What abrasive grit size for lapping cylinders

[AlanWParticipant @alanw96569]

I'm on my first attempt at making a piston and liner for a 1.5cc diesel engine (ME Snipe). I've read plenty about the process but nobody seems to say what size and type of abrasive grit to use for lapping. Axminster sell what i assume to be carborundum in five grit sizes with the smallest at 600; is this fine enough? Or is diamond paste the way to go and, if so, what colour code because they don't appear to have their equivalent grit size specified?

Alan W

[AlanWParticipant @alanw96569]

[JasonBModerator @jasonb]

On the diesels and glow engines I have made I go one grit further and use 1000g for final lapping of the parts and then a very small amount of the 1000g and plenty of oil to finally lap the piston into the cylinder. This is the same silicon carbide that Axi sell from Veritas, the 1000g can be hard to find but usually crops up on e-bay as well as 1200g which would do.

Diamond can have a bit more tendancy to embed in the metal.

[AlanWParticipant @alanw96569]

Thanks Jason. Just the one grit size or start with a coarser one?

Alan

[JasonBModerator @jasonb]

320, 600 then 1000

Have a look at Ramons thread on honing and lapping here about page 5 and a bit from my firefly build here bottom of page

[AlanWParticipant @alanw96569]

Thanks again Jason. Both threads duly bookmarked for reading later. POLISH4GLASS on ebay sell 1200grit silicon carbide, along with the other sizes you mention. I'll order some now. Thanks

Alan

[AlanWParticipant @alanw96569]

Success!

I completed the parts last October but winter weather and other projects saw the assembled engine 'shelved' and overlooked until yesterday. Properly mounted, the engine started and restarted easily; what a buzz! A real confidence boost to tackle a complete build. Thanks Jason for the pointers.

Alan

[john carruthersParticipant @johncarruthers46255]

Try telescope mirror makers and suppliers, they sell grit for optics from 60g right down to 1500g, then tin oxide size (think rouge).
**LINK**

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