Some lapping on the lathe.

[doug gray]

Just wanted to shear this shot of doing some lapping on the lathe. This is a crosshead frame from a PM Research steam engine #6 set of castings. The frame is about 5 inches long, quite a reach for even the biggest boring bar I had available. so after boring i ended up with chatter marks and about 2-3 thousand difference in diameter one end to the other. I have been following RCDON's great articular on building this engine and stole so lapping ideas. the bass bar has 400 grit tapped on to it and copy paper rolled up inside to increase the diameter. The diameter can be adjusted as needed just add or remove copy paper. I turned up a plug gauge for the biggest end and started lapping. The lathe was run at 150 rpm and the crosshead frame counter rotated applying pressure in the areas needed. I used wd as a lub. The crosshead was easily removed out the tailstock end and checked often with the plug gauge. Ended up with a very satisfying fit and finish. Total time "lapping" was less than 20 minutes, spread over 90 minutes of cleaning and checking coffee break etc.

Thanks for looking