Models for grinding HSS Lathe Tools

[ACHiPo]

I milled 0.050" off the right side of the platen. Definitely a step in the right direction. The belt is just proud of the platen, maybe 0.010", so I need to give it a little more, but will wait until I brace it and add the pyroceram.

I dove in an tried my hand a grinding a stainless steel tool. Without pictures, I'm hoping I interpreted the guidance correctly. Here are pics of the tool and the tool in operation. The chips varied between never-ending strings, nice 1" curls, and short (1/4" curls). The tool seemed to cut decently, and I could take 0.050" deep cut with the gear box in its lowest gear without lugging down the machine. I did get a lot of (presumably sulfur?) smoke.


The stainless part I made is on the right. Finish is not great, but no chatter to speak of. I machined the 1/2" section with my stainless tool. I fixed the geometry of my square tool and cleaned up the base with it. The square tool worked much better with more back rake, but the stainless tool worked better yet. The 28º side rake is pretty acute and doesn't leave much meat at the tip. I stopped 3 times and honed the tool.

 

[mikey]

Light cuts with any tool in stainless will string; this has to do with the ductility of the material. Like aluminum, stainless will string with light cuts. You can improve the finish with a nose radius, Evan. You tool as shown has little to none ... maybe my eyes can't see it. You can also improve the finish by angling the tool a little bit more toward the tailstock. Also, if you take light cuts, you can improve the finish by angling the tip of the tool toward the chuck and cut with the nose and end cutting edge; it will string but the finish will be better because the end cutting edge will shear.

Yeah, you're right; a stainless tool has a lot of side rake but that is a good thing. It gets the heat out of the cut faster so you have less potential to work harden the work piece. You still have to use the tool correctly, which means you cannot dwell or pause in the cut.

You might also give Anchorlube a try. I've been using it for stainless steel and it seems to work quite well for that. Considering it is a soap-based product, this was surprising to me. I need to compare it to sulfur-based cutting fluid one of these days to see which works better. If the Anchorlube wins, then I'll use it for threading and knurling and see how that works. I have found that I get less smoke, cleaner finishes and the chips coil more with Anchorlube so that's a plus. It still strings with light cuts but when I take deeper cuts or if I increase the feed rate then I get chips but this is not due to the lubricant; it is due to the geometry of the tool.

 

[ACHiPo]

Mike,
I realized last night the side rake of 28º was taken from the wrong reference, making my side rake effectively 62º. This would explain the fragility of the edge. Man it's been a long time since geometry and trig!





I did use AnchorLube on the last pass of 0.010".

I don't have a feeling for honing a 1/16" radius on the end of the tool. To get a radius I rolled the edge on my fine diamond stone 3-4 times, then honed the back rake. I can certainly increase it. I think I saw that someone honed a 1/32" flat on the edge, then smoothed it. That may be a better way to proceed.

 

[rolleikin]

Hi Everyone,

I know that I am coming late to this party, but we may want to add to this wish list cutting tools for a shaper. The relief angles on shapers are shallower than on a lathe. Unfortunately, I no longer have my copy of Leo St. Claire's book on cutting tools, or I would have provided some references.

Thank you for taking on this project.

Just my 2 cents.
Andrei

 

[ttabbal]

I realized last night the side rake of 28º was taken from the wrong reference, making my side rake effectively 62º. This would explain the fragility of the edge. Man it's been a long time since geometry and trig!

That's pretty easy to do, don't feel too bad.

I don't have a feeling for honing a 1/16" radius on the end of the tool. To get a radius I rolled the edge on my fine diamond stone 3-4 times, then honed the back rake. I can certainly increase it. I think I saw that someone honed a 1/32" flat on the edge, then smoothed it. That may be a better way to proceed.

The best way I found was to use the coarse diamond card and press a bit harder than I do for normal honing. I do a flat a little less than I'm aiming for, then use a rolling motion to round it out and blend with the sides. Once it's there, I don't have to do much to it later when honing the tools. I tried using the belt grinder, but you're trying to remove such a small amount that it's tricky to get it even, even with the finer belts.

 

[ACHiPo]

That's pretty easy to do, don't feel too bad.

The best way I found was to use the coarse diamond card and press a bit harder than I do for normal honing. I do a flat a little less than I'm aiming for, then use a rolling motion to round it out and blend with the sides. Once it's there, I don't have to do much to it later when honing the tools. I tried using the belt grinder, but you're trying to remove such a small amount that it's tricky to get it even, even with the finer belts.

I don't feel bad--I'm learning lots, and pretty quickly. I've gone from not having a clue what I didn't know, to understanding a little more about what I don't know. Progress!

I suspect your technique on the radius creation is what I remembered. My radii are definitely smaller than would be created by smoothing a flat, and likely way too small.

 

[mikey]

The best way I found was to use the coarse diamond card and press a bit harder than I do for normal honing. I do a flat a little less than I'm aiming for, then use a rolling motion to round it out and blend with the sides. Once it's there, I don't have to do much to it later when honing the tools. I tried using the belt grinder, but you're trying to remove such a small amount that it's tricky to get it even, even with the finer belts.

This is how I do it, too, Evan. The nose radius is an important feature, to me anyway, so I take the time to do it well.

As for the angle thing, don't worry. It takes some time to wrap your head around these stupid angles. I swear that if you have seen all the mistakes I made you would wonder how I ever got it straight. You're doing fine. Just keep working at it and you'll sort it out.

 

[mikey]

Hi Everyone,

I know that I am coming late to this party, but we may want to add to this wish list cutting tools for a shaper. The relief angles on shapers are shallower than on a lathe. Unfortunately, I no longer have my copy of Leo St. Claire's book on cutting tools, or I would have provided some references.

Thank you for taking on this project.

Just my 2 cents.
Andrei

Hi Andrei, and welcome to HM.

I don't own a shaper and know very little about shaper tools. However, I am familiar with how it cuts. Not too long ago, I was contacted by one of our members, UlmaDoc, who has a little Aamco 7" shaper. He wanted a tool that would hog cuts in aluminum while leaving a good finish. He was using a traditionally shaped tool that was giving him 0.050" deep cuts but he wanted to go deeper. Our collaboration eventually resulted in a tool that is shaped very much like a lathe tool and it was able to take 0.214" deep cuts with a good finish. He did a video showing how this tool worked:

We also did a tool for steel but I don't know how well that one worked (well, I sort of do; it seems to have worked well but he didn't try really deep cuts). The gist of it was that we tried an oblique cutting tool instead of the traditional orthogonal cutting tool and it worked much better for stock reduction. Of course, when cutting features like dovetails or slots, the tool would need to be shaped for the job but the geometry could likely be altered to improve performance. His little 7" Aamco shaper only has 1/4HP so we needed to get cutting forces as low as possible. Again, I'm no shaper tool expert by any means but a cutting tool is a cutting tool and at least to the extent possible, it seems to have worked

 

[Z2V]

I have a set of model tools available if anyone is interested. PM me if you would like to see them.

 

[TerryH]

I swear that if I could get you guys in my grubby little hands for one hour, I could teach you all I know about this tool grinding stuff.

Given your location, I think we should reconvene this discussion to your house ASAP. I'll bring my sander. Should be an interesting conversation piece as a carry on. lol...