Reduce DP RPM by changing pulleys?

[Gil LaCroix]

I have a Craftsman 13in DP that I'd love to replace. However, I'm having a hard time rationalizing the change...would rather spend the money on some Festool toys!

My main problem is the DP only goes down to 500 RPM. I'd like it to go down as low as 250. It has two 5 step pulleys. Has anyone replaced the pulleys in a similar DP to change the available RPMs? If so, any problems?

Thanks...

[Wilbur Pan]

I haven't changed the pulleys on a drill press, but I did change the pulley wheels on my bandsaw to change the blade speed. It isn't that hard. All you have to do is calculate the correct pulley diameter ratio to get you to 250 RPM. And, if you can't get it exactly 250 RPM, remember that close is good enough.

[Curt Harms]

Hi Gil

I have a similar setup-Delta benchtop radial drill press with 550 RPM the lowest speed. One day I think I'm going to pursue this route:
http://www.factorymation.com/s.nl;jsessionid=ac112b321f43e6c2413d118d4203a50fde e9d8a92185.e3eSc38TaNqNe34Pa38Ta38PbNj0?sc=2&category=13
then scare up a small 3 phase motor. I've heard that used small 3 phase motors are available for cheap. This route may not be as inexpensive as replacing pulleys, but it's a lot more flexible and seems like it'd be SO COOL:). Infinitely variable speed up to a certain maximum, Programmable acceleration and deceleration and reversing. Another issue to consider that I haven't researched is the availability of different sized step pulleys and getting to the correct bore size. Drill presses that have low speeds usually are 12 speed and use a sort of jack shaft arrangement between the motor and quill. Good luck with whatever You decide.

Curt

I have a Craftsman 13in DP that I'd love to replace. However, I'm having a hard time rationalizing the change...would rather spend the money on some Festool toys!

My main problem is the DP only goes down to 500 RPM. I'd like it to go down as low as 250. It has two 5 step pulleys. Has anyone replaced the pulleys in a similar DP to change the available RPMs? If so, any problems?

Thanks...

[Chris Padilla]

The Delta 17-965 16 1/2" DP has multiple pulleys to get its variable speeds. I wonder if you could pick up the two "pulley stacks" it uses and put them in the CMan? Just thinking outloud here.

[Jeffrey Makiel]

A couple of thoughts...

You have to change both step pulleys such that they are identical or you will have different size belts for each speed set up. If your drill press uses an intermediate pulley, it too will have to be changed and be identical.

To achieve a lower speed that is twice as low as what you currently have, the largest diameter step on the quill pulley, and intermediate pulley if you have one, will need to be increased. This is because the smallest diameter step on the motor pulley (and intermediate pulley) may not be made any smaller and continue to handle the torque. That is, belt slip could occur when using something like a fly cutter.

Having said that, it may be difficult to find step pulleys that meet your need of diameter range, shaft hole size and belt size. Also, the pulley diameter may increase so much such that it won't physically fit under the belt hood.

Some things seem simple, but often prove difficult in execution.

Good luck...Jeff :)

[Gil LaCroix]

Thanks to everyone for the ideas...

The DP has two identical 5 step pulleys. In checking sources for step pulleys, the only ones I've seen are 2, 3, 4, 5, 6in in dia. Same as in the DP. No help, unless I find different sizes.

The key to getting lower speeds seems to be the DPs with 3 pulleys.

[Larry Fox]

The Delta 17-965 16 1/2" DP has multiple pulleys to get its variable speeds. I wonder if you could pick up the two "pulley stacks" it uses and put them in the CMan? Just thinking outloud here.

Chris - you mean three, correct? I have the Delta 17-965 and it has three (and it is a pita to change speeds on btw).

[Chris Padilla]

Yes, meant 3 and yes, it's a PITA to change speeds but at least you can. I just didn't want to fork out an extra $400 to get the "easy-to-change-speeds-on" Delta DP...I forget the model number.

[glenn bradley]

Yes, meant 3 and yes, it's a PITA to change speeds but at least you can. I just didn't want to fork out an extra $400 to get the "easy-to-change-speeds-on" Delta DP...I forget the model number.


This is one of those things that may eventually bother me I guess. I just don't find it that big of a deal to move the belts around on the DP. Now, mine stands where I can completely walk around it and maybe that contributes. I know there are other tasks I hate simply because of the 'dance' I have to go through to do them.

[JayStPeter]

If you have a 3600 RPM motor, maybe you can replace it with an 1800 RPM one off e-bay. It would half all your speeds.
I had considered using a 3-ph motor and VFD and eliminating the 3rd pulley from my DP. But, since I really don't like the DP itself all that much, maybe the next one.
Mine almost always sits on the lowest speed setting. Most small bits will drill OK at a lower speed, but bigger bits at a higher speed ... not so much. I have to be drilling lots of holes to bother to speed it up.

