Joined: Wed Jun 22, 2016 8:23 am Posts: 99 Location: Colorado Springs, CO
I've had these issues since I bought a (heavily) used Facetron. 1. When I sweep the stone from front to back, the micrometer raises, so the back of the lap is higher than the front. 2. When I facet on the outside of the lap, the micrometer needle goes back and forth quite a bit, which means that the lap is wobbling. I thought #1 may be caused by a crooked mast, so I took it into a machine shop and they were amazed at the tolerances on it, it was dead straight. Now, where the mast sits on the plate, there are some heavy wear lines going back and forth where the anodized portion is worn off. Should I just replace the base plate and the lap assembly, or take it to a machine shop? I'm pretty sure I don't have the equipment to machine it myself. Is there something else that I may be overlooking? The lap assembly runs about $200 and the plate about $250. I'd rather buy the Adamas Max, but alas, my wife would kill me if I spent $2k on only part of a faceting machine.
Joined: Fri Jun 25, 2010 12:04 am Posts: 257 Location: Idaho
The anodization wears over time, but there should not be a groove in the aluminum that you can catch a finger nail in...
1) Mast to base alignment: Take off the lap and drain bowl, then put on the 45 degree dop (with machine at 45 degrees), and put a brass dop in the 45 deg. block upside down so the blunt end is down. Now lower the head so the dop hits the machine base, and zero it for the micrometer. Sweep the head back and forth and see if it stays close to zero. Then loosen the mast base, and move forward and back, tightening down mast and checking the micrometer at various locations to see if your head and mast are true to the base.
Arbor alignment: If it is, then your arbor may not be perpendicular to the base and is causing the problem. For me, Facetron (in 1990) had put a number next to the arbor, letting me know it was 0.004" off on one side, and they had not corrected it. I loosened the arbor from the base and shimmed it with thin brass to set things right, checking with a micrometer along the way. It can be off front to back and/or right to left.
2) This flutter is due to either 1) the lap being imperfectly flat to the platten (flat disk part on the top of the arbor), 2) debris on the back of the lap or platten, or 3) a bent arbor from mishandling.
The first can be from cheap laps (ie "toppers' and such), or a bent lap. Also, most laps AND master laps are little off, but the flutter (that used to be used as a cutting depth indicator in the stone ages...) can be minimized by rotating the lap on the platten until a rotation is found that gives the least wobble. An indexing mark can be on the side of the platten, and a corresponding mark put on the back of the lap for repeatability. John Bailey of the Faceting Academy calls it "Blueprinting Your Laps", and has a video on it on his site, #11 at the bottom of this page:
Joined: Wed Jun 22, 2016 8:23 am Posts: 99 Location: Colorado Springs, CO
1. Micrometer is lower on the rear of the base, higher on the front. I think its the mast, the mast also has a wear spot on the part that faces the platen. 2. The platen is a little off when it spins, I Blueprinted my platen as per the Faceting Academy Video, the platen has a high side when rotating, but it's about as much as it was in the video. I think I'm gonna take it to a reputable machining shop to make sure the mass is perfectly straight and the platen is flat.
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