Building a New Lathe

[vtsteam]

I stopped down at Lester's old time machine shop. Found Lester in the back and we jawed for a half hour or so. Eventually I mentioned I wanted some hot rolled 1-1/4" round stock to make a boring bar, and my tailstock ram with. I'm using a tailstock casting that I bought from Ebay for a Craftsman lathe. Lester said why didn't I want cold rolled? I said well the bore is actually 1-1/8" and I'm not sure how worn it is, might need to turn it to an odd dimension, etc.

He said, well, I have some 1-1/8 cold rolled. Had it for a long while. I don't use it much. Okay I said, I'll take about three feet of both, then, just in case. So he cut me the hot rolled bar, and hunted up the cold rolled, which was on a shelf in an ancient cardboard tube, that just fit it. When he pulled the bar out, it was just under 3 feet, so I said that was fine. He charged me $22, and I could probably make six tailstock rams with that if I wanted to. He gave me the cardboard tube, too.

Well when I got it home, it was all coated up with sticky preservative stuff. I cut off 7" of it and cleaned it up with kerosene. Imagine my surprise when I saw it was ground polished stock! And the fit in the tailstock was absolutely perfect. perfect sliding fit. Like they were ground for each other.

So I guess I lucked out on that one. Maybe that's why it was in that protective cardboard tube. Thank you Lester!

The ram blank in the tailstock:

[awemawson]

. . . just sometimes all the stars line up, and things work out well 

[vtsteam]

Thanks Andrew. 

I haven't been able to work in the shop the last few days as I'm also working at a job full time (temporarily only -- back to retirement June 1).  But evenings I've been working an hour or so at the kitchen table making up a bluetooth DRO for my mill using a Texas Instruments MSP430 Launchpad evaluation board, one Igaging style scale, and two digital calipers (I hope).

I've also thought of a new scheme for cutting threads simply (and mechanically) on this lathe, without the Arduino electronic leadscrew I had worked up earlier. I'm kinda excited to try it out.   

[vtsteam]

Got a minor bit done tonight -- bored the tailstock spindle  5/8" dia., 2" deep to accept a boring bar I'll have to make up.

You may have noticed I've removed the carriage -- I'm not going to use it to drive the headstock. Instead I'll temporarily connect the headstock to the leadscrew with a bracket. This shortens the length of boring bar I will need, which is all around better for this job. The tailstock ram, temporarily over-long, will be driven round -- acting as part of the rotating boring bar, and the tailstock casting will be its bearing. After the headstock is bored, the tailstock ram blank will be cut down to size, morse taper added, and threaded for the ball handle spindle at the rear.

[vtsteam]

But after playing around with it for a bit, I decided that I didn't like that idea. A cantilevered boring bar worked fine on the old Gingery lathe for a number of reasons that don'tapply here.

So I re-thought the whole process and decided to make a long boring bar that turned in the tailstock ram at one end, and a temporary support at the other end.

First I found a length of 5/8" rod and turned a 60 degree taper on one end. I removed the tailstoick ram and cut it shorter at the front, mostly removing the hole I had bored. Then drilled the other end with a center drill, and reversed the ram in the tailstock.

The new boring bar fits into the center drilled taper. A 5" pulley is slid onto the bar;

[vtsteam]

Next I made up a temporary support at the other end and center drilled an old cast block of aluminum to take the other end of the boring bar.

[vtsteam]

Then I drilled the 5/8" bar where the cutting tool should be, to clear both ends of the headstock when it slides.

I silver brazed on one side of that location a small piece of water pipe, to pad out the thickness for adding a set screw.

Then I filed the hole square to fit a 1/4" tool bit. And added a set screw.

[vtsteam]

Finally this is what the whole setup looks like, so far. I slid the pulley away so you could see things better, but in use it will be close to the tailstock. The carriage has had the cross slide removed and sits behind the headstock. It will be attached temporarily and push the headstock along the ways. Making everything clear on this short but rugged lathe took a little head scratching and positioning for tool bit, and supports, but I should be able to bore both ends of the headstock for the roller bearing recesses without disturbing the setup.

