Mill Misalignment

[Sub MandrelParticipant @submandrel]

[Sub MandrelParticipant @submandrel]

I trammed my mill recently (X2) but I found that changing froma centre dill (short) to a full length jobber’s drill resulted in an error greater than 0.5mm and quite visible to the eye.

 

Now I uses a DTI on a bar held in the same chuck as the drills and a piece of as flat as I can judge glass on the table. The table was showing flat to less than a thou over about 6″ turning the bar from one side to the other.

 

I repeated the exercise three times and the error was consistent.

 

I can only figure out this happening if the column and spindle are far from parallel, but I don’t think they are. There is no play in the spindle or the head to column dovetail.

 

Can anyone think of another cause? Or an alternative test – all I can think of is using a sheet of paper instead of the glass.

 

Neil

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

If the answer to your problem does not become obvious after a bit more inspection then use the toolmakers method to truly check the machine alignment .

 

Make a cylindrical square minimum 3 inches diameter and minimum 6 inches high and place on the table . Using a DTI on a cranked arm in the spindle centre the square to the machine axis at some randomly chosen height from the table . Now use the DTI to run around the cylindrical square at several different heights and do several up and down traverses at different points on the circumference . Record all results . The various deviations from true that you record wil tell you everything about errors in the machine alignment .

 

Table should be locked both ways . Cylindrical square should be heavy enough to stay put on its own .

 

MW

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

And if you want to be a perfectionist repeat the process with table in different positions .

[Martin WParticipant @martinw]

Neil

 

You don’t say in which direction the offset is, is it along the x or y axis. Secondly are you moving the mill head or just using the fine feed to accommodate the length difference between the jobber and center drill.

 

If the movement is on the x axis and you are moving the head up and down the column then it could be that the column is not truly vertical to the table. Just tramming the head will set the spindle axis at right angles to the table and this will remain true for both fine feed adjustment or head movement up or down on the column. However when the head is moved on the column it effectively follows the hypotenuse of a very narrow triangle and the center line traverses the table in the x axis.

 

I found out the hard way on my mill when I found a similar problem, but much less than 0.5mm, between the center drill and a long drill centring points being different after I had adjusted the head on the column.

 

To remedy this I very slightly undid three of the cap head screws securing the column to the base and tapped the column over a bit using a hammer and large block of wood, nipped up the screws, re-trammed the head then re-checked the centering by moving the head between the limits on the column. This was repeated until all was spot on.

 

If I am teaching me gran how to make an omelette without breaking eggs then I apologise.

 

Regards

 

 

Martin

 

 

[John ShepherdParticipant @johnshepherd38883]

Neil

I had the same problem with my X2 (assuming it is the X axis).

The head is in two parts, one with the dovetails and one holding the spindle and if these are not aligned, tramming will only be accurate at one position on the column and give the inaccuracy that you describe.

 

The two parts of the head are held together with 4 cap head screws and there is no provision to locate the two halves in alignment.

 

What I did was to raise the head so that I could get at the screws, slacken them slightly and make adjustments until the spindle and column where aligned. If I remember rightly, I put a straight bar in the chuck, attached a DTI to the side of column and made adjustments until the bar was true when I moved the head up and down. This way the spindle is aligned parallel to the column regardless of the tram.

 

Once that is done and everything tightened up you should be able to tram the column and it will be right whatever the height of the head.

 

Hope this is useful. If you need more detail let me know.

 

John

 

 

 

[Ex contributorParticipant @mgnbuk]

Can anyone think of another cause?

You have checked that the column is square to the table in both planes before doing a trammel check, haven’t you ?

I see a great deal of reference to trammel checks in ME circles, but very rarely any reference to checking that the column is square beforehand.

As an extreme example – if your column was set to 45 degrees to the table and the spindle could be adjusted so that it trammelled true to the table, it would still trammel true when you changed the height of the head on the column, but the position of the spindle relative to the table would be different..

