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PM-25MV Y axis off by .006

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Pcmaker

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#1
Manual says Y axis was trammed by them and should be true. But I used one of those spindle squares with the two indicators and it's off by .006, which is a lot.

Has anyone had any experience tramming the Y axis on this bench type mill? There's 4 bolts holding the vertical part from the base. I'm thinking of just undoing the bolts and putting in 2 small pieces of paper in there since I read paper is about .003
 

RJSakowski

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#2
Before messing with the column, check your z axis gib. Play in the z axis ways will cause head sag which you will see as a y axis out of tram.
 

RJSakowski

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#3
Since the PM-25MV has motion in both the column and the quill, you need to determine any alignment error. If the spindle isn't parallel to the z axis ways, by shaming the column, you would be introducing another error and in this case two wrongs don't make a right.

BTW, this is also true for the x direction.

It is fairly simple to check if the spindle is parallel to the z axis ways. I did so using a variation of Rollie's Dad's Method. I mounted a bar in the spindle and a test indicator on the table. I then measured the minimum and maximum runout and averaged teem at a position close to the spindle face and an appropriate distance from the spindle face. The two averages should be the same. This measurement should be made in both the x-z and y-z planes.

Once you have determined that your spindle is parallel to the z axis, any out of tram condition would be corrected by shimming the column.
 

mksj

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#4
If you do not lock down the gibs the head it will always nod, and will get worse over time because the gibs wear. I would not use paper for shimming, go out and get some brass shimstock of various thickness or some 0.001 and use layers. If it needs to be trammed it may take very little/thin shimstock. Some people use epoxy, not a big fan if you do not get it spot on.

 
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Pcmaker

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#5
I tightened the gibs, shimmed the column and now I am off by .030. I took off the paper shim and I'm still off by .025.

The column is now offset, I think, with just me eyeing how lined up it is with the base. I'm gonna play around with it some more. I'm thinking the base and/or the column's mating surfaces aren't perfectly square.
 

Pcmaker

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#6
Ok, added 10 pieces of paper shim to the rear side of the column and now I am off by .002

I am off to get some cheap feeler gauges to replace the paper with.
 

ttabbal

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#7
I have a couple sets of feeler gauges from Harbor Freight for that reason. They make nice portable sources of lots of different size shim stock. :)
 

Pcmaker

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#8
Tramming the Y axis messed with the X axis. But I got both axis to a thou. I'm not messing with it anymore. I used a spindle square when I was tramming.

Only thing I'm worried about is when I used a machinist square on the quill, it seemed a bit off.
 

stupoty

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