How far would you go?

[SpurryParticipant @spurry]

Following on from the Parting Off Problem thread, I posted a picture of a little 'thought-provoking job'.

How to part off a 20mm slice from a 5 1/2" (140mm) chunk of bar.

Muzzer was the only person to offer advice, so today I decided I really ought to finish the task.

I used an insert parting tool in stages. 1st stage gave me a slot 30mm deep. 2nd – 41mm deep, and 3rd almost 49mm. At that point I chickened out and hacksawed the remainder. Speed was 40rpm and auto feed of 0.10. One hand squirting oil into the slot and the other hovering over the Stop button.

So the question is: Was I being a wimp or just lucky to get as far as I did?

Pete

[SpurryParticipant @spurry]

[Chris Evans 6Participant @chrisevans6]

Good work. I have never had a lathe ridged enough to attempt that. At present making a new cross slide incorporating rear tool post, once fitted and with new lead screw and nut I will attempt more parting off.

[Ian S CParticipant @iansc]

Pete, at that size I chicken out, and use the bandsaw, I'v had a couple of cuts lately through 120 mm steel bar, the cuts were .010" out of square, so no complaints there.

Ian S C

[Clive HartlandParticipant @clivehartland94829]

You did right and it was a normal procedure, a jam up at the deep point would have badly strained the top slide and saddle. Maybe made damage to the tool and tool holder.

Clive

[MuzzerParticipant @muzzer]

I certainly won't rib you for stopping when you were up! You must surely be using the tool beyond its specified range so who knows what would have happened if you'd tried to finish it. The result stands!

Was it noisy, ie juddering and chattering? Did you get proper swarf from it?

Here's a vid of parting off in my Bantam, although on a more modest scale!

[David ColwillParticipant @davidcolwill19261]

I don't think you need fear being called a wimp! I wouldn't have gone as deep but then I do have facilities to bandsaw that diameter. If I didn't then….. Let's not think about that!

Regards.

David.

[Ady1Participant @ady1]

So the question is: Was I being a wimp or just lucky to get as far as I did?

Impressive. It took me over two months to hacksaw 5 slices of 5 inch billet, I would never have dreamed of parting it off, (even if my unknown steel billet hadn't been capable of blunting fagersta wke45 )

Note to self. Part off as deep as possible, close to the chuck, then hacksaw the rest of the way through

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ady1 on 30/01/2016 11:14:47:

Note to self. Part off as deep as possible, close to the chuck, then hacksaw the rest of the way through

.

Ady,

Please accept a small edit:

Part off as deep as possible, close to the chuck, then [*] hacksaw the rest of the way through

[*a] remove from the lathe and

or

[*b] insert a board to protect the lathe bed and

.

I've seen too many examples of damaged lathe beds, so I had to mention this.

MichaelG.

[Swarf, Mostly!Participant @swarfmostly]

Hi there, Pete,

I think you did well there, I've yet to master the gentle art of parting-off! I'll have to practice 'holding my mouth right'!

I did do one thing right, though – the first accessory I made for my ML7 was a 'chuck board'. One advantage of the flat-top bed over the vee type is that a chuck board is so simple to make, just a bit of board or ply with a batten screwed to the underside of its front and rear edges to snugly fit over the bed shears. That was in 1970 and it's still going strong! (Yes, all that time and I've never been brave enough to seriously tackle the 'parting-off ogre'!! )

The only problem is that when it's not in use it's vulnerable to the 'swamp all horizontal surface' fungus!!!

Best regards,

Swarf, Mostly!

[egaParticipant @ega]

I have a faint recollection of an account of some early racing car, possibly one with an aero engine, that needed a flywheel. The makers located a large billet of suitable steel in a scrap yard and sent two lucky people armed with hacksaws and instructions not to return until the necessary slice had been sawn off! I think they were there for some days.

Does this ring a bell with anyone?

[Brian HParticipant @brianh50089]

I've always found that cutting oil or fluid or paste, even if applied with a brush or stick eased parting off no end.

I have a Boxford AUD at present and one day I'll get around to fitting the new coolant tank and pump! At the moment I use Rocol RTD, simply because I have some.

I also hacksaw the last bit because I have the parting tool slightly below centre for big stuff and it doesn't pay to try and go too deep.

[Manny lambertParticipant @mannylambert86533]

Hi every one, I am new to model work. I have a good lathe and I would not have attempted that cut. From my limited experience I have found that as you get deeper the work contracts unto the cutting blade and can jam up.

All the books I have looked at recommend a 3 cut approach to widen the slot, but can anyone tell me if we could mount a coarse tooth hacksaw on a pivot fitted to a rear tool post and then use it as a cut off tool, the work revolves and not the blade it justs pivots.

[davebParticipant @daveb17630]

Bandsaw for me!

[Chris Evans 6Participant @chrisevans6]

My chuck board is always put in place to protect the ways when polishing with emery. Does any one else do this ?

