Homemade low-speed drill press conversion.

[evintho]

I've been meaning to do this for awhile. Finally found the time today. It's amazing how simple this is to put together! Most have seen my DP before. Bought it off of CL for cheap and gave it a light restoration. It didn't come with the optional low-speed conversion. I decided to fab my own low-speed conversion 'cause most of my work is with metal.





Here's a chart from an original Craftsman w/low-speed conversion. I don't know how fast the direct drive is right off the motor but I know it's way too fast for my needs! I'm shooting for the 4th one down. 175 RPM.





If you can find an older Craftsman with the optional low-speed conversion, great! If not, these are the parts you'll need to convert it. In addition, you'll need access to a MIG welder. If you don't have a MIG, you probably know someone who can run a bead for you.



1 - 4 step, 3L pulley. Ordered mine through MSC. I think it was $20 w/corporate discount.

2- bronze flanged bushings. $1 each from Home Depot.

1 - 3" long 1/2" bolt.

1 - 1/2" flat washer (not shown).

1 - 1/2" Nylock nut.

1 - steel cap - homemade.

Closeup of the flanged bushings with dimensions and part #s.



You'll also need 2 belts (not shown). They need to be belts for fractional horsepower motors. The designation is 3L, to match the pulley. Any shop that repairs chainsaws, lawnmowers, etc. will have them. You'll need a 25" belt from the motor pulley to the intermediate pulley and a 29" belt from the intermediate pulley to the spindle pulley.

Now that you have all the parts, you need to cut a blank of 3/16" steel. I used a 2-1/2" holesaw to do the deed.



Next, measure about 3/8" back from the center of the pilot hole and centerpunch a mark. At this point, you'll need to weld up the pilot hole. Once it's welded and cleaned up, drill a 1/2" hole on your centerpunch mark. Insert the 1/2" bolt and weld it to the underside of the blank.



Now set the blank on top of the DP post. Line it up and tack it in. Check alignment and mock everything up to confirm all is good. You may have to jiggle the blank around or maybe even grind a bit off to get the proper tension on the belt. The spindle to intermediate pulley is not adjustable. So, once the blank is finished welded, that'll be your belt tension. If everything fits and the belts have good tension, de-mock it and finish weld the blank to the DP post.



Slip on a flanged bushing.......................



Slip on the pulley......................



Insert the top flanged bushing...................



Remount the motor and all the belts then install the 1/2" flat washer and the 1/2" Nylock nut. DO NOT snug the nut to the washer. You want the washer loose. As little up/down movement of the pulley as possible but don't tighten the nut down! The plastic inner coating will keep the nut in position.



Plug it in and fire it up.............you're done! Now I have a 175 RPM spindle speed. In addition, it's a multi-speed attachment so I can change spindle RPM's simply by moving the belts up or down the pulleys. This thing works great!!

 

[alan camby]

Whats up with the pink Wilton. Everything looked great until i saw that.

 

[A_Pmech]

Cool!

Those high speeds will come in handy too, when you need to drill a 1/32" hole in something.

 

[evintho]

Whats up with the pink Wilton. Everything looked great until i saw that.

It's not pink. That's the camera flash. Rustoleum Gloss Carnival Red.

 

[signcrafter]

That's some creative thinking there!

 

[alan camby]

Nice setup on the drill press.
Interesting way to adjust the belt tension. hopefully you don't have to adjust the front belt very often. If the belt stretches, guess you just have to replace it, doubt if that will be much of a problem though.

I am a little worried about the top bushing. Looks like it will be spinning on the threads of the bolt. Did you lube the ID of the bushings. Do the bushings have a tight fit in the aluminum pulley. If not, I would put some retaining compound on the OD of bushing to prevent it from spinning in the pulley.

 

[alan camby]

It's not pink. That's the camera flash. Rustoleum Gloss Carnival Red.

That looks better

 

[1steve]

Great idea, read NO.5 in your Operation Instructions. Your pulley is now an eccentric, simple belt adjustment just rotate column. Thanks for posting.

 

[alan camby]

I saw the instructions and understand the eccentric (reminds me of how the chain is tightened on a Honda ATV) but, it appears that the belt is tightened all the way.

 

[1steve]

I brought that up because the OP mentioned this in his post.........."Check alignment and mock everything up to confirm all is good. You may have to jiggle the blank around or maybe even grind a bit off to get the proper tension on the belt. The spindle to intermediate pulley is not adjustable. So, once the blank is finished welded, that'll be your belt tension."

 

[Outlawmws]

The basics are OK, but I see some potential issues:

The factory eccentrics were made to be able to turn them within the column; then lock it down. This was to allow the spindle to intermediate belt to be adjusted. In anything but that one position, you are likely to have adjustment issues. (Turing the post is not going to be a simple adjustment, as the head will wind up cocked to the base)

A bolt is not really the smooth ground surface a bushing needs for long wear. Expect that both the bolt and the bushings will wear faster than in usual use. (did you load them with some high pressure grease? they will need it.)


