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My biggest concern is the "flex" in the column. If I grab the top of the column and push back or forwards I get a lot of movement (0.005 or more) in the y-axis testing from spindle to table. The x-axis doesn't have the same problem, and it still shows up the same if I push on the head instead. I tried flexing the stand/base, but that had almost no effect. I tightened the 4 mounting bolts as tight as I could without a big cheater but it still has the problem. How much of this flex is normal? Is there a torque spec for the column bolts? Has anybody run into this before?
 
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I bought a PM 932. I like it a lot I mounted it on a stand I had with casters so I can move it around. I found out that the dial for the Quill is hard to see as I am not tall.When I get my mods dun I will take off the casters. It will be about 5" lower and that will make the dial easier to see. I also took off the head raising crank and added a DC motor and drive. I can now elevate the head and change tooling much easier. I put limit switches so I can then bring the head back to where it was. I like the 932.

Dave
 
View attachment 230315 View attachment 230316 View attachment 230317 View attachment 230318 View attachment 230319 My biggest concern is the "flex" in the column. If I grab the top of the column and push back or forwards I get a lot of movement (0.005 or more) in the y-axis testing from spindle to table. The x-axis doesn't have the same problem, and it still shows up the same if I push on the head instead. I tried flexing the stand/base, but that had almost no effect. I tightened the 4 mounting bolts as tight as I could without a big cheater but it still has the problem. How much of this flex is normal? Is there a torque spec for the column bolts? Has anybody run into this before?

Anyone have any ideas on how to address the flex?
 
are the gibs tight?

did you lower the head or raise it?

lowering the head on my mill, sort of jumpy if a cut is taken

so lower the head, then raise up about a half turn, no more jumps, think its a backlash thingy

Charl
 
I do notice some " flex" in my PM727 column also. with the gibs locked. I measure about .0015 to .0025.pushing fairly hard on the motor with the head at about 1/2 travel up the column. More deflection with gibs unlocked. I realize I did not buy a K&T or the like and am very satisfied with my mill. I just finished squaring the column and tramming, got the column within .002 in 6 inches both directions and of my figuring is correct that's .0003333 per inch which for my purposes should be fine because I don't make any aerospace parts. The mill out of the crate impressed me with the cuts it was capable of and the finish with decent end mills is good. I have found myself chasing zeros when I should not be and have learned that lesson well. Anyone want to comment on .002 in 6 inches?
 
are the gibs tight?

did you lower the head or raise it?

lowering the head on my mill, sort of jumpy if a cut is taken

so lower the head, then raise up about a half turn, no more jumps, think its a backlash thingy

Charl
I did lock the y-axis gibs. However I can replicate the "flex" just by pushing hard on the column so I think it rules out the gibs or head travel direction? I checked all the mounting bolts and they are all tight.
 
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I am thinking about removing the column again and making sure there is no crud between the mating surfaces and possibly touching them up with a stone. Has anyone tried to make the column to base connection more rigid?
 
(snip)Anyone want to comment on .002 in 6 inches?
Most people here (and elsewhere) have never checked their machines for accuracy, and I guess they suppose it must be perfect if they are not having explicit problems. "A test is worth a lot of guesses." For the vast majority of the work we do, it just does not matter. For some cuts, it really does...
 
I noticed the sequence in which the column bolts were tightened played a big part. Just tighten in the same order and torque each time.

I too wondered about the torque spec. Ended up going 55 ft-lbs, then 65 ft-lbs, called it good and made chips.
 
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