# Belt Drive G0704



## Daphharr (Apr 26, 2022)

Greetings!

I just installed this belt drive kit and bought new nachi bearings.  Has anyone had a significant issues with runnout at the endmill +.01 ?  I have a nice vibration  with the draw bar setting off center once tightened. 

Has anyone installed this kit:  https://www.minipro.com/products/g0704

I would love to know what I screwed up on this one.

Best,

Ian


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## macardoso (Apr 26, 2022)

I did a DIY belt drive on my G0704. First of all, I would question your bearing seating and preload.

Second, the upper bearing tube from the original G0704 gear head system had nearly 0.030" runout on the inside bore (a non critical surface). I know this part is replaced in your kit, but verify the new tube is running true.

Finally, you could always pull the spindle and check the taper while running the bearing diameters on Vee blocks.


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## Daphharr (Apr 26, 2022)

I am concerned about the bearing seating it seemed a little dodgy, and is why I went and upgraded the bearings thinking that would only help. It won't help if i buggered up the install.   When pulling the quill out a copper shim or what I think was a shim fell out of the mill.  This part is not on the parts list for the g0704. Never good when you end up with more parts that are not in the manuals.  

I will see if I can get an indicator on the new tube.  The draw bar wiggling is not a big deal?  

thank you for taking the time to help.  I am learning on this one!


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## Daphharr (Apr 26, 2022)

Also.  Preload on the belt how do you know the right tension?


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## macardoso (Apr 27, 2022)

Alright, first off, try to mount the indicator to the head of the machine. This limits flexing off the whole machine frame throwing off your measurements. Also remove the drawbar, no need for it right now.

Measure runout in 3 places of the taper with a dial test indicator (front, middle, back).

Next without touching the indicator (again, mounted to the head itself) push and pull on the spindle nose with about 20 ish lbs of force. See how much deflection you get (it should not be much)

The bearings on the mill are in a back to back configuration and are tensioned with the adjuster nut (item 251/252). This needs to be turned with a spanner wrench to give just the lightest bit of drag on the spindle (no axial play is acceptable.

The front bearing retainer (item 247) needs to be tightly wrenched down. If you changed the bearings to angular contact, then shims need to be added to make up the missing thickness.

If either of the above 2 items aren't done then the bearings aren't supporting the spindle.




As far as belt tension goes, follow manufacturer guidelines unless not available. It does not need to be too tight, in fact looser is better than really tight. Just make sure it does not slip under load.


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## macardoso (Apr 27, 2022)

Decent bearings ($50 range for the pair) shouldn't contribute more than 1-2 tenths.

My G0704 has about 2-3 tenths of runout in the taper grind.


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## Daphharr (Apr 27, 2022)

Thank you!!  This helps a great deal.  I will go through these areas tonight and see where i messed it up our perhaps see that the new parts are out of spec.  I should have tested the parts before installing.  What a hack move to not check and verify.  

Best,
Ian


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## markba633csi (Apr 27, 2022)

I wouldn't expect Nachi bearings to be defective out of the box, their quality control is too good.   Must be something else
-M


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## Daphharr (Apr 27, 2022)

markba633csi said:


> I wouldn't expect Nachi bearings to be defective out of the box, their quality control is too good.   Must be something else
> -M


Probably Me!!! But let's not rush to that assumption!  I will find the problem and if it was me, I will delete this post and tell no one.


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## markba633csi (Apr 27, 2022)

Check to make sure the pulleys are running perfectly concentric on their shafts


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## Daphharr (Jun 7, 2022)

OK...
I figured this might be useful to another challenged person like myself.  

The install was a success. The areas you guys told me to check were perfect the inside measurements on the spindle were on the mark. 

I pulled out the R8 er32 collet chuck and there it was.  The holder had stuff all over it from the install of the belt kit.  

Many things learned on this one: Check the new parts before install and clean everything after installing.

Best,

Ian


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