[PekkaNF]

Pretty good indeed! You have it mostly sorted.

Have you considered the side loading (shift on cutting bit rotation axis) with belt tension? Probably you will move that wheel as close to tail stock point as possible and but drive on front side to bring the error to turn fintting taper.

Pekka

[vtsteam]

I don't quite understand the last part of what you wrote, Pekka, but the gist seems to be worry about belt tension and shaft bend. I think things will be fine. I have a relatively thin belt, and I don't plan on horsing down on the pulleys with lots of tension. Basically they can be relatively loose in practice -- they just have to avoid slipping to a halt. The cutter and depth of cut will be small. Not a lot of resistance to the belt, so, not much tension needed.

If the initial cuts seem problematic, I can always modify the setup. There's a LONG way between the present diameter and the final diameters. Plenty of time to stop and alter. But I think we'll be okay. And of course, I've already done all this before with the Gingery lathe. 

[WeldingRod]

Ah, yes.  I, too started a milling machine build when was at Rice, and had keys to the shop.  I welded and ground a beautiful square way column with two riser blocks.  My mentor gave me an old mill g machine head which I proceeded to graft big tapered roller bearings onto with a shrink fit extension.  I machined an R8 spindle, but I screwed up on the threads for the preload nut.  Still worked, though.  I don't know tha t i got the taper perfectly concentric, though.  I scratch built a brushless dc driver for a 3/4 go m9tor I took out of something.  Blew the crap out of the pass transistors twice with the brake function.  Argh.  Someday I might get back to it.

Sent from my SAMSUNG-SM-G891A using Tapatalk

[vtsteam]

This isn't a milling machine. 

[PekkaNF]

Steve, I have confidence in you, I followed the Gingery lathe build and your previous adventures. I', pretty sure that you will pull it trough with that setup with minimal problems. My rambling are more in the line of "Plan B/C", I'm eternal pessimist on my own projects.

What I ment that the margins are small on this kind of setup. I does not take much side load to bend this slender shaft that is pressed between centres and has cross drilling on the middle. Even without drive it cutting bit will make hula hoops (small) + cutting force will retard the bit a little and then you have a little drive force.

Grinding between centres illustrates this and usually (if precision is the driving force) centres are dead and drive is with separate drive plate, that rotates on it't own bearing to separate the drive as much as possible from the shaft. I relaizi that shaft grinding is a diferent process from linebooring, but setup has few parallels.

Consider this:
http://www.harigmfg.com/lectricctrs.html

Antoher thig....if the slender shaft is a bit more stable when it is on tension, vs. when it is compression. Easy to understand when you think machine ball screws, they are always pre tensioned, not only to prevent play (preload), but also to dampen vibrations and to make then more true. My memory might be failing me, but orginal Gingery setup had a boring bar in tension? Did it?

Pekka

[vtsteam]

Pekka I appreciate the concern, but as I said, I think it will be fine. That's just personal estimate based on my own experience, and the fact that I'm working with the real thing instead looking at a photograph on a forum. You're free to interpret things pessimistically. Maybe I'm wrong. If so it won't be a big deal, as I've said, I'll alter to suit. 

[vtsteam]

Cutting shims from an aluminum iced tea can. These are .004" thick and 5/8" wide. I'll pack them under each side of the headstock cap before boring. I have thinner (.001") brass shim stock on hand. So if I over-bore, I can actually reduce in half thou steps.

[vtsteam]

Catching up on other small but necessary chores before boring the headstock. I cast a clamp piece for the tailstock from some mixed scrap zamac sprues. I was able to use the clamp for my Craftsman lathe as a pattern since the bed and way proportions are the same on the new lathe, and I am using a Craftsman casting for the tailstock.

