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9 x 20 lathe feed prolom

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Little Dave

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#1
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?
 

Z2V

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#2
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.
 

dtsh

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#3
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.
 

Little Dave

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#6
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.
 

Mitch Alsup

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#7
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.
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.
 

C-Bag

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#8
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.
 

vocatexas

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#9
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.
 

C-Bag

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#10
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.
 

Little Dave

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#11
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.
 

vocatexas

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#13
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.
 

Little Dave

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#14
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.
 

Little Dave

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#15
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
 

C-Bag

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#16
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.
 

xman_charl

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#17
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

P1020286.JPG
P1020286.JPG





Charl
 
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