What make and type of mill do you have? Most of the common bench top machines have the upright column, whether round or square, bolted to the base. Square ones directly and round ones via a socket. Pretty simple with such machines to slip shims underneath at the front to bring it back to perpendicular to the table. Nice thing about working with shims is you know the thickness so its relatively easy to figure out exactly what ought to happen after inserting the shim and compare what you expected with the results you actually measure. If what you get isn't what you expect then nothing has been damaged or permanently altered so you can try something else. Trimming alignments can be very confusing until you get a proper concept of whats going on. If you have a good CAD program an hour or two playing around with drawings can be a great help.

On an import Model Engineer market machine its probably a good idea to actually separate the column and base to ensure that the mating faces are true and clean with no itsy bitty contamination underneath. Takes very little to upset things by 0.12 mm. Being made down to a price you can afford production line fitting and fettling is limited with great reliance placed on the parts being made to adequate accuracy in the first place.

If its an older, ex industrial type, machine the problem could well be wear as such machines were normally fitted to an good standard of accuracy when made. Sometiems clever shimming can sort the problems but many machines were made in a manner that preculdes this as in having nowhere to put the shims. Re working to eliminate wear and remove the error is a job for experienced people. Learning how to scrape and align machines is quite practical but you do need a mentor and a lot of time to acquire the skills.

Clive.

Edited By Clive Foster on 04/06/2016 17:47:08

If it is as Iain says that the gauge is held in the chuck and the only thing that is moved is the table then this surely is not a tramming problem but a fault with the alignment of the table in the Y traverse i.e. the surface of the table is not truly parallel with the dovetails in the Y plane of movement. The only way to improve this is to skim or scrape the table surface or scrape the guideways. No amount of packing the column will rectify the problem.

Martin W

Martin is correct, if you tilt the column you will only tilt the cutting face of the milling cutter, the table will still move on the same plane.

The problem is the table and the slides are not on parallel planes. I mill a lot of aluminium, it requires sharp cutters and a cutting fluid, I use WD40 its the only real use I've found for it.

Edited By RonMc on 04/06/2016 20:09:31

Iain, I looked at your photos of your mill in your album, you aren't using a drill chuck when your milling are you, that will cause problems as they aren't designed to deal with the side thrust experienced in milling, they are designed to stand end thrust..

Best Regards Ron Mc

Edit; deleted as was not correct

Edited By Martin W on 04/06/2016 21:38:21

Bum It was OK – Start Again.

Something that might be worth trying and might make any correction easier could be :-

Slacken the gib screws on the X axis, I realise that might seem odd, lift the table and put a 0.1mm shim or feeler gauge between the horizontal surface above the gibs and the table horizontal bearing surface , full length of bearing surface if possible. Snug up the gib screws and re do the Y axis measurement. With luck this should have reduced or corrected the error, by trying various shims it should be possible to establish the thickness required to correct the error. If the rear X axis horizontal slide is reduced by this amount then I think this should resolve the problem. Having mentioned scraping I have to admit that I have never tried it  others more qualified than me have often advocated it use!! A temporary fix would be to secure a shim between the front bearing surface of the X axis.

Martin W

Edited By Martin W on 04/06/2016 22:13:18

Made a mistake in my last post. For Front read Rear and for Rear read Front. Not only that but the font went awry as well.

Martin