Well, I just gave the motor the old "smoke & flames" test. It runs! Thanks for all the good advice. It seems like a great motor.
The VFD I am using is a rather large-cased Lancer GPD 402 (rated at 3/4HP, same as the motor). The VFD was new old stock when I bought it on eBay a year or two ago, perhaps as much as 15 years old. It is primitive enough to require DIP switch settings to program it’s few functions. It seems to work quite well, though. The motor is a little noisy with harmonics at some speeds, but not bad. I have the VFD set to run from 5Hz to 120Hz, it’s maximum range. 120Hz seemed reasonable for a six-pole motor, since it's only going 2400RPM at 120Hz. Wow, that six-pole motor spindle turns slowly at 5Hz. The motor label says nothing about being VFD rated, so I don’t know how long I can run that slowly without overheating. The VFD can be programmed to run the motor at 50%, 100% or 150% of normal torque at low speeds. I’ll leave it at 50% for now, just to be safe.
The drill press I have this setup on is a Taiwan-made Jet brand, about 15 years old. It had a 1/2HP single-phase motor on it originally. It was enough power most of the time, except when running a 5/8” drill though some heavy-wall box-section steel tubing, when it would occasionally stall. I realize that I’ll only get the full 3/4HP out of the new motor when the VFD is set at 60Hz.
The original setup had step pulleys on both the motor and spindle, and an intermediate step pulley between, giving 16 speeds. This was OK, but changing the position of the two belts could be a pain, and I never seemed to get just the speed I wanted. Also, at higher spindle speeds, the whole drill press would shake quite vigorously. I traced this to a sloppy pivot point on the intermediate pulley swivel.
With the new motor/VFD, I removed the intermediate pulley, and flipped the motor pulley top-to-bottom. This gives direct drive between the motor and spindle pulleys. This still allows four speed ranges, with a fifth range to be added when another larger single pulley gets added on top of the stepped motor pulley. The extra pulley will be needed to get spindle speeds as high or higher than I got with the original setup. I wanted the six-pole motor so I could run very slow spindle speeds for tapping, reaming, etc. Is tapping practical in a drill press? The VFD can be set to reverse quite quickly, and it has a separate switch for direction control.
I have a cheap DRO that I also bought on eBay:
It will be mounted to the front of the head casting. It is a bit long, though, and will protrude up into the spindle pulley area. Can it just be shortened, or is there something electrical in the “bar” that would be harmed when I saw the top end of the bar off?
I will probably just use a stainless hose clamp around the quill to mount a block. The bracket on the bottom of the DRO’s “bar” will be attached to the block, and the “slider” portion of the DRO will be attached to a bracket on the head casting.
I’d also like to install a digital tachometer. Any ideas on a cheap, easy way to do this? I could not find any good deals on a true industrial tachometer, with optical or magnetic pick-up. All I could think of was to use a magnetic-pickup bicycle speedometer. I determined that if the correct wheel diameter was programmed into the speedometer, the reading in MPH would actually correspond to RPM. For example, 122.5MPH would mean 1,225RPM.
Thanks,
Darron
[This message has been edited by darronb (edited 08-03-2004).]