# 9 x 20 lathe feed prolom



## Little Dave (Feb 22, 2018)

New to hobby machinist first post. I have a Harbor Freight Central Machinery 9 x 20 lathe. But I have trouble with the feed on the lathe. I have stripped the teeth of the 42 tooth worm gears. This is the gear that mates to the gear on the lead screw. Has anyone else had this problem.? Any suggestions on how to fix it so it does not happen a third time. Is there a way to make the lead screw more rigid in the apron?


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## Z2V (Feb 22, 2018)

Little Dave
I have no answer for your problem, I just stopped in to welcome you to H-M. No doubt others will stop by that have experience with that same or similar lathe that can help you out.


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## dtsh (Feb 22, 2018)

I'm not familiar with the model, but I bet you'll get a lot more advice with some pictures for those who don't know the model, but may have good advice nonetheless.


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## markba633csi (Feb 23, 2018)

Is it a plastic gear? 
Mark


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## Mitch Alsup (Feb 23, 2018)

Little Dave said:


> Any suggestions on how to fix it so it does not happen a third time.



Do not crash the tool into the spinning workpiece.


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## Little Dave (Feb 23, 2018)

After 35 years in machine tool I know not to -crash the tool into the spinning work piece. I was taking a .050 deep cut in mild steel with a carbide cutter on the slowest feed.


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## Mitch Alsup (Feb 23, 2018)

Little Dave said:


> After 35 years in machine tool I know not to -crash the tool into the spinning work piece. I was taking a .050 deep cut in mild steel with a carbide cutter on the slowest feed.





Little Dave said:


> Any suggestions on how to fix it so it does not happen a third time.



Don't try to take 0.050 in a single pass.


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## C-Bag (Feb 23, 2018)

Little Dave, if I may,  I have a 9x20 and while no expert I've been using it and fixing it for a while. You being around machine tools before you might be used to more heavy duty lathes and the 9x20 isn't. There are a lot of shortcomings and just weirdness like if you look at the cross dial it says each mark is .002. So if you take a .050 cut by the dial you are really taking a .100 cut. A .050" is more than I could take without a lot of chatter and mayhem until i did some work on the cross slide and align the head to the ways. The other weirdness is you have to do some out of the box tinkering to really get it to do a fine cut. If you are using it the way it comes even on the lowest setting of the quick change box it's still too fast to do a real fine cut. I also had to replace the halfnut on mine as it was worn from not being adjusted correctly. That took some modification to get it to fully engage properly.


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## vocatexas (Feb 24, 2018)

I bought my 9x20 last year at an auction. The previous owner had a plastic gear meshed to the spindle and a couple of spares in a toolbox. While I have an identical metal gear, I've left the plastic gear there as a sort of 'fuse'. I figure the plastic teeth SHOULD give out before anything else does. I've also found that if I run the shorter belt on the pulleys without engaging the idler the belt will be tight enough it will turn just fine until you start over-loading the machine and then the belt will slip. I haven't damaged a gear....yet.

Off the top of my head, I think the deepest cut I've made yet in steel is .030 (using HSS) and I could tell my machine didn't really want to take a bigger bite.


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## C-Bag (Feb 24, 2018)

I feel like it should be repeated, these lathes like so many bargain tools from HFT are more like kits. Some are ok out of the box, some have minor problems and some are a mess. Then if you bought it second or third hand like me no telling what you'll find. There might have been something out of whack at the factory and the folks before you tried to fix it and just compounded the problem. There are several sites that are dedicated to the 9x20 like Steve Adair's that are full of fixes and mod's.


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## Little Dave (Feb 24, 2018)

C-Bag said:


> Little Dave, if I may,  I have a 9x20 and while no expert I've been using it and fixing it for a while. You being around machine tools before you might be used to more heavy duty lathes and the 9x20 isn't. There are a lot of shortcomings and just weirdness like if you look at the cross dial it says each mark is .002. So if you take a .050 cut by the dial you are really taking a .100 cut. A .050" is more than I could take without a lot of chatter and mayhem until i did some work on the cross slide and align the head to the ways. The other weirdness is you have to do some out of the box tinkering to really get it to do a fine cut. If you are using it the way it comes even on the lowest setting of the quick change box it's still too fast to do a real fine cut. I also had to replace the halfnut on mine as it was worn from not being adjusted correctly. That took some modification to get it to fully engage properly.


My depth of cut was a half turn on the cross slide .030 depth equals .060 diameter. I'll take your advice and cut it in half to 1/4 turn on the dial.


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## Little Dave (Feb 24, 2018)

Mitch Alsup said:


> Don't try to take 0.050 in a single pass.


My depth of cut was a half turn on the cross slide .030 depth equals .060 diameter. I'll take your advice and cut it in half to 1/4 turn on the dial.


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## vocatexas (Feb 24, 2018)

Another thing that might help...if you haven't upgraded your compound base to the four bolt you might have had flex that caused your tool to dig in. I built a four bolt base for my 9x20 and it really made a lot of difference. It eliminated nearly all the flex when turning and parting off is a breeze now.


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## Little Dave (Feb 24, 2018)

vocatexas said:


> Another thing that might help...if you haven't upgraded your compound base to the four bolt you might have had flex that caused your tool to dig in. I built a four bolt base for my 9x20 and it really made a lot of difference. It eliminated nearly all the flex when turning and parting off is a breeze now.


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## Little Dave (Feb 24, 2018)

vocatexas said:


> Another thing that might help...if you haven't upgraded your compound base to the four bolt you might have had flex that caused your tool to dig in. I built a four bolt base for my 9x20 and it really made a lot of difference. It eliminated nearly all the flex when turning and parting off is a breeze now.


