# Chinese lathe mod



## imation (Jul 14, 2017)

Hi All
I recently returned to a smaller lathe after having a 300mm unit for several years, the chucks were a pain to lift and change.
I had owned the smaller 200mm in the past but the 5mm drive belts were a nightmare, breaking at the most inopportune times.(And costing over $30).
I got hold of some billets of aluminium from a local supplier and whipped up a set of pulleys to take a 5/16" belt. 
This has been a great move, still on the first belt, $5 on ebay, no need to release tension every time you start.
Cheers for now.
Mike.


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## Wizard69 (Jul 14, 2017)

Nice move.   One of my projects is to install a Polly-V belt.   Right now this is a project that is on the back burner.

A question though, did you do the timing belt pulleys or did you press some existing stubs into your pulleys?   They appear to be one piece.


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## XD351 (Jul 14, 2017)

Nice work !
I have the same machine just an earlier model (al50g)
One thing that annoys me  is the overload clutch in the pulley that is driven by the toothed belt did you get rid of it when you made the new pulleys ?
Looks like you have changed some of the ratios as well ?


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## imation (Jul 15, 2017)

Wizard69 said:


> Nice move.   One of my projects is to install a Polly-V belt.   Right now this is a project that is on the back burner.
> 
> A question though, did you do the timing belt pulleys or did you press some existing stubs into your pulleys?   They appear to be one piece.



They are indeed one piece, I made a cutter and using the mill (head locked in position) with a rotary table I use a broaching action to form the teeth, very happy with the result.


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## imation (Jul 15, 2017)

XD351 said:


> Nice work !
> I have the same machine just an earlier model (al50g)
> One thing that annoys me  is the overload clutch in the pulley that is driven by the toothed belt did you get rid of it when you made the new pulleys ?
> Looks like you have changed some of the ratios as well ?



I have retained the overload clutch as I think it is important, another small mod was to replace the two bronze bushes with needle rollers.
You are right in the fact that the ratio has been changed but the effect is negligible and I get a good range of speeds.
Cheers Mike.


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## tornitore45 (Jul 20, 2017)

I have the same machine, branded  Grizzly G4000 and after breaking two polybelt in the first year I never broke one in the next 11 years and I have done some heavy machining and threading.  If you are breaking the belt so often you may be doing something wrong (like I did).

The polybelt should not cost more than $7 in the US, search the web.
There are two length depending on what machine version you own:

Gates 8902-710    5M710 polyflex  is 710 mm long
Gates 8902-730    5M730 polyflex  is 730 mm long
Only one will work on your machine.


The polybelt slipped in the lowest speed and baffled me to no end until I noticed the groove in the small (driver) pulley was not deep enough to let the belt grip on the flanks.  A quick turning job fixed it.

The clutch was also a pain, slipping way to soon for my taste.   I disassembled it and drilled the pockets that hold the spheres a little deeper. Problem solved.


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