Building a New Lathe

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vtsteam:
I'd installed the Hall speed sensor in the headstock and replaced it on the ways, but then I spent way too long looking for a small box of disk magnets I knew I had somewhere. Finally my daughter took pity me after I'd searched every storage location in the house at least five times repeating "I know they're here somewhere.....," and plopped a BB sized round magnet into my hand. It was from a clump of them that someone gave her as a gift a few years ago.

No complaints, but that little BB wasn't the most convenient shape, especially because a Hall effect sensor responds to only one magnetic pole, and how do you distinguish poles on a tiny sphere?

But after a little thought, I stuck it to a metal ruler, which caused it to roll with one of the poles directed toward that face. Then I waved the other side in front of a spare Hall sensor I set up with a battery. Nothing. So I rolled the magnet 180 degrees around on the ruler until it stuck fast again, and repeated my waving in front of the sensor. This time the sensor LED flickered. I put a dot of Sharpie marker on the active face of the magnet, and took it out to my tiny shed shop.

The main aluminum drive pulley was drilled to fit the sphere closely at a location that would bring it in front of the sensor in the headstock. But when I pushed the magnet into the pulley, it wanted to come back out a small way, as if it had a tiny compression spring under. I checked under it -- nothing there! Then I remembered there's some kind of induced current equilibrium effect that does this -- I kind of remember coming across something on the web to that effect. Interesting. Anyway, it didn't suit my purposes, and I squashed it down with a dot SuperGlue and a thumb! :whip:

The magnet in the pulley:

vtsteam:
And as a check on positioning and clearance, I mounted the pulley onto the lathe spindle and rotated it until the magnet was opposite the Hall sensor in the headstock. Looked good.

vtsteam:
Next on the to-do list was mounting the stepper motor. I hadn't permanently affixed the headstock yet -- the stepper goes under it, and in back of an aluminum end bracket. The stepper is fairly large -- NEMA 34 case, and barely fits between the lathe shears. I needed to mark the precise location where it would need to mount, with the two pulleys in its train and the only commercial toothed drive belt size available for the small distance I had to span between the stepper and leadscrew.

To find this precise position, I bored out the leadscrew pulley to fit its shaft, then mounted it loose. I grabbed a transfer punch of a size to just fit the stepper's pulley. I stretched the belt between the two, and while holding the punch against the mounting bracket, used it like a compass point to scratch an arc through the paint.

To suit the pulleys and belt, anywhere along the arc would work. Then I scratched a vertical centerline on the bracket, and where the two lines intersected was where the both the stepper could mount between the shears and the belt drive would fit.

Scratching an arc:

RotarySMP:
Making good progress again. I am glad you got back to this build. It is a hell of a lot of work. Respect.
Mark

vtsteam:
Thanks Mark! :beer: Feels good to be moving forward again. :ddb:

Where I am: I got the stepper mounted last night, and headstock back together and mounted. There's still a lot to do to get the intended electronic lead screw functional. A power supply for it arrived yesterday, I already have the stepper driver and the encoder that I bought for it awhile ago. I just also located the dusty half wired up breadboard with Arduino that I re-programmed in FORTH with a leadscrew demo application that I wrote way back at the start of this project. That program does the division and stepping. Now I have to go back and figure out everything I'd already come up with. I've found the Forth program listing, but without remarks, and no wiring diagram. It's going to be interesting reverse engineering myself. People, don't follow my example!

But once the carriage drive is operational there's only one more component needed before I can truly say I "completed" this lathe. And that's making a topslide for it.

Even now, I can use my Gingery's topslide on this lathe, since I cast an adapter plate for it earlier in this thread. And frankly, I haven't needed a topslide at all for anything I've yet turned on the lathe so far in a couple years, so the impetus isn't strong to complete a new one immediately. But maybe, just to say "We're finished!" ......we'll see.

My real drive is to start work on an engine I have in my head that I want to build. And for that I really want to concentrate on creating extended boring and milling capabilities on this lathe. But that will be a separate project in a different thread.

Oh yeah, one more thing. After I get the tach working (I hope today) I have a sneaking suspicion, I'm going to want to build a countershaft for the motor to drop it down 2 to 1. I think I have excess speed at the top end and not enough torque at the low end for bigger boring tasks. But I don't want to think about that yet. If I do anything on that score we'll make that part of the boring/milling project......

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