National standards specify the sequence of alignment checks – levels first, then squareness / straightness of the major elements, then spindle alignments / runout / trammell.

Regards,

Nigel B.

[Martin WParticipant @martinw]

Neil

 

Just looked at a Sieg X2 and realised that to angle the head you need to tip the column. On the mill I have this is done by rotating the head and not by tilting the column so some of my comments are not applicable to your situation , should have looked last night prior to my post. That said the problem, as detailed by John, is similar but the error is in the head alignment rather than the verticality of a fixed column re the table.

 

Hope you get it sorted.

 

Martin

[BERTOParticipant @berto]

Hi Neil.

Martin and John have had the same issue as i have had but mine was after a rebuild because i fitted a belt drive kit

This required the two halves to be split to remove the gears and to fit the sensor for my digital tacho .

I used an angle plate to test the alignment of the column by clocking it vertically then trammed as usuall .

I ended up leaving the head to dovetail screws loose enought so i could tap it with a plastic hammer to adjust then remove and tighten – thankfully nothing moved when i lifted the head off the column to tighten the bolts !

If you don’t own a reasonably large angle plate clamp a parrallel to the one you have to extend its range or if you don’t own an angle plate clamp the largest known good square to the table and clock the blade vertically .

Yes i know it is not as good as a precision cylindrical square but make do !

I suppose if i went insane enough to worry about it i could set the column up on my large mill and machine a locating step into the dovetail bracket and then do the same to the head to locate it parrallel to the column but thats another job to think about !

 

If your readings are in error in the Y axis try removing the column to base bracket and check for burrs or any debris between the mating surfaces – wouldn’t be the first time gunk has been found under there !

 

Ian

[Jeff DaymanParticipant @jeffdayman43397]

Neil mentions putting his drills and DTI in a chuck, to check tram.

 

Is the chuck closing true to the spindle axis? is it repeatable?

 

When checking tram, it is wise to use a known true collet in the spindle, not a drill chuck. The collet must be clean and be known to be true running.

 

Before checking tram, the spindle runout must be checked, Also, quill runout or play must be checked at top of travel and bottom of travel. If the runout/play on either is more than a few tenths of a thou, there’s no point trying to tram the table to a thou, really.

 

JD

[Sub MandrelParticipant @submandrel]

The errors are repeatable jeff – I did it three times.

 

I think John’s explanation fits – I had convinced myself that the spindle must be at an angle to the column. but couldn’t see how.

 

I shall try his remedy tomorrow and see how I get on. I can put a test bar in a collet chuck for the alignment test.

 

I’m still a little unsure which cap screws to loosen – under, behind or on top of the head?

 

Thanks to all for your thoughts on this – if this approach doesn’t solve things I shall have to do some more investigations along the various lines suggested.

 

Neil

[Clive HartlandParticipant @clivehartland94829]

Arc Euro have under machine spares have exploded diagrams of milling machines in their range.

 

Clive

[Sub MandrelParticipant @submandrel]

Thanks Clive,

 

I was just contemplating which of several large piles and ciupboards to search in for the manwel too!

 

For anyone else who comes later the manual is at: Old style X2 Manual

 

I understand better now; it’s more like the mini-lathe than I realised! A chance to lube teh gears and see if they really are metal in my machine.

 

Neil

[Sub MandrelParticipant @submandrel]

Well then! A closer inspection has revealed this:

 

 

I am amazed I hadn’t noticed this crack in the paint! The two parts of the head have clearly shifted relative to each other.

 

Not having much time spare I took the easy way out and just removed the head and ‘joined’ the split in the paint back up, and then trammed the column as normal, rather than doing any direct check on the spindle. The result is certainly a lot better the centre drill/jobbers swap appearing to be sorted now. I will do John’s detail spindle alignment check later.

 

My head hasn’t got metal gears though – it has what look like good quality acetal or nylon ones, not the same plastic as those in the mini lathe.

 

Fixed the loose (since new) gear change lever too!

 

Neil

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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