 Already done


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## C-Bag (Feb 25, 2018)

I found so many goofy things wrong with mine. Like when I went to move QCTP I realized he'd put it in the wrong hole in the slide. There are two holes for the dowel pin to go in and between the two is a semi hole that is where the screw for the cross slide nut is. He had it jammed in there so it wasn't seated correctly, d'oh! The cross slide dovetails were a mess from the factory. There was no way to adjust the gib correctly without it binding on the ends and being totally loose in another spot. Even my noob totally green attempt at scraping them made a world of difference. 

I don't have the chatter and mayhem now because the the gib can be adjusted properly. I see where a lot of guys have said that cross slide housing broke and they made a new one. I'm wondering how many had poorly fitted cross slide dovetails/gibs? Along with that silly tiny cross slide handle its hard to get a good feel for what's going on. I would have preferred to buy a machine I didn't have spend so much time tinkering with but I have learned a lot.


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## xman_charl (Feb 25, 2018)

have both 9x20 and G0602

about 8 years old

They are cheap chinese laths

have four bolt compound mount, did not like it

always loosening those 4 nuts to move it...

use clamps on 9x20 compond mount, as there are 2 holes on cross slide

pin underneath compound, can move closer to chuck












Charl


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## savarin (Feb 25, 2018)

The rigidity goes up in leaps and bounds if you change the compound for a solid plinth.
https://www.hobby-machinist.com/threads/plinth-for-qctp-on-9-x-20-lathe.45628/


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## MetalPlane (Jan 14, 2021)

Little Dave said:


> New to hobby machinist first post. I have a Harbor Freight Central Machinery 9 x 20 lathe. But I have trouble with the feed on the lathe. I have stripped the teeth of the 42 tooth worm gears. This is the gear that mates to the gear on the lead screw. Has anyone else had this problem.? Any suggestions on how to fix it so it does not happen a third time. Is there a way to make the lead screw more rigid in the apron?


I have the same problem. the worm gear binds up. Think it's worn out. Mine is a JET version of the same 9 X 20 lathe sold by HFT, Grizzly, and others (BD 920N). 

Have you found a FIX?


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## MetalPlane (Jan 14, 2021)

What are some of the causes and fixes for a worm gear binding up on the 9X20 lathe carriage feed?

I hit a hard stop when I couldn't stop the feed and it hit my carriage stop. Worked for a while after, but now binds up and kicks out the gears driving the lead screw.


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## MetalPlane (Jan 14, 2021)

Where do you get parts for a JET 9X20 lathe? Are there salvage dealers for lathes?


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## MetalPlane (Jan 14, 2021)

Little Dave said:


> New to hobby machinist first post. I have a Harbor Freight Central Machinery 9 x 20 lathe. But I have trouble with the feed on the lathe. I have stripped the teeth of the 42 tooth worm gears. This is the gear that mates to the gear on the lead screw. Has anyone else had this problem.? Any suggestions on how to fix it so it does not happen a third time. Is there a way to make the lead screw more rigid in the apron?


Have you found a FIX?


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## C-Bag (Jan 14, 2021)

MetalPlane said:


> What are some of the causes and fixes for a worm gear binding up on the 9X20 lathe carriage feed?
> 
> I hit a hard stop when I couldn't stop the feed and it hit my carriage stop. Worked for a while after, but now binds up and kicks out the gears driving the lead screw.


I would pull the carriage gear box and check the split nut. It’s a funky adjustment and it could have gotten out of adjustment, or be stripped. Mine was not adjusted correctly and worn because of that. Bought a new split nut from Grizzly. The 4000 is basically the same machine with some differences.


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## savarin (Jan 14, 2021)

check out this complete post as I had those problems as well.








						9x20 stuffup
					

I'm unsure if it was my fault or the machine. I had two aluminium flanges bolted together on the faceplate with spacers so I could turn the outside dia and bore the inside dia parallel with each other and both end up exactly the same. All was going well on slow auto feed - bore, disengage the...




					www.hobby-machinist.com


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## savarin (Jan 14, 2021)

I forgot to add:-
When you have the leadscrew removed go from one end to the other relieving ALL the sharp edges and corners from the from the keyway groove and also from ALL the edges of the thread, not much just enough so it no longer acts as a tap gutting threads every time it travels.
Your half nuts will thank you and so will the bushes in the worm.


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## Diecutter (Jan 15, 2021)

MetalPlane said:


> Where do you get parts for a JET 9X20 lathe? Are there salvage dealers for lathes?


Last time I ordered parts (which was a while ago) for my  BD-920N Jet lathe, the toll free number was 1-800-274-6848.


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## MetalPlane (Jan 15, 2021)

Diecutter said:


> Last time I ordered parts (which was a while ago) for my  BD-920N Jet lathe, the toll free number was 1-800-274-6848.


Thanks! I found the same number buried in the front of my manual (circa 1994). It worked and was able to order all of the parts. Unfortunately the "4012" worm gear is on backorder until March. Seems it is a regular problem and replaced often. The teeth on my old one are worn down to razor-sharp and climbing over the sliding worm gear on the lead screw. It binds and kicks out the 120T change gear.

I have the plans if there are any hobbyist that would like to make a new one.


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## MetalPlane (Jan 15, 2021)

markba633csi said:


> Is it a plastic gear?
> Mark


No, Cast Iron


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## Little Dave (Feb 12, 2022)

I found my stripped feed screw at Grizzly Industrial. Part number P4000739- $30.00 Hope this helps everyone.
now I am looking for the worm gear frame. The one with the 3 taped mounting holes made from cast iron. Grizzly dose not list it.


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