Tramming – what is acceptable?

[ChrisHParticipant @chrish]

Decided to check my mill this afternoon -it's a circular column Warco 'Economy' mill/drill.

It was not too far out, measured on the table in four corners roughly approximately equal to the spacing of the four holding down bolts I got readings from 0.000 at the start reference to +0.003" max. Shims steel available is 0.001, 0.003, 0.004 and 0.006 thou.

After a couple of hours adding and taking away shims I now have from my 0.000 start reference back left, to -0.0015 front left, -0.0015 front right to -0.001" back right. I could live with that, but feel it could be better.

Question: What is the acceptable error on Tramming, can I expect to get it better on this sort of mill?

Chris

Edited By ChrisH on 16/02/2014 18:03:32

[ChrisHParticipant @chrish]

[Roderick JenkinsParticipant @roderickjenkins93242]

Chris,

It depends on the distance of your indicator from the spindle axis. Those distances you've quoted over a 3 inch radius would keep me happy.

HTH

Rod

[ChrisHParticipant @chrish]

Hi Rod,

Just been out to the shed to measure the radius, from the spindle axis to the indicator – it's a 4 inch radius, so presumable that is a good result but I can't help feeling it should be better.

I will leave it until tomorrow and recheck, see if it holds at that.

Chris

[Tony Pratt 1Participant @tonypratt1]

I would say that is pretty good, I have spent many happy hours 'tramming' turret mills and if I got it within a thou over 4" I would be good to go. On a knee type of mill you can have perfect squareness quill to table but still have faint steps in the work face due I believe to the table being out of square to the column movement?

Tony

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

When tramming a mill/drill it is nescessary to distinguish between the column being crooked and the spindle/quill being crooked – different things .

Bit of a puzzle to get good test results for the two things but worth persevering .

Regards ,

Michael Williams .

[ChrisHParticipant @chrish]

Oh Michael, now you have introduced a whole new bag of worms!

How do you determine if the column is crooked and/or the spindle/quill is crooked, and if any of them are, how do you correct other than by renewing? Other than by Tramming the column to the table that is.

Chris

[Anonymous]

As far as tramming is concerned, assuming that the head moves in straight line on the column, I don't think it matters if the column isn't perpendicular to the table. If the spindle is trammed to the table it stays trammed. The spindle will move in X and/or Y as Z changes, but that's a separate issue.

Andrew

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi ChrisH ,

Sorry if I caused you any headache .

Tramming is not nescessarily the best or only way to find out whether a small machine of the mill drill type is accurately aligned .

A functional test often gives more meaningful information . After all it’s the way the machine actually cuts that matters .

If you want to do some tests then these are my suggestions :

(1) Put the machine back into standard condition without shims .

(2) Mount a sizeable piece of thick Aluminium plate on table on parallels and take some trial cuts .

(3) Specifically :

A surfacing cut using a cutter smaller than the dimensions of the block so that several passes are needed to cover surface . Do one trial feeding front to back and one end to end .

Observe whether cut surface in each case is uniformly flat or is shows series of steps where cuts meet .

Further observe whether block after machining is constant for thickness or whether it tapers off in any particular direction .

With a bigger cutter skim sides of block all round . Observe whether edges are square to skimmed top face .

Bore a reasonably large hole through and see if its going through square to top surface .

Note and mark the orientation of block on machine .

(4) From above observations infer where any errors in alignment of machine are and correct if nescessary .

Notes :

If nescessary to realign colums only use shims for assesment of amount of error . Once determined scrape mountings back to get hard metal on metal bedding again . Permanent use of shims for alignment can cause all sorts of problems .

Personally I would not chase perfection of aligment on this type of machine .

If it performed reasonably well on test and did the work I want to do ok then I would use it as supplied .

Regards ,

Michael Williams .

Edited By MICHAEL WILLIAMS on 17/02/2014 13:51:07

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