Traming mill ?

dlane

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Not to hijack the edge thread I'll ask here, I made a traming aid with two .0005 indicators seems to work good but was woundering
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With the quill extended as pictured would magnify the amount the tram is off resulting in a more accurate tram ,
What say u ?
Thanks
 
Yes, the farther away the more error you will see. Same if you spread out the two indicator farther vs closer.

Edit: My initial answer was incorrect. See corrected response below.

Happy Thanksgiving!
Ted
 
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I don't think it would any difference. The lenght of your bar would make a difference in what you see.
I only tram my vise not my table unless I'm milling directly on the table.
Edit: You're probably right but unless you mill with your quill all the way down. There can be some error in the quill to, correct?
 
With the quill extended as pictured would magnify the amount the tram is off resulting in a more accurate tram ,

The mill with spindle extended is not as stiff as the mill with spindle at home.
But unless those dial indicators are applying large forces at their tips, I can't see how it would change the tram reading, unless the quill sliding bearings are shot.
 
I was wrong. I just took a couple minutes to draw it out in CAD and if the spacing between the two indicators does not change, the error will not change. The delta between the CAD measurements where exactly the same at both positions (5" indicator spacing 3" down vs 18" down from the top (20" up off table) at 10 degrees from vertical). I guess to me it just seems harder to tram a head with the spindle extended way out vs in...

Sorry about that but I learned something today!
Ted

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Technical Ted has it correct, and so does ddickey. The quill extension would not make any difference in the amount of error, but the longer the beam of the tramming tool, the more accurately you can tram the head of your mill.

Keep in mind that a longer beam on the tramming tool would not increase the actual error, but it would increase your ability to see if the tram is off at all. The longer beam would, in effect, make your tramming tool more sensitive. Natually, if the beam is so long that the DTIs don't touch the table, the tool doesn't do you much good. It looks like Derrick made his beam just the right length for his mill.
 
Technical Ted has it correct, and so does ddickey. The quill extension would not make any difference in the amount of error, but the longer the beam of the tramming tool, the more accurately you can tram the head of your mill.

Keep in mind that a longer beam on the tramming tool would not increase the actual error, but it would increase your ability to see if the tram is off at all. The longer beam would, in effect, make your tramming tool more sensitive. Natually, if the beam is so long that the DTIs don't touch the table, the tool doesn't do you much good. It looks like Derrick made his beam just the right length for his mill.

I'm totally new to the hobby machinist scene. I've never used a tram bar shown above. I bought a surface plate the width of the table but it came with 0.002" of wedge in it. The OEM guarantees flatness but not parallelism. I built up one side with JB weld and did a fly cut on it to get thickness measurements within a few 10 thousands. I rotate an indicator in a 9" circle and get fair results. I've seen disks with legs on them so the operator could conceivably tram the head without pulling the vise or rotary table with chuck.
 
Tramming adjusts the orientation of the spindle axis so that is is perpendicular to the motion of the ways. When the spindle is not perpendicular, and end mill in a facing operation will not hit squarely. The leading edge of the end mill will either be higher or lower than the trailing edge and the cut surface will not be flat but a series of scallops corresponding to the multiple passes.

Note that the requirement is that the spindle be perpendicular to the ways, not the table or the vise jaws. Tramming will not cure a taper problem. If the table is parallel to the ways, all is well and good. Likewise, regarding the vise. However if a non-parallel condition exists with the table and/or the vise, tramming to them does not produce a perpendicularity condition.

It is fairly easy to determine whether the table and/or vise is parallel to the ways. Sweeping the surface with a test indicator will accomplish this. Unfortunately, curing a problem with the table is more involved as it would require resurfacing the table. A solution would be to use an intermediate plate; http://www.tosatool.com/shop/modular-tooling-plates/tt1634c-hobbiest-modular-tooling-plate/ or https://saundersmachineworks.com/collections/all. One can also easily make their own. Once the plate is properly mounted to the table, the surface can be skim cut with a small diameter end mill to provide a surface which is true to the ways. Truing a vise is an easier task as it can be shimmed.

If it is necessary to tram a mill which has a non-parallel table, A suitable piece of plate can be mounted on the table and the surface skim cut with a small diameter end mill. The plate can then be used to properly tram the head as the difference in height difference on the surface will only vary by a fraction of a thousandth in the worst case. It isn't necessary to skim the entire surface, only the points where the tramming tool will be making measurements.
 
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