Vertical Parting Tool

[DICKEYBIRD]

Well, regardless of all the naysaying, what you've shown makes sense to me in promoting a more rigid parting setup. I have way too much other stuff on my plate to try it out right now but have added it to my tooling wish list.

[Forestgnome]

This is probably heresy around here, but a good tool design should strive to reduce the need for good "technique."

The easier you make the operation, the less error prone it tends to be. Designing something that requires a high level of operator skill is generally not a good idea all other things being equal.

I suppose that's true to an extent, but if machining parts was so easy that anyone with a machine could do it, I probably wouldn't make parts. For me the trials and tribulations in achieving the skills is the rewarding part. The improvements come not in reducing skill required, but in adding capability.

[jackary]

IMHO a "vertical parting tool" serves the same need as putting chrome on a hearse.

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

[RussZHC]

Using the hand analogy, would not the placement need to be as directly under center as possible?
Since if it was off to either side of that vertical center line, depending on rotation (CW or CCW, mentioned so as to include rear parting tools), would not the rotation tend to kick it over as the force would not be directly down on said center line? So a wide base is better?

If that is the ideal scenario, then does not one have the difficulty of raising the cutter as the surface you are cutting would be, in effect, moving away from the cutting edge as you cut?

To me, what is being described is similar to say a Hardinge cutoff (and Webb?) that gets pulled/pushed down from the top, except in that "ideal" situation, it would rise from the bottom.

[Rosco-P]

To me, what is being described is similar to say a Hardinge cutoff (and Webb?) that gets pulled/pushed down from the top, except in that "ideal" situation, it would rise from the bottom.

A vertical cutoff slide like this: http://www.wademachine.com/ocs.htm For the Wade 94/94 and similar machines like the Hardinge, it bolts right to the face of the headstock. I have one on my Wade 94. Don't think you can get much more rigid that that setup.

Import lathes usually have a rectangular, boxy headstock. Probably possible to build something similar for them.

[DR]

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The idea is being shown for interest and comment. If you do not like the idea please ignore it and carry on as you have been doing,

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Alan

It seems as though you are making the assumption that "conventional" parting tool setups are not rigid with their tools having a moment arm.

That may be true of the junk, smallish hobby lathes. Not so with higher quality lathes though. That's why a number of us are somewhat skeptical of the concept.

The concept is being shown for comment, my comment is, you've solved a problem that does not exist in a rather complicated fashion.

To your original question, why has this not been tried before, because it isn't needed.

[lwalker]

I don't think he's saying that at all.

If you can load the parting tool and its holder in compression, then you need a lot less material to resist deflection than if you have the load cantilevered. Take this principle to its logical extreme and you can have an extremely rigid machine light enough to carry around in one hand!

I believe that this was the principle behind the Giddings & Lewis (& perhaps others?) hexapod milling machines: convert the bending forces to tension & compression as much as possible and you have a lighter weight mill.
http://www.youtube.com/watch?v=7TowJZQi-qY

That it results in a more complex assembly may be one of the reasons it's not a popular design, but I think its certainly worthy of consideration.

[Boucher]

This has been a good discussion of parting which may not be a problem on big rigid lathes but is increasingly more difficult on smaller lathes. The concept of straight-line compressive force has significant merit compared to the cantilevered design of conventional parting blades.

Thanks to John Stevenson’s recommendation I replaced my Compound slide with a tool block riding myself of the problem I was having keeping the gibs adjusted. This resulted in a big improvement in parting. This design also attaches directly to the cross slide which is definitely better.

I am curious about the question regarding parting 3” mild steel in the home shop. How many do that? I bought the largest Kennametal A3SC cutoff tool. It only goes to 2.44” Diameter. It is a very good tool which is worth the cost when needed.

Alan, thanks for posting. The video is good but a picture would also be nice to go in the to-do file.

[jackary]

Byron,
Here are three photos for your to do file. You will see in the last photo that the original idea was to use a standard parting tool, but I replaced it with a wider sheet with side relief for the cutting tool in both directions.
Alan

[rohart]

Seemed a pretty good idea to me.

As jackary noted above though, the modern insert holders are pretty deep and do a lot to reduce tool flex. I use a 3mm seco I picked up cheap in a Dickson holder. I'd rather have a 2mm tool, but my pocket won't support it. I've use it, with two insert, for a year, and only recently did I have a hiccup - not a proper dig in, just a hiccup.

Most times I set it off, jab a bit of cutting oil in every ten secods or so, and I get by.

I used to use a 2mm HSS tool, with relief, and it was forever digging in, even when I would withdraw it every 1/8th inch.

I may try making a replica of my seco insert holding tool, but for vertical parting. Hmm... There goes another day or so.