Well, since I posted that, and didn't get a reply until now, I've since found some motor drivers that are probably even better for about $18 a channel at http://www.futurlec.com
. The SMCCV2. Ready made cards, just mount, move the input jumpers, and cable them all together 3 to the cable. They also have a dual 8255 board, (PCI8255) giving 72 lines of I/O for around $75, also with that same 34 pin IDC header for a connector. They all daisy-chain on a hunk of 34 pin floppy cable so that you can select on the individual motor driver board whether it responds to portA, portB or portC of the particular 8255 you are plugged into on the pci card.
Coupled with a $16 5/+12/-12 volt (#TMO2PWS4574) with independant ground for the 5 volts psu from Herbach & Rademan, and a handfull of their 24 volt 1 degree, 23 oz/inch steppers (TM93MTR2344), I'm down to doing the software, and actually hooking the motors up to the handwheels on the mill.
I have shaft couplings machined for the motors, but I'm still mulling over how best to actually mount the motors and mate the shaft couplings to the hand-wheels. Probably by cutting little pieces of steel out and rewelding them into the finished product with my mig welder. I'm still designing that part as I'd like to be able to pull the motors out of engagement with the wheels, and then let them hinge down, or to one side and out of the way. Its somewhat complicated by the fact that the bearing houseing the mills drive shaft can enter the base casting by about 1.020" in both the x and y directions and that makes the motor mount shaping a bit of a problem unless you can weld, or have a metal brake able to do 14 gauge steel. I don't have a brake, darnit. Nor a sheer able to handle 14 gauge steel, so that will exersize my 70 year old arthritic joints a bit cutting all that out unless I do that on the mill too, slow though.
But I'd imagine thats a bit hard on one of those dremel 1/8" solid carbide bits unless I can rig continuous cutting oil to it. I've also found that Bosch makes a solid carbide router bit, 1/4" upcut spiral, that can toss alu swarf all over the place, limited only by the puny power in the mill head itself. About a $20 bill at Lowes. I've carved up a pound or so of alu with it so far and no sign of dulling yet. Keeping it wet with oil to seal out the oxygen no doubt helps, as does cutting shallow but rapidly to reduce the time for the oxide film to form as the fresh alu is exposed by the cut.
The motors I have, are 8 wire motors, so I can do them as 12 volters by paralleling the windings that would normally be driven one at a time, and use the pwm current limiters built into the driver H-bridge chips to control the heat, still banging them with about 30 volts at the turnon point. So I should have well over a kilohertz in stepping frequency while maintaining decent torque.
Now if I can interface that dual 8255 card to linuxCNC for the software frontend, using some of the sample code that came with the driver boards, I should be home free by the time the snow flies here in WV, USA.
Or so it says here, but the pci card has not arrived yet. And I am going to argue with my card issuer, the prices on the futurlec web page are in USD, but MC is charging me approximately a 10% premium for the USD->AUD translation. So beware of your card if you order from futurlec. However, the fabrication quality looks very well done and I'm impressed for the about $18 they cost.
Thanks for the reply.
I may be back with more questions if I hit software problems, but beware, there is no M$ software allowed in this house.