Parting tool chatter

[goldstar31]

Out of curiosity, just how wide is a so called commercial blade?

I'm sort of amusing myself with access to a variety of tool and cutter grinders----- as my hacksaw is blunt

Next damn silly question is when does a normal lathe tool become a parting tool?

And what about this 'chip breaker' thing?

And when does one change from a 10 degree grind to a 5 degree grind.

Ian Bradley in his ancient book on Lathes and Shaping Tools-- Oh yes, I have a copy- change to THREE angles in a lathe cuttig tool? And Why?

Oh, yes

Of course, its an old book so what about grades of diamond dust paste?

Well the post has been drivelling on and repeat eating itself.

Clears throat--- WELL?

 

[BaronJ]

Out of curiosity, just how wide is a so called commercial blade?

I'm sort of amusing myself with access to a variety of tool and cutter grinders----- as my hacksaw is blunt

Next damn silly question is when does a normal lathe tool become a parting tool?

And what about this 'chip breaker' thing?

And when does one change from a 10 degree grind to a 5 degree grind.

Ian Bradley in his ancient book on Lathes and Shaping Tools-- Oh yes, I have a copy- change to THREE angles in a lathe cuttig tool? And Why?

Oh, yes

Of course, its an old book so what about grades of diamond dust paste?

Well the post has been driveling on and repeat eating itself.

Clears throat--- WELL?

Hi Norman, Guys,

Well the only commercial parting blades that I have are 3/16 and 2 mm both 1/2" or 12 mm wide. The only other parting blade that I have used is 25 thou and 6 mm wide. Though in the past I've used Stanley knife blades and hack saw blades all with some success.

As far as insert parting tips are concerned, I've seen them used but I've never used one.

When you get around to chip breakers and changing angles, I've always used two or three degrees of top rake and 7 degrees of front rake. I've not altered them for years.

Best move I made for parting off was a rear tool post.

 

[goldstar31]

mThanks John for the details.
I'm 'experimenting' AKA 'Fiddling on' with Chinese Deckel clone. Interesting beast

More Anon

Cheers

Norman

 

[dazz]

Hi
One of the main causes of problems with HSS parting blades is flank wear. Both sides of the tool wear creating a wedge shape that is plunged into the work. The wedge shape jambs into the parting groove leading to all sorts of chaos and mayhem.
The solution is to either reverse taper the blade (wide at the tip, narrowing further back, or better still, use carbide parting tools.

Dazz

 

[goldstar31]

Hi
One of the main causes of problems with HSS parting blades is flank wear. Both sides of the tool wear creating a wedge shape that is plunged into the work. The wedge shape jambs into the parting groove leading to all sorts of chaos and mayhem.


Dazz

Respectfully, your comments fail to hold water. In all my years- well since the early 70's when Thomas wrote up in Model Engineer Volume 142 and I made up a rear parting tool, I have NEVER had to regrind the flanks of my inverted tool. I still---- HAVE THE SAME TOOL. I apologise for the shouting but no one is reading either my comments or more importantly, the book on which included Thomas's designs and thoughts. Again, a long established firm- Hemingwaykits has not only continued to sell kits etc for the 7 inch lathes but has enlarged the drawings and casting to accommodate the same priciple for larger lathes.
ALL that has been necessary over these years has been to 'lick' the front of the tool.


Me, well, I have bought a new set of castings to make another to go on the back of my other lathe- a Sieg C4. With tomgue in cheek, I actually bought another 'Model Engineers Workshop Manual-- and gave the very grubby one away to a member of this Forum.

So apart from the unfortunate creatures who do not have the facility to mount a rear parting tool, I cannot see that buying a book is so seemingly impossible.

So moving on a tad, I have 'done' a normal lathe tool on the Deckel copy thing and honed the 'little radius' with a 600 gret diamond 'stone' and am ready to further hone the corner with a white Arkansas stone-courtesy of my late wife. Yes, a black stone would have been marginally better.
well, I now have to have a *** in what is really my only slightly adequate eye.

 

[johwen]

John Here,
One thing i have found is that use the narrowest parting blade you can. I have a 1mm blade and a .5mm blade. i make sure that the blade is exactly at right angles to the work and the cutting edge is dead square. This eliminate any side thrust you can put a slight v in top cutting edge this will cause the chip to slightly fall in making it narrower than the width of cut and less likely to jam. I use my blade upside down so chip will fall away and not jam Lathe is o cause running in reverse and use constant feed pressure to stop chatter and if it is a large diameter I use power cross feed. make sure all your slides are of cause adjusted neat without any slack. This works for me i also use 'T" blades. My lathe is a Chinese same as Brian Rupnows

 

[Steamchick]

