Tramming issues pm 835

B

Batmanacw

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I'm hesitant to post this issue as I'm sure I'll get insulting and stupid answers from people who won't bother reading my post but here goes.

I can't get the mill to tram correctly and stay in tram. I've been working on this issue for days.

Today I trammed the spindle to the table within 0.0002" in a 4" circle with my Starrett back plunger indicator. I was very careful to have the x, y, and z locked while I did it. I checked the tram again in 4 locations on the table. In one location it was 0.001" off on the Y plane. The other 3 within 0.0002"

Cutting with any type of cutter I get the back end of the cutter dragging in only one direction. Left to right. I cannot get cross hatching on the X plane at all. It doesn't matter the diameter of the circle I tram or the type of indicator used or how the indicator is attached to the spindle.

With a 3/4" endmill in aluminum I get a couple tenths difference between the right and left side of the cut along the X axis travel along with all the tool marks showing the same radial direction no matter which direction I feed.

I get cross hatching on the Y with much less measurable steps in the cut.


I trammed the spindle and test cut dozens of times yesterday. It's not some one off issue. It seems impossible to get the measurements of the spindle to the table to translate into actual squareness during a cut.

Y feed
20210210_155541.jpg


X feed

20210210_155611.jpg



I have less than 0.001" table droop that goes away tightening the table locks. The table reads within 0.001" running back and forth under the spindle with very little droop if any at all. I checked it meticulously.
 
Does your tram change after the cut?
Any chance you vise is rocking?
Any chance the bits clamping the tram adjustments only look like they are clamping?
Slop between the quill and head casting?

Since I'm not familiar with that.machine. can I get a photo of the adjustment areas?

Sent from my SM-G892A using Tapatalk
 
I would be interested to see what a test like this tells you. Also, did you run the knee up/down after the tram and before doing the test cuts?
 
A couple questions...
What type of mill?
How are you moving the table? Hand Crank, Power Feed?
If it was trammed when locked, to make the cut an axis has to be unlocked..... How well are the gibbs adjusted on that axis. I've seen my table move along unwanted axis's when under cutting pressure or feeding, if the gibbs were a tad too loose.

I have seen a mini mill where the lead screw nut slightly offset from the axis of the lead screw (mfg error). When the gibbs were set too loose the table would move in Y and Z axis's in addition to the desired X axis. Very noticeable on the ends as the lead screw would start to bind.
 
Firstly - I echo @Aukai . No matter one is making even the silliest fumble, or coming at something with zero knowledge, you will get help with respect. I am pretty sure the folk here would not put up with mean posts to anyone!

I am bothering to read the post, because I am starting from a point of near complete ignorance, and I want to figure out what is happening. This is because my mill is still in it's crate, awaiting the day the shop is built (starting this month we hope). I don't have a back plunger indicator. You have triggered me into a Google exploration. What you say has me wondering whether something about the spindle "leans over a bit" when loaded with anything heavier than a Starret indicator.

Already @DAT510 has replied while I have been typing. I expect the other folk will help us wring this out, and I get a free lurk on something I really want to know.
 
Have you checked that the quill moving up/down is perpendicular to the table after the tram? I had a new mill once where I could tram the head/column, then then tram would change when the quill was moved up/down. The quill cavity in the head was not co-planer to the attachment flange to the column. Put a machinist square on the XY table mounted vertically, an indicator in the spindle indicating to the vertical leg of the square, and run the quill up/down - see if the indicator changes. Do this with the square facing x, then facing y.
 
The amount of tram error you are seeing could also be sloppy gib adjustment in the XY table. Here's a procedure for checking that. And here are my similar tests on my PM935 - in aluminum, dead on, with 304 SS, 2-3 tenths row-to-row variances which I attribute to some combination of material attributes and rigidity limitations of a J-head mill.
 
Well. I feel a bit foolish. I finally put an indicator on the Z to check if it was shifting while the table weight was moving. It was by 0.003". I fixed it and now things are better. Not perfect but within 0.0002" in the width of a 3/4" mill. I still need to figure that one out.

This was the first time my fly cutter touched on both ends feeding in both directions.

20210210_190223.jpg


This was my 3/4" 2 flute

20210210_190138.jpg
 
davidpbest said:
Have you checked that the quill moving up/down is perpendicular to the table after the tram? I had a new mill once where I could tram the head/column, then then tram would change when the quill was moved up/down. The quill cavity in the head was not co-planer to the attachment flange to the column. Put a machinist square on the XY table mounted vertically, an indicator in the spindle indicating to the vertical leg of the square, and run the quill up/down - see if the indicator changes. Do this with the square facing x, then facing y.
Click to expand...

I actually trammed it with the quill extended and it matched up perfectly retracted. I was pretty happy about that.
 
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