X3 Mill tramming thoughts

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John Hasler
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Re: X3 Mill tramming thoughts

Post by John Hasler »

jmpharrington wrote: Wed Apr 21, 2021 7:08 pm John,
How is that accomplished?
My table is bolted to the flat top of the knee casting (it's a frankenmill). I shim the bolts.
jmpharrington
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Re: X3 Mill tramming thoughts

Post by jmpharrington »

I cleaned the mating surfaces between the base and column, which were covered with a layer of gunk. Tightened bolts and no improvement...

Based on my math using similar triangles, the calculated shims I then added only took out about half the column lean forward. I will continue this exercise tomorrow to get the forward tilt out, experimenting with different thickness of shims.

As I went through this, I noticed several things:

The X axis which was “on” now has the column tilted left a bit over 0.001” in 4.5” after shimming the front bolts only.

The head has a nod, and a left to right movement of 0.001” to 0.002” when changing directions from up to down.

Putting a generous force on the side of the head produces a side to side movement of nearly 0.005” in each direction. Is it possible that pushing on the head can put this much twist in the column??

I tightened the Z gib, with no improvement to any of these.

(EDIT) I believe the tapered column alignment pins need to be re-driven after shimming. (Not sure of the best way to do this without damaging the threads in the center of the pins)

I realize this is not a 2,000 pound knee mill, but it isn’t made of rubber either - or am I expecting too much?

-Jimmy
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Harold_V
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Re: X3 Mill tramming thoughts

Post by Harold_V »

jmpharrington wrote: Sun Apr 25, 2021 9:02 pm The head has a nod, and a left to right movement of 0.001” to 0.002” when changing directions from up to down.
That indicates slop in the quill. Is the housing split, or is it cast solid, with no adjustment possible?
Putting a generous force on the side of the head produces a side to side movement of nearly 0.005” in each direction. Is it possible that pushing on the head can put this much twist in the column??
Most likely yes. Looking at the picture, that's a decent mechanical advantage, and it's not necessarily very broad. Greater width (and depth) would make a huge difference.
(EDIT) I believe the tapered column alignment pins need to be re-driven after shimming. (Not sure of the best way to do this without damaging the threads in the center of the pins)
I suspect that your best option would be to insert a long screw, so you engage the maximum number of turns of the thread, yet the screw bottons on the end. Drive by striking the head of the screw, which should prevent deforming the pin. Using the thread, alone, may be enough, but by bottoming the screw on the end of the pin the added support to ensure the pin isn't damaged. If the pin seats deeper than the surface, it stands to reason the head of the screw should be reduced a few thou smaller than the end of the pin.
I realize this is not a 2,000 pound knee mill, but it isn’t made of rubber either - or am I expecting too much?
Could be you are. I am not familiar with your machine, but in machine tools, weight is everything. Even robust machines display some deflection--it's a matter of degree. When I take a heavy roughing cut with my 12" Graziano, the dip in the tool as the cut engages is obvious. The machine weighs over a ton.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
jmpharrington
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Re: X3 Mill tramming thoughts

Post by jmpharrington »

Well I finally got back to this today…

A few months back I removed the gib and lapped it, as it was “banana” shaped, which took out most of the head nod. I shimmed the rear of the column at the bolts with U-shaped shims made from “heavy duty” aluminum foil, and had the column within 0.0005 in 4”. Further fussing with additional steel shims caused it to lean too far in the other direction. I considered that satisfactory.

Today I came to the conclusion that most of the issue was the head, not the column. I installed 0.003 shims at the lower bolts on the head, and was able to achieve less than 0.001” across the full swing of the indicator at about a 6” radius. I’m calling that “good”.

Tha lack of rigidity in the column, which can cause at least a 0.003” deviation (when I put my weight into it) to the above readings is an issue that I will need to learn to work around.

Thank you all for you recommendations and advice. Time to make chips.

-Jimmy
GregE
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Re: X3 Mill tramming thoughts

Post by GregE »

Hi Jimmy,
I have the same mill, and just reading this thread today- was going to suggest lapping the gib, so I'm glad you found that!
I had the same issue with movement of the head when I got it new, and improving the fit of the parts resolved enough of the issues that the machine continues to do a good enough job for me 12 years later.
If you haven't seen it yet, or for others with one of these mills, this guide for disassembly and cleaning/re-lubing is very helpful:
https://www.arceurotrade.co.uk/machineg ... -Guide.pdf
Greg Easter
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Bill Shields
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Re: X3 Mill tramming thoughts

Post by Bill Shields »

Perhaps expecting too much for what you are starting with

a big heavy tool will probably deflect the mechanism as much as you are seeing in the DTI...
Too many things going on to bother listing them.
pete
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Re: X3 Mill tramming thoughts

Post by pete »

Depending on the effort anyone is willing to go to with one of these dovetail column mills and how much previous Google checking they've already done? There's quite a bit of information about using what's called an Epoxy/Granite mix. It's based on some pretty good industrial based results of cold casting it into some extensive and complex shapes as the main components on quite high end machine tools. As good as cast iron castings are at vibration absorption, that Epoxy/Granite mix is apparently even better. Down at our more basic and less engineered levels, it can still work very well for items like stiffening up the hollow base casting on these mills and especially so for that rear column. Depending on any openings or internal parts in the base or column, it takes some well thought out methods to build internal dams for access to and operation of some parts before that mix is ever poured into any hollow casting. I don't know about the X3 sized mills, but some of them have the Z axis feed screw and nut inside that column. In the past I've seen quite a bit of detailed information about it's use on forums like this one. https://www.cnczone.com/forums/ It's also not quite as simple as it looks. There's a definite mix ratio of that Epoxy to Granite by weight, and on average a lot drier mix than would seem reasonable. Vibration and/or a vacuum pump to help remove any air bubbles is supposed to be very helpful as well. It's just one more method that can at least be done by most in an average home shop environment. There's even a few on those forums copying more industrial level efforts and casting complex machine tool parts from scratch with embedded steel threaded inserts, cast iron or steel way surfaces etc. After curing the parts are then ground for surface finish and alignment. It's strength to weight ratio is a bit poorer than a homogeneous cast iron casting, so heavier cross sections are also required with stand alone castings.

It's something I want to investigate further for at least my lathes head and tail stock. The cheaper off shore machines cut a lot of corners on just those two items and use the minimum wall thickness of metal. It could be a method of working around and increasing the rigidity of those built in poor design choices they made to lower the costs.
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Bill Shields
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Re: X3 Mill tramming thoughts

Post by Bill Shields »

Studer and Hardinge have been at it for years. (Decades)

The epoxy is good stuff but it takes a lot of experience and experimentation.

You do not just replace iron with epoxy.
Too many things going on to bother listing them.
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