# Lead Screw/Feed Rod Stopped Turning - Jet GHB-1440



## jaychris (Feb 10, 2013)

Before I do something drastic like draining the gearbox and opening it up, is there anything else I should look at as to why my lead screw and feed rod suddenly stopped turning?

I _did _just swap the change gears to metric for a short time and then swapped back.  The change gears are meshed nicely and rotating correctly when the lathe is running.  I verified that the feed rod direction selector is engaged and that the feed rod/lead screw selector is also fully engaged.  It doesn't matter whether I select the feed rod or the lead screw, it still doesn't turn.

I can turn the lead screw by hand and the feed rod rotates with it.  Power doesn't seem to be an issue, the lathe fires up and runs no problem. 

The only thing I can think of to do at this point is drain the gearbox, pull the cover, and see what I can see.


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## pdentrem (Feb 10, 2013)

Just a couple ideas

Have you tried removing the gear going into the gearbox and try turning the shaft it is mounted by hand to feel anything? Can you feel some resistance as you will be turning that gear train by hand. If it spins freely then you have to look inside I guess.

Missing a key for a gear so the shaft is not turning but the gear is?


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## jaychris (Feb 10, 2013)

I did and it turned pretty freely, which made me think the gear was not engaging, like you were suggesting.

So then, of course, the second I go through the trouble of opening up the gearbox to inspect it, it starts working again.  All of the gears looked like they were in good shape, nothing loose, no odd bits of metal on the floor of the box.

So, it's working again, but I have no clue why.


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## pdentrem (Feb 10, 2013)

Mr Murphy is in the house!

Maybe the transfer gear was just out of position? I do not know, but likely whatever it was it must of been disturbed when you opened it up.
Pierre


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## atwatterkent (Feb 10, 2013)

I've had those boxes open and changed gears in them. I feel your pain.


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## ranch23 (Feb 10, 2013)

Some of them have a, went completely braindead, key that breaks if you accidentally engage the feed and the threading at the same time. Before you get too far, check for that.


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## jaychris (Feb 11, 2013)

I checked things over very carefully before I buttoned it back up and couldn't find anything that looked suspicious.  I did notice that one of the gears looked worn towards one side, but not majorly so.  It's clearly wearing a bit asymmetrically though.  It didn't look bent or anything, but I don't know how to check it for trueness while it's in use on the feed rod.  Just rotating it by hand didn't show any real obvious runout.

After closing up, I ran the lathe, engaged the feed rod and lead screw, engaged the half nut and power feeds and everything seemed to be working normally again.


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## pdentrem (Feb 11, 2013)

Worn on one side. Do you mean on the surface of the teeth or on the side face of the gear? If it is on one side of the teeth then naturally the gear is not fuller engaged. 
Pierre


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## jaychris (Feb 11, 2013)

pdentrem said:


> Worn on one side. Do you mean on the surface of the teeth or on the side face of the gear? If it is on one side of the teeth then naturally the gear is not fuller engaged.
> Pierre



On the surface of the teeth.  If it's not fully engaging, I'm not sure how I would go about fixing it.  I know how to access the gears, but I've never tried adjusting them before.


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