Mini Mill Tune Up And Power Feed

Christmas and New years have past so I’m back to tuning/cleaning up my mini mill. I saw in the Princess Auto flyer (the Canadian version of Harbor Freight) they had white lithium grease on sale. Any time I go to Princess Auto I take a wander through the surplus section. Most times it’s like going to the dollar store but I have found some good stuff, brand name tools, heat shrink, zip ties and once Mitsubishi NEMA17 and NEMA24 stepper motors.
I’d seen these worm shaft motors in surplus for a while but with no nut, an unknown voltage and the absence of any other spec I wasn’t interested. But I’d been thinking of adding a power feed on the X axis so I looked up the part number on the internet and low and behold.

P/N: 5503740 D
Power Seat Tilt Motor for a Chevrolet Malibu
RPM: 190 RPM @ 12 Volt DC
1.5A No Load /17A Stall @ 12V.


I figured if it had got enough power to lift my 210lb butt in a car it should work as a power feed and the 190 RPM seems about right so I dropped the $9 Canadian and took one home. Messing around on the bench I couldn’t stall it with my hand at 5V so it’s got some torque and at 12V no way was I going to stop it.

So this is my rough plan. The frame will be 1/4” aluminum where I need rigidity and 3D printed where it just needs to keep the chips out. A few years ago when I first got into casting I was lucky enough to be gifted a lot of aluminum scrap from a local fabrication shop and a lot of it was 1/4” plate so I think I’ll mock up the frame just to get a better feel of how things are going to fit.


The motors are sold as right hand and that would put the motor above the bed. I don’t think I have ever had anything on this little mill sticking out to where this could become an issue but I don’t like the idea. It turns out that you can just undo the 4 screws and swap it around making it left hand and that will put the motor down below the bed.

Haha, probably would have bought one. On a Mill with 4 mm screw pitch this would go about 760 mm/min. Probably good enough, if you can slow down properly. Worst case it does not work as you hoped.

On my mini Mill the motors stick out to the side. You need to check if anything is in the way when you drive the y-axis full stroke.
Is your mill on a stand? Is vertical down any option? If possible, I would also try to keep everything below table top, just in case you will have a part that is longer than your table. The day you decide to mount something, you will need to drill a hole in the end of a table leg .
I would even try to move the clutch handle to the front, not up.

The next thing I wonder would that be suitable for a quill feed? Or can it raise and lower the head of the mill?

Success and keep posting how it is going.

Greetings Timo

Will definitely be following this one! I have pondered something similar but was unsure about how to power a DC motor.

terry123 said:

Will definitely be following this one! I have pondered something similar but was unsure about how to power a DC motor.

Click to expand...

To power the DC motor I would use something similar to this one with a microcontroller to do PWM control. (does not have to be that brand, similar devices are available elsewhere)

https://www.pololu.com/product/2991

With those extremely cheap ones. I had mixed results, as they tend to state "magic smoke Amps" instead of the matching motor rating. So we need to be careful with those. I have a smaller version similar to the one on the picture on my míni drill press. It constantly trips when starting the motor with too high throttle. (slowly speedig it up it is fine, it is small and in a metal box, so when it catches fire it will not be an issue )
They tend to state values that are mixed collection from the datasheet. e.g. Absolute max. Amp together with absolute max. Voltage.
So instead of 60Vx20A = 1200 W the thing might be only capable of 9V*5A=45W or 12Vx3A=36W. at 60V it might go up in smoke or at 20A whatever comes first.


o

Greetings Timo

p.s. at our hobby use, it is sometimes even good enough. Degrading over time, but used sparse enough to give sufficient life span. (low price)

Hi Timo. Murphy's law would dictate you are 100% right on something coming up as soon as it’s installed. My Mill sits on the bench and I have around 4 inches of clearance to the bottom of the bed. Good call on the clutch handle, I’ll definitely set it up so it’s in the front. I’ve been playing around with the motor and for a small motor it has a ton of torque so when you say “quill feed” on something like a drill press it could work. My mill is a Craftex CX605 and uses a rack and pinion on the head and I cant visualize how it would work.



Terry. For power . . . Ya. What Timo said

Hi, here's what I made, similar 12v motor layout. Used micro switches to start/stop and reverse. Also put microswitch x2 on the mill bed to prevent overun/crash. Has a dog clutch so traverse hand wheel can remain in use. Hope pictures are useful.

Quill feed I had something like this in mind.

Depends of course how the machine looks. And it depends what is necessary to put the motor on.

I have had a seat motor power feed on my Mill-Drill for years.
It is powered by a battery charger with a light dimmer for speed control.
It works quite well.
Scott

cheepo45 said:

I have had a seat motor power feed on my Mill-Drill for years.
It is powered by a battery charger with a light dimmer for speed control.
It works quite well.
Scott

Click to expand...

