If we assume you've got 1hp to play with then a cut of 0.1" depth, at 4 thou per rev, and a surface speed of 200fpm should be about the maximum, assuming carbide tooling. At the larger size, 200fpm is roughly 127rpm. That gives 6 minutes per cut, in theory. Roughly 2 hours a part. Of course as the diameter decreases then the speed can be increased.

Two hours seems like a long time, but unless you have some serious cutoff style saws I suspect that grinding is going to be difficult and just as time consuming. Plus you'll have to finish turn anyway.

You're welcome to borrow my lathe (3hp), but I'm quite a long way from Cheshire.

Regards,

Andrew

PS: Is that a VFD control box over the screwcutting gearbox? If so then all calculations go out of the window, unless you can ensure that the motor is running at, or above, base speed.

A Carbide tool and auto feed (screwcutting feed)

Shouldn't take too long on a boxford

All you do is crank it back, set a bit deeper, and re-engage after each cut

If you do a parting off cut just beyond 80mm near the chuck(backgear can be useful for that) then you can rough cut in both directions with a pointy carbide tool, saving yet more time

edit: That's a pretty mincy looking cutting tool setup you've got there btw

Something a bit stiffer will make a huge difference, like a cutting toolpost directly on the cross slide

Compounds are really for more detailed work

For Metal munching have a toolpost you can put directly on the cross slide, and secure the overhanging end with a live centre

(If you had a rubbish hobby lathe you would learn all these things the hard way)

Double edit

Is that a magnetic chuck you're holding the workpiece on with??

Edited By Ady1 on 12/06/2013 12:31:52

Edited By Ady1 on 12/06/2013 12:33:55

In case you missed my edit

Use a live centre on the overhanging end, it makes a big difference for stiffness

Is that a magnetic chuck you're using??

Edited By Ady1 on 12/06/2013 12:37:53

Ian,

Would use a centre in the tailstock anyway to keep the job pushed into the jaws, it cannot come out then. As said before beef up the tool-holder…..

Trevor

If I understand your description correctly, you are making a part with a 50 mm spigot 80 mm long, with a main part 160 mm in diameter. I must say if I were making something of these dimensions I would be looking at fabrication – either Loctite or silver solder to fix a spigot in a bored hole in the disc. Much quicker and cheaper. However, I do understand if it's for someone else, and they specified it and supplied the material, you may have to go that way.

Just out of interest – if you know – where did you get the EN24T from? Lovely stuff, used it a few times myself.

David

Yes, I made one of those for my S7 many years ago – from a Hemingway casting IIRC. Most useful for doing large chunks of iron. Not sure, but it may be possible to adapt it for a Boxford; I'd guess Kirk (did I remember that right?), the new owner of Hemingway Kits would know, seemed a helpful guy when I spoke to him a few years ago.

David

Edited By David Littlewood on 12/06/2013 16:15:12

Scotch tool – annular cut into face of work as deep as it will go – part off ring – repeat as nescessary to get full metal removal – probably 3 or 4 go's will do it .

Optionally do it the other way round – part deep grooves into work and allow rings to break off as a continuous annular cut meets each groove .

As a general principle the worst way to remove a lot of material is to reduce it to swarf . Always worth looking for two different direction cuts which will intersect and cut off whole pieces .

For interest – most efficient ways of shaping metal are casting , forging and sawing – turning and milling are way down the list .

MikeW

Edited By MICHAEL WILLIAMS on 12/06/2013 17:24:29

Hi Ian,

During previous employment in an oilfield equipment manufacturing business the machinists worked on large billets (4130/4140 as most basic material) up to inconel 718. For bulk removal they generally prepped the workpieces on large manual lathes using large trepanning bars (generally made in-house with Sandvik TC tips and holders fitted) to remove cores for internal diameter roughing. These were tubular with relief added for chip removal around the tips. Basically a large holesaw but with tipped cutters fitted. This could be done but might add significant time for trenapping and also grooving/parting.

Many thanks,

Neil

If you're taking heavy cuts off a chunk like this, apart from a more rigid set up (like the Gibraltar tool post already mentioned) I'd be inclined to use a tailstock centre too to push the metal towards the chuck. If you get a dig in, that's a large chunk to come flying out and the urge to cut faster and heavier on this sort of job is likely to lead to just such a problem.

I might try getting a core drill into it, then attack from the side with a parting tool.

But with so many teeth in action at the same time, a beefy motor might be needed, and core drills can have problems with clearing chips from a deep annular groove.

Andyye