2nd post and it will be a doozy! LOL. Logan 200 NON-QCGB conversion with southbend A QCGB

G

gloud

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I have had a logan 200 since 1998 I didn't really do any threading until last year when I did a LOT. (gun build) as my Logan doesn't have a QCGB and I had to change gears the threading was the fast part, changing the gears took longer. I have been looking on the Bay for a 820 GB but the prices are nuts. South bend model A gearboxes are much more reasonable. I realize I will have to fab custom mounts and adapt the lead screw etc, Not an issue I have done much harder. (used to build custom 4wd suspensions and tcase setups as my hobby)

I have not found any evidence(Web) of anyone doing this, but looking at the leadscrew TPI (both 8 ) and making sure the gearing from the spindle to the Gearbox is the same I can't see how this wouldn't work. (both gearboxes can do the same number of common threads for example)

If you can come up with any issues I would like to hear them. (yea I know it is a crackpot idea and would be easier to just buy another logan but I have this one setup for what I do very well and I am happy with it but for the lack of gearbox. )

My time spent is hobby time so do not use the cost of my labor as a factor please.

Thanks and I have had a great time reading the forum so far. and If when I do the conversion I will document it here.
Glenn
 
I don't know ! But I have seen car transmissions on drill presses so I say you can do it. How easily is another story,if you decide to do it please post the journey...Thanks and Good Luck
 
I bought an old lathe back in the fall thinking it was a southbend. I was taking it down and having problems with parts not matching southbend schematics. When I took the gearbox off, I found that it was a Seneca Falls Star lathe. Someone in the past( it was supposedly owned by an old gunsmith) had put the southbend gearbox on it. So it can be done.
 
Well the gearbox will be labeled and the lathe still has its name plate so whoever gets the lathe after I die should be able to figure it out. I will document it to go with the lathe and tell my son where it is. But it is a good point.
 
I'm trying to do this on my 200 I got a gear box from a 9" Asian lathe for 40$ which was a lot cheaper then a real Logan. I'm going to try using timing belts and gears to connect it. I'll replace a change gear with a timing gear and run it to the gearbox then another timing belt to the lead screw. It looks like ill need to notch the guard to fit the gearbox where I want it.

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Definitely cheaper than the sb I just bought off ebay. but I also got the lead screw gear so that will make it easier. I see why you have to do some jigging as the input for the Gearbox and the output look like they are on different planes. Thanks for sharing. and keep us updated.

Ebel440 said:
I'm trying to do this on my 200 I got a gear box from a 9" Asian lathe for 40$ which was a lot cheaper then a real Logan. I'm going to try using timing belts and gears to connect it. I'll replace a change gear with a timing gear and run it to the gearbox then another timing belt to the lead screw. It looks like ill need to notch the guard to fit the gearbox where I want it.
Click to expand...
 
Yes your right it would be hard to get it all lined up if not immposible. Plus It's only got 9 different speeds so I'm also hoping to be able to get more with the change gears and possibly different timing belts.
 
just to follow up I finally installed the SB gearbox.

I have had my logan for 15 years about, and had to deal with change gears to do threading. logan gear boxes are very $$ (in the 600-799 range) and honestly I would have bought another used logan before I went that route.

I got to looking at affordable gearboxes and the southbend model A stood out as the best to refit. about the same size and thankfully the same input shaft size as I found out. the lead screw pitch is the same also (8tpi) on the 2 lathes. the only gear I had to purchase is a 20t gear to drive off the top change gear set. ( the upper gears end up being a 1-1 rate on both lathes) so that was easy.

I just had to match the ratio on the bottom drive gears, (20t on the drive gear and 56t on the qc box. with the original southbend using a 80 intermediate I used my 72 t I had in my gearset already. ( the intermediate doesn't affect the finished ratio. )

the big thing I had to do is figure out the mounting which is different on the 2 lathes. I went with a piece of angle iron and made an adapter that is counter screwed into the top of the gearbox, and then the assembly mounts onto the front of the bed like normal. I did have to mill .079 (approx measure your lathe) to get the lead screw where it should be.

I also had to space the box forward 1/8" (if I had been more careful I could have prevented this) I drilled and tapped 4 holes into the side fo the bed to mount the box to.

I had to cut 7.250 out of my existing lead screw to fit the box in place, and I made a sleeve to press the two halves into and then I silver soldered the sleeve. (after checking the runout on the lathe , it just fit through the headstock! I soldered it.

the southbend drive gear came with the gearbox that goes onto the lead screw. it fit my logan leadscrew without and mods. I just used a logan spacer and the nut and secured it.

The job of mounting the gearbox and the saddles skirt was like juggling but I got it done.

I had to bore open the end of the change gear banjo to fit the gearbox to 2.00" and I had to mill off .100 on the back of the banjo to get things to line up right. (the gears) You could just use a southbend one .

I was able to source a gear from boston gears on amazon for under $20.00 (20 t) with the right pitch (18dp) and the correct hole size. (.625 if I remember right) I used my 56t gear from my gear set with a sacer as the shaft on the gearbox was smaller than the opening in the gear.

got it under power and everything looked right so I did a test thread cutting to see if everything was ok. I did a 13t run on some scrap and it turned out great right on the nose according to my thread gauge set.

I still have to trim my safety cover so it will clear the gearbox but it is working and that's the big thing.

Total cost was $150.00 130 for the gearbox on e-bay and and 20 for the 20t gear. and lots of shop time lol.IMG_1862.JPG IMG_1863.JPG IMG_1864.JPG
 
Nice job- if you polish off the heat discoloring on the leadscrew it will look just like factory OEM
Mark S.
 
Yea I was pleasantly surprised that I did not have to make a new end piece for the lead screw. I still have a few little touch ups to do I will polish the discoloration. It is so much nicer than having to change gears.
 
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