Slowing Drill Press RPM's

[slowneasy]

Probably like most of us, we have drill presses that were more or less designed for drilling holes in wood. And so the RPM's are higher for this kind of use. However, most of us probably use them as much or more so for making holes in metal. And larger bits than say 1/2" require lower RPM's and >1" even s-l-o-w-e-r.
I picked up a vintage King brand drill press in decent condition but the slowest RPM handles 3/8" in steel okay. So I'm really looking hard at options to slow this (jet) motor down. And I'm not very good at this kind of thing (or much of anything really). It seems I have basically two options-
1) source parts for an add-on pulley with jack shaft and fabricate a mount
or
2) local a 3 Phase motor and VFD controller

I don't know anything about either. Advantages or Disadvantages of either. From what I've read (and don't know if true or not), on 1), the jack shaft needs to be the same diameter as the motor shaft? If true, why?
Also, an advantage of option 1) is that I have all the torque of the motor at lower(est) RPM's, yes?
On option 2) I may not have torque at the lower speeds?

What are you experiences and thoughts/recommendations?

 

[twhite]

Depending on your drill press you can add a set of reducer pulleys. I have an old Craftsman 150 that I made the reducer for. Works like a champ.
I can post a picture later if needed.


Cutting oil is my blood.

 

[aliva]

Cost wise a jack shaft would be cheaper than a VFD and a 3-phase motor. A VFD will give you variable speed control, but a proper sized pulley arrangement will get the rpm to you desired level. Concerning shaft diameter having to be the same as the motor I can't see why, other than maybe being able to handle the torque. You didn't mention if the drill press already has stepped pulleys to vary the rpm.
If you decide on the jack shaft option here's a site to help you with the rpm calculations.

Pulley Calculator. RPM, Belt Length, Belt-Surface Speed, Animated Diagrams - Metric

www.blocklayer.com

 

[great white]

My King 13” drill press will go down to 220 rpm:



it has three pulleys though. Might have a look at yours and see if a simple pulley swap might give you low enough rpms (spindle speed) for what you want to do.

Power wise, pulleys will be better. It allows you to run the motor full speed (ie: better cooling, better torque, etc) while still keeping your spindle speed low.

Some might comment that swapping belts on a pulley system is a PITB, but mine almost exclusively does metal work so I don’t change the spindle speed very often.

YMMV…..

 

[Jimsehr]

Could you find a motor with lower rpm? Both options below cost about the same? $159 bucks. I think I would GO wiTH anew motor for cutting metal.

 

[Bi11Hudson]

+1 on using a jack-shaft. It will be necessary to increase the reach of the pulley enclosure, but they are usually light sheet metal. You might find it advantagous to reinforce the area where the jackshaft is mounted. That depends on the construction of the OEM machine.

A while back(20+years) I needed a drill press with lower speed. My solution, while not entirely satisfactory, did get the job done. What I should have done was acquire a magnetic drill and build a stand to run it horizontally. Or dismantle the small tractor and use a regular drill press on the part. What I actually did was (heaven forbid) buy a Craftsman 17 inch floor model, find a piece of tubing for a short mast, and using "C" clamps hung it on the machine. It worked, with a few busted knuckles and considerable frustration.

Today, I have several drill presses, some are used on wood, some on metal. I ran into work that required a slower drill speed than even the big floor standing machine so acquired a Horrible Fright mini-mill to regulate the machine slow enough. It doesn't have near the torque of the full sized drill press, but does the work I need it for.

There are several disadvantages to using a 3 phase / VFD to get slower speed. An extra step (or two) of pulleys will provide the necessary speed reduction much better. And take much less engineering to fit to the machine. At the slow end of the belts, gear reduction may be advantagous. I include a document to make a geared speed reducer from automotive parts. It looks complex but is doable on a mini-lathe and Wally World drill press. Fitting it to a small drill press will take some finagling, it was first tried on a small lathe. But the ~3:1 reduction works fine and doesn't take much space. A possible solution. . .

 

[RJSakowski]

Probably like most of us, we have drill presses that were more or less designed for drilling holes in wood. And so the RPM's are higher for this kind of use. However, most of us probably use them as much or more so for making holes in metal. And larger bits than say 1/2" require lower RPM's and >1" even s-l-o-w-e-r.
I picked up a vintage King brand drill press in decent condition but the slowest RPM handles 3/8" in steel okay. So I'm really looking hard at options to slow this (jet) motor down. And I'm not very good at this kind of thing (or much of anything really). It seems I have basically two options-
1) source parts for an add-on pulley with jack shaft and fabricate a mount
or
2) local a 3 Phase motor and VFD controller

I don't know anything about either. Advantages or Disadvantages of either. From what I've read (and don't know if true or not), on 1), the jack shaft needs to be the same diameter as the motor shaft? If true, why?
Also, an advantage of option 1) is that I have all the torque of the motor at lower(est) RPM's, yes?
On option 2) I may not have torque at the lower speeds?

What are you experiences and thoughts/recommendations?

If you choose to use a jack shaft, keep in mind that you will have to flip the motor pulley. You might want to use the motor pulley on the jack shaft and a new cone pulley for the motor.

 

[slowneasy]

Thank you all for these ideas, this is half the fun (right?)!
This drill press is a 17" with a 1 1/2hp motor spinning a 24mm shaft. The motor tag (only tag/identification on this machine) states the RPM at 1730. The spindle is a 3MT. It has three pulleys, a three step cone on the motor(which as it is now, can not be flipped upside down; the small step in on the top), a four step intermediate in the middle and a four step on the spindle.
I do realize that going with a jack shaft pulley setup, that it will require either removal or modification of the belt cover but I am unsure if the jack shaft needs to be the same diameter as the motor shaft. Doesn't really matter to me, I just need to know and would like an understanding as to why?
I really want to avoid the three phase honestly simply because out of convenience of 110v outlets. So definitely leaning towards the jack shaft mounted pulley. But nothing is in stone yet.

 

[C-Bag]

Thank you all for these ideas, this is half the fun (right?)!
This drill press is a 17" with a 1 1/2hp motor spinning a 24mm shaft. The motor tag (only tag/identification on this machine) states the RPM at 1730. The spindle is a 3MT. It has three pulleys, a three step cone on the motor(which as it is now, can not be flipped upside down; the small step in on the top), a four step intermediate in the middle and a four step on the spindle.
I do realize that going with a jack shaft pulley setup, that it will require either removal or modification of the belt cover but I am unsure if the jack shaft needs to be the same diameter as the motor shaft. Doesn't really matter to me, I just need to know and would like an understanding as to why?
I really want to avoid the three phase honestly simply because out of convenience of 110v outlets. So definitely leaning towards the jack shaft mounted pulley. But nothing is in stone yet.

Hmm, you mention you already have a 3 pulley system, what is your lowest rpm now? Your best bet is just changing pulley’s as you are already as good as a jackshaft setup would be you just need the correct size pulleys.

 

[GeneT45]

Don't rule out a DC motor. A friend picked one, with controller (get one *with* a controller) off eBay for ~$50. He retrofited his small mill with it, but I don't see why the same wouldn't work for a drill press.

GsT

Edit: meant to mention that what he got was a treadmill motor.