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PM727M excessive backlash on X axis

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GunsOfNavarone

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#1
So my "new" purchase hasn't been without issues...I guess to be expected. On the Z and Y, it's awesome. Hand wheels turn easy and without really any back lash. The X however, like .025" . The PM has a backlash adjuster under table on X axis lead screw nut. All that does is makes the hand wheel harder to turn, backlash is the same. Any ideas here blokes and geezers? Mills are a new kind of fun for me, not gonna go at the haphazardly. I believe PM suggests around .003 so I got a ways to go!
 

GunsOfNavarone

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#2
Just spit ballin here, since the play is unchanged from end to end and in the middle, are there shims that can be used at either end of lead screw? Or does this point to lead screw nut? I hear PM is great getting parts, between that and their support, seems like they are pretty great to deal with...
 

vtcnc

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#4
Yup...loose X-nut....damn you PM for always being right. Well, clean everything on the X axis...and new thrust bearings on the way.
Glad to here you have a resolution for this. Nice to have PM close by on the forum for the members.
 

GunsOfNavarone

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#5
FWIW, the underbelly/guts of my used PM are nicer than the outside of my brand new Grizzly G0602z....maybe it's superficial...but again, for whatever it's worth. PM is close to the Forums? I wasn't aware, but yeah, doesn't sound like a bad thing!
 

dcsleep

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#6
Odd - I just went thru the same thing on my recently purchased PM-25MV. I found I could move the table noticeably by just pulling/pushing on the end of it. I reached down and could feel the x-nut moving when I moved the table.

When tightening the nut, did you do anything to ensure the screw was parallel to the ways? When I first put it back together I noticed that one end didn't line up as before (using the paint as a reference). I made a slight adjustment to get it to match up more closely as I didn't want anything to bind or put pressure on the screw. Not very precise but given the amount of play in the screw/nut it seems that close is probably good enough.
 

GunsOfNavarone

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#7
When I was getting ready to apply loctite to the threads, I thought I don't want to have to do this anytime soon again. That crossed my mind but something PM said to me sunk in. "This isn't a high precision machine". And honestly, the threads on the lead screw/x-nut have a fair amount of play (by wear and design) being you can adjust the x-nut backlash as it does, it's kind of supporting to that. It would be so difficult to get it 100% parallel and you would pretty much have to disassemble to adjust/retighten. I have mine 90% back together, just waiting for the thrust bearing from right side lead screw tomorrow. In theroy, everything is great and x-nut is parallel, I'll find out. I will say, my x-nut didn't have much play to be off...maybe 1/2 degree?it's
I'm my head, if backlash should be .0005" ....that seems like we're dealing with high precision. I think I was overly complicating it. We'll see. Best luck to both of us!
 

vtcnc

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#8
FWIW, the underbelly/guts of my used PM are nicer than the outside of my brand new Grizzly G0602z....maybe it's superficial...but again, for whatever it's worth. PM is close to the Forums? I wasn't aware, but yeah, doesn't sound like a bad thing!
Yes, Precision Matthews has been a sponsor of the site for quite some time. If you search the forum threads you will find sponsor specific support.
 

shooter123456

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#9
FWIW, the underbelly/guts of my used PM are nicer than the outside of my brand new Grizzly G0602z....maybe it's superficial...but again, for whatever it's worth. PM is close to the Forums? I wasn't aware, but yeah, doesn't sound like a bad thing!
They hang around here and often provide support directly on the forum. When I got my lathe from them a few years ago, I had some trouble with changing gears, and they were offering me potential solutions at 3 PM on a Sunday afternoon. They really do go the extra mile for their customers.
 

RIMSPOKE

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#10
I HAD THIS PROBLEM WITH MY 727 .

THERE IS A NUT FOR THE LEADSCREW UNDER THE CENTER OF THE TABLE .
IT BOLTS TO THE FRAME OF THE CROSS SLIDE AND IS LIKELY LOOSE .

YOU CAN CHECK IT BY STICKING A ROD ALONGSIDE THE LEADSCREW TO TOUCH THE NUT .
WHEN YOU TURN THE CRANK , IF IT IS LOOSE , YOU CAN FEEL IT MOVE .

THIS ISN'T HARD TO FIX . YOU CAN REMOVE THE TABLE TO GET TO IT .
I REMOVED THE BOLTS , CLEANED THEM AND RE-TORQUED THEM WITH SOME LOCKTITE
TO MAKE SURE THEY DON'T DO IT AGAIN .
 
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