# Need advice with the knee on my Clausing 8520 vertical mill.



## rchrdinaz (Oct 8, 2014)

Hi folks, 

I bought my Clausing 8520 vertical mill a year ago and it's been working great up until about last week.  I noticed that when lowering the knee I get a bit of chatter at the lower end of travel. When it chatters I see the knee drop about a 1/32 of an inch. I can stop the problem by turning in the two locking bolts to apply friction. The chatter does not happen when I am raising the knee, only when I am lowering it. I have suspicions on what it is but it's my baby and I don't want to go at it blindly. Can anyone suggest on how to start troubleshooting and what to look for? As always your help is greatly appreciated. 

Thanks, 

Richard in AZ.


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## chuckorlando (Oct 8, 2014)

Maybe you got a broke piece of the thread down low?


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## Bishop (Oct 9, 2014)

Sounds like the gibs are too loose/tight and binding up then releasing when the screw pulls down on knee. 

Shawn


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## 12bolts (Oct 9, 2014)

You probably dont want to be doing this.......


rchrdinaz said:


> ... I can stop the problem by turning in the two locking bolts to apply friction. .....


What you are doing here is creating enough friction that the knee is not falling under gravity but being dragged down by the thread. You will be increasing wear on your ways considerably.
The root cause is probably worn ways. The area you normally/continually operate has worn and with your gibs adjusted correctly for this area start to bind when you area getting into the unworn areas. Or you could be lucky and find its just a build up of crud.

Cheers Phil


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## JPigg55 (Oct 9, 2014)

It does sound like you need to adjust your gib screws.
Sanity check, might check the lube on the screw and dovetails too.


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## wa5cab (Oct 10, 2014)

I'm inclined to agree with Phil's diagnosis.  Just to confirm, try loosening just the bottom gib screw.


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## rchrdinaz (Oct 10, 2014)

Thank you all for the great advice and confirmations. Since it is just a wee bit older than me, maybe it's just a little crud. :rofl:  They seem pretty simple but I't better ask. Is there any special technique for adjusting the gib? I will probably be attacking it next weekend.


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## Bill Gruby (Oct 10, 2014)

Phil i9s correct. I had the same problem with my 8520 when I first got it.

 "Billy G"


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