Using an existing part as a pattern was a little tricky. Normally I use a wood screw as a handle for withdrawing a wooden pattern. This cast iron pattern was very hard to grasp -- I tried tweezing it out with small artist's spatulas but it was too heavy and dropped back into the mold, damaging it. The metal was ready to pour. What to do? I ran back into the shop and grabbed an old hard drive magnet, and that worked well as a handle for the pattern. Quickly repairing the cavity as best I could with spatulas, I closed up the flask and poured.

Here's the result after shake out:

[vtsteam]

After a quick hacksaw and file session to get rid of the sprue, flash and vent wires, the result was better than I expected, or deserved after damaging the mold. Actually perfectly usable copy, and after trying a securing bolt -- the head was properly trapped in the slot, just like the original.

If I'd done a better job, I probably could have picked up the part numbers, but I was happy just to get a proper fitting part after. I'll remember the magnet trick in future.

[eskoilola]

The hard drive magnets are quite strong and I assume they may also damage the mold when they snap on the pattern. I suppose dropping the pattern back into the mold is far more worse though.

[vtsteam]

Man I'm starting to understand why Rob abandoned fora.

[Neubert1975]

Hi
Nice work, looks like you will soon be ready for the first tests of the new lathe 

[NormanV]

I miss looking at Rob's welding!

[eskoilola]

Pheewwww....

Have been reading this 3 year old thread for some hours now. Enjoyed every minute of that. I am quite impatient, so You should consider this as a statement.

I actually like the boring setup for the head stock. This way it is guaranteed that the head stock will become perfectly aligned with the tail stock.

From my very short experience on machining I would suspect some vibration. Bending the rod is not an issue as one can take thin cuts and use a razor sharp tool to do that. My experience on line boring is equal to no experience. I will be following this thread as I do have a use for this kind of a setup.

How did You set this up ? I mean, how accurately does the support behind the head stock need to be aligned? I would have a lot of difficulties in getting the rod aligned with the ways (I suppose this is how it should be).

After reading Your thread I assume You know all the common tricks to dampen vibration on this setup. Probably You also know a few not so common too. Mind sharing those with us? Asking this without knowing anything about zinc alloy vibative properties.

All in all - nice and partly really funny thread. Pleasure to read. Thanks !

P.S. Sorry about the snapping magnets. I just happen to have a bunch of those hard drive linear actuator magnets and those are very attracted to anything and especially wit each other. One can hurt fingers with improper handling of those. Why do I have a lot of those ... I am an DWH specialist ... go figure.

[vtsteam]

Norman, me too. I miss everything he did. Always amazing and interesting.

Eskoilola, just put something other than fingers in between magnets and what you want to pick up. You can glue sheet rubber onto one face, or leather, and vary the thickness to vary the amount of attraction. You can also transfer magnetism down a rod at reduced levels to pick things up. Lots of ways to skin a cat. If you turn the magnet on edge, and it's still attached to its backing plate, as mine was, you can also reduce the snap. I was wearing leather gloves to pick up the cast iron clamp, so I was able to ease it down that way, and didn't mind trapping a little of the glove under. I had hot metal ready to pour and did what I needed in a "pinch". 

Got 'er done.

[vtsteam]

Thanks Neubert. 

[vtsteam]

And to all......it's hundred times better to do something than theorize about what could possibly happen if you did. Discussing results before boring, is well.....boring.

Ya know, there's a wasp nest in the ceiling above the shop, and maybe while I'm cranking the leadscrew, a wasp might sting me on the eyeball, and I'd then start cranking too fast and not notice I was boring too deep, or if it's raining lightning could hit the lathe and melt the zamak at a different rate than the steel, and I'd have wished the lathe had been cast in iron.....or rubber. Or an earthquake might swallow up my whole shop before I had that headstock bored, and then where would I be? In the "other place" where I belong, no doubt.

Or I could just wait and see what happens when I actually start making a hole in the metal I want to make a hole in.