I wonder if this modified VFD drill press gives up torque on the low end with big drills? I like the idea of doing this if you don't sacrifice torque on the low end. Maybe the answer is a bigger motor than stock so you don't lose low end torque.
Here's the link I forgot:
You normally get constant torque up to the rated RPM of the motor. If you slow the speed through gearing, you get the mechanical advantage, for example 10:1 gearbox, 1 ft lb in at 1750 RPM converts to 10 ft lb out at 175 RPM, less the losses for efficiency. With the equivalent on a VFD, you can slow it down to 6 Hz (+ slip comp) but you only get 1 ft lb out at 175 RPM. Seems like, on VFD applications, they size the motor for the torque needed, once you get the motor to rated HP, they become constant HP, as the RPM goes up, the available torque goes down.
RogerN
VFD conversion are pretty common on drill presses. The problem is many of the people who would most benefit from them don't have 230 in their home shop. That pretty much limits them to 1HP. There are some high speed motors and 110V VFDs for higher HP, but those motors really need to be turning over 8000 RPM in use. I have not seen a 110V-230V VFD that is larger than 1HP, and I've been looking. I do have a couple 230 circuits in my shop, but they are already in use. AC, welder, Hurco mill, and compressor.
If there was one that did 110-230 for 2HP they would probably be able to sell a bunch of them to folks with benchtop mill drills like the RF30/31 or the G0704/BF20. Heck, I'ld put one on my old RF30. I don't use it much just because its kind of a pain to change speeds all the time.
In my shop I have a drill press, a lathe, and a mill with 240v VFDs on them. On the SAME circuit. Because I will never be using more than one at a time. Even if I were to, the 15A circuit would easily handle the load (15 x 240 = 3.6kva; 4hp +-). The welder does have its own circuit for the much higher current.
Bob
I do have two items on my compressor circuit... well just one at the moment. Its got a plug for my table saw by the back overhead door, and a plug in the corner for the air compressor. Someday I'll have a big two stage air compressor to plug into it. LOL. Right now my 18-20 year old Campbell Hausfeld roll around is the shop compressor. LOL.
I can see me using the RF30 manual mill and the big CNC mill at the same time, and the compressor kicks on as needed. I suppose with some planning... I never use either of my two drill press, the noname mill drill, or the manual lathe all at the same time. LOL. In fact at the moment they are all plugged into the same work bench shop strip for that reason. Actually now that I think of it, I have probably been power feeding on the small lathe and drilled or tapped something really quick on one of the drill presses.
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