# My G4000 lathe: Fun and frustration



## jlmanatee (Oct 30, 2020)

I bought a Grizzly G4000 in 2006.  At the time, I had a ball modifying it in many ways.  For instance, I replaced AC motor with a DC motor and variable speed control.  I installed a tumbler reverse, added a QCTP and several other mods.  I think it's a pretty decent little lathe.... except for one big problem.  In the apron, there's a worm gear that slides along the lead screw and provides for the carriage power feed.  This worm gear EATS it's neighboring 41 tooth gear for breakfast.  They rarely last even one job before the teeth are ground to powder.  And it doesn't matter if I take a very light cut or even no cut.  At least one of the problems was that the apron casting held the worm gear so sloppily that the 41T gear was hardly mated to the worm gear.  Also, the worm gear appears to be a much harder material than the 41T gear.  Maybe it's even powered metal, at least if grinds up like powder.
  While I should have complained to Grizzly back then, I didn't.  Instead, being the a DIY kinda guy, I tried boring the apron out and installing bronze inserts.  That certainly took the slop out of the worm gear.  Still  the 41T gear turns to sludge.  One hope I have, 15 years later, is that Grizzly found this to be a recurring issue with the G4000 and have remedied it with a better version of the apron.  And indeed, if I look up the parts, I see that the description for the apron says  *Grizzly P4000701 - APRON CASTING V2.01.06 * (notice the V2.01.06).  I have no idea what version of apron casting my 2006 G4000 had.  I wrote to Grizzly to see if maybe their support folks know the history of the castings and can confirm that my problem can be remedied by the purchase of this version.  Even if this is so, I still worry that the 41T gears from Grizzly are made of butter.
  My other option is to hob my own 41T gear from decent material and with a concave & helical profile that will have a chance to mate better with the worm gear.  I wish the ghosts of my grandfather and father, both toolmakers, could help me out here.
  A third, and exciting option would be to buy a new/better lathe.  But I don't think I could sneak a new lathe past SWMBO.   If anyone has ideas or advice I'd sure appreciate hearing from you.


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## fitterman1 (Oct 30, 2020)

Hi Jim, sounds like they used sintered gears.
Yes your idea of making your own has a lot of merit cause I wouldn't trust any replacement. Give it a go and make sure its a rigid assembly.


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## chip maker (Oct 31, 2020)

I've bought my 4000 in 2000 and mine doesn't have a problem with anything in the apron as of yet. I'm not using my lathe every day but it has made alot of parts for many things including itself. Grizzly has always been good to me if I have questions and help with problems if they can if you get the right person an the phone or thru e mail. They even helped me with my G8689 and I purchased it 6mo. old from someone else. I know that many people feel that the 4000 isn't that great of a lathe but I feel it has served me very well and am still glad I purchased it.


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## jlmanatee (Oct 31, 2020)

chip maker said:


> I've bought my 4000 in 2000 and mine doesn't have a problem with anything in the apron as of yet. I'm not using my lathe every day but it has made alot of parts for many things including itself. Grizzly has always been good to me if I have questions and help with problems if they can if you get the right person an the phone or thru e mail. They even helped me with my G8689 and I purchased it 6mo. old from someone else. I know that many people feel that the 4000 isn't that great of a lathe but I feel it has served me very well and am still glad I purchased it.


Thanks Chip, that's encouraging.  I'll see what Grizzly has to say.


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## markba633csi (Oct 31, 2020)

Some import lathes are like some cars;  problems that don't stay fixed for long.  Maybe time to shop for another machine?
Sounds like the 41T gear was made from the wrong material
-Mark


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## Mitch Alsup (Oct 31, 2020)

markba633csi said:


> Sounds like the 41T gear was made from the wrong material



The gear turning the 41T could also be the culpret.

I would start by machining the 41 out of real steel (like 4130) and then also machine the driving gear out of similar.


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## hman (Oct 31, 2020)

Really sorry to hear that your 4000 is misbehaving that way.  I've owned two at various times and been happy with both of them. Best wishes finding a solution!


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## jlmanatee (Nov 4, 2020)

Since I just don't trust the parts and how they function in the design of the apron, I'm not going to put more money into replacement parts.  Instead, I'm going to experiment with driving the handwheel with a timing belt and a DC gearmotor.  My plan is to replace the handwheel with a timing belt pulley.  The 120 tooth pulley I have on order looks like I can add a handle for manual use.  Then a timing belt will go to a 15 tooth drive pulley.  With an inexpensive 100 rpm gear motor I should see handwheel rpms of no more than 12.5 rpm.  Add a speed control to the setup and  I can vary my apron feed speeds accordingly.  Once I've proven that the little gear motor will handle the job, I have to figure out a disengagement strategy.  Either an idler wheel arrangement or a sliding motor mount plate.
My other option was to go the CNC conversion route, but this depends upon the suspect worm/wheel in the apron.  Thread cutting has not been a problem as the lead screw and half-nut seem to work fine.
All this to provide for cleaner final cuts.


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