Vertical Parting Tool

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

I really like that. Is it steel you're cutting ? Going to have to put that on my list,Thanks.

Yes John it is cutting mild steel

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

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

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

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

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 .

Alan, Just been looking at your lathe http://www.lathes.co.uk/stepperhead/index.html

Thats a beautiful piece of kit.

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

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

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

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

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

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

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

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

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

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

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

Mike