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Problem With King KC 20-VS Mill

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snub:
I recently purchased a KC 20-VS milling machine. It is almost identical to the Grizzly G0704. I haven't used it much for anything with critical dimensions, so never bothered to check the accuracy of the graduations on the handwheels. I decided to add Digital Read Outs and got them installed on the X and Y axis. Much thanks to 75Plus for his tutorial on doing this.

So first I check the accuracy of the X axis handwheel versus the DRO. It is spot on. Ran the table 6 inches and both readings the same. Then I checked the Y axis. Ooops. Not even close. When I rotate the handle .020", the DRO reads .016". When I rotate the dial .100", the DRO reads .078". And so on.

My first thought is that the DRO must be at fault so I grabbed a "portable" DRO to check. Turns out it is the handwheel graduations that are inaccurate. That being said, I did have to remove the handwheel to facilitate the install of the DRO.

Is it possible I buggered something up when I did this. I just removed the nut and handle, then reinstalled. I can't believe the handwheel could be that far off. I looked at the "inspection report" that was done at the factory, and apparently this isn't something they check. I wish I had when I first got the machine but I just assumed it would be good.

75Plus:
There is no way to corrupt the readings by removing or replacing the  hand wheels. What you need to establish is the number of threads per inch that is on the "Y" axis lead screw. My G0704 has 10 tpi lead screws so one complete rotation of the hand wheel will move the table 1/10" or .100" The scales have .002" divisions with major marks every .020". I just wonder if you may have a metric lead screw in the "Y" axis and an inch scale on the hand wheel. This could explain the large difference.

I think your first move is to determine just how far exactly one rotation of the hand wheel moves the table. That will tell you what the thread pitch is.

Let us know what you find.

Joe

12345678910:
I have a mill, not the same as yours but same country of origiin.


The graduations of all three axis are incorrect.

Not by a little bit either.


the junk factor is frustrating.

awemawson:
The first Mill / Drill that I bought decades ago had the same issue on the down feed. It was a while before I realised that as the screw pitch didn't give whole numbers of 'turns per inch' they had engraved a dial in reasonably accurate thou but the start and end were discontinuous. So it was ok for moves less than a full turn !

RussellT:
The odd thing is that if it reads 0.016 when you move it 0.020 then it should read 0.080 when you move it 0.100.

That might be accounted for by 10tpi feed screw if the knob was made for an 8tpi feed screw.

Russell

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