lapping and polishing works best if only a minimal amount of material is to be removed. I am not sure what is the process to make your ceramic parts, but practically always grinding to close final dimensions is standard. In fact with .002" grinding should be completely adequate and no lapping needed (maybe just a touch of polishing for better surface finish). I grind ceramic parts held in toolmakers vice on jig grinder and on a surface grinder. Using diamond wheels of various grit and lots of coolant.

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I currently diamond grind on a surface grinder, so the polishing would be almost entirely for surface finish.

Thanks for the input.

zipfactor said:

I currently diamond grind on a surface grinder, so the polishing would be almost entirely for surface finish.

Thanks for the input.

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Looks that a simple single disc metallurgical polishing machine will do. Manually polishing each surface with diamond slurry should take just a few minutes. Lapping machine would be an overkill, not to mention the expense and setup time needed for each run.
I now very seldom use the Abralap model 421/432, but it is capable of sub-micron accuracy.

billzweig said:

Looks that a simple single disc metallurgical polishing machine will do. Manually polishing each surface with diamond slurry should take just a few minutes. Lapping machine would be an overkill, not to mention the expense and setup time needed for each run.
I now very seldom use the Abralap model 421/432, but it is capable of sub-micron accuracy.

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What lead me to a machine versus hand lapping was the need for around 50 samples, 2 sides per sample to be lapped / polished. It seems like on a 15" diameter table, I'd be able to polish 3 sides / run.

Are the 3 rings that hold the part in place during lapping, as well as the conditioning ring to condition the lap easily made? They seem like nothing more than cast iron rings.