Help with drill-Mill conversion

[Ross77]

You could try adjusting the tension of the base mounting bolts; on a small machine like yours it might flex the post enough to correct the tram. Are the semi circles left by the cutter the same side when machining left to right and right to left? If the side swaps (i.e. the cutter is only cutting on the leading edge, then it could be the whole machine is flexing with the cutting load) lighter finishing cuts should fix it.

cheers didnt think of adjusting the pillar I'll have to check the cutting again to see if its flexing, before i go adjusting anything

BTW the correct way to test the tram is with a DTI mounted on arm a few inched away from the chuck, so it can be rotated aroung the table (use a parallel between the table and the dti to even out irregularities in the table surface)

I'll try that then, I've seen the dual gauge ones and always asumed you need both gauges to cancel the error, Duh..

The bottom of the groove looks like something has come loose in the tool chucking.

I think thats from when i tested the repeatability on the z, it produced a different cutter pattern for half the length but is the same depth.

I think you have other things to fix before you start worrying about tram :naughty:

Im sure your right, :cry: I was just so happy it was finally working. the other point is that I only have the single phase motor running at 1:1 so the cutter might not be quick enough.

[Robin Hewitt]

I only have the single phase motor running at 1:1 so the cutter might not be quick enough.

Or, maybe, too fast

Irving may disagree with this next bit :naughty:

There are published tables for cutting speeds but there are also tables for chip loadings. If you go for the official cutting speed the feed rates have to increase in proportion to keep the chip removal rate and up goes the side loading.

I simply don't have enough iron in my round column mill to hold against the side loading and smaller tools don't have enough meat to avoid bending. I reduce the revs and feed rates dramatically, I may be wrong but it works for me.

Get it wrong and first the tool digs in removing too much, then it rubs for a bit before the next dig in. Surface finish goes to pot.

When a tool starts to rub, rather than cut, it introduces a bending force. You can go around the finishing cut until the cows come home without fetching it to size. Increase the hole cut size to get past the rub and Whammo, you've cut oversize.

The trick is to rough out and leave an even excess all the way round the job then get the revs and feeds right on the finishing pass. Ignore the tables, find out what works on your machine. Even then the problems may come back when you change direction.

The routers of aluminium cut uphill, but they are usually making pretties rather than working to tolerance.

The millers of aluminium have a lot more rigidity in the system so they have can afford to cut downhill, meaning the tool shies away from the finished size rather than in to it. This does mean removing the backlash. If you compensate for backlash in the software you can't afford any side loading on the tool which can move the slides, a severe restriction on feed rates, and hence, spindle revs.