QCGB assembly: is this correct? I have some gears binding

Wow, not sure i've ever seen that type of failure! You might be able to fix that with a torch and some careful hammering, though remaking that gear would be easy enough with a mill + dividing head.
 
How annoying, but at least you found it! Looks like that's a press fit onto the bushing? In which case, you may find that the fit gets loose if you bend the tooth back, so use of some loctite might be wise. I think I can just see from the photo where it's picked up the thin body of the gear away from the bushing, rather than bending the tooth itself so much.
 
Caution, Caution, Caution, the old ZAMAK will be prone to breaking if you bend it cold. And won't take a lot of heat. . . If possible, and practical, that gear should be replaced. Worst case, I would file it down a fuzz and keep using it. Cutting a small gear like that in aluminium shouldn't be too difficult. Reshaping the tooth should not be too much a hiccup for threading if you're not doing high precision work. The gear does timing, not power transmission. . .

.
 
ARC-170 said:
I found the problem: a bent tooth on one of the gears. I took apart the assembly and meshed various gears to see which ones went together smoothly. I put them on the shaft and engaged them because just doing it freehand didn't simulate them being engaged. I traced it to one gear. I managed to ascertain the location of the "sticky-ness" on that gear and noticed that the gear teeth were a very small amount farther apart than the adjacent ones. It would be easy to miss if you weren't looking for it.

Here is a picture. The arrow indicates the bent tooth.
Click to expand...

Great sleuthing!

:clapping:
 
I bought a new gear. I'm not set up to make gears yet and I need the lathe for a project.

I had two other broken gears in this QCGB, so I think it may have been crashed at some point. The other two gears had really thin amounts of material at the base, as if they'd been bored out and re-sleeved for new bushings. This weakened the gears so they failed at some point. I couldn't inspect them and I didn't run the QCGB thru all the settings when I bought the machine .

Everything else on the QCGB looks really good, though. The shafts are not grooved or worn, the other gears all mesh nice, the bushings are not loose.
 
I was typing and didn't see your post on buying the new gear.

Do you need the gear with the bent tooth to do your project? If not do the project and worry about fixing/replacing the bent tooth gear later. I would file the bent tooth so the lathe runs smoothly until you can deal with it. It might not take much filing and may work ok after you file it.
 
Bill is absolutely correct. Zamak is not malleable. like cast iron, it will usually break before it bends.
 
QUESTION
So, now that I have replacement gears, what should I do with the old ones? The bigger gears on all of them are still good.

MY THOUGHTS
A. Press out the inner gears and sell the outer ones.
B. Make smaller gears at some future date, press out the broken ones and press in the new ones.
C. Sell as is.
D. Use as paperweights.
E. Other (please specify)
 
Paper weights for the immediate future until you stick them somewhere that you can't remember where you put them.
 
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