# G0704 z axis backlash improvements



## TXmudman (Dec 27, 2013)

Hello. I am wondering if anyone has suggestions on how to improve the stock z axis screw and nut to minimize backlash, without going to the CNC type ball screws. I have nearly 40 thousandth inch of backlash.  I have tried every adjustment possible with little improvement. Gears mesh properly and the gib is a good fit, so I figure that the backlash must be in the nut/block assembly. Advice appreciated.


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## pestilence (Dec 28, 2013)

I'm curious too.  I just assumed a non-knee mill has gravity working against it and lock my Z and do vertical feeds with the quill.


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## TXmudman (Dec 31, 2013)

pestilence said:


> I'm curious too.  I just assumed a non-knee mill has gravity working against it and lock my Z and do vertical feeds with the quill.



Thanks for your comment. Perhaps there is not much to be done about the backlash.


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## wrmiller (Dec 31, 2013)

The only way I know of to cure this would be to employ a split nut or double nut on the leadscrew. Maybe it was/is defective and Grizzly will replace it? Wouldn't hurt to call customer service.

Just FYI, I don't have this issue with my new PM25 but will likely be going to a ballscrew once I figure out what/how. I always lock the z-axis anyway, so I'm not worried about the head moving under load and it will be smoother during traversing.

Bill


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## TXmudman (Jan 3, 2014)

wrmiller19 said:


> The only way I know of to cure this would be to employ a split nut or double nut on the leadscrew. Maybe it was/is defective and Grizzly will replace it? Wouldn't hurt to call customer service.
> 
> Just FYI, I don't have this issue with my new PM25 but will likely be going to a ballscrew once I figure out what/how. I always lock the z-axis anyway, so I'm not worried about the head moving under load and it will be smoother during traversing.
> 
> Bill




Thanks.  I will try the double nut idea. The vertical leadscrew nuts are only $10 from Grizzly, so I ordered two.


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## kd4gij (Jan 8, 2014)

Did you take off the head and see if the nut mounting screws are loose?


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## Gregg1342 (Aug 2, 2020)

I was just looking at that problem on my g0704 and when I look down the slot of the Z axis I can see the lead nut block moving when I rotate the leadscrew. I looked at the nut assembly in the parts drawing and found that it is on a large pin that fits into a hole in the fixing block. There does not appear to be anything holding the nut assembly (pin) tight to the fixing block, and the fit of the pin is allowing the nut assembly to rock. I am thinking about taking it apart and doing...something...about it. Not sure what, but drilling holes using the Z axis carriage adjusting crank is pretty much out of the question as it is now....so much play the drill grabs, and bounces and makes a mess of things. Interested in anyone else's suggestions for a fix as this surely must be a common problem...


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