Sieg SX2.7L tramming advice?

[Gordon BParticipant @gordonb]

Many thanks both. I've dug out some brass shim stock (assuming that will be OK), and will try to attack the mill with a torque wrench in the next few days.

I spent a bit of time adjusting the wedged gibs and got the X and Y axes to a good point (just a little drag, but still moving smoothly).

I also managed to get the Z axis gib wedge sufficiently tight, but only by removing the bottom gib screw. Removing the wedge I see it's 180mm long (the same height as the head); so there's not a lot of adjustment with the gib screws fitted. Interestingly I see Arc's spare part (https://www.arceurotrade.co.uk/Catalogue/Machine-Spares/SX27-Mill-Spares-All/SX27-Mill-Spares/SX271-68-Z-Axis-Gib) is 240mm long; so that does reinforce Jason's earlier comment about them needing to be trimmed down to fit. Looks as though the one I have needs about 10mm taken off the bottom and I think it'll snug up with both gib screws fitted.

[Gordon BParticipant @gordonb]

Mixed results with shims this evening. I suspect the machining of the top of the mill's base and the bottom of the column are maybe not that great, as small movements of the position of shims has an effect on the tramming.

With a couple of shims on the right side of the column I got the left/right tramming (as far as I can work out) pretty much perfect; I get about 0.02mm of movement on a DTI over 70mm of column travel (DTI on 123 block), but that error is consistent and opposite when I rotate the DTI and 123 block 180 degrees. In other orientations I get slightly different errors, but again consistent and opposite. I assume therefore that the column is vertical and I'm measuring the "out of squareness" of the 123 block.

Nod on the column has proved more tricky, with results changing quite a bit due to the placement of shims. I'm wondering if it might ultimately be better to drill and tap some holes in the base of the column to fit grub screws and use them instead of shims.

I could fit 2 grub screws on each side, in the area of the red X marks. There's probably not quite enough space to put them in the locations shown by the blue X marks.

Obviously the area of a grub screw is much smaller than a shim, but they would then be applying force at consistent locations. Is this a good idea, or should I just keep persevering with the shims?

[Neil LickfoldParticipant @neillickfold44316]

Some machines are just very difficult to get any where near to right. On a much larger machine , I got the quill hard chrome plated, with hindsight, should have got it over chromed and ground. Anyway on a ZX45 mill, the quill bore is a long way out to the casting of the dovetail side. So will get it bored and sleeved from the local engine reconditioner . He said he was willing to hone it to size for me to fit the existing spindle diameter. If it works out well, he will do their own little mill as well.

I see that you are trying different shims etc, on some machines, leaning the whole machine base , forward or backwards a little , can allow the casting to move enough to correct what you are chasing. Sometimes the base casting needs to be shimmed against the frame it is being held on to as well.

Sometimes the base of the castings require fitting or scraping in to correct for the mass produced finish on the parts too.

Once you get it all sorted out, I am sure that you will be happy with it.

Neil

[JasonBModerator @jasonb]

Try to keep any shims/screws as far apart a s possible otherwise things will be more prone to flexing as the effective "area" of contact becomes smaller eg you would not put 4 feet of a table right in the middle and not expect it to wobble or fall.

[Gordon BParticipant @gordonb]

Think I've worked out what was "tricking me"; when checking the tramming side-to-side I had a 123 block on one of the table's rails (between tee slots). However, when checking the front-to-back tramming a 123 spans the rails across the tee slots. That wouldn't be a problem… if it weren't for the fact the table isn't actually flat.

I realised the blocks could tip slightly (messing up any readings I was taking) so checked the table, and I can fit a 0.038mm shim under a straight edge near the rear of the table. Not great.

In an attempt to work around it, I bolted another 123 across the table (for consistency) and measured a 123 block sitting on top.

I've ended up with 5 thou (0.127mm) of shims on the right side of column; which pleasing was pretty much exactly what I'd calculated should work based on the initial measurements.

I needed a tiny bit of shimming at the front, but I don't currently have anything thinner than 1 thou, so I've compromised slightly with a single 1 thou (0.025mm) shim at the front left, and not put anything on the right front as it upsets things.

Checking against a 123 block it looks as though the column tilts to the right by 0.014mm for 100mm of vertical travel, and leans backwards by 0.011mm over 100mm. That doesn't feel too bad.

Sweeping a DTI over the table surface (a sweep diameter of around 130mm) shows the head tilts to the right by about 0.01mm (reading at 3 o'clock position of 0, and -0.01mm at 9 o'clock). That's so close to the measured column tilt that I'm going to assume it means the head is aligned with the column, and it's down to the column tilt.

The 6 o'clock reading at the front of the table is -0.02mm; which would be consistent with a bit of backwards lean in the column. Unsurprisingly the 12 o'clock reading is way off at -0.07mm, but based on the shim test showing that part of the table is about 0.04mm low it maybe means the column and head are now pretty well trammed.

At least… I think. I may be fooling myself.

Not really sure what to do about the table though. Short of having the table ground (or attempting scraping it); neither of which kit or skill I posses. The vise I have will be bolted down using the tee slot nearer the front of the table, so maybe it won't affect things.

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