[Beezle]

Setting up a new Lathemaster LMT25L. Generally the machine seems good, but I noticed that the head can be less than rigid and this led me to the Z axis tapered gib.

Once I finally read up on adjusting them - and that's not consistent - I realized that this gib is just not fitting very well.

So I removed it and indicated it with dye and reinstalled it and ran the head up and down for a while and the results actually surprised me. There was very very little contact.

I got here by way of noticing the using the lower lock deflected the spindle by about 0.015 or more. I can see it move. And the above test showed almost no contact for the lower third or so of the gib while the top is in what contact it makes.

Right now I'm missing the lesser plate and set screws gibs because I know I could just make it flat then adjust it well.

But what should I do here? Do I need to examine the taper on the saddle? Then make the gib flat then match that? Or just try to lap the gib flat? The gib has hand scraping on the contact side. On a surface plate and indicated on a surface plate shows about the same (lack of) contact.

Sigh. I don't enjoy this part nearly as much as making stuff. I would pay three times the price for a machine I could just use. Just went through this with vises. Try a high end Chinese vise. No, get another. Not that bad, but bah - buy a Kurt. Perfection!

[photomankc]

I have the same thing on my PM25-Mv. It just doesn't fit right. The head moves a good bit as you lock the bottom and then the top one brings it back almost all the way. Going to need to address it because even with the gib as tight as it can be made to go if I don't lock it there is a lot more slop in the head. That's going to impact CNC work.

[Beezle]

There has to be a way to improve it. I've already modified the machine quite a bit so it's a keeper.

Next time I am in the mood I will pull the head and have a good look at the taper on the saddle and the parallelism of the ways. If those are reasonable, I'll just find a way to make or buy a better gib.

The one that came with it could be repairable, but as I measure it by the time it's flat it will nearly fall through the machine before it stops. And even then will the taper be off?

I'm wondering what the advantage of this type of gib is when it is so highly dependent on that taper being right. And I'd like to meet the person that made this one so I can ask him why? I'd say contact per the prussian blue test was about 10%.

Also: are they tapered across their width or is their shape a parallelogram?

PS, I wonder if it's the weight of the head? The top of the gib would naturally have more force in Y applied to it. Naw, the head doesn't move in Y like it does in X. For me.

[Beezle]

Looking at it again, the head doesn't deflect at all in Y when the lock pushes on the gib. Nothing. The bottom of the saddle just deflects counter clockwise as the lock pushes against a part of the gib that isn't up against the dovetail way.

And that lock is at the edge of the back of the gib. Given where I saw contact down there, I would say it is twisting the gib a wee bit.

Anyway, my temporary solution is to use a set screw there so the head doesn't deflect during cutting. The top lock works as I would expect.

photo - didn't you say your head deflects by 0.002? I'd be happy with that to be honest.

[photomankc]

Nah, more than that. It was more like about 0.005" then the top lock drags it back over by about 0.003" when I set that but that really depends on what you measure, tram vs X edge ect. I get the same thing, it's all in the X axis not the Y.

[arizonavideo]

My gib is the same on my Weiss 30. I will need to fix it too someday. I am starting to think that it would be easier to correct the slide rather than the strip itself. One setup but it best be right. Which brings the question.

Is the gib strip wrong or is the slide mis machined.

I could measure my gib which is way to thick at the big end and someone who has a good one could tell us what they have.

Anyone with a good one want to check their gib?

[Beezle]

After a bit of reading it appears to me that these gibs are best hand-fit using scraping and prussian blue indicating. I don't know how to do that and I am not sure I want to learn just yet, but it led me to at least try to improve the fit of the gib I have until I can get another one to try.

It seems that the G0704 gibs are simply ground. The gib on my (also) Weiss made LMT25L has scraping marks on the contact side, but the fit was dismal at best. I would imagine those marks are mostly cosmetic/for oil retention.

So I pulled the head and went after it hand grinding using water stones. Same thing could be done using wet/dry sandpaper, cutting oil and a surface plate. I tweaked both sides until I had better contact and it is behaving a bit better.

But the fit was so poor that I had to stop short of good fit because the gib is now sitting about as low in the pocket as it can given the length of the slide and the screw at the bottom. I tried a shim just for grins, but that wasn't stable enough.

I am getting another gib to try from LM, and I'll go from there.

I did check the ways on the column while I had the head off using a calibrated straight edge, etc. and it looks pretty good to me. I don't exactly know how to test, but they are flat and parallel to each other.

A few other things along the way - I can already smell burning diodes or capacitors so I predict the electronics are not long for this World. I may try to find the culprit and replace them with better quality stuff. Some of the wiring was rather sloppy as well and needed to be re-crimped. There's a big relay block in this machine - not there in the G0704 so far as I can tell - and that was just floating on the wiring. A short circuit just waiting to happen.

I should have an EE friend have a look and see if they can recommend a way to beef up the controller and the power supply. If these are standard bits that could be replaced with better ones I'd love to know.

The bearings in the spindle were sounding dicey and I started thinking about doing Hoss' AC mod, but that turned out to be the draw bar sleeve being tight against that clip and that apparently overloaded them. Not sure what to do there as it will come loose otherwise. Blue Loctite I suppose.

Is the spindle bearing replacement just the inner spindle bearings are are the larger ones replaced as well? Seems those need to be pulled and pressed. Of course what I'd love is to get rid of the quill. This one is useless anyway and loosening the lock even messed up the tram.

I'll post on this again after I get a replacement gib and have at that.