You may be better off long term making a second plate, making a new axle for the pulley for that plate, and making it so is pivots on the post you made (shortened somewhat), and letting it swing free and use that pivot motion and the motor to get both belts in tension. The middle pulley would then float on the fixed pin, and swing around it.

Use some ground 1/2" rod for the "axle" and center drill one end for a screw/washer set to keep the pulley from lifting off.

 

[balane]

I don't think I keep my power tool belts as tight as some of you. In fact, I would say my belts are slightly slack even. Definitely not tight like a car engine V-belt.

Now that I'm using link belts on everything adjustment is not even an issue. I just add or remove links until I get it where I like it. Never even have to loosen a bolt. I'm betting link belts would work great in your new three pulley system. And you get the added benefit of a little lesser vibration as well, if you aren't running your drill press a lot anyway.

 

[jtbinvalrico]

Slick setup. Have you run it up to the 10,000 rpm range yet? I thought mine was going take off and fly away when I did that.

 

[larry4406]

Interesting. The intermediate pulley is fixed to the top of the column via welding. Not familar with Craftsman, but this then precludes moving the drill press head down the column? Also, pivoting the head left to right around the column would seem to reduce the belt tension.

 

[jkherd]

I like that, I'll have to add that feature to my old Craftsman drill press.

 

[evintho]

Interesting. The intermediate pulley is fixed to the top of the column via welding. Not familar with Craftsman, but this then precludes moving the drill press head down the column? Also, pivoting the head left to right around the column would seem to reduce the belt tension.

The head can still slide up/down the column if I need to remove it, or whatever. For my needs I'll just raise the table. If I need to pivot the head a little, it shouldn't affect it too much. I have several belts I could swap to adjust the tension too.

I know this is far from perfect but it certainly works for me and what I intend to do. I'm sure I could have spent a lot of time engineering and building it so all bases were covered but I just wanted to devise a cheap, simple low-speed reduction setup that I could use to drill holes in my wishbones and axle, for now.

 

[thehazmatguy]

That's a really interesting set up. Turning the column for the belt tension isn't that big of deal, so that's pretty slick. Nice job!

 

[bagged89s10]

Nice job. I am going to build a similar setup in mine.

 

[kerrylbuxton]

I've been meaning to do this for awhile. Finally found the time today. It's amazing how simple this is to put together! Most have seen my DP before. Bought it off of CL for cheap and gave it a light restoration. It didn't come with the optional low-speed conversion. I decided to fab my own low-speed conversion 'cause most of my work is with metal.

Here's a chart from an original Craftsman w/low-speed conversion. I don't know how fast the direct drive is right off the motor but I know it's way too fast for my needs! I'm shooting for the 4th one down. 175 RPM.

If you can find an older Craftsman with the optional low-speed conversion, great! If not, these are the parts you'll need to convert it. In addition, you'll need access to a MIG welder. If you don't have a MIG, you probably know someone who can run a bead for you.

1 - 4 step, 3L pulley. Ordered mine through MSC. I think it was $20 w/corporate discount.

2- bronze flanged bushings. $1 each from Home Depot.

1 - 3" long 1/2" bolt.

1 - 1/2" flat washer (not shown).

1 - 1/2" Nylock nut.

1 - steel cap - homemade.

Closeup of the flanged bushings with dimensions and part #s.

You'll also need 2 belts (not shown). They need to be belts for fractional horsepower motors. The designation is 3L, to match the pulley. Any shop that repairs chainsaws, lawnmowers, etc. will have them. You'll need a 25" belt from the motor pulley to the intermediate pulley and a 29" belt from the intermediate pulley to the spindle pulley.

Now that you have all the parts, you need to cut a blank of 3/16" steel. I used a 2-1/2" holesaw to do the deed.

Next, measure about 3/8" back from the center of the pilot hole and centerpunch a mark. At this point, you'll need to weld up the pilot hole. Once it's welded and cleaned up, drill a 1/2" hole on your centerpunch mark. Insert the 1/2" bolt and weld it to the underside of the blank.

Now set the blank on top of the DP post. Line it up and tack it in. Check alignment and mock everything up to confirm all is good. You may have to jiggle the blank around or maybe even grind a bit off to get the proper tension on the belt. The spindle to intermediate pulley is not adjustable. So, once the blank is finished welded, that'll be your belt tension. If everything fits and the belts have good tension, de-mock it and finish weld the blank to the DP post.

Slip on a flanged bushing.......................

Slip on the pulley......................

Insert the top flanged bushing...................

