# Stuck G threading gear on Shop Fox M1112 lathe



## ericc (Sep 9, 2019)

Hi.  From searching on the Internet, it seems that the Shop Fox M1112 lathe is similar to the Grizzly G4003G model.  I am helping some folks at a maker space get their shop fox lathe working.  The G gear in the threading gear train is stuck.  It is necessary to remove this gear in order to do metric threading.  The F gear comes off with difficulty, but the G gear seems to hit a metallic obstruction.  It is not tight, but seems to be hitting something when one tries to pull it off.

Internet forum searches seem to give two interesting results.  One is use a big fat gear puller to force the gear off.  I am afraid to do this, since I broke a lathe this way.  Another thread suggests that the key may be sheared or cocked due to a jammed gearbox or a crash.  Does anybody have some suggestions about how much effort is required to remove this gear.  On my home lathe, the gear bores are tight, precise, well-lubed, and silky smooth.  Not one hint of trouble.

People say this is why you should buy a lathe with a QCGB.  But the M1112 has a QCGB and has a problem, while my all change gear lathe is just perfect.  Is there a quality problem with gear/shaft fit?


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## ErichKeane (Sep 9, 2019)

Could you possibly get some Morse-style wedges (perhaps shop made for that length) behind it and essentially just press it off?  

A gear puller should also work, but you may want to find a set with long 'feet' so you aren't on the gear teeth.  Alternatively, what making a round plate cut in half to sit behind it and support the gear puller feet?


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## ericc (Sep 9, 2019)

Good.  So there isn't some hidden catch holding this gear on.  I don't think that Morse-style wedges would work, since there isn't much room.  Also, there's no slot in the shaft for the wedges to go through.  It says in the manual just remove the gears, but it is not coming off without a fight.  My gear puller reaches far enough back (I have a huge one).

I actually broke two gears on the same lathe.  On the first gear, I got to work with the puller right away.  I didn't account for the fact that the gear had an inner sleeve.  The gear stuck to the first half of the sleeve, and the second half of the sleeve stuck to the shaft.  They sheared apart and shattered the whole inner sleeve, which was a real chore to repair.  On the second gear, I got clever.  I made a slotted disk to pull from the back so that the sleeve would actually be pushed out along with the gear.  It appears that these things are really weak under tension, but many cheap materials like this are much stronger under compression.  I started pulling, and nothing moved.  I pulled harder and still nothing.  Suddenly BANG!  Broken parts!  On closer examination, there was a hidden pin that locked the sleeve to the shaft.  I didn't see this, since it was covered by the gear bore.  The pin sheared and cracked the sleve, and it was fortunate that I didn't break any more gears.  Even the google "x-ray" did not reveal the hidden pin location until I broke parts.

Rather than curse my lack of skill, I cursed the designer and builder of the lathe's threading gear train.  But, I quietly filed away this humbling experience so I could ask for advice before breaking someone else's lathe.


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## Mitch Alsup (Sep 9, 2019)

Yes, there is nothing that SHOuLD be holding the Gear on.
But it should pull off with "not that much" force.
I suspect a buggered key.
Try penetrating oil overnight.

You have looked for an allen set screw on the flange of the gear, have you not?


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## ericc (Sep 9, 2019)

Yes.  There was an allen set screw.  It was loosened all the way, and eventually removed.  The F gear was tight, but there was no barrier feeling.  I would suspect a cocked key, but it didn't look bad.  I'm not sure penetrating oil will work, since the gear wobbles on the shaft.  It just won't come off the end.  It has a narrow range of axial play in which it is loose.


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## Mitch Alsup (Sep 9, 2019)

With the gear wobbling and still not coming off, it is pretty clear that the key is buggered.
After you get the gear off, you are going to need to TIDY up the key.

Gear puller time, gently, gently my friend.


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## ericc (Sep 10, 2019)

Hi Mitch.  Thanks.  When removing the F gear, we had to push on the key a bit.  This lathe was bought at an auction and had a few missing pieces.  It seems to run just fine, but there are a lot of moving parts.  It took forever to get the jammed T-nut out of the compound, which had to be done.  It drills, turns, and faces just fine, with good finish and stability.  Hopefully, we don't damage the shaft too much when the key is raked kicking and screaming out.


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## tlrascal (Sep 15, 2019)

Some time the set screws sre locked  in place  by another set screw.  Make sure there is not another set screw you need to remove.


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## ericc (Sep 16, 2019)

tlrascal said:


> Some time the set screws sre locked  in place  by another set screw.  Make sure there is not another set screw you need to remove.



That's a pretty good idea.  But the gear becomes loose on the shaft once you remove the set screw.  That wouldn't happen if there were back to back set screws.  Anyway, I will soon pull out the big fat gear puller with the jaws that reach beyond the teeth.  It make sense to me that the key is somehow tweaked in there.  By the way, breaking that first lathe was a necessary (for me) step on the path to my current setup.  Without freeing that gear, that little lathe would have never run.  The problem about the current lathe is it does SAE threading just fine.  And it is not mine.  There is some risk associated with a crude fix.


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