Need help with drill press motor

[TDKPE]

Poindexter,   love the photo.  BTW ,  the motor mount looks similar to the Craftsman 113 table saw mount on a saw I just rehabbed for a friend.

Resilient cradle.  Very useful for things you want to run smooth.  They also absorb torque to some degree, and you can see the motor twist on its mount when started.  Not a strong start in my case, as it's just a split phase motor, but strong enough for a DP.  I also left off the bottom bolts to make it easier to jump the belt.  It's been working that way for decades.

[kurt18947]

Resilient cradle.  Very useful for things you want to run smooth.  They also absorb torque to some degree, and you can see the motor twist on its mount when started.  Not a strong start in my case, as it's just a split phase motor, but strong enough for a DP.  I also left off the bottom bolts to make it easier to jump the belt.  It's been working that way for decades.

I have the descendant of that drill press, Delta name but Asian origin. My motor was/is okay but I wanted slower. The slowest in stock configuration was around 550 RPM which is too fast for large forstner bits, fly cutters and the like. I decided to get a new 3 phase 1/2 h.p motor (stock motor was labeled 1/3 h.p.) and VFD. The combination cost me just over $200. I wasn't able to reuse the motor's step pulley, the bore was an odd size, I think 15 mm. Because I wasn't worried about high end speed I just got a single groove pulley. My questionable calculations say lowest RPM is around 200-250 RPM, highest around 2200. That's with the motor 10 - 80 Hz (I think). It will run slower but torque really starts to drop off, I can easily stop the chuck by hand at 4 hz.

No shifting belts and as a nice bonus getting rid of the motor's step pulley got rid of an annoying vibration that was there since new. I'm pleased with the modification.

[TDKPE]

I have the descendant of that drill press, Delta name but Asian origin. My motor was/is okay but I wanted slower. The slowest in stock configuration was around 550 RPM which is too fast for large forstner bits, fly cutters and the like. I decided to get a new 3 phase 1/2 h.p motor (stock motor was labeled 1/3 h.p.) and VFD. The combination cost me just over $200. I wasn't able to reuse the motor's step pulley, the bore was an odd size, I think 15 mm. Because I wasn't worried about high end speed I just got a single groove pulley. My questionable calculations say lowest RPM is around 200-250 RPM, highest around 2200. That's with the motor 10 - 80 Hz (I think). It will run slower but torque really starts to drop off, I can easily stop the chuck by hand at 4 hz.

No shifting belts and as a nice bonus getting rid of the motor's step pulley got rid of an annoying vibration that was there since new. I'm pleased with the modification.

I did essentially the same thing with my old 1460 wood lathe, using a 1 hp motor and WEG VFD.  I use the step pulleys to select a working range, slow for larger work and fast for small work, but run it anywhere from 16 to 120 Hz.  The slow end I only use for checking for balance, so I can sneak up on a faster speed without the piece flying out, and the fastest I don't normally go to but it's there.  These small VFDs run in constant torque mode below 60 Hz, and constant power above (torque decreases with speed), which is why I went with an "oversized" motor - at 30 Hz, it's a 1/2 hp motor since torque is constant.  It does drop off eventually, but as I said, I don't actually work it that slow except for maybe some light, low speed sanding disc work.

I tried a 6-pole (1200 rpm) single-phase motor, but the bottom end was still too fast.  I'm very happy with how it works with the VFD.