Remount the motor and all the belts then install the 1/2" flat washer and the 1/2" Nylock nut. DO NOT snug the nut to the washer. You want the washer loose. As little up/down movement of the pulley as possible but don't tighten the nut down! The plastic inner coating will keep the nut in position.

Plug it in and fire it up.............you're done! Now I have a 175 RPM spindle speed. In addition, it's a multi-speed attachment so I can change spindle RPM's simply by moving the belts up or down the pulleys. This thing works great!!

I am going to use a 3" long steel plug to fit into the dp post and thought of using a shoulder bolt and carefully determine the length needed for the pulley and two bushings. Does the 1/2" washer between the nut and bushing ever spin?

 

[evintho]

Does the 1/2" washer between the nut and bushing ever spin?

Yes it does. I didn't want to crank down on the nut and cause the bushing to bind so I used a nylock nut. I tightened it down to where it was just snug then backed off 1/4 turn.

BTW, I use this all the time and have never had any issue!

 

[Keel]

nice..
Couldn't this have been done with a motor speed controller (foot pedal or knob) instead of machining a new pulley set?

 

[Packard V8]

nice..Couldn't this have been done with a motor speed controller (foot pedal or knob) instead of machining a new pulley set?

Short answer, no. Most fractional horsepower motors would lose too much power when slowed down with most simple motor speed controllers. Some won't work at all with them. That's why the dual belt pulley setup exists.

And yes, once one has used a VFD/3-phase setup, the slow speed center pulley would be for sale.

jack vines

 

[Outlawmws]

Short answer, no. Most fractional horsepower motors would lose too much power when slowed down with most simple motor speed controllers. Some won't work at all with them. That's why the dual belt pulley setup exists.

And yes, once one has used a VFD/3-phase setup, the slow speed center pulley would be for sale.

jack vines

This^^^!!!

you need an AD/DC class motor for those to work and as mentioned, you lose power.

And I would say MOST motors, not some, the HF foot controllers are intended for AC/DC tools like routers. not AC DPs.

I have a variable speed on a treadmill motor, and that works well for my DP, but at speed its also 2-1/2HP so can afford to give some up...

 

[exmaxima1]

I don't think I keep my power tool belts as tight as some of you. In fact, I would say my belts are slightly slack even. Definitely not tight like a car engine V-belt.

Now that I'm using link belts on everything adjustment is not even an issue. I just add or remove links until I get it where I like it. Never even have to loosen a bolt. I'm betting link belts would work great in your new three pulley system. And you get the added benefit of a little lesser vibration as well, if you aren't running your drill press a lot anyway.

I use a linked belt as well on my 3-pulley setup, but find that a notched belt works better for the smallest pulley diameters. The link belt is convenient for dialing in the right length, and is a bit quieter than a standard belt.

In the pic you see the third pulley I made for my Delta DP-225 (similar to DP-220) drill press. I used a standard pulley and bored the ends to fit ball bearings. It fits in the column in the customary fashion and rotates to tighten the belts--no need to rotate the entire column.

 

[Musicinabottle]

Whats up with the pink Wilton. Everything looked great until i saw that.

See, I never even saw it until you mention it. That look back just totally friggin blew it for me. Hopefully the explanation will smooth over the experience......

 

[Keel]

Short answer, no. Most fractional horsepower motors would lose too much power when slowed down with most simple motor speed controllers. Some won't work at all with them. That's why the dual belt pulley setup exists.

And yes, once one has used a VFD/3-phase setup, the slow speed center pulley would be for sale.

jack vines

Ok.... nice to know..

I may try a set of mountain bike gears and derailers. to have slow to mid speed drill press... 21 speeds. sounds like a plan.. with the ratchet type gear selectors that click the cable to that gear..
This way no need to lift top, loosen belt, swap pulleys, and tighten belt..
I have a cheap d/p to test this on.. before I'd try it on a keeper..

 

[Packard V8]

Interesting. When a solution to a common and long-standing problem, using readily available parts, is proposed, one must ask, "Why haven't we seen this before?" Please build it an report back.

Jack Vines

 

[Outlawmws]

The bike chain and sprocket is interesting as an idea, but there may be some issues with implementing it.


A DP has larger and smaller pulleys at each end; some smaller some larger than their mates at the other end. this is so the spindles speed can be faster or slower than the fixed motor speed.

A bike has a fairly large sprocket on the drive side, and comparatively smaller gear cluster at the driven end. so you can change speeds, but the drive side is always lower RPM's that the driven side. Unless you have a Gear cluster at each end, toy can't get the driven side slower than the drive side. Not saying this can't be done, but it will take some thinking.

Also, the bike chain is a fairly low speed drive in "surface feet per minute". Compare that to the belts on a motor going 1728 RPM on a 4-6" pulley. I'm not sure I woud want to be around a bike chain at those speeds?

