What the hazelnuts is going on here! Work piece and tramming results not matching

akjeff said:
That parallel could possibly be bowing under the clamping forces, if you really reefed on the handle? Sweep across the parallel in the Y axis, and see if has a hump in the middle.
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I guess it is as I just indicated across the middle, right and and then left end. I got about 2, 4 and 6 thou differences respectively.
What's up with that?
 
I just indicated x and y with a 123 block clamped in as that item is going to be a lot less prone to bowing than a paralell.
I got no movement either way.
My work pieces are pretty stiff, unlike the paralells. So I'm assuming they are not bowing as well.
 

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Has anyone mentioned locking down your table? You could be getting some table movement.
My first opinion was out of tram.
Did you retorque everything after the tram?
Just raising the flag to see if anyone salutes.
 
Are your Y and Z gibs well adjusted? Are you locking them down? Loose Z gib can let the whole knee roll over under cutting force, so that is something to look at. Y loose can let the table lift one side, but that's unlikely by comparison.

Grab the table by an end on full X travel one way, try and pull it around by hand. I'd bet you find something loose. Won't be a head tram issue in this case.
 
Lo-Fi said:
Are your Y and Z gibs well adjusted? Are you locking them down? Loose Z gib can let the whole knee roll over under cutting force, so that is something to look at. Y loose can let the table lift one side, but that's unlikely by comparison.

Grab the table by an end on full X travel one way, try and pull it around by hand. I'd bet you find something loose. Won't be a head tram issue in this case.
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I did that and got no movement. I also lock all non-moving axis down when milling.
 
I have seen this on mills with bigger tables, like the Series II or Series II Special, but it could also be there is play in the knee to the column. Typically that is seen when longer movement is made and the weight of the table physically makes the knee move left and right. Put it into the middle of travel and lock your knee down, that might help.

Jon
 
I would suggest using vise hold downs for skinny work, Starrett and others make them.
 
In post #4 you said "I trammed the Y axis on top of the vice and I got zero movement." Are you saying that you tram the vise and not the table?
 
Canus said:
In post #4 you said "I trammed the Y axis on top of the vice and I got zero movement." Are you saying that you tram the vise and not the table?
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I should say "checked" using the vise rather than trammed. My initial tramming was done with the table.
NOTE: My knee gib was not tightened yesterday. I tightened it down today and got the results I expected/wanted to get. I can't believe I'm getting movement in that knee and I guess that must have been the cause of the issue as I did not have it today.
Thanks all for your comments. Love this site.
 
Aluminum plate or bar has a lot of locked in stress. Milling one side will result in a banana. You are using a Kurt vise or a clone. I doubt that jaw lift is a problem. If your part is gripped high in the vise jaws clamping pressure will bow the middle of the part upward. I use light to medium blows of a lead hammer to seat the part on the parallels. I keep tapping the jaws while I tighten the vise, then I check to see if the parallels are tight. Use moderate pressure when tightening the vise. Most people over tighten.

The milled surface of the plate shows evidence of a built up edge on the cutter. Use a cutting lubricant like kerosene or WD40. Better yet use a fly cutter for large surfaces. For facing there is no benefit to using a roughing end mill. Roughers have a benefit when cutting with side of the cutter.

There are a lot of things to sort out. Tackle them one at a time.

To see if you are over tightening the vise put an indicator on top of the part before tightening the vise. Watch how much the part bows as you tighten the vise.

I hope this is helpful.
 
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