Pm932m-y Tram Off .003 Over 4"-y Gib Adjustment?

Apparently I did do something to get the spindle square out of calibration. Sorry about that you were correct. I'll be back. Hang tight please!

Gburgswmich said:

I squared it on a brand new calibrated inspection plate prior to use. I'm taking it out and doing it again now but I don't believe that's the issue.

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Ok I've got it calibrated to the table now...ill be back with more soon thanks!

tmarks11 said:

Squaring it on an inspection plate won't work. Regardless of what the instructions claim.

Put it in the spindle, put a gage block at the +Y extent. Zero one indicator on the gage block, spin 180 degrees, and zero the second gage block. That takes out any errors (such as slight alignment error in the spindle square shank).

See below at time 1:00

They use a magnet, but the gage block works just as well. You can also go right against the table, but then you really need to hold both DTI up while rotating, which is a PIA.

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Thanks! I am not sure how much weight I'm moving. I think the hoist is a gradual way of moving the head and column where I can control it closely. It's good to know you could move it that way.

sanddan said:

Are you sure you need a hoist? I was able to tilt mine enough to slip shims under the front of the column by pushing with my left hand and using my right to insert the shim. Not that hard just be sure you only loosen the bolts, not remove them. I backed the front bolts off a lot and the rear only enough to allow the head to tilt. You aren't lifting the head, just tilting so shouldn't require a ton of force.

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Is there something other than gage blocks that will serve the same purpose? Say a 1-2-3 block? I don't have a set of gage blocks yet, only gage pins.

tmarks11 said:

Squaring it on an inspection plate won't work. Regardless of what the instructions claim.

Put it in the spindle, put a gage block at the +Y extent. Zero one indicator on the gage block, spin 180 degrees, and zero the second gage block. That takes out any errors (such as slight alignment error in the spindle square shank).

See below at time 1:00

They use a magnet, but the gage block works just as well. You can also go right against the table, but then you really need to hold both DTI up while rotating, which is a PIA.

Click to expand...

1 2 3 block, yes, but use the same block, the same corner of it. It doesn't have to be anything special, just so that the same point on the block is used for each setting.

Reading the above discussion, re: a cylinder square, I realized that I had one, purchased at an auction, in the 1980's in Dayton. It has stamped on one end, Feb. 48, I have to imagine that was date of mfgr. Its about 2 inches in diameter, 5 1/2 long, It was still cased in brown wax. I'd never had occasion to use it before. I cleaned my PM25, ditto the cyl square, and set it up at 0 0 0 0 at the top. I moved the quill down 1.675 (as far as it would go) and circled around it. Y was 0 0 , X was ±.003. Thrilled to find that the spindle was square with the column, or at least the table, but I thought I'd fixed the X earlier.

I broke down the Cyl Sq set up, cranked the head down so that the quill was up and the indicator would just clear the table, and clamped the column and the quill. I got out a pair of .050 Jo blocks and with the indicator as far out as it would go (7" radius) got a .014 variation between left and right. It took three or four corrections, now its within (I hope) .005, that's the reading on the indicator, but it doesn't repeat as well as I would like. Anyway, I can't complain on .005 in 14 inches.

Well calibrating the spindle square off off of a 1-2-3 block on the table has me much closer than where I first believed. It looks like I'm only out .001-.0015 in Y over 4". I appreciate the info guys. There is as much bad info out there as good info so it's hard to know what to use as guidelines. I built a sweeper I'm going to try out to see if the results are consistent.

Well, I watched the video and couldn't wait till tomorrow. I used that method to calibrate my spindle square and re-trammed the head. It was off in the x direction about .002" so I adjusted the head and tightened up the bolts. I checked the Y direction and it was off .004". I got that back to zero and re-checked the X direction and it was still dead on. I then set the spindle square on the table to see how far it was or wasn't off. It was shifted off .0005" each direction for a total of .001" compared to the "magnet" version for calibrating. Now I have to figure out why the head was so off when the gage isn't that far out. I think it moved when I tightened the bolts last time I trammed it.

Gburgswmich said:

Same machine or smaller than the pm932? Seems like this would be ok for a smaller machine but the pm932 head is pretty heavy and my concern would be what effect this would have on the spin

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It had no effect whatsoever. The bearing load rating is much higher than a few hundred pounds, which is what the head weighs.

Tom S

sanddan said:

Now I have to figure out why the head was so off when the gage isn't that far out. I think it moved when I tightened the bolts last time I trammed it.

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And that is the part that makes tramming a mill frustrating... even on a bridgeport where you don't need shims. Tighten the bolts a little at a time in a cross pattern, checking several times as you get the bolts near tight to make sure it doesn't shift. Even more annoying is that adjusting the Y-axis tram can affect the X-axis tram.

Well it turns out that after I squared up my X, I'm only nodding .001" over 6" in Y. Checked by sweeping and with a spindle square. That .001 bothers me but I'm not sure it's worth lifting the column to attempt getting it perfect, at least not right now. Thanks for the help all!