[Mark P.Participant @markp]

As an aside has anyone used those chip breaker HSS parting blades,and what is their opinion of them?
Mark P.

[SpurryParticipant @spurry]

Thanks for the comments

I admit that I did have one heart-stopping moment, when the tool was moved out for stage 3. It dug in briefly before I hit the button. I found the tip was chipped on the left-hand side, replaced it, and carried on. It was only after completion that the tip must have been chipped at the start for the rough finish, and the shiny section shows where the new tip started.

Posted by Muzzer on 30/01/2016 11:07:08:

Was it noisy, ie juddering and chattering? Did you get proper swarf from it?

No chattering – only when I started at a higher speed. Got to the slowest of 40rpm and the chatter stopped. Also have the VFD, so could increase revs as the cutting diameter decreased. The swarf was small chips but perfectly formed.

Pete

[SpurryParticipant @spurry]

I had watched the v large bandsaw at the stockholders sawing through this bar and it was taking that about 20-25mins. I was standing watching it, imagining cutting it by hand….

Posted by Ady1 on 30/01/2016 11:14:47:

It took me over two months to hacksaw 5 slices of 5 inch billet, I would never have dreamed of parting it off, (even if my unknown steel billet hadn't been capable of blunting fagersta wke45 )

Pete

I have yet to work out how to insert more than one quote without losing all previous typing….

[SpurryParticipant @spurry]

Posted by Manny lambert on 30/01/2016 15:55:20:

Hi every one, I am new to model work. I have a good lathe and I would not have attempted that cut. From my limited experience I have found that as you get deeper the work contracts unto the cutting blade and can jam up.

All the books I have looked at recommend a 3 cut approach to widen the slot, but can anyone tell me if we could mount a coarse tooth hacksaw on a pivot fitted to a rear tool post and then use it as a cut off tool, the work revolves and not the blade it justs pivots.

I think that depends on the actual cutting face of the parting tool. The one I use has, for want of a better expression, a hollow centre, bending the swarf inwards on both sides and the swarf comes off in small coils which don't seem to jam up the same, as with a straight-across cutting edge.

If you used a hacksaw like that you would only be using a tooth or two. I have heard of some who use the lathe at slow speed whilst cutting with the hacksaw. *I* could not possibly admit to doing such.

Pete

Edited By Spurry on 30/01/2016 18:57:27

[Brian HParticipant @brianh50089]

Posted by Mark P. on 30/01/2016 16:56:19:
As an aside has anyone used those chip breaker HSS parting blades,and what is their opinion of them?
Mark P.

I find it depends on the material being cut; With fc brass and steel and CI I wouldn't bother as they chip by themselves but aluminium, and ordinary mild steel I prefer a chipbreaker to prevent the swarf from wrapping around everything in sight, especially fingers!

[Ian S CParticipant @iansc]

Even the band saw is not fool proof, about twenty years ago (job for the same bloke as the one above, different tractor), I needed to cut a 6" dia bar of unknown steel, so I put it in my then new band saw, and started cutting, all went well until about 3/4 the way through, then the saw slot suddenly closed up, and stopped the saw, switch off, wiggle the blade, scratch my head. I took the blade out of the saw, turned the bar and blade over, put in another blade, and started the cut from the other side, saved the first blade, and decided that that was the last cut in that bit of steel, the 14" left over makes a good door stop.

Ian S C

[MWParticipant @mw27036]

I would say that you did a pretty good job of it, you followed good advice and kept the feed and speed nice and slow with a tip hard'n rigid enough to take the cut,

i'm sure we've all got our stories but i attempted a similar cut whilst making a lathe back plate from cast iron, it was pretty hairy to begin with, hot sparks going everywhere, so i slowed it right down and she duly obliged and took it nice and slow through the whole metal, about 3 or 4 inch deep cut with a similar insert tool, i now know you've got to treat cast iron with a bit of respect.

someone i knew once told me you can back the tool out and move it a few mm and start again to widen the cut. Also, if you don't have a through hole to run into at the end, watch out for the centre height!; there's the time its most likely to snag if its a little off.

Ps: i'm surprised to hear about a similar problem with a band saw, i think it happened to me with a 4 inch block of standard aluminium.

Michael W

Edited By Michael Walters on 31/01/2016 10:47:13

[AdrianhParticipant @adrianh95127]

Very lucky to do this with this tool!

At this cutting depth you need to provide additional clearance for the swarf, I do this at work on a much larger machine by taking 2 small cuts, 1 approx 2mm offset (for a 3mm too)l away from the chuck to a depth of say 25mm each time. This allows coolant in and the swarf out. At the smaller diameters you need to speed up the chuck to maintain an adequate surface speed at the tip.

When these tools seize they tend to snap the holder below the insert – very expensive!

Also always a good idea to push against the job with a revolving steady to stop it moving out of the chuck.

[Author]

Posts