Help with drill-Mill conversion

**Robin Hewitt** · 05-11-2009

Originally Posted by Ross77

Glad you found it funny.

I'm £50-60 out of pocket now to replace it tho

I've done worse, not on the large hadron collider scale perhaps, but whaddya do? Personally I remind myself that it's business and in business you always start from where you are now.

OTOH, being business I do get to buy the cloud of smoke pre-tax and reclaim the VAT :whistling:

I understand your pain :nope:

**Ross77** · 13-03-2010

Seems like ages since the last post but finally managed to find some workshop time and have made quite a bit of progress. bolted the headstock to clamping collar, fitted new bearings to the spindle and modified the belt guards. just need a new belt and stepper drivers and it should be good to go.....

For now I have decided to use the original 1 phase motor as a test. I think it will be better to just get it working and then upgrade parts if needed.

I've also been wondering if I should take off the steppers and refit the hand wheels so I can check that it works as a manual mill. anybody agree?

**Ross77** · 23-03-2010

Nearly there, should be making chips at the weekend, :dance:

For the sake of my sanity and desire to get this working I've put the homemade drives on hold and splashed out on some PM542's from Gary. very nice drives no buzzing or crackling like the other ones.

Just need to fit the limit switches and get used to mach 3 now.

**BillTodd** · 24-03-2010

Look's nice and purposeful :)

Love the drill-table monitor stand :LOL:

**Ross77** · 24-03-2010

Love the drill-table monitor stand :LOL:

yeah I like it

. its got to be one of the most over engineered monitor stand

**Ross77** · 28-03-2010

:dance::dance::dance::dance:It works..............not finnished by any means but milling Al under Mach 3 control...

Its happy cutting 0.5mm deep in Al and seems to have a 0.02mm resolution (probably change when I cut a bigger test piece)

the surface finnish is quite good, not very good pics tho. I think the mill is a little out of tram (if thats the word) the cutter is leaving small ridged as if each pass is sligtly semi-circular.

Is there an easy way to fix this? as I can only think of shiming the X-Y table but that will be a nightmare.

**BillTodd** · 29-03-2010

Is there an easy way to fix this? as I can only think of shiming the X-Y table but that will be a nightmare.

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.

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)

**Robin Hewitt** · 29-03-2010

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

The sides of the pocket look like a tool which can't decide if it is rubbing or cutting. Maybe a tool cutting uphill that is flexing to remove the allowance for the next pass.

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

Also 0.5mm sounds awfully light.

**Ross77** · 29-03-2010

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** · 30-03-2010

Originally Posted by Ross77

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.