# PM727M excessive backlash on X axis



## GunsOfNavarone (Aug 20, 2018)

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!


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## GunsOfNavarone (Aug 20, 2018)

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...


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## GunsOfNavarone (Aug 22, 2018)

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.


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## vtcnc (Aug 22, 2018)

GunsOfNavarone said:


> 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.


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## GunsOfNavarone (Aug 22, 2018)

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!


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## dcsleep (Aug 23, 2018)

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.


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## GunsOfNavarone (Aug 23, 2018)

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!


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## vtcnc (Aug 24, 2018)

GunsOfNavarone said:


> 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.


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## shooter123456 (Aug 29, 2018)

GunsOfNavarone said:


> 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.


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## RIMSPOKE (Sep 8, 2018)

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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## Driveslayer45 (Dec 22, 2019)

I just had this issue tonight had about .090 of back lash, discovered the nut mounting nuts had worked loose. My machine isn't that old, I'm wondering if I've overtightened the anti-backlash and caused excessive wear ... The best u had it down to, before tonight, was about .009..anyway it's fixed now. I'll price out a replacement but just in case..


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## GunsOfNavarone (Dec 22, 2019)

Yeah DriveSlayet, I don’t know if you were first owner, but my had all kinds of issues, I finally got FULL x axis DRO working, changing the spindle bearings this week. Everything was loose & sloppy & out of calibration. That lead screw nut took me awhile to figure out, even as people told me that was it, any poking proding didn’t point to that. I’m glad my problem & thread fixing it helped you, it’s the great thing about this place, there is a wealth of knowledge here, that for the better part, really try’s to be patient. No matter the simplicity or complexity, it helps this place hold a large value. I hear PM is on this board, which is great, but I’ve had many phone calls with them, they sure as hell don’t try hard to sell you parts, they point me elsewhere all the time. Is that good or bad? I could go either way.


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## Driveslayer45 (Dec 23, 2019)

I am the original owner, but its my first mill so this is certainly a case of i don't know what i don't know. i kept tightening the anti-backlash screw trying to take out the slop until finally by BL jumped up to 90 thou... at that point i started digging, figuring something was wrong...  this thread certainly saved me some heartache...


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## Buggy Chief (Jul 2, 2021)

GunsOfNavarone said:


> 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.
> 
> View attachment 274316


I am having to do this to my 727 as it is super loose.  How did you get the lead screw out?  I have taken both ends off from the table and their are keys on each end of lead screw.  how do you get those off to slide bearings off?  Thanks in advance.


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## Buggy Chief (Jul 2, 2021)

Buggy Chief said:


> I am having to do this to my 727 as it is super loose.  How did you get the lead screw out?  I have taken both ends off from the table and their are keys on each end of lead screw.  how do you get those off to slide bearings off?  Thanks in advance.


Nevermind...I called PM and all I had to do was take the Rapid Feed off and essentially use the hand wheel to crank to the right to expose nut.  thx.


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## KevinM (Jul 2, 2021)

Buggy Chief said:


> Nevermind...I called PM and all I had to do was take the Rapid Feed off and essentially use the hand wheel to crank to the right to expose nut.  thx.



Even with loctite my X axis got loose again.  It has stayed tight now that I remember to unlock the table before activating power feed. DOH!!!


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