A wild idea for my worn lathe

I have a hare-brained idea for coaxing a little bit of accuracy of a lathe with worn ways. I'd welcome comments.

First, a bit of a background. Out here in the sticks where machine tools are scarce, I've given up on ever finding an accurate lathe. I have two Sheldons, I had high hopes for one of them, but as it turned out, it produces a very serious taper.

In its first lifetime, my other lathe was used in an automotive shop for doing commutator work. Therefore, all the wear on the ways is over a very small area.

Here's my idea. For the rare occasions when I need to turn something accurately between centers, I could chuck up a 6-inch length of sturdy drill rod and turn a 60° taper (center) on the outboard end.

That way, I'd shift the carriage travel out beyond the worn spot, where the ways are pristine and like new.

What do you think?

Of course, I'd have to jury-rig a catch-plate and I might have to add the support of a steady rest near the outboard end.

As I see it, the extended center would be no more flimsy than the protruding 5C collet adapters that are made for lathes with spindle bores too small to accomodate the 5C collet.

If this thing would work out, I could make a super-sturdy spindle extension out of 2¾ or 3-inch round stock or heavy wall tubing. It would thread directly onto my 2¼" spindle. The outboard end could have, say, a 1½" X 8 TPI thread, shoulder and register to accomodate small chucks.

I probably wouldn't bother with turning a Morse taper at the far end because I wouldn't mount a center out there, anyway. I usually use ad hoc centers made of chucked round stock.

If this could work, it would put an end to my futile search for an accurate lathe.

Thank you for your comments and suggestions.

Regards,

Orrin

I

There are a couple of things that are not optimum about the concept but this is a clever idea that can be tried out in less time that it takes to think about all of the disadvantages.

The idea can work - but I gotta wonder what kind of taper it's turning? Is this a benchtop lathe? You can usually shim the feet to twist the bed and take out the worst of tapers.

Damon, for evenly worn lathes your suggestion has merit. But this doesn't turn a taper. From a couple of inches out from the headstock and all the way to the tailstock the subject lathe turns a true cylinder.

There is a short "whoop-de-do" worn spot near the headstock. There's no way any kind of leveling or bed-twisting is going to correct it without seriously impairing the accuracy of the remainder of the carriage travel.

As I've been mulling this thing over, it occurs to me that I've got some truck axles on hand that I could use for the extended center. They're already annealed and ready to go. A trial run shouldn't cost me anything but my time.

I might add that I'm a home shop machinist who builds model hot air engines, mostly. This extended center won't have to support much weight. The spindle bearings are pre-loaded tapered rollers, so there's next to no spindle "slop" as one would have with plain bearings.

Regards,

Orrin

You might try googling "brush plating". The process is used to locally build up areas of shafts or slides to estor dimension. A nickel brush plate can be applied up to about a 16th of an inch and placement is controlled by the handling of the brush. Kind of like "anti-scraping" to do a repair.

Orrin, I think that's a great idea. I think Donie on the EE forum has a Manufacturing EE with a similar problem, and he just works around the worn spot by keeping parts out from the headstock where the wear is...hopefully he will clock in and expound further details.

-Matt

Really, the world is a much smaller place than it used to be.

If you need a better lathe, locate one, buy it, and take a weekend road trip to get it. Buy a bag of 10 McDonald's 89 cent hamburgers at your first gas stop and eat them on the road to save time. Wear your most comfortable clothes. Don't shave. Use the water fountain at a rest stop to wash only the discolored parts of your body. If your trip runs long, have your wife call in to your boss and tell him you have "personal problems" and won't be in Monday. And maybe not Tuesday, either. An artist must suffer a little for his art.

With LA on the same coast, there should be be plenty of lathes within a couple days of you.

Orrin,

I like your idea.

One issue is that of rigidity, with the extension away from the headstock bearings. Any play in the headstock bearings will be amplified by the extension, but six inches isn't too much.

I suppose you could make a "third headstock bearing" and place that six inches out from the headstock. One way to do this would be to find a stock sealed ball bearing which has the inside diameter to match that of your drill rod extension. You can hold this bearing snugly within the jaws of a steady rest.

Good luck, and please let us know how your project works out.

Jon

Ya, Matt pulled me in on this.
To avoid the most worn area on my old EE, I use a aloris multi tool holder and slide the tool post as forward as possible. Also extend the work from the chuck jaws if possible.
This keeps the carriage back on the less worn area of the bedways.
Still can squeez some more out of a machine that has been in service for over 50yrs.

Ah I see. Would it be possible to build up the bedway somehow? NiPlate was mentioned, possibly you could use Moglice and do it yourself ?

Or can you do the nickel just with a brush, or is there a dunk and bath step too?

Considering that the saddle guideways are likely what... 10 to 12" long, and that the machine has been run back and forth over a 6" area, and that the saddle is going to be worn to fit to some degree, I don't see how moving the saddle 6" further out really accomplishes very much. Moving the worn saddle onto the good ways should still result in a lousy fit.

How much taper does this machine show? How are you testing it? A between centers test can be totally misleading.

Lathes are only milling machines turned 90 degrees. Tool and cutter grinders can be made- use a cheap DE grinder if the headstock is too far gone.

Go back and buy another one!
Sit and watch the ideas growing.

Norman

STUPID REPLY .......now deleted

We have one of the Brush Plating units ... My business partner thinks it is the cure for everything, but it has it's limitations... It is great for applications , such as a bore or shaft, that is going to be pressed on, to stay. But for an application on a way, where there will be sliding, I do not think it will hold up... The few times I tied to use the plating for things like that, it flaked off in a short time..

I did a search on brush plating and found some claims of high wear resistance and machinability using hard-chrome. I for one would love to hear if this is scrapable.

Ha Ha, I didnt say moving the carriage back on the less worn area of my well worn 51 EE would bring it to the accuracy of my tenth splitting 83 EE, but it does help. Give it a try, might be good enough.

Don

I'd try putting some epoxy steel on the ways after a thourough cleaning and little bit of rough sand paper to get tooth. Then scrape it using a precision straight edge to check it. I't would probably last the rest of you life if you kept it oiled and clean. What do you have to loose?
I was going to do it on my old time lathe till I got the Rockford planer. Now I've changed the plan to planing everything true.

Seeing how wild ideas are being tossed about here....I don't know how your Sheldon is built but couldn't you just move the headstock down to straddle the troughed out area? Possibly shorten the shafts accordingly if needed or let them hang out the tail end. Better than dumping it.

Bluechip beat me to it. I was going to suggest moving the headstock up to the worn spot, but not straddling it. But then you'd still have the same problem whenever you needed the carriage dialled in that far towards the headstock. But the idea has merit- possibly repair using epoxy or whatever is suitable, then mount the headstock over that area. Less of the bed length would be used up than if you straddled the worn spot. The benefit is you wouldn't ever have the carriage riding over the filled spot. Of course, you'd be in for some headstock alignment issues. As far as that goes, you may not need to use a filler to build it up, depending on what does the aligning, and where accurate metal is actually required under the headstock.

Some one on here once posted though I have no idea of how ture it was a story of how machinist one day found all the good lathes to be taken except the one machine that had a really worn area right on the first few inches of the bed. So the guy simply chucked up a 6-10inch long 4-5" dia peice of barstock, put on the steady rest, and machined the end identical to the spindle. Then he chucked up onto his new spindle and machined away in the less worn part of the bed. No idea how true that story is but sounded prett cool.