I have a home-ground WC tool on my rear tool post for parting anything up to 1/2in. Dia. But it isn't ground for deeper penetration. 0.1in wide. My commercial tool is 1/16" wide, and as a long blade in a holder can be extended to go deeper.. I have successfully cut-off softer materials at 1 1/2" dia. Curiously, the top face of the long blade has a few degrees of side taper for the clamp in the holder. This hardly affects the cut, although I have been told to grind the top to a flat , but haven't needed to.
Incidentally, I parted some ordinary stock mild steel this morning, 1/2" dia, using my hand-ground tool in the rear tool post, starting at 350rpm, and increasing to 500 rpm at about half depth. No problem.
I wonder what speed all the experts would use?
Ken

 

[Steamchick]

The tool in the rear tool post is inverted so I run the "normal" direction.
This loads the saddle correctly to the design of the lathe.
K

 

[goldstar31]

Perhaps it should be mentioned that the GH Thomas tool will cut up to 2" in diamer.

But to muddy the waters somewhat the Late Martin Cleeve wrote in Model Engineer that his Myford ML7 would cut 3" diameter stock 'faster faster than his machine hacksaw.
Now I should qualify the remarks and add that "Cleeve's machine was not a common or garden ML7 but had two motors driving line shafting and one motor was a full one horsepower.
He wrote that his lathe saddle was a Myford 'special' and not cast iron but steel.

For those whoo posses his book 'Screwcutting in the Lathe' will note difference once surprise of his dog clutch and a gear train which contained a transposing 127 tooth gear which was NOT the expected 20DP.
So it is all there but two things must happen.

One is the open one's pocket book and secondly actually test what both both writers described.

To muddy the waters further-- Cleeve( Kenneth C Hart) used a --- curved blade. He also increased the 'diameter' of the saddle handle---- and added his own power feed-- from the rear of the the lathe spindle.
As I wrote-- More Anon

Norman

Norman

 

[OrangeAlpine]

Reducing speed simply changed the chatter frequency, no impact on when the chatter stopped. Oil seemed to make the operation go smoother. Nothing really definite. It seems that my lathe (12" Enco, belt drive) crossfeed is too fast, have to do all parting using manual feed. You can say my improved results are due to my improved technique, if so, then tell me how my improved technique totally eliminated chips as an issue.

I did use a different chuck, a 6" monster instead of an effeminate 5 inch. I will look into this as a possible factor.

I hope you can see pics of my parting tool holder. It is made of various mystery steels, the tool is .090", industrial refuge from 60+ years ago.

 

[BaronJ]

Hi
One of the main causes of problems with HSS parting blades is flank wear. Both sides of the tool wear creating a wedge shape that is plunged into the work. The wedge shape jambs into the parting groove leading to all sorts of chaos and mayhem.
The solution is to either reverse taper the blade (wide at the tip, narrowing further back, or better still, use carbide parting tools.

Dazz

Hi Daz,
I'm sure that you will be aware that a lot of parting blades have a tapered cross section that intended to be used in a specially made holder that compensates for the taper by holding the blade truly vertical. The use of one of these blades in a normal holder causes the blade to be slightly lent to one side !

This means that the blade will try to twist as the cut gets deeper and will jam or in severe cases break.

All the parting blades that I have and use are parallel sided, they have a rectangular cross section. In a normal holder this ensures that the blade will be held truly vertical. I can and have parted 60 mm stock with a 2 mm thick blade, but it is vital that the blade is set dead square to the chuck face.

 

[goldstar31]

When I bought my 2nf casting kit, I wanted Hemingwaykits to supply both blades( as BaronB suggests)

Alas and alack, the narrower blade is not available at the same width as the thicker one.
So Thomas's split - clamping turret has to be altered. Unless I have a magnetic table and a Clarkson grinder to reduce the thickness.

All go, but then I have to grind the 140 degree kerf along the 'top' which is upside down of course.
Once all this malarkey is done, it only requires a like at the front. None of this fiddly and faffing which is a continuous time waster-- with indifferent results-- as I read happens.

You see I have a professional jig to alter the shape of grinding wheels ---as supplied.

And we haven't got round to that yet.
Perhaps more anon? Be patient as I have THREE air bubbles in my injected eye. Still it can't be bad as as the injector lady gave me a magnifying torch and - a great big stand to put books and. plans under neath.
Oh and and a new face mask.
I never thought that really old people were treated with such courtesy !
So I'm waiting for the black spots to go

 

[Ken I]

As Goldstar states the holder must have a matching angle to hold the blade truly vertical with the clearance equal on either side.
When you hold a commercial blade horizontal then any required rake has to be ground at the cutting edge.
The double bevel on the top edge is meant to narrow the chip - so you are not really supposed to grind it away - instead the blade should be held in a holder that inclines the blade to the rake angle.

Re: Above Images :-

Top :- Blade horizontal - rake ground to remove double bevel - no more !
Middle :- Blade horizontal - rake ground below bevel - parting depth now limited to where the blade widens.
Bottom :- Blade inclined to rake angle - you only grind front clearance - leave double bevel as a chip "folder".

