Unimat 3 mods.

[david bennett 8Participant @davidbennett8]

I have ditched the belleville wahers on my Unimat3. The 28 lbs. or so of thrusts seem excessive to me, so I have gone for a solid preload.I had a spare headstock, so single pointed a 17 x 1 mm. thread on the spindle (between centres for a special long nut, which abuts the bearing, and a locknut. The bellevilles have been replaced with a 6mm wide spacer against the bearing. The small external circlip has also been ditched.

 

 

I had to drill another tommy bar hole, and the automatic feed is disabled. I have cut a variety of spacers for any future experimnts.

So far , the results are promising, if not dramatic. That annoying squealing when you pause a longitudinal cut is gone. Blue pivot steel cuts better,so does parting off. It is early days, but there is no apparent downsides. Everything is reversable except the extra thread and tommy bar hole, and it was all done on the u3. I can post further details if anyone is interested.

dave8

[Michael GilliganParticipant @michaelgilligan61133]

Bring it on, David

… always interesting to see experiments like this.

MichaelG.

[SillyOldDufferModerator @sillyoldduffer]

Delighted to see this report.  The important part for me is Dave experimentally confirming there’s an improvement.   One hidden thing to look for though is excessive wear, likely to take a few hundred running hours to appear.

My guess is the lathe designer chose a Belleville washer as a cheap simple way of managing bearing life.  I believe it’s a compromise: if the bearing is left loose, the lathe performs badly.  Therefore tight is better.   But, as tighter causes more wear and tear on the machine, it’s important not to overdo it.

Worst case, the lathe performs brilliantly for a few hours, then seizes in a cloud of smoke.   More likely, the extra wear and tear will be  slow, perhaps taking years to become obvious.

This kind of problem is often detected in critical machinery by periodically sampling the oil and having it analysed for metal content.   Gives a good insight into how fast wear is happening, and often which parts are failing fastest.   Used to improve safety by taking rapidly wearing engines out of service early, and to save money by deferring servicing of engines in good condition.      Analysing the oil feels over the top on a Unimat though!

Dave

[david bennett 8Participant @davidbennett8]

Dave, my bearings are adjusted to have a small positive clearance. I consider this is less likely to produce wear than 25lbs. of thrust. That’s what made me do this.

dave8

[david bennett 8Participant @davidbennett8]

PS. I note the Emco Compact 5 uses just one wave washer for thrust.

dave8

[Author]

Posts