Sherline Gear-Driven Power Feed

My main reason for the top speed of 300 rpm was mostly to allow for a more rapid movement of the saddle when I needed to move it long distances. I don't know how many times I had to move the saddle to get room for a measurement or something and at only .05 travel for every revolution of dial, it got old very quickly.

Oh, I know exactly what you mean! You are going to absolutely love a reversible VS DC motor, trust me. It is a real treat to be able to adjust speed and feed on the fly. All those guys with VS lathes are still forced to live with feeds tied to their gear ratios - not us!!!
 
Well, I've messed around with this power feed a little and found that I could easily stall the thing when trying to feed at a slow rate. I'm going to change out the 300 rpm motor for a 200 like I mentioned earlier. Meanwhile, here are two pix of what I came up with. The rotary control has an "off" position with a distinct feel and sound. The rocker above the dial is to select direction and it has a center off position. The red switch on the right is for main power. It is always lit up, so I know power is applied to the unit. I feel that's a plus, as the visual reminder will help me remember to unplug it when not in use. No sense taking a chance on burning anything up. The second pix shows how I got power into the control. It is a computer style power entry point. I did this so I wouldn't have to deal with six feet of power cord flopping around if and when I need to open the box.
Oops, almost forgot. The motor and external bracket are attached to a 3/16" thick aluminum plate inside the box for support. The box is made up of .04 aluminum and it would never be able to handle the stress.

Russ

Feed controls.JPG

Power entry .JPG
 
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Came out nice, Russ. Has everything you need in a clean package.

Is the speed of the motor you're using tied to the torque it produces? That is, will the 200 rpm motor produce more torque than the 300 rpm one? You need torque more than speed in this application.
 
I'm pretty sure it will. Both motors are advertised to turn at 5000 rpm rotor speed that is then reduced through a gear train. With everything being equal before the gear train, giving up revs through the gearing to get a slower output should increase torque at the output shaft.

Russ
 
Keep us posted, Russ. When you get it working well, post up the motor info if you will. Other guys might follow your lead. Again, nice work!
 
Okay, I just purchased a 200 rpm motor this morning. When it arrives and I swap it in, I'll take some pix of everything and post them along with details of what's in the box and the mods to make everything fit.

Russ
 
60 rpm little gear motor that should be fast enough for turning. I wonder how many inch pounds of torque it develops because if you take a really healthy cut, say 0.050 - 0.060" deep, in mild steel then I wonder if it can keep up. I can tell you that the original Sherline power feed motor struggled to keep up with the cuts my tools can take, although to be fair it turned at a constant 100 rpm.

My Leeson power feed motor is bigger than the main Sherline motor, can go up to 100 rpm and has tons of torque. It will drive the carriage no matter how big a cut I take. This might sound trivial but if the motor is struggling then that will show up in the finish so keep that in mind when choosing a motor.
 
Okay, the 200 rpm motor arrived the other day and everything is back together again. I made a few unscientific tests and I'm satisfied with the results I got.

Now, I know this isn't going to be for everyone, but it works for me. I tend to take fairly light cuts when turning. Usually .01 per side, but sometimes .02 depending on the material. I have seen mention here and on other sites of cuts around .05 deep. That's just not my style. I may baby this lathe, but again, that's just me. If you decide to do something similar, all the components I used were found on line with very little searching. There are plenty of choices to make, and with some careful shopping, this can all be done for less than $50.

Be sure the lathe is properly adjusted, cleaned and lubricated. I noticed a change in the pitch of the motor as the saddle moved along the length of the bed. I found some light corrosion and dust on the bed ways from sitting unused and uncovered for about a month. Also, be sure your tooling is sharp, secure and set up properly.

So, here we go. This first picture shows the difference between the two motors. The large one weighs around twice as much as the smaller one, and a lot of that is due to a larger armature. It was advertised as "high torque" and compared to the smaller one, this is true. One simple test I did was to try to stop the motion of the saddle with my finger. Barely slowed it down. Making a .01 deep cut in steel didn't strain the drive much at all. Now it's just going to be a process of finding settings on the speed dial for things I need the drive to do.

Motors.JPG

This next picture shows the various electrical components in the enclosure. It took some time through trial and error to come up with something that worked, and this can still be improved upon. I plan to clean up the coil of black wire, as it takes up too much valuable space in the little 3x4x5" box. The circuit board on the bottom of the box is the power adapter. It was removed from the shell it came in and hot glued to a piece of plastic that was hot glued to the bottom of the box. Mounted vertically at the left end of the power supply, is the speed control. It came with a pre-wired switch to handle direction changes for the motor. I know it looks kind of cluttered in there, but sometimes you just need to think differently. This is what I needed to do to get everything to fit. The small blue block you see near the bottom center of the picture is a terminal block that made hooking up the 12VDC output from the power adapter very simple.

Wired up.JPG

Here is the shell of the power adapter. I cut it along the parting line with a hobby saw, and when the two halves came apart, I cut the two main power leads from the back side of the prongs that plug into the wall. I was amazed at how little was actually inside that shell. I performed the surgery on the shell when it couldn't be make to fit in the space available in the box.

Adapter.JPG

The last thing I want to show is how to ground the main power coming into the metal box. The power entry port I used made this very easy, as it has blade type connectors on the back. All three lugs are marked as to how they should be hooked up. Line, neutral and ground. The circuit board from the power adapter was also marked for polarity, as are the connections on the speed control. As long as you watch for polarity markings on the different components, it should all go pretty smoothly. The first motor I tried ran in the directions called for when the switch was set for left or right. The larger motor has a mark that I took to be for the positive lead, but it ran backward compared to the first one. Test these things before final assembly to save time and effort. Mark things up so you know where leads go if it is taken apart, and there should be few problems. At least I didn't have any smoke come out of mine.

Ground lead.JPG

And finally, here is the same picture from a previous posting showing the completed control in place.

Feed controls.JPG

Okay, I think I've covered everything. Now I need to find excuses to make some chips.

Russ
 
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