what lap material for lapping brass?

Hello. What material (material for the lap tool itself) can the group recommend to lap a ~1/4" hole in a piece of brass? I'd like to try and reduce the amount of embeded abrasive that ends up in the piece itself, and the only abrasive I have on hand is SiC and AlO. All comments welcomed. TIA Art

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If you want the abrasive to imbed in the lap then it will have to be softer than the brass, Possibly copper or alum might serve this purpose. I havn't done it myself, all of my experience is with flat castiron lapping plates. Did a lot of seals and such for turbine engines that had to be flat to 3 heliun light bands, usually using diamond compound for the final polish. gives a mice mirror finish :-)

James Crombie

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James P Crombie

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You'll have to probably go to lead for lapping, the lap material has to be softer than the work piece. Both your abrasives will probably embed in your workpiece, Brasso might work, tripoli, rouge or rottenstone might be other choices. Test pieces would definitely be in order.


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Greetings Art, If you can't buy some Timesaver brand lapping compound and can only use what you have on hand then a lead lap will work. But it must be a soft lead compound. Pure lead would be best. You can pour it into a hole drilled on the center line of two aluminum blocks. This hole should be smaller than the lapped hole. When cool, roll the lead cylinder on the abrasive, pushing down hard so that it embeds into the lead. Next, wash the lead lap with solvent and a brush to remove any loose abrasive. Drill another hole in the aluminum blocks that is the same size as the hole to be lapped. Put the lead lap into it and use a punch to "upset" or expand the lead into the hole. You are now ready to lap the part. You can upset the lap in the brass too. Just be careful not to jam the lap. Go slow and you should be OK. Use kerosene or solvent as a cutting fluid. ERS

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Eric R Snow

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