Slowing Drill Press RPM's

[Jake M]

View attachment 425225
This is just "mocked" up, the pulley on the motor is just sitting on the shaft, not all the way down

The first thing that I'm seeing is that you appear to have four speeds on the spindle, four speeds on the idler, and three on the motor. That screams to me that the motor and motor pulley got changed at the same time. Part of the "magic" of these stacked pulleys is that they're a specific size in relation to each other, so the tensioner comes out right in any speed. That might be an issue.

Looking at the available speeds you have, I would suspect that if you have the motor pulley mounted high, with the smallest pulley driving the largest idler pulley, (highest belt position) and the smallest idler pulley driving the largest spindle pulley, (lowest belt position) you "should" be at or about a hundred RPM. If you don't have the actual RPM nailed down yet, you know the RPM of the motor- Put the belts on the slowest speed, sharpie mark the spindle and the motor pulleys, and turn the motor pulley by hand, and count the motor rotations per one spindle rotation to get an approximate ratio. Knowing what speed you have right now might be key information, as if you're already in the hundred RPM area (I'm visually estimating), or even in the sub 200 RPM area, I think any big upgrades are going to be well past the point of diminishing returns.

Not to knock down a project to build exactly what you want. If that's the point and the purpose, then heck yeah, all in. But if the purpose is to make holes, and you're under 200 RPMs with a horsepower and a half..... You can do a lot with that.

 

[Weldingrod1]

I used a 900 RPM motor ony Craftsman drill press...

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[slowneasy]

Okay, I must not be understanding/inputting the correct numbers/measurements. Using the above pulley RPM calculator, on the smallest motor pulley and largest on the spindle, it says the RPM is 118. hmmm

 

[intrepid]

Here is another easy option if you have the room.

 

[slowneasy]

Here is another easy option if you have the room.

whether I have the room or not, that is ingenious! I really like that....now why can't I think of these kinds of setups

 

[slowneasy]

screams to me that the motor and motor pulley got changed

My thoughts exactly but in this case, I don't think it was a bad thing (yet)

so the tensioner comes out right in any speed

How would I know if it is correct or not? And if I could find a stepped cone pulley that had smaller/larger sizes than what is on it now, would it automatically work or not?

belts on the slowest speed, sharpie mark the spindle and the motor pulleys, and turn the motor pulley by hand, and count the motor rotations per one spindle rotation to get an approximate ratio

~1 turn (on the spindle) to 10.5 turns (on the motor). So 1:10.5?

 

[C-Bag]

Here is another easy option if you have the room.

I don’t know about easy, but I’ve never seen that. I’ve been wracking my brain to figure out how to slow my UniDrill which has a Reeves drive and 24” radial arm which severely limits the motor size. The motor needs to be very short to clear the arm and the slowest it goes is 450rpm.
thanks for posting this.

 

[slowneasy]

Guys, if I'm putting these measurements/numbers into these pulley calculations correctly, I may not need to do anything to make this thing spin any slower...... In this case, I hope I'm not wrong

 

[Charles scozzari]

I would consider swapping over to a treadmill 2hp dc motor and rheostat. Plug and play with plenty of torque. Look online the pricing is reasonable.

 

[rwm]

I should also add- having pulley reduction is great, but the main thing I like about my drill press is infinitely variable speed on the fly. This makes if very easy to dial in the chip for any size drill and any material with minimal effort. Changing pulleys is painfully cumbersome and I always found myself avoiding it. The sewing servo motor goes all the way up to 4000 rpm so the pulley reduction that is in place already multiplies the torque considerably.