Vertical Parting Tool

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Vertical Parting Tool

This topic has 26 replies, 12 voices, and was last updated 4 May 2012 at 17:04 by chris stephens.

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22 April 2012 at 20:31 #38118
Alan Jackson
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@alanjackson47790
A vertical parting tool for the lathe
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22 April 2012 at 20:31 #89563
Alan Jackson
Participant
@alanjackson47790
I have just made a vertical parting tool for my Stepperhead lathe. I first tried a normal parting tool mounted vertically but it suffered from scuffing on the parallel sides of the tool which is at the last part of contact with the metal being cut. So I made a one piece tool by silver soldering a small part of a high speed steel parting tool to a slightly thinner sheet of steel. Then I ground the high speed part to have clearance in both directions and it worked very well. It is nice and rigid in the cutting directions, with no bending for the parting tool. The mandrel rotates in a clockwise direction for a rear tool post which will be a problem for lathes with screwed on chucks so they would have to have the tool mounted at the front of the lathe. Here is a short video of it operating. It is only cutting off a 20mm dia. because I could not hold the camera and apply cutting oil with a brush at the same time but I will try it with larger diameters. But so far so good. Why has this not been tried before?
http://www.youtube.com/watch?v=S8HvS…lSWeYLoFlU2iA=
Alan
23 April 2012 at 07:20 #89580
john kennedy 1
Participant
@johnkennedy1
I really like that. Is it steel you're cutting ? Going to have to put that on my list,Thanks.
23 April 2012 at 09:57 #89585
Alan Jackson
Participant
@alanjackson47790
Yes John it is cutting mild steel
23 April 2012 at 11:09 #89588
Ady1
Participant
@ady1
I'm confused

It looks like you're running the lathe backwards and cutting normally.

So if you put the tool on the front and run the lathe normally won't you get the same result??

…sorry 'bout this…

Looks like a damn fine system btw

Edited By Ady1 on 23/04/2012 11:11:54
23 April 2012 at 12:49 #89592
Ian S C
Participant
@iansc
If you have the tool in the rear toolpost, turn it upside down, and run in the normal foreward direction, if nothing else, it helps with clearing the swafe, gravity is free so might as well use it. Ian S C
23 April 2012 at 13:09 #89595
David Littlewood
Participant
@davidlittlewood51847
Alan,

Sorry to rain on your parade, but I'm not entirely sure what advantage this has over a normal inserted tip parting tool. I use A Q-cut:

http://www.greenwood-tools.co.uk/ishop/728/shopscr23.html

but there are others out there. As others have said, there is no point in using a rear tool and running the lathe backwards, you might as well follow Ian's suggestion and run normally with the tool inverted. Still little or no advantage over a front tool in a QC holder though.

David
23 April 2012 at 13:15 #89596
JasonB
Moderator
@jasonb
I suppose the advantage is meant to be that there is a lot more support under the cutting edge so the loading goes straight down rather than a conventional tool that has an overhang from its holder and the forces will tend to bend the tool down.

I assume its rear mounted so it can stay in place and there s no need to change tools.

I don't have problems using the greenwood type or an Eclipse blade in a Dickson holder, suppose it comes down to the rigidity of your lathe or lack thereof.

J
23 April 2012 at 13:36 #89599
MICHAEL WILLIAMS
Participant
@michaelwilliams41215
This type of parting tool is a style variant of the well known peg leg tool of antiquity . I remember that somebody , possibly Tubal Cain , wrote some articles about them in ME about 30 years ago .

This type of tooling does have some small advantages in very heavy turning but since conventional tooling does everything needed in almost all cases the idea has rarely been pursued in industry .

I have heard of one application :

The Bristol engine company made a type of radial engine where the barrels had many closely spaced cooling fins . At one time these fins where cut into solid metal all in one go by a bank of , essentially , parting tools . I understand that there were endless difficulties with tool breakage until someone remembered the peg leg idea and special tooling was made with support legs .

Michael Williams .
23 April 2012 at 14:07 #89600
john kennedy 1
Participant
@johnkennedy1
Alan, Just been looking at your lathe http://www.lathes.co.uk/stepperhead/index.html

Thats a beautiful piece of kit.
23 April 2012 at 15:55 #89602
Ady1
Participant
@ady1
Right enuf, that's some rig out there, impressive stuff

I'm sort of jealous, but even after 70 years you'd need to blow up my old clunker of a Drummond with dynamite to break it.

