Tight spots in carriage feed

[epanzella]

While turning a long gun barrel with a left hand tool I my carriage went nearly to the end of my available bed. I don't think it hit anything but I did notice it was harder than usual to to shut off the feed like it had a load on it. Immediately after that I noticed intermittent tight spots while traversing the carriage down the bed with the handwheel. The carriage lock is backed off. The feed rod and lead screw don't appear to be bent and function perfectly. The machine is a Grizzly G4003G and has a shear pin in the feed rather than a clutch. The pin did not shear. Could I have bent something in the apron?

 

[benmychree]

I would suspect that the pinion that meshes with the rack gear is bent or one of the teeth on it has been displaced.

 

[Robo_Pi]

This probably has nothing to do with your problem but one thing I would inspect closely is the half-nut gib adjustments. (see page 73 in the manual figure 123). Actually if you are feeling tight spots when moving the carriage with the handwheel it probably has nothing to do with the half-nut. But if you were feeding using the half-nut when it happened it wouldn't hurt to exam the half-nut gib and alignment. Since the half-nut alignment is adjustable on that machine it is possible that under stress it was pushed slightly out of alignment.

Just a thought. Probably not related to your actual problem.

But it does sound like something either bent or was pushed out of alignment.

 

[markba633csi]

Could be some Cosmolene or greasy gunk and chips at the very end of the bed which got into the carriage- try cleaning and lubing the ways
Also check the rack and pinion as John suggested
Mark

 

[epanzella]

I got in close with a light and can see that the gear in contact with the rack has some malformed teeth. Time to order another one. Now to figure out how to get this thing apart. Thanks to all.

 

[sportfan]

I had a similar problem on my PM1130 lathe. It was hard to hand crank the carriage back and forth. It turned out to be the carriage lock bolts had to tightened just right to free it up yet keep play out of it. I don't know how your Grizzly is made, so this may not help.

 

[epanzella]

I had a similar problem on my PM1130 lathe. It was hard to hand crank the carriage back and forth. It turned out to be the carriage lock bolts had to tightened just right to free it up yet keep play out of it. I don't know how your Grizzly is made, so this may not help.

This is an old thread and I apologize for not following up on this. The shaft that was integral with the pinion gear was bent and the runout was causing intermittent pressure on the rack as the carriage was run along the bed. I got a new piece from Grizzly (around $25 I think) and that fixed it. At least I got a crash course on how all the gears and halfnuts work by taking apart the apron. Thanks for responding.
Ed P