PM-727m New mill has arrived!

[Sloth2009]

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?

 

[David VanNorman]

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

 

[Sloth2009]

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?

 

[xman_charl]

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

 

[tweinke]

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?

 

[Sloth2009]

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.

 

[Sloth2009]

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?

 

[Bob Korves]

(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...

 

[TheGov]

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.

 

[Bob Korves]

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?