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View Full Version : Truing Up My Grinding Fixtures



JoeLee
11-23-2014, 01:22 PM
I've been wanting to do this for quite some time. I started with the base plate, made sure it was dead flat and no rocking when on the surface plate. I did have to dust the bottom on the grinder to cure the .0005 high spot that was in the center. Using the method in the pictures of checking each component of the fixture, I found the one that was the real problem. It happened to be the swivel base, it was out of square by almost .002 from top to bottom as shown with the shim stock between the base and protractor. When the 2nd axis was mounted to the swivel base there was a .002 rise from front to back as indicated with the cube and dial. Since there was no real easy set up to cure the problem and any thing that I might do could very easily make matters much worse. I don't know how KO made these but I'm sure that it involved more than one set up and operation which may very well be the reason aside from them not being overly fussy.
Since the vertical surface needs to be square with the base I thought I might be able to set it up on the faceplate of the lathe with a precision angle plate bolted to the lathes face plate, but that was going to be a lot of time wasted and with no guarantee of the desired accuracy. So............ a quick thought came to mind, If I could make a flat bar that would rotate in a circle off the center of the fixture's hole I might be able to sand the high spot out with out the risk of making it worse or removing too much material. So what I did was turn a PVC plug to lightly press fit by hand into the fixtures hole. I mounted a 1/4" dowel pin in the center and made a flat aluminum bar to fit the dia. of the fixtures head. I made sure the bar was flat. I put a small piece of 150 grit sand paper on one end and a couple layers of masking tape on the other end to make up for the thickness of the sand paper, this way the bar sat flat. I then rotated the bar back and forth over the high area and periodically checked for progress. Surprisingly enough it worked out perfectly and the sand paper marks look like the original turning marks, very uniform. Once I got the whole thing together I have about .0002 overall flatness.
Plenty good enough for any one. Next I'm going to tackle the universal work holding fixture.

JL.......................

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Toolguy
11-23-2014, 01:47 PM
Very creative! Great job.:D