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View Full Version : 9x20 problem..imagine that.



Phil McCrackin
12-24-2008, 02:54 PM
Well first off Merry Christmas to all, and thanks for the help on my DOC questions in my last post.

All of your suggestions helped very much and I am/was getting pretty decent cuts on my lathe now.

However, I think I tightened the gib(or is it jib) screws too tight and I stripped out the power feed worm gear feed wheel under the apron. :(

I called KBC tool where I bought it from and they want $125.00 for the assembly, and I can not find any other replacement for it anywhere. I have been searching for 2 days.

It has 42 teeth and is 1 3/4" in diameter, made of some cheap steel.

I have been thinking about hobbing one, if I have too. I found a very large bolt that has a 'nearly' identical thread pitch, and I milled a couple of slots in it, to make it look like a tap(kind of).

So do you guys think that if I made it out of 6061 Al, it would last, or should I try to use some steel for longevity.

I don't have any brass, and I am not sure I have any more options.

If I did try it in steel, would I have to harden it somehow?

Do you think a regular 42t spur gear would work, instead of a 'worm gear wheel'?



Any help is appreciated.

Mark Hockett
12-24-2008, 03:26 PM
Phil,
Did you try Grizzly? They have a good stock of parts and their prices on the parts I have bought from them have always been reasonable. Many of their manuals are on line so you can compare your lathe with Grizzly's 9 X 20 and see if they look the same. I had a saw that I bought somewhere else and they had the part to fix it.

If you decide to make it you will learn much from it and be able to make replacements in the future if needed. There are others on this BBS that can describe the process for making the gear much better than I can.

kendall
12-24-2008, 03:35 PM
Can you have Grizzly send you replacement parts? As far as I know those 9x20's use the same parts.

They're pretty good with parts, the most expensive gear I saw was $18 (US)

Ken.

Phil McCrackin
12-24-2008, 03:48 PM
That is a great idea.

I just checked and they have a 41 tooth.

The lathe picture looks identical to mine. I might order it and see what happens.

Considering the machines quality, fit, and finish, do you guys think that 1 tooth will make that much of a difference?

I think the worst case scenario would be that I have to order the matching worm gear.

Any other opinions?

Phil McCrackin
12-24-2008, 03:54 PM
I stand corrected, I just looked at the "interenal apron" parts vs. just the "apron' parts.

They do have a 42 tooth.

Christmas miracles do happen.

Thanks guys.


(Now lets see it gets back ordered)

Teenage_Machinist
12-24-2008, 05:17 PM
Remember-- All mini lathe parts are the same, except for some "old" style lathes and the Micro Mark inch screws

All mini mill parts are the same, ditto screws

All 9x20 i belive to be the same


I wonder if I could update my lathe with the 9x 20 gear box. Could be interesting.

S_J_H
12-24-2008, 05:27 PM
yep, like I said before the 9x20's worm gear feed is really sloppy and they wear quickly.
There is a fix, add a bearing surface to the worm to give it support. The factory setup just let's it float and it gets cockeyed and then wears the gears. It also affects the surface finish.
This is what I did to my 9x20 years ago. I turned down the worm gear ends to accept bearing surfaces that I made. The apron needs to be machined for this as well. The new bearing cages were then bolted through the apron and the worm is now rigidly supported.
This made a tremendous difference in the feed smoothness and gave a better surface finish and even with heavy feeds I never had a problem with wear.
http://i109.photobucket.com/albums/n48/S_J_H/APRONMACHINED.jpg
http://i109.photobucket.com/albums/n48/S_J_H/worminstalledinbothblocks.jpg
http://i109.photobucket.com/albums/n48/S_J_H/insideviewofnewblocks.jpg
Steve

Jack772
12-24-2008, 08:56 PM
I got the 42 tooth gear for my 9x20 from Grizzly for less than $20.
Jack

kendall
12-24-2008, 09:18 PM
Mark must have been typing while I was looking at the Grizzly site!
Nothing there I really need, but every time I get there it's a browse-a-thon.

Ken

Fasttrack
12-25-2008, 03:55 AM
What in the heck is the keyway in the leadscrew for if they use a worm gear for feeds?? Why not just do it the "good old way" with a sliding key like SB? I don't expect a second feed rod, but driving off the leadscrew with a worm gear seems kinda shody. Once that leadscrew gets worn, it makes funny looking threads when you engage the half-nuts.

SJH - that looks like a very nice job. Is that the stock worm? Why not bronze or something that would wear before the leadscrew? Or maybe thats not an issue for the expected life time and duty cycle for one of these machines. What does that worm drive? I can't quite make out whats going on in there.

S_J_H
12-25-2008, 11:06 AM
Fasttrack, I'm not sure what you are seeing. The 9x20 uses the same system as the South bend, just not nearly as well made. The 9x20 worm has a key and the lead screw passes through it just like on the SB.
Here is my SB apron, steel worm and gears . The worm is much more robust and well supported than on a 9x20.
http://i109.photobucket.com/albums/n48/S_J_H/SOUTHBEND%209/sb9after003.jpg
http://i109.photobucket.com/albums/n48/S_J_H/SOUTHBEND%209/sb9after005.jpg

Steve

Fasttrack
12-25-2008, 08:05 PM
Ahh! I see. For some reason, it looked like the worm was sitting ontop of the leadscrew in that first picture. Thanks a bunch!