Tag Archives: lathe

Low-Speed Mod for my PM3520B

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I added a 150 ohm resistor to the ground-side of the speed control potentiometer. I had done some measurements and that was the right resistance to let the lathe run at its lowest speed (48 RPM on the low pulley) when the speed control is all the way down. It used to stop the motor.

When I needed to run the lathe really slow, it was tricky to find the spot with the speed knob.

I may someday want to be able to turn the motor off with the speed control again. If that is the case, I’ll get a switched potentiometer to replace the original one. Then I can turn it down all the way to get low speed, and just click the knob to switch it off.

Headstock Lock

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My Powermatic 3520B (and Jet 1642) are lacking when it comes to locking or indexing the headstock. I don’t do indexed work, but do want to lock the headstock.  Usually, I want this when I’m sanding a section or otherwise want the piece held still while I work.

The provided option is a set screw that you have to wind into the indexing holes. Probably good for holding the shaft in place, but not easy to lock and unlock.

So I took an old drill bit of appropriate size and epoxied it into a handle I had laying around.

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I tapered the end slightly, and now it fits into the indexing holes.  And I can lock the headstock in place quickly and easily.

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Remote Control for my Lathe

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I made a remote control for my Powermatic 3520B lathe.  I didn’t like reaching around a spinning chunk of tree to hit the controls – especially if things go south and I need to hit the off switch.

You can purchase a remote, but it’s just a shutoff switch, and seems a bit expensive.

So I turned the standard control pannel into a remote.

This sort of remoting should work with just about any VFD controled lathe.  I’ve done it on my Jet 1642 also.

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I got a cable (about 10′).  You need 5 wires – cable usually comes with 6, so one doesn’t get used.  I think I used about 16ga.  It’s a low voltage control circuit, so doesn’t need much.

Next, I found a PVC electrical box that the control would fit on/in, and a mix of plumbing and electrical PVC parts to reduce the large opening down to a cable strain relief .

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I cut an opening in the box’s lid for the lathe’s panel. The box had another outlet on the back, which I cut off and sealed up with some epoxy and a panel cut from a PVC outlet box.

Wiring is easy – the cable should fit thru the back of the headstock, where the other control cables go thru.  I suggest photos and notes of the wiring before you start, in case something gets confused. With the lathe unplugged, detach each wire and attach a wire from the cable.  Hook up the control panel to the same wires. Some terminal connectors and wire nuts are helpful here.  Get everything neat and secured inside the headstock, making sure it’s all out of the way of the belts.

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Add a cover to the opening left in the headstock.  I made a cover from some 1/4″ ply, but I might go back and replace that with something from steel someday – I have found that I want to stick the control on the headstock sometimes, and the door to the belts just doesn’t seem sturdy enough to hold it up (I already replaced that plastic hinge once).

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I added 4 rare earth magnets to the back, but didn’t do it well and the control wouldn’t sit flat on all 4. So I replaced that with a big round magnet screwed to the back of the box.  the only issue I have is bed ways on the 3520B are curved, and don’t let the magnet grab as securely as I’d like.