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Pm-932m-pdf

richz

Active User
Active Member
#1
On the z axis gib adjustment should I be able to tighten it so it is hard to move the head. I have tried adjusting it but cannot seem to get it tight. I have removed the lower gib adjustment screw and the gib slide half way out. . When I loosen the head locking levers the DRO shows a movement about 20 thousandths. No matter how I adjust the gib adjustment screws I cannot get rid of this movement. Has anyone else had this problem. Could I possibly add a shim. Who would be a good person to contact a Quality machine tools about this.
 

wrmiller

Chief Tinkerer
H-M Supporter-Premium
#2
I have a similar machine, and what I do when adjusting the Z-axis gib is to lower the head onto a piece of bar stock positioned between the head and table to remove the forward cant/loading of the head. I then adjust the gib to a snug, but not overly tight fitment as felt through it's adjusting screws. I then remove the head prop and test the head movement. I also look at the delta on my DRO when tightening/releasing the Z-axis locking levers. I try to achieve a balance between freedom of movement and accuracy. For me, a delta of about 2 thou seems to be a good trade off and repeats consistently.
 

gb1551

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#4
I have the same problem with my MP 932m pdf and I have been wanting to call Matt about problem this but I keep on forgetting.
The gib for my Z-axis seems too thin. Even with the bottom ajustment screw out and the top adjustment screw turned all the way in, the gib itself has play in it. In the meantime, I have been keeping the head locking levers snug to cope with the issue. I have no problems with the proper adjustment on my the Y-axis or X-axis.
 

T Bredehoft

Active User
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#5
I have experienced a similar condition on my PM25, I adjusted the head gib until I felt drag on the hand wheel, but when I clamp the two head/column clamps, the head moves .008 in X.
 

TomS

Active User
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#6
I adjust my PM-932 Z axis gib using a method suggested by jumps4. Tighten the gib screws until a .002" feeler gauge will go in between the column and slide about 1". Checked spindle to column parallelism after and I'm within .0015" over 7". Close enough for me.

I also have the problem of the gib being too thin. I used a socket head cap screw of the proper length and made a heavy/thick washer that pushes on the end of the gib.

Tom S.
 

gb1551

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#7
I tried that idea with putting washers on the end of the screw. But in my case, I would need an 1 1/2" more travel before the gib starts to get tight. I just believe that the gib that was installed is the wrong part for this machine.
 

TomS

Active User
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#8
I tried that idea with putting washers on the end of the screw. But in my case, I would need an 1 1/2" more travel before the gib starts to get tight. I just believe that the gib that was installed is the wrong part for this machine.
Agree. Wrong part or machined too thin. Have you tried putting a shim behind it?

Tom S
 

gb1551

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#9
Not yet, I think I will contact Matt first. The mill is still under warranty and maybe he'll send me a replacement gib. I see from these posts, others have the same issues so it must be somewhat of a common problem?
 

richz

Active User
Active Member
#10
Last night I removed the gib. It was .309 on the top and .219 0n the bottom. I started wit a .020 shim but it was to tight. ended up at .011 and this took care of that problem. Next problem, with an indicator mounted in a collet and the indicator on the face of the column I am getting a difference of .o22 from top to bottom when extending the spindle. The bottom is closer than the top. What should be my next step?
 

Bray D

Active Member
Active Member
#11
I don't have anything worthwhile to add, but I thought I'd chime in. I have a 932 as well, but I've yet to take any serious time to check out my Z gib. I appreciate you guys looking into it and posting your findings/solutions.

.022" is huge. Makes me want to throw an indicator in my spindle and check it against my column as well. My initial thoughts would be that it's a head-to-column issue. Shimming between the head and the column would be a bear though.

Just to clarify, which surface are you indicating against on your column?
 

TomS

Active User
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#12
Last night I removed the gib. It was .309 on the top and .219 0n the bottom. I started wit a .020 shim but it was to tight. ended up at .011 and this took care of that problem. Next problem, with an indicator mounted in a collet and the indicator on the face of the column I am getting a difference of .o22 from top to bottom when extending the spindle. The bottom is closer than the top. What should be my next step?
Did you try the feeler gauge method I suggested in my post above? It would be interesting to know what the clearance is at the top of the Z saddle. I thought I had my gib adjusted correctly until I checked the top clearance. Had .012" clearance. You might also try Bill Miller's method mentioned above. There's a lot of weight you have to overcome to get the proper gib adjustment.

Tom S
 

richz

Active User
Active Member
#13
I used Bills method and believe I have the gib adjusted correctly. I was indicating on the larger machined surface of the column and getting a difference of .022 between the spindle all the way up and all the way down.
 

TomS

Active User
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#14
I used Bills method and believe I have the gib adjusted correctly. I was indicating on the larger machined surface of the column and getting a difference of .022 between the spindle all the way up and all the way down.
Have you removed the head and Z axis slide and checked for burrs and measured the mounting surfaces for parallelism? Just thinking out loud.

Tom S
 

rherrell

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#18
I don't understand why you are using the Z axis. I set the Z axis "close", lock it down, and then use the fine adjustment on the quill, been doing it that way since day one with my 932.
The Z axis does move some when you lock it down but if you tram your machine with the Z locked then it doesn't matter how much it moves.