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Upgrade drill press motor to DC variable speed?

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Forum topic by luthierwnc posted 01-29-2016 01:54 PM 1026 views 0 times favorited 21 replies Add to Favorites Watch
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luthierwnc

115 posts in 1244 days


01-29-2016 01:54 PM

Hi All,

I’m doing some serious shop reorganization and right now the focus is on my drill press. It is a utility Rockwell 15” model from 1957. The machining is excellent and everything is original. But it has a couple drawbacks. The first is that the table is a sliding-clamp type which makes it hard to make fine adjustments. I started a thread on that a while ago. It is a basic model with two 4-step pulleys on the motor and spindle shafts.

The other issue is that the lowest speed is 680 RPM. That makes even light metal work and large wood-boring projects shaky and hot. I’d like to add something around half of that. At first I was looking at putting an idler pulley on the pillar. There are some nice examples of that on the web. But in lurking I also found people replacing the original AC motor with variable-speed versions—mostly repurposed from treadmills.

As usual, my studies came up with too much information rather than enough and my decision points come down to two areas: mechanical and useful speeds.

Mechanically, other builders are all over the map because of the press they are retrofitting. I expect you just get a motor with a sturdy mounting bracket and start the real design work when it’s in hand. Offshore motors usually have a 17mm shaft. My press has a 1/2” shaft so I’d need a new 3/4”-bore 4-step pulley and a bushing to adapt. Both are readily available. Domestic motors are usually 5/8” so I need a new pulley no matter what. All of them come with a serpentine belt pulley but that assumes you can get all the speeds you need by putting the same kind of pulley on the spindle. Some folks have. It only takes 10 seconds to move the belt on my drill press and I don’t mind doing that. I don’t do it much anyway. I’m mostly after getting a low speed option.

The speed issue is more confusing. Offshore motors are usually rated for 6700 RPM but the controllers are preset to about half that. Baldor versions start a more conventional 1750 with most models coming in between 2 and 3k. I’m pretty handy with electronics but wouldn’t mind some helpful hints on matching motors and controllers. It looks like there is a trim-pot on the controller board as a governor and you replace the panel speed control with a rotary pot for our industrial application.

If anyone has done this with either a drill press, lathe or some other shop gizmo, I’d enjoy hearing about your controller experience. Thanks for any help, sh


21 replies so far

View bdresch's profile

bdresch

121 posts in 1076 days


#1 posted 01-29-2016 03:21 PM

Find a 1/2hp 230VAC and use a VFD. I don’t know anything about DC, I’m sure it’s do-able but putting a VFD on a 230vac motor and feeding it with 120vac single phase is very straight forward.

View luthierwnc's profile

luthierwnc

115 posts in 1244 days


#2 posted 01-29-2016 04:08 PM

Thanks, again; information overload—but in a good way. I read your response and then poked around on Ebay for motors and controllers. Lots of motors both new and second-hand. I need to get into the basement and pull the drill press from the wall to check the frame size and clearances. Fortunately, I have both 240v and 120v right there so whichever motor has the best other features gets the nod. Prices seems to be more about condition than horsepower.

Controllers don’t go back as many years so I’ll need to do more work for a good fit. I just ordered a Duff-Norton linear actuator and an (on) – off – (on) momentary switch to control the table movement along with assorted fitting hardware from McMaster-Carr. I went out of my way to get a 120v unit because I didn’t want to mess with a 12v converter/controller for that. The wiring won’t take much real estate so if I go with the 3-phase solution (or whatever else) it makes sense to put it in the same box.

I’ll keep exploring and I hope other L’Jocks will chime-in, Cheers, sh

PS does the horsepower translate evenly? I’d have thought I’d need a little more power to replace a 1/2 HP 1-phase motor.

View MrUnix's profile

MrUnix

4247 posts in 1667 days


#3 posted 01-29-2016 05:17 PM

You can get a decent DC motor and controller for free or very cheap – treadmills show up on CL all the time (I’ve got 4 in the last year for free). Although, you will have to do a little fabrication to make it work, but you will also get lots of other goodies out of it, like the stepper motor, rollers and deck that can be re-purposed for many tasks. Another popular option, and one frequently used by the OWWM crowd is to do like bdresch suggested – a 3 phase motor and VFD. Those motors can typically be found really cheap since most people are afraid of 3 phase motors and don’t know how to use them. They also will typically mount without modification – those presses came in both single and three phase flavors, and should have IIRC a standard NEMA 56 frame. The VFD will be around $100 and you can run it on your existing 120V circuit, and in combination with the step pulleys you have, will give you a very wide range of speed options.

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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luthierwnc

115 posts in 1244 days


#4 posted 01-29-2016 06:54 PM

I’m breaking the feasibility study into two sections: cost and effort. In a lot of cases, effort converts to cost if I end up needing to get something welded or milled—especially since I’m doing this project for expanded capability.