Simple does have certain advantages
23 April 2012 at 15:58 #89603
Alan Jackson
Participant
@alanjackson47790
Andy1 & David littlewood, Thanks for your interest and you certainly have not rained on my parade. My reasoning for a vertical cutting tool is that in both cases front or rear mounted parting tools, the cutting tool is subjected mainly to bending stresses. The greater the cutting depth the bigger the cantilever and the greater the bending moment. In essence the extended cutting tool is just like a ruler in classroom; where kids love to hold it extended over their desk edge and flick it so that it viabrates. By mounting the cutting tool vertically it is supported from below and the cutting forces are mostly directly downwards putting the cutting tool in compression rather than bending, because the cutting edge is directly supported below with no cantilever. I suggest that this avoids resonance due to a cantilevered support and avoids the stress concentration where the cutting tool meets it support block. It also allows the cut swarf to freely exit over the top of the tool. All these advantages allow the cutting edge to be thinner which also reduces the cutting forces. The downside is that you have to have a lathe that can safely rotate the mandrel clockwise without the chuck unscrewing, so threaded mandrel noses are no good for this. Parting off has always been a problem with model engineer size lathes which has been helped by the greenwood tool mentioned but the geometry still exists.

Alan

Edited By Alan Jackson on 23/04/2012 15:59:41
23 April 2012 at 16:10 #89604
Ady1
Participant
@ady1
The problem I found when I went for total stiffness was that all the load from any niggles with the swarf or a slight dig-in got transferred directly through the tool tip and this could be fatal for it

It didn't budge, so it failed

A tiny amount of flex allowed the tool tip to survive any problems, especially when there was already high loading issues, like when cutting threads.

At the end of the day any set up wll vary with the materials and the task being demanded.

It definitely looks impressive when everything is set up right though
23 April 2012 at 17:04 #89605
SteveW
Participant
@stevew54046
You've got me interested Alan! Any chance of a picture or sketch showing the tool looking towards the chuck from the tailstock?

If my visualisation is correct the tool could be reversed and put nearer the front of the lathe to cut with anticlockwise (forwards) rotation? I know that would get in the way of the normal tool holder etc so not a practical solution. I'm just trying to visualise the cutting forces and the tool being vertical.

SteveW
23 April 2012 at 18:16 #89607
David Littlewood
Participant
@davidlittlewood51847
A major issue with parting is swarf geting trapped in the groove, which gets worse the deeper you go. One of the vital features of the Q-kit (and its larger industrial brothers) is the shape of the tip; it has a curved depression in it, which curls steel and other stringy swarf into a shape narrower than the groove being cut. It thus cannot sieze up in the groove. If you've never experienced the difference then you will find it hard to believe just how much better it is.

David

Edited By David Littlewood on 23/04/2012 18:16:46
24 April 2012 at 11:00 #89641
Alan Jackson
Participant
@alanjackson47790
Andy & David I do agree with what you say but a vertical parting tool seems to be an approach not tried. Because it avoids the rotating forces applied to the topslide and cross slide whether the cutting tool is mounted on the front or rear of the lathe. I suggesthese rotating forces create movements at the cutting tool which can create chatter and dig ins etc. Even with well fitted slides etc when a parting tool digs in it is suprising how much movement is instantly created. So that is my reasoning/justification/food for thought.

SteveW, I have added a couple of pics in my album I don't know how to do it here in this message hope they are more illustrative

Regards

Alan
24 April 2012 at 11:21 #89642
Ady1
Participant
@ady1
Edited By Ady1 on 24/04/2012 11:21:59

Edited By Ady1 on 24/04/2012 11:22:30

Edited By Ady1 on 24/04/2012 11:23:02
24 April 2012 at 11:24 #89643
Ady1
Participant
@ady1
The album images are larger if required. I reduced the size to prevent deformation

http://www.model-engineer.co.uk/albums/member_albums.asp?c=46944

Edited By Ady1 on 24/04/2012 11:28:37
24 April 2012 at 12:00 #89644
chris stephens
Participant
@chrisstephens63393
Not wishing to rain on anybody's parade but who saw the tangential (also vertical) parting tool working on the SMEE stand at Ally-Pally in January?

chriStephens
24 April 2012 at 12:15 #89646
Ian S C
Participant
@iansc
Michael, yes I think you are right about Tubal Cain, his tool was mounted conventionally, in the front.

