Parting off problem

[Sterob]

Hi Guys,
I was parting off some spacers out of 30mm dia, with 12 mm hole in centre, mild steel, today, on my new AL-335 lathe, and I noticed a problem.
The tool seemed to be moving towards the chuck as I cut deeper into the metal, consequently, the cut was getting wider and the back face of the spacer had a conical shape to it. I had to move the tool out and pull the cross slide out towards the starting point and continue cutting.Very strange.
The carriage was locked to the bed, the tool post was locked, the tool was square to the job, the lathe was running at around 200 RPM and the tool was cutting nice with no chattering, etc.
Has anybody come across this sort of thing before? I certainly haven't.
The only thing I can think of that could cause this is the stock creeping out of the chuck (chuck was tight) or the cross slide being forced to move towards the chuck ( no noticeable backlash) , neither seem plausible.

[graemet]

You'll probably find that the pressure on your parting tool was pushing it back which was turning your toolpost very slightly in an anticlockwise direction. This will have the effect of moving the tool toward the chuck. Tighten your toolpost.
Cheers
Graeme

[Sterob]

I checked it for tightness twice, but what you say makes sense. Maybe I have to look deeper. I have a look at it tomorrow.

[Article99]

You'll find the cross slide has a small sunken hex head on it to lock it to the carriage, do it up nice and tight. Slow the RPMs down a touch and ease up on the cutting pressure. It sounds dumb, but this problem can also be caused by the parting tool running above centre. (Job pushes on the front clearance of parting tool rather than the cutting edge and forces it away, rather than cutting.)

[Metal Head]

Was your parting tool (holder) screwed down tightly as you said everything else was.

When you said was was square to the job what did you check it with?

MH

[Sterob]

"...the cross slide has a small sunken hex head on it"
Nothing like the carriage locking cap screw. There is a grub screw on the side of the x- slide that I assume is for adjusting the dovetail fit. Is that what you mean?

Parting off tool is the one in the 9 piece chinese kit from H&F and it is the correct height for this machine ( 16mm) I have not checked it.

Tool holder was tight in the tool post.

For squareness, I relied on the stop on the tool post. Tool holder was flat against the tool post.

It seems to cut ok, no chattering and swarf looked ok. It was almost as if the round bar was being drawn out of the chuck as I cut. Very strange .......

[Article99]

Yes, that's the one. You can use it to lock, or make the cross slide fit tighter. (Useful when you're turning tapers and don't want the thing rattling around and leaving chatter marks on the job.)

When you align the tool square, use a bright coloured piece of paper underneath the gap made between the tool and the job. (I use those fluro sticky notes, myself.)
It doesn't matter how cock-eyed the toolpost looks at this part, just the tool itself.

There was another thread not too long ago (See here), where the various geometries of parting and grooving tools was discussed. Scope it out and check the various clearances on your tool. (The Chinese don't seem to be able to make things straight, let alone at defined angles. But then, neither would I at 50c an hour.)

If you can, use the parting tool to do some light facing cuts on the front of the job, so you know it's running on centre.

[Metal Head]

It doesn't matter how cock-eyed the toolpost looks at this part, just the tool itself.

Personally I do feel it is important to have the toolpost square to the job especially if the toolholder is locked flat against the support wall of the toolpost.

I do it of 2 ways. Place a square on the item (located in the chuck) and check it is square with the parting tool. Or alternatively you can offer it up to the front face of the chuck and lock it in position. If you are having trouble understanding the tribble, then please let me know and I will hopefully get the opportunity to take some pictures at work to explain what I am talking about.

Regards
MH

[Article99]

Personally I do feel it is important to have the toolpost square to the job especially if the toolholder is locked flat against the support wall of the toolpost.

If it's a cheapo Chinese tool that has a soft shank, how can you trust it to be straight and true behind the cutting edge and side clearance? Or even for the clearances to be correct? That'd be why it's important to ensure the cutting edge is square to the job, with the appropriate side clearances ground on the tool. After that'd it'd just be down to tool holder rigidity, surely?

[Metal Head]

Hi AT99,

I don't think you read all what I wrote. As I said "Place a square on the item (located in the chuck) and check it is square with the parting tool". What I was saying in regard to the toolpost was if that is square and the toolholder is pushed up roughly square (obviously this depends on the important squareness as mention above in RED) to the backface of the toolpost then it should not move unless something hasn't been tightened down hard enough. Fortunately I have never used dud tooling in my life thus I wouldn't know about el cheapo Chinese tools.

Btw, are you a qualified machinist? If so, what machines were covered in your apprenteship?

Cheers
MH

[Article99]

Hey MH,

I didn't ask whether you'd used dud tooling. That's quite irrelevant. I was merely pointing out that neither of us have any idea of whether Sterob has a bogus tool or not.

My only reason for questioning you as such is that you're using the word 'if' an awful lot. When troubleshooting, 'if' should never be used. It either is or it isn't. (Something that must be checked if all is not working as it should. A square's a start, but certainly not the end. And when using it, you must be specific. What part of the parting tool should be square? The side clearance? )

For all we know it could be a case of the parting tool hanging out a bit too far and flexing under pressure.

And if you need to have a piece of paper to work out how to use a parting tool on a lathe, you're probably more suited to wearing an apron and doing sheet metal work, mate. Plus/Minus 10mm kind of deal.

Oh, btw, if you read my profile, you'll spot the word 'apprentice' in it. Notice, however, that it says Toolmaker afterwards, rather than butcher. When you can grind carbide tooling accurate to a few microns on machinery built before WW2 started, get back to me. Until then, don't even dare to look down your nose at me because I'm an apprentice.