 

[AnEv942]

Curious why an off the shelf intermediate pulley couldn't be adapted as an other option. Spindle pulley height?

$50, Already has bearings, swing arm, only single hole for the arm pivot required.

Center Pulley Assembly
For a 17" DP searspartsdirect.com/model-number 137.229171

 

[Outlawmws]

If the spacing and belt width match, it would work with some adaptation...

 

[Keel]

The bike chain and sprocket is interesting as an idea, but there may be some issues with implementing it.


A DP has larger and smaller pulleys at each end; some smaller some larger than their mates at the other end. this is so the spindles speed can be faster or slower than the fixed motor speed.

A bike has a fairly large sprocket on the drive side, not so on mountain bikesand comparatively smaller gear cluster at the driven end. so you can change speeds, but the drive side is always lower RPM's that the driven side. Unless you have a Gear cluster at each end, toy can't get the driven side slower than the drive side. Not saying this can't be done, but it will take some thinking.

Also, the bike chain is a fairly low speed drive in "surface feet per minute". Compare that to the belts on a motor going 1728 RPM on a 4-6" pulley. I'm not sure I woud want to be around a bike chain at those speeds?

As far as the bike chain.. and the speed.. the d/p has a cover over the pulley/belt set for a reason.. same reason you'd use one on a chain drive..

it's an idea.. Was throwing it out there.. Ideally, you'd be able to buy an optional low speed pulley set for your d/p.. as that be the simple answer..

 

[My Old Tools]

Curious why an off the shelf intermediate pulley couldn't be adapted as an other option. Spindle pulley height?

$50, Already has bearings, swing arm, only single hole for the arm pivot required.

Center Pulley Assembly
For a 17" DP searspartsdirect.com/model-number 137.229171

That swing arm is pretty slick when you think about it. When you tension the motor belt, you are also tensioning the drive belt. Solves the problem of the fixed pulley in the middle.

 

[PugetDude]

Curious why an off the shelf intermediate pulley couldn't be adapted as an other option. Spindle pulley height?

$50, Already has bearings, swing arm, only single hole for the arm pivot required.

Center Pulley Assembly
For a 17" DP searspartsdirect.com/model-number 137.229171

That is exactly how my 3o+ year old G-1200 Grizzly Drill Press works. Simple, quick speed changes, and still running with the original belts after thousands of holes.

 

[AnEv942]

Ya pretty much works like the eccentric mount of the Craftsman kit-splits the tension applied to one side-just easier to come by.

"Keel...as that be the simple answer"

Ya but not as fun as imagineering, executing and having it work like OP
however there is a member making slow speed sets for older DPs

 

[crguy]

I really don't like the idea of welding the plug to the top of the column for several reasons. There are better, and easier, ways to fab an intermediate pulley setup.

 

[Cruzan80]

Is anyone else thinking that the eccentric swing arm would be a great idea if you used a threading die to attach a bolt, and drilled a hole in the top cap? Then it could be removed from the pole, and still prevented from coming loose due to the bolts.

AnEv, can we get spacing and diameter information? Thanks.

 

[pfmg]

Nice job, I have been gathering parts to do something similar, just a different approach. Rogue fabrication sells a kit, im trying to copy their design. It's pretty slick.

 

[BFBOB]

I've posted about this before, but it's been a long time. This attachment solves the problem of belt tension- unscrew the handle at right and the arm holding the intermediate pulley out releases. make your changes, swing thehandle back out to tension, and screw back in to hold. The back view shows the double joint on the tensioner - nothing is spring loaded, so the tension is applied equally to both belts. This was a commercial product, but decades out of production. My BIL had one from way back. I was going to copy it- not that complicated a deal, but he discovered he had a second one and gave it to me.
One of the advantages to this is that it mounts on the motor mount so my radial drill press can still move the head without disturbing the adjustment. Wouldn't be hard to come up with a variation that would mount into (not weld into!) the center column.

 

[AnEv942]

Nice job, I have been gathering parts to do something similar, just a different approach. Rogue fabrication sells a kit, im trying to copy their design. It's pretty slick.

Thats holenuther ball game!
I have center pulley, 170 rpm- not going there but with 4:1 kit, that'd give me 42.5, jeesh...

 

[454ragtop]

Nice job, I have been gathering parts to do something similar, just a different approach. Rogue fabrication sells a kit, im trying to copy their design. It's pretty slick.

A few years back I picked up a Buffalo 14 drill press with a ho made slo speed attachment very similar to that, except it used multi step pulleys for even more speed range. Some pics as rec'd here http://www.owwm.org/viewtopic.php?f=77&t=92224&hilit=Buffalo
I ended up removing all of it, replacing it with a 1 HP 3 ph. motor and a VFD, nothing better than speed changes with the twist of a knob.