Gib strip to thin

On my PM30, I made a test piece today, first cut in metal, and before doing so, I tried to adjust all 3 of my gibs.

I noticed that on my Y axis, I can push the taper as far as the screws will allow, and it still is not overly tight. By hand,

My X and Z both are able to be completely locked down by tightening the gib strip, and I needed to back off the gib quite a bit to be able to run at a reasonable rapid speed for both X and Z.

I don't have any slop that I can feel in any Y axis, but in my test piece, I noticed a lot of chatter in the Y direction, which I am somewhat attributing to the gib not being tight enough.

To be fair, my stand is not very sturdy at all (stand that came with mill), and the only 2 screws from the base actually line up between the mill base, and the stand, so it is probably not overly tight there either. So, between the lack of overall rigidity in the machine, the stand being flimsy, and the mill not being attached great to the stand, there is probably plenty of variability contributing to the chatter. All of those other things can be worked out short of rigidity.

The reason I am leaning towards the Y gib, my X axis has a bit of chatter, but not nearly as bad as the Y, which is quite bad. I ran the same speeds, and the X should be subject to the same variables as Y, so I am deducing the Y gib.

My main question is, is there anything I can do with my Y gib strip? Can I shim it somehow, and if so, how?

I assume a new one could be made, but I don't really know the dimensions, nor the process for making a new one, so that would be last resort.

I know that QMT does not even offer the PM30 anymore, so not sure I could even buy a new one from them.

So if anyone has any thoughts or suggestions, I would appreciate hearing them.

Yes you can shim the gib. Shim between the gib and the non sliding surface (backside of the gib). This will allow the adjustment screws to be used effectively. The other option would be to order a new gib from Weiss, Grizzly, HF or someone who offers the same class of mill.

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Originally Posted by Fastest1

Yes you can shim the gib. Shim between the gib and the non sliding surface (backside of the gib). This will allow the adjustment screws to be used effectively. The other option would be to order a new gib from Weiss, Grizzly, HF or someone who offers the same class of mill.

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Thanks Fastest1, I can certainly order one from Grizzly, but I suspect the G0704 gib must be smaller than the PM30 gib that I have right? I am going to call up QMT today. I will also give shimming it a shot like you mention.

Does anyone know how to order parts from Weiss? I was on their website, and I don't really see a way to buy a gib strip from them.

Just call them, they got me a motor for my 0704 at 1 time. A 1000 watt replacement. It is running nice now.

Note: the gibs you get will most likely be raw stock and will require machine and scraping. See my build thread for details, I just went through this. Called and talked to a Grizzly service guy too. I doubt that Weiss would sell a drop in gib, they must be fit to the individual machine.

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Originally Posted by mhackney

Note: the gibs you get will most likely be raw stock and will require machine and scraping. See my build thread for details, I just went through this. Called and talked to a Grizzly service guy too. I doubt that Weiss would sell a drop in gib, they must be fit to the individual machine.

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Just read through your build thread, crap! I really don't feel like machining a new one.

I suppose if I have to, I will.

My backlash on Y is around 0.0005, so maybe I am OK and I can attribute the chatter to something else. I would think if the gib was that far off, I would have either slop by hand, or, bad backlash.

I may try some very thin shim stock in there to see what that does as well.

Eeegads! If your backlash is really .0005" DON'T TOUCH IT! What are your speeds & feeds, material, coolant, and end mill size/quality?

you sure its not .005? If my backlash was .0005 I would brag all day long.

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Originally Posted by rs4race

you sure its not .005? If my backlash was .0005 I would brag all day long.

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Originally Posted by mhackney

Eeegads! If your backlash is really .0005" DON'T TOUCH IT! What are your speeds & feeds, material, coolant, and end mill size/quality?

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Yeah, I am definitely in the 0.0005" backlash range for both X and Y, Z is around 0.002". Not that I would get that type of real cutting accuracy. The mill is just not rigid enough, and once cutting forces are applied, those numbers will not be achievable.

I have a starrett DTI with 0.0005" ticks on it, and I actually get a hair of movement on the first opposite 0.0005 mach3 step, and the second step goes a full 0.0005 on the DTI. If I zero everything out in one direction, and then switch directions for 0.01, I end up right around 0.0095 or so.

I ran another cut today, without doing anything to the gib's. I used a better end mill, and sped up the feed on the finish cut, and I got a much better finish. Still not great by any means, but far better. I think the lack of rigidity of the stand itself, and the mill to the stand is going to leave a bad finish no matter what. When my mill rapids, the entire stand and mill rock, so I can only imagine the cutting forces are causing motion, contributing to the finish.

I also have a Tormach 1100, when I run the exact same piece with the same end mill, same speeds, the finish is nearly perfect.

Overall, for the second cut in metal, I am very pleased. I need to build a stand for this, but I think the CNC conversion will end up being great overall.

Thanks for the suggestions.

Knowing the rigidity of both the Tormach and G0704 are different, did you shrink the cut on the finish pass of the 0704?

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Originally Posted by Fastest1

Knowing the rigidity of both the Tormach and G0704 are different, did you shrink the cut on the finish pass of the 0704?

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I actually have a PM30 not a G0704, but similar enough.

I am not exactly sure what you mean by shrink the cut on the finish pass.

I use HSMexpress, and I use an adaptive clearing at full DOC and a WOC of 0.05, leaving .015 width of stock, and no stock depth for a finish cut.

I then do a contour at finishing speeds to finish the cut. I did it exactly the same way for both machines. I'd love to hear what you mean by shrinking the cut, perhaps that can help out, which would be great.

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Originally Posted by Fastest1

Knowing the rigidity of both the Tormach and G0704 are different, did you shrink the cut on the finish pass of the 0704?

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he has a pm30 not a 0704 there dude, the pm30 is twice as big as a 0704.

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Originally Posted by treyjugson

he has a pm30 not a 0704 there dude, the pm30 is twice as big as a 0704.

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While true, the Tormach is still at least twice as heavy as the PM30, so I would think the concept would still apply, maybe just not to the same extreme

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Originally Posted by AVRnj

While true, the Tormach is still at least twice as heavy as the PM30, so I would think the concept would still apply, maybe just not to the same extreme

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yes but not the extreme he was thinking. he's suggesting you take a lighter pass on your finish cut, maybe half of what you take now.

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Originally Posted by treyjugson

yes but not the extreme he was thinking. he's suggesting you take a lighter pass on your finish cut, maybe half of what you take now.

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That makes sense, I will give it a shot.

I'm probably at the point where I need to come up with a more permanent stand solution as well.

I get very different results as I change the size of the finish pass. I usually leave .001 or so in the bottom for the finish. Too small or too large of a cut both get bad results.

There are so many factors at play to achieve great wall finishes. Direction (climb or conv can play a role too)

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Originally Posted by Fastest1

I get very different results as I change the size of the finish pass. I usually leave .001 or so in the bottom for the finish. Too small or too large of a cut both get bad results.

There are so many factors at play to achieve great wall finishes. Direction (climb or conv can play a role too)

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Yeah, I'll have to play around with it and see what works best on this machine.

Thanks