I have been kicking around ideas for a low cost power feed on my mini mill for a year or so. The AC to DC transformer has been the main stumbling block. If I might ask-how many amps does your charger produce and how does it hold up under extended usage?

bmac2 said:

Christmas and New years have past so I’m back to tuning/cleaning up my mini mill. I saw in the Princess Auto flyer (the Canadian version of Harbor Freight) they had white lithium grease on sale. Any time I go to Princess Auto I take a wander through the surplus section. Most times it’s like going to the dollar store but I have found some good stuff, brand name tools, heat shrink, zip ties and once Mitsubishi NEMA17 and NEMA24 stepper motors.
I’d seen these worm shaft motors in surplus for a while but with no nut, an unknown voltage and the absence of any other spec I wasn’t interested. But I’d been thinking of adding a power feed on the X axis so I looked up the part number on the internet and low and behold.

P/N: 5503740 D
Power Seat Tilt Motor for a Chevrolet Malibu
RPM: 190 RPM @ 12 Volt DC
1.5A No Load /17A Stall @ 12V.
View attachment 163739

I figured if it had got enough power to lift my 210lb butt in a car it should work as a power feed and the 190 RPM seems about right so I dropped the $9 Canadian and took one home. Messing around on the bench I couldn’t stall it with my hand at 5V so it’s got some torque and at 12V no way was I going to stop it.

So this is my rough plan. The frame will be 1/4” aluminum where I need rigidity and 3D printed where it just needs to keep the chips out. A few years ago when I first got into casting I was lucky enough to be gifted a lot of aluminum scrap from a local fabrication shop and a lot of it was 1/4” plate so I think I’ll mock up the frame just to get a better feel of how things are going to fit.
View attachment 163740

The motors are sold as right hand and that would put the motor above the bed. I don’t think I have ever had anything on this little mill sticking out to where this could become an issue but I don’t like the idea. It turns out that you can just undo the 4 screws and swap it around making it left hand and that will put the motor down below the bed.

View attachment 163741

View attachment 163742

View attachment 163743

Click to expand...

Hi Bmac2,

I did a very similar thing using a car window wiper motor. For what its worth you could just reverse the power supply and the motor will run in the other direction.
I tend to run mine at about 6 or 7 volts from a 3 amp variable voltage power supply. At 30 volts it gives me a fast traverse.

I incorporated a tumbler reverse so I can simply change direction by moving a lever. I did this because wiper motors don't like running in reverse. But I think that you will find that your motor won't care either way, since that is what would happen when lowering the seat.

bmac2 said:

Christmas and New years have past so I’m back to tuning/cleaning up my mini mill. I saw in the Princess Auto flyer (the Canadian version of Harbor Freight) they had white lithium grease on sale. Any time I go to Princess Auto I take a wander through the surplus section. Most times it’s like going to the dollar store but I have found some good stuff, brand name tools, heat shrink, zip ties and once Mitsubishi NEMA17 and NEMA24 stepper motors.
I’d seen these worm shaft motors in surplus for a while but with no nut, an unknown voltage and the absence of any other spec I wasn’t interested. But I’d been thinking of adding a power feed on the X axis so I looked up the part number on the internet and low and behold.

P/N: 5503740 D
Power Seat Tilt Motor for a Chevrolet Malibu
RPM: 190 RPM @ 12 Volt DC
1.5A No Load /17A Stall @ 12V.
View attachment 163739

I figured if it had got enough power to lift my 210lb butt in a car it should work as a power feed and the 190 RPM seems about right so I dropped the $9 Canadian and took one home. Messing around on the bench I couldn’t stall it with my hand at 5V so it’s got some torque and at 12V no way was I going to stop it.

So this is my rough plan. The frame will be 1/4” aluminum where I need rigidity and 3D printed where it just needs to keep the chips out. A few years ago when I first got into casting I was lucky enough to be gifted a lot of aluminum scrap from a local fabrication shop and a lot of it was 1/4” plate so I think I’ll mock up the frame just to get a better feel of how things are going to fit.
View attachment 163740

The motors are sold as right hand and that would put the motor above the bed. I don’t think I have ever had anything on this little mill sticking out to where this could become an issue but I don’t like the idea. It turns out that you can just undo the 4 screws and swap it around making it left hand and that will put the motor down below the bed.

View attachment 163741

View attachment 163742

View attachment 163743

Click to expand...

The biggest problem I found with building a power feed is a simple easy to build cluch.

I have used electric clutch not cheap but work great.
Did this on a 6,000 pound horizon mill.

A good DC drive and controller is 60 to 1 so will go to as high as 100 to 1. That is great for power feeds and fast speed aka (rapid Traverse).

It just finding good easy cluck today.

