Building a New Lathe

Gallery, Projects and General > Project Logs

<< < (163/171) > >>

vtsteam:
The headstock was replaced by the end of the day. I had to make a "special" tool to do it -- basically just an Allen wrench with the shorter leg ground back to only about a quarter inch long. This allowed it to fit up above one of the cross members of the lathe bed, and tighten the 4 bolts now clamping the headstock onto the ways.

I reassembled all the other parts -- spindle and roller bearings, shims, cap, dust rings, tooothed belt pulley, tightened the spindle nuts to put just a slight preload on the bearings and re-attached the leadscrew bearing. The spindle looked great, clean and shiny, and the bearings still well greased. Everything turned smoothly. I replaced the motor and belt, and ran it for a couple minutes at different speeds to check for vibration. Looks good.

I put Morse taper dead centers into the headstock and tailstock and brought them together. They matched point to point, both with the tailstock ram retracted, and extended. This means the ram bore is parallel with the ways. I'll turn a test bar at some point in the future to see how close we are overall.

Next on the to-do list though is eliminating the problem of the carriage half nut jumping out of mesh occasionally. I'll check and adjust the leadscrew bearing positions, and checki the hand-filed halfnut detent shape and the spring tension.

Even though I want to move on and make new things, this tune-up process feels very satisfying.

vtsteam:
Today I made two way-wipers for the front of the carriage. They were bent from sheet brass. I first made paper patterns using the cut and try method. Then estimated a bend allowance and cut them out with tin snips and Dremel tool. They were bent simply in the bench vise.

I have whole sheet of felt leftover from making the headstock spindle wipers, and it was easily cut out with scissors. Then I punched the felts with a bargain bin multi-puncher -- which has turned out to be an excellent investment. I drilled and tapped the carriage 8-32, and screwed the wipers on. Seems like a fairly simple job overall, but it took a surprising amount of time -- particularly setting up the carriage to be drilled, since that had to be done off of the lathe. It's an odd shape to support.

I plan to do the rear carriage as well, but this was all I accomplished today.

Wiper pieces:

And mounted on the lathe:

vtsteam:
Oh yes, forgot to mention, I solved the half-nut issue by relocating the halfnut dog. As it was, the dog's detent was acting a little early, before full halfnut engagement. Short of remaking a new dog, or a new halfnut, I eventually figured out that it would be a simpler matter to just relocate the lever's pivot so that the dog was in the detent with the nut in full engagement. So I drilled a new pivot hole in the dog, and then set everything up engaged, and transfer punched through a new pivot hole location and drilled and tapped for a new pivot.

It strikes me this is really the way I should have set up the halfnut in the first place. When building the lathe, I had logically (it seemed at the time) cast the halfnut, then bored a hole in the apron for its shaft. Then I had made the dog -- a lever with a spring at one end, drilled the lever, and apron and mounted a pivot screw. The business end of the lever fits in a notch which, as the last operation is filed into the half nut. This filing is very tricky to get right; if you file the notch slightly wrong, the halfnut won't engage properly and you're sunk. You can't re-file the notch or move it.

If it were to do it again, I would NOT make the pivot first, but wait until after I'd filed the notch. I'd drill the pivot hole in the lever, but not the apron. Then line everything up with the dog in the notch. Then simply transfer and drill the pivot location through the hole in the lever. Easy perfect alignment! :doh:

awemawson:
Well Steve, when you start your production run of small lathes you can write it into the operations procedure :clap:

vtsteam:
Thanks, Andrew :beer:. Maybe someone reading this thread and intending to build a lathe will benefit from the mistakes I made.

Actually, if you're building a Gingery lathe the same thing applies, as my new lathe uses the same style halfnut and dog. And actually even more generally, if you are building anything where you need to engage a dog in a filed notch, that is in a blind location, this might be helpful as a setup procedure.

I should also add that because on my lathe (and the Gingery lathe) everything IS mounted blind behind the mounted apron, but must exactly line up with the leadscrew, and yield a detent in the exact right position, there is one additional way to ease the task of parts placement. Also it's something I learned only in correcting the carriage yesterday after two lathe builds where I had struggled with locations.

With the apron off the lathe, just engage a short (say, foot long) length of leadscrew stock in the halfnut. This is easy to set straight and parallel and to check for alignment, and also sets the proper position for the detent. Sure beats trying to do that with hidden face measurements, (and guesswork) while the apron is mounted on the lathe, and filing and testing, repeated removal and remounting, etc. Another one of those, "duh, why didn't I think of that before," moments. :loco:

Navigation

 Message Index

Go to full version