euromill z axis nut jammed, how to free it?

[cryptopsy1]

Hey there,

I have a fus32 Marghita milling machine, similar to Emco FP3, Maho 1000 and TOS toolroom mills. The z-axis nut is jammed pretty hard on the screw, but not fully seized. I can turn it by forcing the handwheel, barely. There are signs that someone has tried to fix it ... machine is like 40 years old. Z axis powerfeed coupling was off the machine when i got it. The pin at the bottom of the z-axis screen holding the screw to the base was sheared.

I jacked up the table, gibs are not blocking the z-axis, its just the bronze nut tight on the z-axis screw. Is the bronze nut adjustable? On the face of it there are 6 or 8 holes, but I don't see any screws. Are they set-screws deep in the nut or are they just missing as it seems? Even with the missing screws on the nut, I am not able to free it from the spinning element above. With a vicegrip on the outside of the nut, I can force it to turn, but I wish I could just give it more backlash... I don't see how (don't see any features allowing for backlash adjustment). What should I attempt as my next move (pun not intended)? I wish I had a technical manual showing me where the backlash can be adjusted to free up the nut..

 

[deltap]

Could the holes be for a spanner wrench? Could the nut be a two part threaded together to adjust backlash? Just guessing. Could you look on a parts drawing?

 

[cryptopsy1]

I can't find a parts drawing - that would be sweet. I felt inside the holes in the nut witha bicycle spoke (fine thread) something like teeth, so there might be a thread inside - not sure if setscrew on setscrew locking. Gripping it from the outside with a vicegrip achieved the same result as a spanner. I seem to be the first on this machine to have tried this as there are no teeth marks. On the last inch of the Z axis screw there are teeth marks suggesting someone has tried to get a grip there.

Will report back with pictures after my morning tee, though not sure what can be seen. Machine is worth repairing as original scrape marks are on all ways, no broken gears and the price was right. I bought it with a minor Z axis repair in mind. The next major problem after this fix is swapping 1-2 relays and finding ways covers for the Z-axis (possibly chips got between the nut and screw .. the cause of the problem).

 

[cryptopsy1]

Here are some pics of the nut and abov the nut

 

[cryptopsy1]

The bronze cylinder rotates with the steel cylinder above it tightly on the screw. If I uncouple the screw from the base the whole assembly spins freely, gears and all. I don't or feel any screws in those 6 holes in the bronze nut but I feel some threads inside. The threads seem to be up in the steel piece. I'm not exactly sure or confident about how to remove those two pieces. Maybe there's another counter nut in the steel part. Don't these nuts usually have a way to adjust backlash?

 

[alphonso]

Guessing here. Bronze nut is the backlash adjustment. Been screwed tight to the steel section. See if you can get it to back off from the steel.
Holes in bronze could be for bolts to hold it at a fixed distance from steel.

 

[cryptopsy1]

No chance without heat. Trying to get a butane source or 1m long pipe wrenches. Any idea about how to make a high torque wrench? Couldn't put a chuck on the nut as my Rohm chuck was gripping on the screw before touching the nut

 

[cryptopsy1]

Can't get it unjammed even with heat from a propane torch. I need reallybig auto-locking plyers or maybe i'm doing something wrong?

 

[Bill D]

A Chain wrench can often get into smaller spaces.
Bill D

 

[janvanruth]

first unload the z axis nut by taking the weight off of it.
it should make working on the z axis nut so much easier.
backlash adjustment on the z axis nut?
isn't that nut always loaded in the same direction?...