Tramming SX3 Mill

Checking with an indicator confirms my suspicion that my SX3 mill needs tramming; shows approx 0.10mm discrepancy over about 300mm of table on X-axis and 0.02 on Y-axis.
While light weight compared with more 'grown up' mills the head and column of the SX3 are still heavy enough to be non-trivial when it comes to raising them enough to insert the necessary packings - has anyone advice on this - would be much appreciated.

The Dore Westbury is a heavy beast but I found it easiest to slacken the four mounting bolts of the base casting to be able to lean it back and insert a shim. The correction was always to correct forward nod and that avoided the need to lift things

Before mucking about with the column fixing are you sure the rotating head is set true as most of your error seems to be in X that is the likely cause.

If you are going to shim the column then pull the dowel pins out first, loosen bolts and just push column to one side to slip in a shim. No real need to lift anything. If you want you can put some wood on the table, bring the head down so the spindle nose touches that and keep winding which will jack the column up slightly.

Thanks Jason B. Yes, the locating pin for zeroing the head is far from precise, and I've been able to get rid of errors by tweaking the head rotation position in the past - but things have now gone beyond that - I know not why!
I tried using the head to raise the column as you suggested, but before any appreciable lifting of the head I got a very alarming noise of the pinion drive for the Z leadscrew jumping out of mesh - so gave that up very quickly.

The column/base joint is unlikely to have moved, look at the head gib strip and also set head rotation true without the pin so it trams as close to zero to the table. Then check vertical travel against a quality square. Only then look at column joint.

You only need to get the column to move 0.2mm to get shims in so should not come up enough to affect mesh. Do make sure those dowel pins are pulled first as they go in at a slight angle and will make it hard to separate.

Jason B: Ah, I hadn't thought of tramming the head with the locating pin removed, so that's a very helpful suggestion - having removed any misadjustment there I can proceed to check the column, as you say, with a known good square.
Should it come to it, do you know if the column dowels have a lead-in chamfer - I'm very lairy of withdrawing dowels where realignment can be difficult, I've been caught before.
Adjustment of the column gib is something that has given me difficulty: tightening up enough to remove all play results in binding and the head lowering in a series of jolts. Reference to ARC elicits the response to make sure that both top and bottom adjusting screws are snug - but this I do. Funnily I can still feel some play on the jib side when all play has gone from the other.

If you have 0.1 mm misalignment over 300 mm, than using a 30 mm end mill would create 0.01 mm deep grooves.

My BF16 has a head that can be set in an angle. I have to loosen 2 bolts and tram the head (X-axis) by a set screw.

Tramming by adjusting the head is all very well but if the column was to be subsequently shimmed then the head would then be out of tram again. The column needs to be adjusted first, then the head. This pre-supposes that the machine has been manufactured with the spindle axis accurately parallel with the column Z axis, (which I would expect).

All quite a lot of bother for small return IMHO.

Clive, the OP says he was able to tram the mill previously so must have come out the factory OK.

"I've been able to get rid of errors by tweaking the head rotation position in the past"

Therefore unless the column has moved which is unlikely it is the head that is probably out be it rotation or gibs

Edited By JasonB on 14/02/2023 10:03:01

Fair comment Jason, but my point was that if the column is to be corrected, then that needs to be done first.

To be honest, I wonder how much is to be gained by chasing these small tolereances with "hobby mills". I suspect my WM16B would show slight tram differences depending on the X- position of the table and where the vice was bolted down.