[John Bush]

I have a 15 1/2" Heavy Duty (?) Craftsman DP that has two pulleys that are aluminum, are shaped like steep sided cones, have 12 speeds/grooves that are narrow~~1/8 to 3/16 wide, and the belt is the same width. It is very easy to change speeds; there is a tension release lever on the motor mount, but the lowest speed still seems to fast for some procedure, i.e., using a circle cutter, or drilling metal. I haven't gone higher than the 4th groove, and that was for sanding with a small drum. I really like the drill press, but would like to slow it down a little more. I think the lowest speed s ~250rpm. I'll check tonight. I quess the point is there are two pulley systems with 12 speeds for Craftsman DPs and Ill see if the speeds are listed on the machine tonight.

[Jeffrey Makiel]

When I change my belts, my fingers are black. Then I have to leave the room to wash my hands or risk marking the material I'm working on. I've wiped everything off with paint thinner but the black dusty grease comes back.

Perhaps I need to change the belts. They're about 20 years old.

I like the thought of dialing in the speed on a brandy new variable speed drill press. But I can't justify it due to some hygiene requirements. Now, if the darn thing happened to break?! ;)

-Jeff :)

[Larry Fox]

Yes, meant 3 and yes, it's a PITA to change speeds but at least you can. I just didn't want to fork out an extra $400 to get the "easy-to-change-speeds-on" Delta DP...I forget the model number.

Agreed - I was in the same boat when I bought mine and I came to the same conclusion.

[David G Baker]

My father was a machinist. On his drill press he added a pulley on top of the drive pulley and another on the chuck pulley. The pulleys slowed the chuck's RPM to under 300 RPM. He worked a lot with stainless steel and needed the slower speed. I don't think the pulleys were fastened to the pulley shafts but were bolted onto the top pulleys. I think he had to raise the pulley cover a little to clear the pulleys.

[Rod Sheridan]

The one issue not discussed is torque.

If you use a pulley or gear reducer to change a motor speed, you get an inversely proportional change in torque.

This a great advantage in using larger diameter cutters such as fly cutters, forstner bits etc.

Using a variable speed drive such as an inverter type, results in the same torque at lower speeds, so it's not a good application for wide speed change ratios in drilling applications. (That's why mills and drill presses used variable ratio pulleys coupled with gearboxes in some cases.)

Regards, Rod.

[Al Willits]

If your finding the majority of your drilling is done at slower speeds, I think Jay hit it with the slower speed motor, prob easier than finding a pulley set I'd think.

Al

[Curt Harms]

I hadn't know that. Thanks.

Curt

The one issue not discussed is torque.

If you use a pulley or gear reducer to change a motor speed, you get an inversely proportional change in torque.

This a great advantage in using larger diameter cutters such as fly cutters, forstner bits etc.

Using a variable speed drive such as an inverter type, results in the same torque at lower speeds, so it's not a good application for wide speed change ratios in drilling applications. (That's why mills and drill presses used variable ratio pulleys coupled with gearboxes in some cases.)

Regards, Rod.

[Eric Haycraft]

If you are real adventurous, you could try this: (A CVT transmission)
http://www.mie.utoronto.ca/staff/projects/cleghorn/Research/mmo4.html#cooliris

[Gil LaCroix]

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[Gil LaCroix]

The motor is 1750 RPM. Based on all the responses, I think it's time for a new DP. Thanks to everyone...

[Alan Schaffter]

I tinker alot so am drilling wood one minute and metal the next- but I hardly ever changed speeds since it was such a pain to move the belts on my three pulley Delta DP. My solution was to change the motor to 3 phase and add a VFD. I also increased the motor hp so the loss of torque wouldn't be such an issue. I added a tach so I could see the RPM.

VFD hanging off the back of the DP

http://www.ncwoodworker.net/pp/data/500/DP-8.JPG

The small toggle switch starts the DP motor turning; the knob controls the RPM. The original Delta plastic switch housing made for a neat installation. (Here is a link to the full thread (http://www.ncwoodworker.net/forums/showthread.php?t=6189&highlight=drill+press) with more pics about my installation)

http://www.ncwoodworker.net/pp/data/500/DP-7.JPG

[Jeffrey Makiel]

Alan...Wow! You're really into it!
-Jeff :)

[Rod Sheridan]

Very nice Allan, the tachometer installation looks very nice, and I liked the receptacle installation for the power cube in the belt area.

I went the other route and purchased another drill press for metal, although I like the VFD installatio you did very much.

Regards, Rod.