Bulk Metal Removal, Any suggestions?

I foolishly agreed to make some (4) custom wheel hubs for a car enthusiast but did not take into account how long! it will take just to reduce the barstock to a size where I can do the detailed bits.

I need to reduce the 160mm diameter to 50mm for a length of 80mm. The material is EN24T so machines beautifully but on a 5" Boxford is going to be long job.

I dont have a hacksaw machine but considered using a angle grinder/thin cutting disk to take of chunks (chord shape) which would have the side benefit of giving a few useful EN24 chunks.

If anyone with a big lathe who is running short of swarf wants to restock, I am open to some sort of colaboration.

Ian P

Edited By Ian Phillips on 12/06/2013 10:44:05

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.

Cold Chisel + 24lb Sledge Hammer

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

Thanks for the advice,

I guesstimated at least 4 hours based on the biggest cuts I normally take. The complications are, being certain the part is not going to come out of the chuck whilst I'm roughing it out, also the (550W) motor power is restricted by the last belt in an underdrive Boxford being a link type. It prone to slipping so I normally revert to using backgear. I can then take substantial cuts but safe workholding is hard to guarantee and this is a heavy lump!

Once I get it near to size I can mount it on my only faceplate (Drive dog carrier plate with 220 x 10mm ali disk fastened on).

Andrew, thanks for the offer. The diecast box is is the VFD remote.

IanP

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

Good idea about missing out the compound, I normally have a Dickson mounted but that has built in overhang. The tool shown is a cut down 20mm square Seco one. It is overhung only because the carriage was too high to get under the job.

Did you mean mincy or wimpy!

Not convinced about the parting groove gap, I find it quickest not to stop the lathe between cuts (to reverse the idler gears) so just wind back manually between powered cuts.

Ian P

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

Ady

Not a magnetic chuck, its a 4 jaw on its limits!

Ian P

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

You are going to get bored and leave it to it's own devices and forget and.......
Set up an emergency limit switch before it's too late.

Didn't Tubal Cain or one of the old hands about 40 yrs ago in ME often mention his 'Gibraltar' tool post - big lump like a rear toolpost. missing out the topslide. Another one from the old days was a holder with a vertical bar dropping down to the cross slide for support.

Depending on what is going to happen to the 'inside' currently up against the chuck you could drill/tap and run a bit of threaded bar up the spindle to pull it in tight.

David

The customer supplied the material. In the past I have bought it from Mike at Noggin End who will get sizes in that are not shown on their website.

I have fabricated similar proportioned parts (bolted, shrunk, loctite etc) but this part was not amenable to that construction.

Bazyle

Bolting through the spindle is a whizzo idea, The part will have a clear bore later so I will put in an M12 thread, that'l hold it! I will also rig up a solid toolpost in place of the topslide.

Ian P

Thanks Ian. I have used Mike quite a few times, just wondered if there was another useful source to add to the list!

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

I think I would have used a bandsaw to take chunks out (like Ian suggested), making careful use of depth stops to ensure no mistakes. Would leave a nasty interrupted cut to clean up but less swarf. Not sure how much use the awkwardly shaped chopped off bits would be. You could be turning one while another was being sawn.

Chris

Edited By Chris Heapy on 12/06/2013 16:23:50

Michael

I've not heard of a Scotch tool but an extra deep Starrett type holesaw would produce a really useful ring of EN24 (which I would never find a use for anyway!)

Another efficient way of creating objects is by additive manufacturing. Sintering would be another although 'efficiency' in all these cases is quite a complex subject if all the processes from the ore to the end product are taken into account.

Ian P

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'm with using a bandsaw to rou rough it out

Neil