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| 3D Printed External Lapping Tool |
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| Joules:
I dug out some finer Emery papers, 600 and 800 grit. Need to get some finer stuff, the new 600 paper soon ate 10 micron off the brass in just a few mins. Had to go gentle with the 800 paper, then finish with normal paper and Autosol at about 1000rpm to polish. Very pleased with the result, though working up-to a small shoulder isn't a great idea. The Emery papers just needed a wash and should be good to go many more times. The little SU1 mill just earned itself another star, as a lapping machine, very easy to mic the work in this setup, it uses much less energy than the big lathe. The combination of Emery and paper really works well, the paper holding slurry and oil. I will try a piece of steel when a bit just over 18mm diameter is to hand, picking up some 1200 grit paper is also on the shopping list. |
| RotarySMP:
What is the tolerance on the diameter along the bar? |
| Joules:
+10 micron over 60mm with a 20mm wide lap. The Emery paper was more aggressive than I expected on the brass and ended up with a hollow I couldn’t work due to the small shoulder. I didn’t go below 18mm, steel should be interesting. No detectable out of round from the lap anywhere along the length lapped. From the hollow here to the front is +5 micron, I should have undercut the material at the shoulder for the lap to over run. |
| RotarySMP:
Thanks. I look forward to trying this on the test bar. Still have to finish the taper. |
| RotarySMP:
I tried out your method of using sandpaper with the 3D printed lap. Worked pretty well. Bit of a PITA to load the sand paper into the lap, but you get the hang of it by the time you get to 2000 grit. The bar is an unhardened stainless steel. I managed to get it to within 3µm over 200mm with a couple of hours work. Thanks for testing that Joules. Mark |
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