The 3-phase option seems to be about cost since the motor will bolt where the old one is and the wiring is fairly uncomplicated. Motors aren’t too expensive but shipping can add 50% or more to the outlay. For some strange reason, Craigslist is an absolute bust for tool and equipment around here. You’d think in a former hub of furniture-making there would be lots of equipment but I can’t ever find anything I want. VFD pricing seems to be a tighter market. In favor of this choice is reversing and soft-starts.

The treadmill motor is half cost and half effort. They don’t naturally fit old machinery so there is some modding necessary. My DP has a very simple hinge-mount for the motor with a single knob to hold the belt at tension. Taking off the DC motor flywheel gives you a 17mm shaft which can be bushed out to 3/4” with what looks like a well-made sleeve on Ebay. 11 bucks or so for that plus either boring the pulley or getting another. The controllers are generally as much as the motors and take a little programming. One guy on Ebay parts treadmills out and sells the drive components as a package for $125 or so.

I started the journey looking at jackshafts. That seems more about time than cash but leaves more unanswered questions about fabrication. You’ll find a promising DIY gizmo on Google and the description goes well until the guy says all he had to do was chuck the part in his $3500 lathe and shave off a half-millimeter to make it fit. Everybody but me seems to know somebody who can weld something quickly on-the-cheap :) Plus there is messing with the head height to align the various pulleys. If the idler isn’t in the column, it either sticks out dangerously or needs a cover fabricated by another non-existent sheet-metal buddy.

I won’t make any decisions fast but this will probably be near the top of the priority list in the shop reorg. I’m planning to build a big Shaker-style workbench and I keep finding spots where I need to bore big holes in hard wood or ream a piece of metal for vise accessories. I’ve got a small pile of formerly sharp bits blued out of temper by spinning them too fast and I’d like to break that habit.

Thanks all and I’ll keep watching this thread, sh

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luthierwnc

115 posts in 1244 days


#5 posted 01-30-2016 03:31 PM

More research:

It seems some of the newer 3-phase motors are wound and rated for variable use. The Baldor “Super-E” series are a case in point. Other motors aren’t and run fine anyway. For my limited use that won’t be a deciding factor. On the machining forums (where this is a hot topic) there is some concern that running any motor at low Hz also slows the cooling fan. In a wood shop it seems easy enough to put a line from the dust collector near the exit ports and tape a vacuum filter on the input side if needed.

A silly but real concern is that most of the small 3-phase motors on Ebay don’t have mounting feet. They fit on the shaft-end like water pumps. Aftermarket mounting brackets aren’t available. Some clever craftsmen have rigged plates with large hose clamps for side mounting but I’m guessing they did that because they had the motor in hand. I don’t so I’ll have to get a look at the bottom of the unit before biting.

I’ll stay on it. Keep those thoughts coming, thanks, sh

View dhazelton's profile

dhazelton

2326 posts in 1764 days


#6 posted 01-30-2016 03:46 PM

This popped up near me and looks like a super deal. Doubt they’d ship.

View luthierwnc's profile

luthierwnc

115 posts in 1244 days


#7 posted 01-30-2016 04:02 PM

That seems to be the going rate. I wonder how many of these are sold that so many sat on shelves getting dusty.

A thought came up since my last post. These VFD units seem fairly fragile. Do you suppose they should have surge protectors in series from the wall? The motors could probably withstand a good jolt but the VFDs look pretty fryable with lightning or hillbilly voltage swings. If I’d do it for a computer, I should budget it into the project. It will need a stout box anyway. I planned to fuse that. add an emergency stop and a pot to bypass the digital speed control. Then I suppose the question is if the very act of fluctuating the frequencies would trigger the device or if that shows on the output side only,

sh

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luthierwnc

115 posts in 1244 days


#8 posted 01-31-2016 04:14 PM

OK—I started ordering parts going with the VFD format. I’ve got a 1 hp TECO JNEV-101-H1 VDF on the way which will power a new 3/4 HP Leeson 3-phase motor—also on the way. I’m building a BOM for an enclosure to hold the bits. It won’t need a dedicated breaker since that circuit already has one.

A couple things that will be different than I’ve found on the net: the box will also contain the (on)-off-(on) momentary control for a linear actuator to control the table height. That’s also a 120v unit so I don’t have to cram a 12v converter in there. Then I’m thinking of replacing the original Cutler Hammer on-off switch on the front of the head with a remote speed pot. That’s a relatively long run so I’ll used coax. I mimed the ergonomics of using the controls and decided I don’t want to take my eyes off the work to reach the flimsy little pot on the TECO. Better to have something close and large for greasy fingers.

The panel box will also have an illuminated on-off switch in series from the main which will double as my emergency switch. I’m always cautious but most of panels I’ve seen with dedicated push-button kill-switches are on mills or lathes where stuff can go a lot worse in a hurry. If the electronics call for it, that may go further downstream. The only other mod will be a muffin fan blowing in from the top covered by a fiber filter with a couple of the knock-outs removed for circulation.

