The Stovebolt Site Forums The Shop Area The Tool Chest Modified my drill press!

Not necessarily new, but definitely "modified"! For a lot of years, I've been getting by with an old drill press I rescued from the graveyard, better known as ""School Surplus" where worn out, or obsolete equipment goes to die. It was retired from one of the many woodworking shops in the city school system that got closed down when the school board bean counters and legal beagles got afraid that Little Johnny might get a splinter in his finger, causing some sleazeball ambulance chaser to file suit for "pain and suffering"! It's a good-quality machine, but it only had four speeds, all too fast for metal working. A couple of months ago, the motor finally bit the dust. I wonder if drilling all those 3/4" holes in a piece of steel with a machine with a 1/2" capacity chuck had anything to do with that?

Anyhoo, I'd been threatening to add a jackshaft and another set of speed-change pulleys for several years, and this situation simply got me off my butt and put me to work. I ordered another pulley and some ball bearings from Ebay, and made several items necessary to put an intermediate spindle in the center post of the press. With two short belts replacing the long one, plus a belt-tensioner idler, I now have a 12-speed drill press. But- - - -like Paul Harvey used to say- - - -"Here's the rest of the story". The replacement motor I bought has a shaft coming out of both ends. By modifying the motor mount plate, I can add another motor and a set of 3:1 speed change pulleys to slow things WAAAAYY down. The main motor becomes an idler when the low-speed motor is running. I need to fabricate a drive pulley with a one-way Sprag clutch in it so the low-speed motor doesn't get driven at 3 times the speed of the main motor, but that's a fairly simple modification on a 6" pulley hub. Once that one arrives and I do a little more machining, I'll have a 24-speed drill press! (Better known as a light-duty milling machine!)

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Fun and games- - - -I love taking somebody else's junk and making it work better than new!
Jerry

Nice work Hotrod!!

I agree. Nice work!!

Very nice. Its amazing what ingenuity can accomplish when coupled with ability.

You made me look at my inherited CTT and I see it has a 9/16 dia hole cast in the head. It's apparently all ready to to receive a center post. Plus, I have a brand new tread mill motor looking for a new purpose, I'll have to check it's hp output at low rpm now. Great idea man, thanks!

Outstanding work! Fantastic platform to tinker with too!!!

Caso, both motors on mine are 1/2 HP, 1725 RPM. On the low-speed application, I'm pretty sure a 1/3 HP motor would be sufficient because of the 3:1 speed reduction involved requires less power. The speed ratio is figured by dividing pulley diameters- - - -mine is a 2" pulley driving a 6" pulley. I'm working on a one-way clutch hub for the low speed motor so it won't get over-revved when the high speed motor is running. The part that allows that to happen is called a "Sprag clutch", and several of them are available on Ebay with different torque capacities. I'm going to machine out a housing for the clutch that will be attached to the center of the 6" pulley that is attached to the lower shaft of the high speed motor. It will allow the low speed motor to drive the press, but the pulley will freewheel when the high speed motor is running. The other option would be to simply remove the belt from the low-speed motor when it won't be needed.
Jerry

Jerry, why not just pop the belt on and off when you need (and don't need) the low speed motor?

Grigg

HL, I took a peek at my treadmill motor and its rated 2.5 hp... maybe I'll use it somewhere else as that seems a bit over kill. Still, I really like how its designed to run at variable speeds. What do you think, Kill it or over kill it?

Nobody says you have to run it wide open- - - -if the motor can develop sufficient torque at the lower speeds to power the drill press, I'd definitely consider using it. That would be good to miminize the number of speed-change pulleys the setup would require, since a variety of drill bit speeds can be had by simply varying the motor speed.
Jerry

I'm somewhat lazy at times- - - -I prefer to flip a switch to get low speed, rather than fumble with a belt. I'm well into designing and building the one-way clutch, which even includes a Torrington-type flat needle bearing between the parts of the low-speed pulley hub in addition to the Sprag clutch.
Jerry

If you put your mind to it I wouldn't be surprised if you got that drill press to be reversible

Too cool.

Yep, that's possible, but those lefthanded drill bits are expensive!

Jerry

Nice job! I bought a Delta floor stand model back in the 80's and got a cross vice from Harbour frieght( had to get it in the mail back then) and I have done a lot of mill work with it, I build flintlocks and work on old single shot rifles as well as my autos. You can realy do some good work if you take your time. Good luck and have some fun. Steve

I'm waiting on one needle bearing to be able to complete the one-way clutch for the low speed system. The upper 12 speeds work great. The "California" eBay address for the bearing turned out to be quite a bit west- - - -like China!

