# Options for Checking and Adjusting Quill Tram



## TomS (Nov 17, 2014)

My machine is a PM-932 and I have a question about adjusting quill tram.  I've searched the internet and read quite a bit on how to tram the head using a dial indicator and shimming the column base.  This I understand and have done it successfully on my RF-31 clone.  My questions are related to checking, and if necessary, adjusting the front to back quill perpendicularity.  I believe this is called "nod".  I've read/seen where a cylindrical square is used to check quill perpendicularity.  My questions are; after tramming you find that the quill is not perpendicular front to back how do you adjust for that?  Do you machine the Z axis mounting flange to compensate?  Or are there other options?  Is there another way to check the quill without have to buy a cylindrical square?  They can get expensive!

Tom S


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## darkzero (Nov 17, 2014)

Nod would be front to back & would be checked using the same method you use to check side to side tilt to the table You don't need a cyl square for that, that would be used to check perpendicularity of the the quill to the column (along the same axis). But it's not absolutely needed to check that either. No logical easy way to adjust for this without scraping. This is the only video I have seen that shows how to measure this using an alternate method. hossmachine

To adjust for nod on these benchtop column mills you will have to shim the column. I suppose you could shim the mounting flange for the head to adjust quill to the column perpendicularity but I say not logical because that is where side to side tilt gets adjusted.


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## TomS (Nov 18, 2014)

Thanks for your input.  I watched the video and it opened my eyes.  It made perfectly good sense using the Rollie's Dad's Method to check quill alignment to the column.  Hopefully it will check out OK and I won't have to do and scraping.

Tom S


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## TomS (Dec 18, 2014)

Got my mill back together to a point where I can check the quill to column tram both in the X axis and Y axis planes and spindle to table tram.  I watched Hoss's video and the process was easy to understand.  First thing I did, and what was shown in the Hoss video, was to check the X and Y to column tram.  Got the X axis to within .0015" over a 5" distance.  At this point in the build this should be close enough.  Once the mill is up and running and has a few hours on it I will tweak it a bit closer.  

Then I checked the quill to column perpendicularity (Y axis plane), also as described in the Hoss video, and discovered it's out .005" in 6".  I've got 17" of Z axis travel so theoretically this thing is out of tram about .015" over the full Z axis travel.  I was expecting it to be out some small amount due to nod but much closer than this.  By the way, I adjusted the gib until the drill motor I was using started to bog down.    

I also checked the spindle to table tram and had to add .009" of shim under the left side of the column to table flange.  I've got about .0015" TIR.  I'll adjust this as well once the machine is broken in.

Getting back to the nod issue what should I expect to see?  I'll have to do the math to find out how much to machine and/or scrape the head mounting flange to correct this.  I'm not at all happy knowing I have a new mill that's out this much.


Tom S


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## jbolt (Dec 19, 2014)

Head nod is an inherent evil with dovetail column mills. You have to have some slack in the gibbs for the machine to operate. Using it as a manual mill you can lock the gibs after moving the head to the desired height. With the head motorized for CNC you have to accept some error in order for the gibbs to move.

If you really want to drive yourself crazy, with everything locked down, put a test indicator on the front of your spindle/gauge pin and pull down on the gear head. Keep in mind it's not a Bridgeport. 

I have my gibbs set to where the nod is between 0.002" and 0.003" using a 300mm R8 test bar. I don't find the average import R8 collet to be super accurate. One of these days I will buy a real Hardinge collet. After setting the spindle I used stainless steel horseshoe shims under the column and evenly torqued the bolts. Bolt torque and torque differential will have an effect on the column position when using shims.

Jay


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## TomS (Dec 19, 2014)

Thanks for your comments.  Maybe I'm expecting too much.  I'm going to put an indicator on the test bar in the Y plane and tighten the gib and see what the indicator does.  My thought is if the parts are machined correctly then with zero gib clearance the spindle should be perpendicular to the column.  That's my theory anyway.

Tom S


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## wrmiller (Dec 19, 2014)

With zero clearance your head may stick/drop any time you attempt to lower the head. There has to be clearance of some amount. Also, the design of a bed mill has the head pulling on the head/column interface exacerbating the clearance you leave in the sliding interface.

And just a suggestion, but you never measure tram or cut on a bed mill without the head cinched down. Measure and adjust so that you have acceptable measurements only with the head locked. Then never cut with the locks loosened. This is how you get repeatability on these things in my experience.

I measured about 1.8 thou head nod in 6" on the Y axis on mine. Almost 2 thou! Terrible. 

Until I figured that I seldom mill 4" deep pockets on my mill or anything else that requires super tight specs in Z, and the inaccuracy in 2" isn't even worth measuring let alone worrying about, and the 1" or less stuff I do would be laughable. I have a Chinese mill and don't hold mil-spec tolerances for my hobby stuff. If you are (holding tight tolerances), you need to spend a lot more money on machines. 

I used to get wrapped up in chasing zeros on hobby machines (< $20k) and realized that was just stupid. When I trim the hood on a 1911 barrel and miss by .001" I used to get so ******. Then I realized that is about 1/3 the thickness of a single sheet of paper and started laughing at myself. Then I figured that too tight of fitment has the gun start locking up/jamming as things heat up and expand (Doh!). When I milled my soft jaws last weekend I was measuring and noticed some thickness variation end-to-end. Almost a thou. Probably tilted in the vise. Normally, if I want to hold to that kind of tolerance I would surface grind the part but can't do that as I no longer have access to my friends machine. So, being the hack I am I grabbed a #2 file, some sand paper and a small granite block. Perceived problem solved. But it wasn't really a problem other than a minor ding to my ego...

Oh, and very nice mill. You should enjoy that for a long time.


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## TomS (Dec 20, 2014)

wrmiller19 said:


> With zero clearance your head may stick/drop any time you attempt to lower the head. There has to be clearance of some amount. Also, the design of a bed mill has the head pulling on the head/column interface exacerbating the clearance you leave in the sliding interface.
> 
> And just a suggestion, but you never measure tram or cut on a bed mill without the head cinched down. Measure and adjust so that you have acceptable measurements only with the head locked. Then never cut with the locks loosened. This is how you get repeatability on these things in my experience.
> 
> ...



Thanks for responding and giving your perspective.  I truly appreciate it.  I wasn't going to run the mill with zero gib clearance.  It is a test to see how close it comes to zero.  I'll adjust it for clearance after the test.

Tom S


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