The new motor is getting a new pulley with a larger bore (also in a box on its way) but with the stock diameters. I couldn’t prove it but I’ve always heard that you get better power transfer using the larger-diameter sheaves and that the 2” ones are less efficient. With the original four settings available I should have lots of mechanical flexibility without taking the electronics to the edge of their torque comfort-level. I’m not too proud to raise one a little to approximate stock RPMs at 60hz. The old motor (which has two shafts) will make a handy buffer.

If anyone is interested, let me know and I’ll start a new sticky thread on the progress. This seems like an exciting new technology for rehabilitating older 3-phase equipment for shops on the 1-phase grid. Maybe there is a nice lathe in my future if I can figure out how to get it in the basement.

More to come, sh

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luthierwnc

115 posts in 1244 days


#9 posted 03-01-2016 12:41 PM

The project is complete except for shimming the base.

This was a journey but thanks to my friends here and at Sawmill Creek it is up and running. There were several objects in the project:

a) the 1957 machine has a friction-based column clamp which is heavy and hard to position precisely. It also took brute force to clamp hard enough to hold. Subsequent derusting and oiling those parts fixed that. Still, I wanted to install a linear actuator for better control,
b) this is a pure woodworking machine with a minimum RPM of 680. I wanted half that for boring large holes and light metal work and
c) the original bearings were getting a little noisy.

All fixed. The machine will now run at any speed I reasonably want—forwards or backwards. I also put in a jog momentary switch for tapping. In the panel box are the actuator control, a muffin fan to keep things cool, an LED gooseneck lamp and a digital tachometer to see the actual revolutions on the chuck. Except for the VFD, all the parts are garden-variety hardware-store items.

I went with a Teco JNEV-101 VFD drive and an NOS Leeson 3/4 HP 3-phase motor. I used a main control panel directly behind the press and put the remote controls in an outdoor 2-gang box where the original on/off switch was on the front of the head.

I hope this helps anyone considering this kind of technology. The manual is a bit intimidating but it can be understood with repetition. If any wants, I can also post the schematic and VFD settings I used. Parts too.

Cheers and thanks, sh

View Mk10's profile

Mk10

5 posts in 131 days


#10 posted 08-01-2016 08:53 PM

Hello.

I’m trying to convert a benchtop drill press to use a DC treadmill motor. I was wondering if anyone could tell me what specs outside of 2-3hp I should look for on a DC motor, and what kind of control unit would be applicable for it.

I appreciate everyone’s time, and any information folks might be able share with me.

Thanks,

Mk10/Chris

-- Chris, Missouri USA

View MrRon's profile

MrRon

3927 posts in 2711 days


#11 posted 08-01-2016 10:11 PM

This place carries a good assortment of new treadmill motors and controls, but you will have to devise a mount for the motor. https://www.surpluscenter.com/CAT284/Catalog284.pdf

View MrUnix's profile

MrUnix

4247 posts in 1667 days


#12 posted 08-01-2016 10:19 PM

A treadmill should have pretty much everything you need to get started – motor, power supply, choke coil, controller and wiring. The only fabrication you would need to do is figure a way to mount it (which should be pretty easy) and find a proper pulley for it.

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

View luthierwnc's profile

luthierwnc

115 posts in 1244 days


#13 posted 08-01-2016 11:16 PM

YouTube has several in-depth vids on redoing a drill press. I went with a new 3-phase motor and VFD but I expect it works well either way. Mostly, you are looking for torque at low RPMs for big bits and light metalworking. sh

View Mk10's profile

Mk10

5 posts in 131 days


#14 posted 08-02-2016 12:23 AM

The AC 3-phase with a VFD is beyond my pay grade. I live on a fixed income that doesn’t leave much after paying bills unfortunately. These DC motors can be had on the cheap, so that’s my focus for now. Believe me, the VFD route looks fantastic, and if I was working it wouldn’t be a problem. But it is now.

So far I’ve been able to come up with these:

1. 2HP 90 VDC 3800 RPM 19amp Griffin Motor Engineering F-Class insulation JM01-003.

2. Nordic Track 2HP 130VDC 14.3amp 5650RPM H-class insulation.

3. Scientific American 1.5HP 10.8amp 120VDC 4800RPM unk insuation class.

I’m getting the idea that a lot of them can be used, but the controller that controls them costs more if they’re at certain specs.

Rigging a mount is something I can figure out, it’s the raw specs and the cost of the controlling unit that would be the largest problem for me.

I really appreciate everyone’s responses, and any feedback on those motors would be great, and also any raw specifications that might work and use a lower-priced controller would be great.

Thanks again everyone,

Chris/Mk10

-- Chris, Missouri USA

View MrUnix's profile

MrUnix

4247 posts in 1667 days


#15 posted 08-02-2016 12:46 AM

Lower priced controller? I’m not sure how much lower than FREE you can get :)

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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