This makes the chip narrower than the cut and helps reduce hogging. It also makes resharpening simple and consumes less blade.

Regards, Ken

 

[goldstar31]

Thanks Ken

If you grind a vee- or perhaps easier- a rounded kerf, the inverted tool should cut-- and roll the narrowed swarf-- into little ccurlies.

Cheers and Thanks

Norman

 

[Ken I]

Thanks Norman - I should have mentioned that - for flat blades I do it on the edge of the grinding wheel or with a Dremmel - like you say "curlies"

Regards, Ken

 

[ShopShoe]

Norman,

I just gotta tell you that I do read and appreciate your posts. I also appreciate that the ones who have gone before have had a lot of good advice that we should consider before the "Woe is me....."

I am also inspired that you keep going despite whatever life throws at you.

--ShopShoe

 

[JRSherbundy]

When I bought my 2nf casting kit, I wanted Hemingwaykits to supply both blades( as BaronB suggests)

Alas and alack, the narrower blade is not available at the same width as the thicker one.
So Thomas's split - clamping turret has to be altered. Unless I have a magnetic table and a Clarkson grinder to reduce the thickness.

All go, but then I have to grind the 140 degree kerf along the 'top' which is upside down of course.
Once all this malarkey is done, it only requires a like at the front. None of this fiddly and faffing which is a continuous time waster-- with indifferent results-- as I read happens.

You see I have a professional jig to alter the shape of grinding wheels ---as supplied.

And we haven't got round to that yet.
Perhaps more anon? Be patient as I have THREE air bubbles in my injected eye. Still it can't be bad as as the injector lady gave me a magnifying torch and - a great big stand to put books and. plans under neath.
Oh and and a new face mask.
I never thought that really old people were treated with such courtesy !
So I'm waiting for the black spots to go

Sorry to hear about the air bubbles in your eye. I am setting here now with one bigger bubble in my right eye. Been there since August 20. On that date, the entire eyeball was one big gas bubble. It is getting progressively smaller. Sometimes the bubble breaks up into two or more smaller bubbles. Only happened once this time. Same problem happened to same eye seven years ago. That time the bubble would break up into many smaller bubbles often. Finally the bubble is small enough I can see over (really under the bubble, just looks like it is over. Still a giant pain. Depth perception is worthless, so using and applying cutting or drilling tools is a hit or miss proposition. Nice thing is no more black spots since when they took all my existing eyeball juice, the black spots were removed as well. For seven years I had this big monster floating around in there. Gone now. Looked like one of those Space Nebula things you see in those outer space pictures. So my advice is be careful. Aim twice, apply cut once.

 

[goldstar31]

Thank You, Sir, for your 'clear insight' despite what to others and myself seem impossible to comprehend and we wonder just how you can cope.
Coping with advancing age and deteriorating health is, as you well know, a difficult task. Moving to more private things, I've just been stunned to learn of the untimely death of a friend's wife and yet another phone call to learn of heart problems of yet another long friend. It's not easy to know what to say.

Moving further away from our happy hobby, we must not only be cognisant of a difficult world that many have no alternative but try to endure but to actively try in our own individual ways to try to eradicate the suffering of others.
Perhaps, I should say that the first to put others first- instead of our own selfish desires.

I recall those three words from the Acts of the Apostles and realise that other Faiths share the same aspirations .
I leave you Sir and all others with the concept of 'Faith, Hope and Charity' realising that we all have to endure extra problems again escalating in every part of the World.

So may I try humbly to emulate those strictures and look forward to a better New World for all of us- and those who follow on.

Most sincerely and as some of us say'I greet you well'

Norman Atkinson


.

 

[dazz]

Hi Daz,
I'm sure that you will be aware that a lot of parting blades have a tapered cross section that intended to be used in a specially made holder that compensates for the taper by holding the blade truly vertical. The use of one of these blades in a normal holder causes the blade to be slightly lent to one side !

This means that the blade will try to twist as the cut gets deeper and will jam or in severe cases break.

All the parting blades that I have and use are parallel sided, they have a rectangular cross section. In a normal holder this ensures that the blade will be held truly vertical. I can and have parted 60 mm stock with a 2 mm thick blade, but it is vital that the blade is set dead square to the chuck face.

Hi
That is not what I mean. Flank wear tapers the blade width. Close to the cutting edge, the blade wears narrow. Moving back from the cutting edge, the blade is wider (not worn). The result is a fine wedge that jambs in the cut slot.

Dazz

 

[jack620]

Hi
That is not what I mean. Flank wear tapers the blade width. Close to the cutting edge, the blade wears narrow. Moving back from the cutting edge, the blade is wider (not worn). The result is a fine wedge that jambs in the cut slot.

What you state makes perfect sense- in theory. In practice I’ve never experienced this, nor have I ever read about it in any of the lathe “bibles”. I suspect that any wear on the sides of the blade is so miniscule it is more than compensated for by the fact the blade gets shorter as it is sharpened.