View Full Version : QCGB repair?

03-20-2012, 03:19 PM
Howdy Folks,

Digging into my new Clausing 5917 this afternoon turned up why the QCGB likes to pop out of gear...


In case the pic isn't clear, there's 2 huge score marks on the tumbler shaft and the hole on the lever is quite egged out. :(

Seeing as a new shaft and lever (if even available) would run me almost $300 (according to the 2005 price list I found) I'm wondering if there'd be any issues with simply bush the lever and turning the shaft down a bit to clean it up, locktiting on a a sleeve and then turning it back down to proper size. The shaft is 0.750" dia and the grooves look to be ~0.725" dia and aligned right where the lever would be if it were positioned where the broken tooth on the index plate is.




Dr Stan
03-20-2012, 03:50 PM
Why not just get a piece of 3/4" dia material and make a new shaft? That would be a lot less work and much more satisfactory in the long run.

03-20-2012, 04:12 PM
I'll second the new shaft - much easier unless the gear at the end is an integral part, and if it is you could always cut it off, bore it and pin/loctite it to the new shaft!

Pictures like that make me so glad my QCGB's fully-enclosed with taper-roller bearings and runs in an oil bath. The corrosion in the unobtainium bearings due to coolant getting trapped in it makes me so sorry my QCGB's... You get the picture!

Dave H. (the other one)

03-20-2012, 04:17 PM
I've used TGP (Turned, Ground, Polished) 1045 shafting to replace QCGB shafts on a couple of lathes. You'll want to rebush the lever too, as long as you have it apart.


03-20-2012, 04:29 PM
Unfortunately turning a new shaft is a no-go, as the end is threaded and with the gearbox not working right I'm not sure it'll go very well. Then there's that big diameter in the middle, which may or may not be a separate piece... If it isn't, turning the shaft from scratch would be a lot more work than sleeving.


03-20-2012, 04:48 PM
Are we talking about the same shaft here? The one in your photo looks to be the 700-113 shaft with the 12-tooth gear pinned (convenient!) to it, but you're describing the "tumbler shaft assembly" 4900-26? The tumbler shaft looks to be the one with the cone of gears, unless the one you're aiming to repair / replace is a lot longer than the part shown in the photo?
A scan / pic of the whole of the QCGB parts page (rather than just a corner...) might help, we'd be able to see what goes where!

Dave H. (the other one)

03-20-2012, 04:49 PM
My guess is that the "big diameter in the middle" is a gear that slides along the shaft (by using the "lever")and is in effect an "idler" required when it is moved between the various threads and feeds etc. Just fill the grovves with a good metal filler and turn/smooth off. Any clearance will be of little or no effect.

The lever can be bored and sleeved. There may be a part of the lever bore that has little or no apparent wear. Use that to locate to for boring the lever and the sleeve (after it is pressed into the lever).

You should be pretty right to go after that.

There will or may be a "mesh" adjuster screw at each gear position - re-check and if necessary readjust them to a good mesh fit - with a little "slack" or back-lash.

03-20-2012, 05:36 PM
Howdy Folks,

I'm wondering if there'd be any issues with simply bush the lever and turning the shaft down a bit to clean it up, locktiting on a a sleeve and then turning it back down to proper size.



People are always using mig welders and such to build up a shaft and then turn it down, but that can cause distortion and such due to the heat.
I can't see any reason why using loctite on a sleeve would be bad, Since you are not cutting a key way or anything and it seems to just be a support that is likely oversized anyway and does not transmit significant amounts of torque for its size.

03-20-2012, 06:45 PM
The large diameter appears to be a collar pinned in place. It also appears that the shaft is hollow for some distance as there is an oiler in one end. With that in mind, if there is enough material to leave sufficient strength, I see no problem with your approach.

Once the shaft is in hand, make a dimensioned drawing of it and when repairs are completed, make a replacement. This will ensure the repaired shaft will not fail in the future.

03-21-2012, 09:34 AM
'Morning Folks,

Here's a better pic with most of the clutter removed and the wear spots marked in red (sorry for the huge pic). I'm thinking at this point it's probably best to simply disassemble the QCGB and pull the shaft before deciding which way to go, since it'll have to be out regardless if I sleeve it or make a new one. I'm still leaning towards sleeving, but will reserve judgement until I get the shaft out.



Bill Pace
03-21-2012, 09:58 AM
I recently had an almost identical situation with a SB heavy 10 gear box. I remade the shaft from a piece out of the scrap box and bushed the housing and handle with oilite bushings. The only tricky part was getting the gear box housing and the handle mounted/centered in the mill and lined up for the boring - the holes were so egg shaped, but it turned out great and made a nice repair. In fact, I remade some 7 shafts and installed bushes for the SB in total - and several gears. When you got a 60+yr old machine, you dont have a lot of choices.

03-21-2012, 03:52 PM
Wow. I'm used to working with equipment that's been horribly abused and allotted a couple hours to get that shaft out. It only took 10 minutes, including cleanup and putting the covers back on. :D

Good news is that the large diameter was indeed a collar held in place with a roll pin. Bad news is sleeving isn't likely to work... there's a keyway down the shaft.


Guess I'll be picking up some 3/4" TG&P and whatever size die is needed for the threads in the end. Oh, and a pair of bronze bushes for the lever. Good Lord is that thing egged out!

Thanks for the help everyone!

03-21-2012, 04:40 PM
Actually, scratch that plan. Partially keyed TG&P shaft plus a 1/8" x 1/2" Woodruff cutter plus a 5/8"-18 die from McMaster came to ~$115 and the new shaft from Clausing is $130. Going to save myself a whole lot of time/headache and order the new shaft. Will bush the lever myself though; no way it'll cost me ~$170 for a pair of bronze bushings....

03-21-2012, 05:42 PM
It seems like every one has over looked the full length key that is not shown, but if you look at the gear that is slid with the change handle you can see the key.

03-21-2012, 06:55 PM
Quite possibly. I didn't see it until I got the shaft out today, so didn't know about it. It's not full length, btw... Shaft is smooth under the brass bearing the quadrant lever clamps.

03-21-2012, 08:12 PM
My 1969 Clausing 4902 has the same type (if not identical) setup and had no wear at all. I and guessing the previous owner left it in gear all the time?

03-21-2012, 10:12 PM
2 owners ago... Guy I bought it from got it when he bought the building. Supposedly it was a gunsmith shop, but the old school formed plastic labels on things makes me think there was a school in its past. In any case the index plate has a broken tooth right where the lever would sit to create the wear, so I guess the broken slot and wear are related.