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Re: Unimat 3 / PC Cross Slide Backlash from HANDLEWHEEL

 

Hi Jpow,

Having come the same way as you do, I just would like to toss in here my humble 2 cents of wisdom without any claim to UNIMAT 3 lathe mastery at all, but here goes:

In this rather comprehensive (and recommended) , published by the then importer for Unimat in the Netherlands, in Utrecht (still in existence), I stumbled upon the below passage on page 58 (see scan).?

The main point here is about the "transporteurs"? - the spindles for the different movement feeders (longitudinal, cross-slide and tailstock). According to this manual, the backlash ("speling") on the spindles is on purpose and one should not try to reduce the backlash. Coming to the field of metalworking as a woodworker, I was not surprised: when dealing with cast iron woodplanes, one encounters the same backlashes when adjusting the cutting iron.?

What one should do is to 1) either keep a record when the cross slide spindle starts to engage and the slide starts to move, or 2) avail oneself of a set of adjustable handwheels that allow you to set the wheel at zero the moment the spindle engages.?

As much as I would want to take out the backlash (I have a history of maintaining motorcycles, mopeds and bicycles, where it is all about reducing friction and taking out backlash) I have come to live with it now.?

Now hoping to hear from a few others whether this makes any sense,

Herman

?

Op 05-04-2023 09:11 schreef jpow <powster@...>:


Hey all,

I'm having this really irritating problem with backlash coming from the Unimat PC cross-slide handwheel.

My understanding is that backlash (for the Unimat) can come from two sources

A) Play in the slide lead nut / screw itself; OR

B) Having too much of a gap between the threaded handlewheel and the cross slide itself.


My main issue is with B)


Following the Unimat instructions, I screw in the threaded handlewheel all the way, and back it out JUST a bit, before tightening up the locking nut (on the outside).

For the life of me, I can never get it "just right". If I tighten enough so everything JUST rotates smoothly, the backlash is too much (0.07mm). If I tighten anymore, the backlash is a bit better, but the handwheel starts to bind and it is difficult to turn freely.

(The binding is strange in the sense that "tightness" occurs at certains angles of rotation only, rather than a constant heavy friction).

Could this be some issue with the bushings or something? I tried putting in small thrust bearing between the handlewheel and where it is mounted, but it didn't help much.


Appreciate any advice thanks :)
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