horizontal turntable lathe

[darryl]

Having had the problem of trying to turn large diameter workpieces from time to time, and not wanting to buy a very large lathe (which I don't have room for anyway), I've toyed with this idea several times. With a horizontal turntable and over-arm system, you can fixture a large diameter workpiece, then machine on it with a travelling 'spindle head'. It's a gantry mill, basically, but with a rotating table instead of a linear sliding table. You could mount something on it, like a flywheel as Cuemaker is having trouble with currently, and because it's horizontal, the flywheel or whatever just lays there while you take pains to center it. A jig or two helps you center it, then you clamp it down. The spindle head mounted on the overarm is under leadscrew control for horizontal positioning, and there would be a vertical range as well.

You have the options of rotating the table under power while using a stationary cutter (like a lathe), rotating the cutter only, rotating both, indexing the table, and supporting the center of the overarm with a removable post through the turntable axis (if the workpiece has a through hole big enough).

The turntable is basically a large faceplace, or a circular slotted milling table- whatever you would call it. It would have a hollow central shaft which is stationary, with a large bearing surrounding it carrying the table. The outer rim of the table could have support bearings as well to limit flex, or it could just be so solidly built that it wouldn't need that. I'm thinking it would be about two feet across, and probably have a maximum speed of about 300 rpm.

Normally, a workpiece that large in diameter wouldn't be very long, so a fairly short vertical range for the spindle head would not be much of a limiting factor. This could be the equivalent of a 24x10 inch lathe, or in some sense the equivalent of a mill with a 12 inch throat. If the overarm was able to travel over a range of about 12 inches in total, that would be roughly equivalent to a mill table having a Y range of about 12 inches with an X range of 24 inches. If you considered the overarm spindle to be the lathe spindle, you could mount stationary tooling on the turntable and use that as a sort of turret tool-holder. With the table held stationary and the overarm spindle stationary, the thing could be used as a shaper or slotter.

The worst use of it would be for long slender workpieces and threading, where a normal lathe of even modest size would suffice perfectly anyway.

Ok, so I either go down in flames, or you all will give me even more ideas and constructive criticizzleum.

[knedvecki]

http://www.garagejournal.com/forum/s...d.php?p=241806

[Dr Stan]

darryl,

Sounds to me like you're talking about a small CNC vertical turret lathe AKA vertical boring mill with live tooling.

Stan

[J Tiers]

So you seem to have invented the Vertical turret lathe..... Call up Bullard and see if you can get royalties from them !

I have thought about this...... obtain a cheap large swing lathe with decent headstock and shredded bed.

Cut off most of the bed, retaining enough to hold the carriage and give some travel.

Turn it up so spindle is vertical, and use the crossfeed and leadscrew or turning feed to move the carriage and tool. it might be pretty important not to drop the halfnuts or turning feed out of gear, so you might want to proactively take precautions......

Get a big faceplate for it and there you are.

Goofy, but it could work if you ensured the carriage gibs were tight.

[RussZHC]

Your phrase "gantry mill"...how about something similar to those gantry style CNC jobbies that pop up on woodworking forums BUT then develop a feature like a tombstone you could have in one corner of the square outside of the inscribed circle this table would form...pull the router off the gantry and attach it to the similar system contained within the height of the tombstone...it would allow you to have the choice of "more horizontal" or "more vertical" depending on what the work called for [sort of means you could always be working on a face instead of a face and a side...? am I even close to what your description envisions?]

[jugs]

Vertical turret lathes

Very small - http://www.youtube.com/watch?v=55KviJAUVzw

Small - http://www.youtube.com/watch?v=wLq2yX9a_6Y

Med - http://www.youtube.com/watch?v=pPz0z...feature=fvwrel

Big - http://wn.com/turret_lathe

Very Big - http://www.youtube.com/watch?v=9kfNX...eature=related

[darryl]

Maybe if I sold my house I could afford the lube for one of those machines for a day-

Yeah, I've re-invented the vertical turret lathe I didn't expect that I'd be the first one to come up with that idea, but maybe there's a way I can get one to appear in my shop- it would probably have to be classified as a micro VTL. I'm thinking of some kind of nano tech- you know, under 500 lbs

Got some good ideas, thanks.

[Timleech]

I've 'turned' shoulders for starter ring gears on big (23" dia) flywheels on my old Elliott combined turret/horizontal Omnimil.
I used a motorised rotary table (with stepper motor, driven from the controller on my CNC Bridgy) and a big endmill or small facemill in the vertical spindle. The results were very good.
Then used a gear cutter in the horizontal spindle to cut the gear teeth.
I did have pics on a web page with my old Onetel account, but they eventually took that down a couple of years after I closed the account.

I haven't done one for a while, as my 19" DSG will actually *just* swing 23" dia close to the headstock even though there is no gap.

Tim

Edit to add - pics here of the close fit in the lathe if you're interested, though it's away from the topic:-

[uncle pete]

I've seen old drawings from during the steam age for what they called "Pit Lathes", Just a huge headstock bolted to the floor and a monsterous faceplate large enough in diameter that it required a wide and fairly narrow pit in the floor so that part of the faceplate and large work attached to it was more than a few feet below floor level. The short lathe bed and cross slide were a seperate piece that was really carefully aligned to the headstock during the permanent installation of both parts of the lathe. On a smaller scale and with a really heavy duty purpose built bench the same thing could be done today.

I've had the same idea as JTiers about shortening a big old lathe just for doing larger diameters. I think it could work real well.

Timleech, That's about the tightest job I've ever seen that still fits to turn it. If a coat of paint had of been added you probably couldn't have spun that part.

Pete

[jugs]

So you seem to have invented the Vertical turret lathe..... Call up Bullard and see if you can get royalties from them !
I have thought about this...... obtain a cheap large swing lathe with decent headstock and shredded bed.

Cut off most of the bed, retaining enough to hold the carriage and give some travel.

Turn it up so spindle is vertical, and use the crossfeed and leadscrew or turning feed to move the carriage and tool. it might be pretty important not to drop the halfnuts or turning feed out of gear, so you might want to proactively take precautions......

Get a big faceplate for it and there you are.

Goofy, but it could work if you ensured the carriage gibs were tight.

Can see some problems to sort -

Most BIG old lathes are oil (splash/pump) lubricated so up-ended the oil is in the wrong place & the oil seal on the (Now bottom) spindle isn't designed to hold standing oil.

The bearings are designed for the component/faceplate weight @ 90° to spindle & the cutting thrust in line, turning on end puts all forces in wrong direction.

Most headstock's are bolted/doweled to bed (only having to resist cutting forces), turning on end puts the bolts into shear with combined - component/faceplate weight + headstock weight + cutting forces.