I build custom rifles, flintlock and centerfire types, so the press will see a lot of sight dovetail milling jobs, etc. I've also got two variable-speed Bridgeport mills in storage, waiting for a few final touches to get done on the shop before I put them into operation.
Jerry

Hi Jerry,

This has turned into a good thread. Thanks much.

Would you be willing to give some details of the center pulley shaft in the drill press post? Did you machine an insert? Bearings? I don't have the capacity for machining, but I still love to get ideas on how others have done things.

I follow the OWWM (old wood working machines) forum quite a bit.
http://owwm.org/
Many of the guys and gals on that forum buy their new bearings from Accurate Bearing Company in Addison, Illinois. They provide great service for the hobbyist. I have no connection other than being a satisfied customer.

Jerry, I knew we had something in common. I display at the Md. Arms Collecotors show every March around St. Pattys day. Said to be the biggest on the east coast. Over a Thousand tables and people from all over the world. I took an award this year for my slant breech sharps display. I know it's aways from TN. But its worth the visit. I build alot of things to because I can't get them. Is'nt that what they did back in the day? Steve

Sure, no problem! I ordered a piece of solid aluminum billet from Ebay, just a few thousandths larger than the inside diameter of the hole in the main post of tthe drill press and made it about 3" long between the bearings. I machined it to be a close slip fit into the post, then drilled and tapped the post for a couple of Allen head setscrews to keep it in place.

Next step- - - -center-drill the billet about 1/8" larger than the shaft I intended to run, (5/8") to match the ID of the 4-step pulley which I also bought on Ebay. I bought two 5/8" ID sealed ball bearings (Ebay again!) and counterbored the ends of the billet to be a snug slip fit for the OD of the bearings. A 5/8" shaft collar on each end secures the bearings into the counterbores, and a couple of drops of green LocTite keeps the outside races of the bearings from spinning in the aluminum. The shaft and support is secured into the post with the setscrews, and the pulley is installed in the proper direction to allow four different spindle speeds by moving the belt up and down. a belt about 1" longer than the pulley spacing is used, and the spring-loaded idler tightens it so it can pull without slippage. A second short belt goes from the motor to the center pulley. For every pulley position of the belt from the drive motor, there's 3 remaining pulley sheaves from the idler to the spindle, resulting in 12 speed options total.

When I get the low-speed motor into operation with the 1-way drive, there will be a total of 24 speeds available. The high-speed motor becomes an idler shaft when the low-speed motor is pulling. The Sprag clutch prevents the low speed motor from overspeeding when the main motor is the source of power.
Jerry

Question, how would you find the RPM's at the chuck so you know what speed its turning?

Pulley diameters determine RPM, so it would be necessary to do a little math. The motor turns at 1725 RPM, so you'd need to measure the diameter of the pulley at the motor, and calculate the speed change up or down for the idler, then do the same thing for the spindle pulley. It would give a good calculator a workout to get specific chuck speeds. I just sort of eyeball the speed of the drill bit, sanding drum, milling cutter, or other accessory, and adjust the speed up or down for the best cutting speed. Generally, the bigger the hole, the slower the speed needs to be. Milling cutters have a fairly narrow speed range where they cut effectively, and it's important not to overdo it on the depth of cut. I'd rather make several shallow cuts with a fast-turning cutter than try to hog out a big cut at low speed in one pass. It's also important to have the workpiece clamped down securely. Getting launched across the shop can do some nasty things to a project!
Jerry

You could also use a hand held tachometer or revolution counter to check actual speeds.
I'm with Jerry though, just look at the task at hand and judge if it looks fast or slow enough, adjust from there.

Grigg

I found this handy for these sorts of questions about belt speeds and rpm's

Handy Pulley Calc

It works! I just finished the final assembly and wiring. Now I've got a toggle switch on the motor mount for the high/low speed selector, and the regular on/off switch on the front of the power head. The one-way clutch does its job, letting the low speed motor stop when the high speed one is running. A quick guesstimate on speed puts the lowest speed at around 100 RPM or a little less. I haven't done any heavy-duty drilling yet, but I did mill a key slot in the one-way clutch assembly a few days ago using one of the lower pulley speeds available with the original 12-speed setup. With the 12 slow speeds working, I should be able to do some serious big-hole drilling. I've got Silver & Deming drill bits up to 1 1/8" diameter for steel, and Forstner bits for drilling wood up to 2 1/4" or so.

Now I can concentrate on getting my table saw, jointer, two bandsaws, and a radial arm saw, plus another metal lathe and a Bridgeport mill in operation! The tire changer, wheel balancer, beadblaster, and hydraulic llft are next in line!
Jerry