Sorry I wrote above site unseen, but upside down is the way to run tools in the rear tool post, if at all possible. Ian S C
24 April 2012 at 12:19 #89647
Michael Cox 1
Participant
@michaelcox1
Posted by chris stephens on 24/04/2012 12:00:06:

Not wishing to rain on anybody's parade but who saw the tangential (also vertical) parting tool working on the SMEE stand at Ally-Pally in January?

chriStephens

Hi Chris, I did not go to Ally Pally so I have not seen this tool. Can you provide more info?

Mike
24 April 2012 at 13:06 #89650
John Stevenson 1
Participant
@johnstevenson1
Also interested Chris, perhaps in a new thread to keep Alan's intact ?

John S.
24 April 2012 at 13:26 #89653
chris stephens
Participant
@chrisstephens63393
Hi Guys,

I did not mean to hijack the thread. I would post pictures but I can't find the charger for the camera, when I do I shall start a new thread. I shall add here that I have already lost interest in the tool as I have moved on to another project or two. Thanks for the interest shown so far.

chriStephens

PS any SMEE member can see the tool on page 20 of the April '12 journal

Edit, please don't reply, my mistake for the hijack

Edited By chris stephens on 24/04/2012 13:27:56
4 May 2012 at 11:03 #90200
Alan Jackson
Participant
@alanjackson47790
In order to clarify the operation of a vertical parting tool here is my rather macabre description of how I think it works.

Imagine that you are the parting tool holder whereby your two hands are held straight out from you body. You hands are gripped together and your fists are the cutting edge. You have a friend who represents the metal being cut and he (If you are a front parting tool) pushes down on your hands while you do you best to resist him pushing down. You can see that he can quite easily push your arms down. If you want to now become a rear parting tool you can turn round 180 degrees and your friend would now push your hands upwards, still he can easily overcome your resistance to him pushing up. So in order to stiffen you up, say you are frozen solid or have rigor mortise and are wearing a large pair of lead diving boots to anchor you down. When your friend (or should I now say de-parting undertaker) pushes down on you hands he will not be able to move your arms down because they are rigidly fixed to your body and he have to apply more force until you tip forward on you toes. Note that as you tip forward you rotate about your toes moving your cutting tool hands deeper into the metal being cut. If you are now rotated 180 degrees to become a rear parting tool your friend (some friend) now has to apply more upward force until you tip backwards on your heels. Also note that your cutting tool hands now move away from the metal being cut as you rotate backwards on your heels. Now you have to play the part of a vertical parting tool as I am proposing, so you now can be thawed out or de- rigor mortised. So lay flat on your back and push one arm vertically upwards and clench your fist to form the cutting tool. Your friend now has to apply considerably more force to overcome your vertical arm. Your arm will be in direct compression and until your elbow or wrist give way you will have much less a problem resisting his downward cutting force. It will also not matter if you are a front or rear vertical parting tool as long as the rotating force is pushing down on your hands. You can now get up and go back to your work or whatever you were doing. I apologise for being so flippant but I hope it does explain the reasoning.

Regards

Alan
4 May 2012 at 14:00 #90214
chris stephens
Participant
@chrisstephens63393
Hi Alan, and the rest of the Guys

I am coming around to the idea that it not the tool per se, but the operator. Why else would some users suggest using a stiff tool, whilst others are advocates of sprung ones. Whilst yet others say rear is the only way to go, despite the fact that others have no problem in the front. (I know sprung tools have not had much mention here but they were demonstrated, with great success, at Harrogate a few years ago.) Could it be, rather like faith healing, that if you believe it will work than it does.

Having said the above does not mean that any old bit of tooling is going to work as well as a properly thought out bit of kit.

As with all self taught activities the only way to find the best way of doing something is to try every technique you can and decide for yourself.

chriStephens

PS the vertical tool, mentioned at the start of this topic, does sound like it has merit. Certainly if a dig in happens, and something has to give, the blade breaking is less likely to be the outcome. Of course a dig in is less likely if the operator has the "knack" or can hear when trouble is going to happen.
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