What's new
What's new

Adjusting Z Axis Jib

As I said above, if it were an issue of 'it's too hard to lift because of weight that I am not used at' then it would have considerable difference when you moved downwards.
So it's something else
I just think as the difference is small between up and down with an even resistance, i.e its not a case of sticking and then getting lighter, it's either jib or dovetail causing the friction. I know shallow scraping does not help retain as much oil, but there is plenty of oil on the slideway when the table is raised and lowered.
 
Last edited:
I suspect some issue with the screw nut or thrust bearing or gearing.
The fact that you already tried loosening the gibs with no appreciable change and that the effort is pretty much the same going up or down suggests something other than simple a heavy part.
Adjust gibs close but not tight.
Try lowering the vertical slide as low as possible where you can still get a wrench on the bolts that secure the “Z” nut.
Block the slide to prevent any further lowering.
Loosen the bolts on the nut, and rotate the hand wheel slightly to take all the weight off the nut ( allow it to float)
Look at the clearance between the nut flange and the machine casting. Be sure they are parallel. .( nut could be 180* out and may have worn in at another position)
If all is flat, take the table load ( snug) via the hand wheel and tighten the retaining bolts.
Lube the screw w/ way oil ( ISO 68 or 220)
Try the effort test again.
Any difference?
Cheers Ross
 
I suspect some issue with the screw nut or thrust bearing or gearing.
The fact that you already tried loosening the gibs with no appreciable change and that the effort is pretty much the same going up or down suggests something other than simple a heavy part.
Adjust gibs close but not tight.
Try lowering the vertical slide as low as possible where you can still get a wrench on the bolts that secure the “Z” nut.
Block the slide to prevent any further lowering.
Loosen the bolts on the nut, and rotate the hand wheel slightly to take all the weight off the nut ( allow it to float)
Look at the clearance between the nut flange and the machine casting. Be sure they are parallel. .( nut could be 180* out and may have worn in at another position)
If all is flat, take the table load ( snug) via the hand wheel and tighten the retaining bolts.
Lube the screw w/ way oil ( ISO 68 or 220)
Try the effort test again.
Any difference?
Cheers Ross
Thank you Ross for the detailed reply very thorough as usual.

We are on the same wavelength, after fiddling with the jib clearance I also thought it must be something to do with the nut or the splined drive alignment. I did check this before but overlooked the fact I could have put the nut on 180 out of wack, however there’s a small notch in the nut which lines up with a hole in the column, I assume this lets excess oil out if you overfill the column with oil.

I just re-checked all the above and it’s all fine, taking the weight off the leadscrew the nut and handwheel turn freely and smoothly.

I checked vertical alignment by raising the nut 0.5mm checking with a feeler gauge the clearance all around the nut and the support column which are all square. I also tried loosening the splined shaft drive unit, all of which has made very little difference.

I have ordered some long feeler gauge shim so will have another go with jib clearance when it arrives, also take out the jib and make sure it’s ok.

cheers Adrian.
 

Attachments

  • WP_20240305_007-1.jpg
    WP_20240305_007-1.jpg
    264.8 KB · Views: 8
  • WP_20240305_009-1.jpg
    WP_20240305_009-1.jpg
    317.4 KB · Views: 8
  • WP_20240305_011-1.jpg
    WP_20240305_011-1.jpg
    273.9 KB · Views: 8
Last edited:








 
Back
Top