Dave

The battery charger for my power feed is 6 amps.
I have been using it for almost 30 years and it still works fine. I wired a reversing switch to it. I do have a couple of big capacitors in the DC circuit to smooth out the movement.
For the clutch I machined a sprocket to fit over where the handle used to be, drilled holes in it to match the tapped holes in the handle adapter. I just screw a bolt into it when I want power feed. I had everything laying around, so quick and dirty it is! Scott

cheepo45 said:

The battery charger for my power feed is 6 amps.
I have been using it for almost 30 years and it still works fine. I wired a reversing switch to it. I do have a couple of big capacitors in the DC circuit to smooth out the movement.
For the clutch I machined a sprocket to fit over where the handle used to be, drilled holes in it to match the tapped holes in the handle adapter. I just screw a bolt into it when I want power feed. I had everything laying around, so quick and dirty it is! ScottView attachment 163807

Click to expand...

Thanks! Looks like I will be getting more serious about adding one to my mill.

Hi Bmac2, Guys,

One advantage of a tumbler gear mechanism is that you don't need a clutch to free the hand wheel. It remains connected and is available as soon as the tumbler gears are in neutral.



This is a picture of the tumbler gear. The aluminum back plate supports a Nylon plate pivoted around the left hand, hand wheel boss. In this picture the hole has not been fully bored out. The large headed screw simply acts as a stop and prevents the Nylon plate from coming away.



This pictures hows the detent that sets the forward, neutral and forward positions of the tumbler gears. The three studs and spacers are the mountings for the wiper motor.



This is the plastic gear that is fitted to the end of the table leadscrew. There is a slot for the drive key machined into the hub and the six M3 screws go through the plastic gear into flange behind. You can just make out the corners of the 32 mm hex brass bar that I used to make the hub.

Burns - I really like the slim compact look of your drive. I’m going to try for something similar.

Timo - that is a cool setup. I don’t think it would work well on a Mini Mill where the entire head moves with the Z axis.

Scott – Good to hear I’m not wasting my time. The motors do seem to have a lot of power in a small package.

Doorsmith – I’ve got a couple of these and they lock up solid when engaged but there a bit big and rated at 30v. I honestly think I scavenged them from a model 33 teletype. Use to be able to buy these monsters from the company’s surplus sales for $5.00 (1982-83?). Would strip out the fun stuff over lunch and toss the rest in the bin. I had one in my apartment as part of my first computer (S100-Buss) and LOVED being able to save programs on paper tape (crap I’m old) but it was so loud I had to get rid of it. That’s not my picture. That is what my wife would call “a very busy table cloth”.






Cheepo – A small battery charger is great when all you need is a regulated DC source and there are probably 100’s of them cheap in garage sales and swap meets.

It took a bit of fiddling to get the mount right. That base is just the dimensions it ended up at after truing. This is more just a “proof of concept” at this point.
Drilled and counter sunk the end piece. Squared up and clamped I used a transfer punch to mark the base plate. Drilled and tapped, and hooray! Everything lined up and it sitting nice and square.






I milled a shallow recess in some 1/2in for the plate that would mount to the mill. No real reason, I just thought it might help with alignment. It’s a just a scrap piece I had in the bin about the right size and the extra holes won’t be in the way.



Some ware around there. I got the hole for the motor shaft bored out and screwed things back together.





Made up a piece of ½” for a middle bearing and clamped it up and drilled through M3 tap size then opened the holes in the base a snug M3 clearance, and tapped the bearing mount.



With everything screwed down tight I bored out the holes to fit some 3/8 bushings. They came out ok and with the bushings pressed in everything’s nice and straight. With the middle wall in place I had to elongate the bottom hole to get the screw in for the motor.

bmac2 said:

Timo - that is a cool setup. I don’t think it would work well on a Mini Mill where the entire head moves with the Z axis.

Click to expand...

That is correct it is for a quill feed eg. for boring with a boring head (just saw it on the youtube), to move the head up and down a little different system is required.
My CNC minimill has no quill. A big stepper motor is moving the head up and down directly attached to a ball screw. That would also work for a small manual machine, just needs a pulse generator of some sort. (Then there would be no handwheel anymore at all, but not a big problem)

I’m not sure what happened here but man is this thing out. When I took the threads off and shortened the shaft I held the shaft in the lathe and worked between the chuck and the worm gear. To my thinking this should have kept things concentric. The only thing I can think of is that the shaft is not centred in the worm or the shaft was bent. Or I just screwed up.

Were in the middle of a snow squall with the temperature sitting around -20 with 60 to 70 kph winds, and I’ve got a head cold so ya, I’m going to blame it on the weather.

It will still work but it will need an Oldham coupling. I’ve made them before and they’re pretty straight forward. It is going to get a bit snug but it will work.

I’m going to use a dog clutch. If you’re interested I found a great video by ‘Tom Make Here’

For the layout and machining I started with a piece of ¾” aluminum in the lathe and drilled/reamed a 3/8”hole deep enough to make both parts and keep the holes concentric. Then cut the recess for the fork in one and parted them off the length.

Setup it up in the rotary table and milled them out following Tom’s video.





Broached the keyway in the lathe and after some light filing they mesh nicely. After dialing in the shaft I drilled and reamed a 1/8” hole in the mating ends for a pin. My thought here is that it will help keep the two shafts aligned then made up a fork.