Cheerio ,

Article99

[Metal Head]

Hey MH,

When you can grind carbide tooling accurate to a few microns on machinery built before WW2 started, get back to me.

Cheerio ,

Article99

Hi Article99,

As Arnie would say I am "BACK".

I did my apprenticeship (toolmaking – press tools) and some post apprenticeship experience at the largest car component supplier in the UK (and most of Europe).

I manufactured machined, sheetmetal work, piping & welded parts for Harrier, Tornado, Hercules etc aircraft in the RAF as well as ground support systems and I have worked at 3 universities whilst here in Melbourne. So I think I know a little bit to know what I am talking about mate. Grinding aircraft parts is more exacting carbide tips. Why don’t you do yourself a favour whilst you are young enough and join the armed forces and travel the World and get paid for doing what you enjoy doing.

I use the word "if" quite a bit here because most posts do not contain pictures thus a lot of presumptions can be made.

MH

[Article99]

Sorry, carbide tips? LOL. Think more along the lines of extrusion dies, step drills, profile cutters etc. We actually supply the aircraft industry, too. Quite fun making profile tools for those guys. Max of 2 micron runout and 3 micron diameter tolerances plus the actual profile itself. C?*ty stuff.

That said, I will take a moment and apologise. If you're a grinder, you'll know where I'm coming from when I say the majority of tradesmen in Aus aren't craftsman at heart anymore. It's all done on an NC lathe at a million miles an hour, plus minus 100 micron.

Myself, I spend the majority of my time on a cylindrical or a tool and cutter. The lathe and mill are really only there for making jigs and doing foreigners.

Don't really like the idea of boring gun barrels for an assault rifle thats gonna get used at less than 300 yards. Just not the same calibre (lol) as what I do now.

Anyways, matey, thanks for clearing up your own background and correcting me in the same hit. Had you figured for a run of the mill fitter & f*cker doing the odd bits and pieces in some maintenance depo. Glad to know it isn't the case.

Peace.

[Metal Head]

Sorry, carbide tips? LOL. Think more along the lines of extrusion dies, step drills, profile cutters etc. We actually supply the aircraft industry, too. Quite fun making profile tools for those guys. Max of 2 micron runout and 3 micron diameter tolerances plus the actual profile itself. C?*ty stuff.

That said, I will take a moment and apologise. If you're a grinder, you'll know where I'm coming from when I say the majority of tradesmen in Aus aren't craftsman at heart anymore. It's all done on an NC lathe at a million miles an hour, plus minus 100 micron.

Myself, I spend the majority of my time on a cylindrical or a tool and cutter. The lathe and mill are really only there for making jigs and doing foreigners.

Don't really like the idea of boring gun barrels for an assault rifle thats gonna get used at less than 300 yards. Just not the same calibre (lol) as what I do now.

Anyways, matey, thanks for clearing up your own background and correcting me in the same hit. Had you figured for a run of the mill fitter & f*cker doing the odd bits and pieces in some maintenance depo. Glad to know it isn't the case.

Peace.

Hi Article99,

No need to apologize it isn't what I was after. You seem to have a similair outlook of the industry as I do. I have never worked on a NC, CNC etc and I don't want to. I accept there is a lot of skill required do the program and setting the machine up but it has never turned me on - pardon the pun. I prefer manual machines, getting a blank piece of material and making something precise out of it and being able to say I made that with my hand skills.

I remember as a kid having to walk a mile and a half to school and walking past a mates house. It was one of the biggest houses in the village and I thought what job does his Dad do to be able to afford that - he was a toolmaker (plastic injection moulding). Initially I thought they made things like spanners, screwdrivers etc but I was wrong. So in my last year at school I decide to look for an apprenticeship as a toolmaker. I was very fortunate to get the only one at the car supply company I spoke about previously. There were some excellent tradesmen there whom I learnt a lot from. Decades ago being a toolmaker was quite a well respected job by many folk but that has disappeared. Doing tool and cutter grinding is a very demanding & a precise job and I would imagine very satisfying? Do you get much variety at the company you work for? At least once you have finished your apprenticeship you can go either west or north of the country and make some big bucks - unless the resource sector falls into a heap. However, I don't see that happening whilst China keeps powering on.

I take my hat off to you Article for having the b---s to offer an apology but it wasn't warranted. Just remember our job here is to keep reminding these woodies they chose the wrong materials (trade) to be in.

Have a great weekend
MH

[Article99]

Hmm.. I must admit, I'm of a slightly different persuasion on the great NC debate. They have their place, like any machine. -Production. Nothing more. If you want absolute accuracy, you have to chase it by hand. No amount of servos and ball-screws will deliver it.

Variety's quite good where I'm at. Yesterday I was grinding a batch of blanks to go O/S, today I dismantled and serviced the work head spindle on an old J&S Cylindrical. There always seems to be something different to do. Especially on the factory maintenance side of things. (Nothing gets fixed until its been broken to the point that its only good for off-hand grinding. And even then...)

Strange nowadays, tho. I really thought there'd be more new toolmakers coming through than there is. In my class of 60 at Swinburne, I'm one of only two there. All the other lads are pretty much just maintenance.

Here's hoping you have a great weekend too and we've got another twenty posts of angry woodies to have fun with.


... Nearly forgot. We've still gotta get Sterobs parting tool working for him. Hey sterob, if you're still tuned in, can you take a few pics of your setup, mate?