Wood carbide insert holder for the metal lathe.

[More4dan]

Danny, After seeing your original post about negative rake carbide tools I've made a negative rake tool for my magic skew and two tools (onefor plastic, one for wood) for my metal lathe. I plan on giving them each a try today. Thanks for the inspiration.

Happy to be of service. As has been said many times here, no pictures it didn't happen. I'd love to see what you built and how they work.


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[Bryguy]

Happy to be of service. As has been said many times here, no pictures it didn't happen. I'd love to see what you built and how they work.


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Here is what I built. From the top down.
Negative rake for Magic Skew (I learned how to center my 4 jaw chuck!)
Wood tool for metal lathe
Negative rake tool for metal lathe.
I just ordered the parts for your DRO design. Keep coming up with these great ideas. You are the man!

 

[More4dan]

Very nice work Bryan! Thanks for sharing.
Have you used them "in anger" yet? How are they performing?

Just remember to set the cutting height at or just below centerline.

Danny


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[Bryguy]

Very nice work Bryan! Thanks for sharing.
Have you used them "in anger" yet? How are they performing?

Just remember to set the cutting height at or just below centerline.

Danny


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Tried them yesterday and they work perfectly!

 

[FGarbrecht]

Got my tool yesterday and used it to turn down some ebonite; worked very well. Very nicely done, good meticulous design!
I still got some circumferential ridging in my ebonite, but I always do not matter what tool I use. I haven't decided if I just haven't discovered the magical combination of tool, lathe speed and feed rate yet or whether my lathe just needs some more tuning up

 

[More4dan]

Got my tool yesterday and used it to turn down some ebonite; worked very well. Very nicely done, good meticulous design!
I still got some circumferential ridging in my ebonite, but I always do not matter what tool I use. I haven't decided if I just haven't discovered the magical combination of tool, lathe speed and feed rate yet or whether my lathe just needs some more tuning up

Thanks for the feedback, Frederick. The only tool I've had luck with getting a completely smooth blank is with a square (2" radius) carbide mounted with a 20 deg negative rake. The contact area is wide enough to smooth out the ridges left from the feed speed. For the same reason it doesn't do well in depth of cut without chattering. I've seen others use a 1" wide scraper to make a final pass by hand to get a similar result.

I've turned a little ebonite. I think some of the issue is because its relative softness. It deflects inward and springs back out when cutting leaving an uneven surface. I've had what looks more like tearing than cutting too.

Danny


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[FGarbrecht]

Thanks for the feedback, Frederick. The only tool I've had luck with getting a completely smooth blank is with a square (2" radius) carbide mounted with a 20 deg negative rake. The contact area is wide enough to smooth out the ridges left from the feed speed. For the same reason it doesn't do well in depth of cut without chattering. I've seen others use a 1" wide scraper to make a final pass by hand to get a similar result.

I've turned a little ebonite. I think some of the issue is because its relative softness. It deflects inward and springs back out when cutting leaving an uneven surface. I've had what looks more like tearing than cutting too.

Danny


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Hey Danny
I read a bit more about ebonite turning on a couple of sites and there seemed to be a consensus that ebonite is very hard on carbide for some reason and a couple people recommended using PCD inserts instead. I may experiment with grinding some HSS to make a flat scraper and see how that does. I concur with your observation that chattering is a problem; I was turning a relatively long (150 mm) piece of 18 mm ebonite, and even with tailstock support was getting bad chattering in the middle of the stock at medium to high speed; much better at low speed. Maybe a combination of the round carbide insert tool for roughing and a flat scraper for final surface prep may work the best. It seems that ebonite may be the worst of materials in terms of being abrasive enough to wear down even carbide quickly but not rigid enough to turn without flex and chatter . Hopefully I'll be able to try the round insert tool on some other materials soon (I've got some nice brass and some drill rod to try out), maybe even some wood! I'll report back.
Thanks again, really nice work.
Fred

 

[More4dan]

Hey Danny
I read a bit more about ebonite turning on a couple of sites and there seemed to be a consensus that ebonite is very hard on carbide for some reason and a couple people recommended using PCD inserts instead. I may experiment with grinding some HSS to make a flat scraper and see how that does. I concur with your observation that chattering is a problem; I was turning a relatively long (150 mm) piece of 18 mm ebonite, and even with tailstock support was getting bad chattering in the middle of the stock at medium to high speed; much better at low speed. Maybe a combination of the round carbide insert tool for roughing and a flat scraper for final surface prep may work the best. It seems that ebonite may be the worst of materials in terms of being abrasive enough to wear down even carbide quickly but not rigid enough to turn without flex and chatter . Hopefully I'll be able to try the round insert tool on some other materials soon (I've got some nice brass and some drill rod to try out), maybe even some wood! I'll report back.
Thanks again, really nice work.
Fred

The 30 degree edge on the carbide designed for wood might not fare well with brass and steel. You might get away with it on Aluminum. Usually for metals they use 7 degree rake to provide some strength under the edge. I did just try a round cutter designed for metals on my mini metal lathe. They worked great. Curious what you find to work for ebonite.

The long piece of ebonite was likely flexing in the middle, I've even had 5" long acrylic do the same, I had to back off the tail stock pressure a bit to help.

Danny


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[NT_2112]

Mine works pretty well on Ebonite. I'm turning at a fairly lower speed.
Here's a picture of the pen section right after turning and before sanding.
Seems to work best if I can get it pretty close to dead center middle.

 

[FGarbrecht]

Mine works pretty well on Ebonite. I'm turning at a fairly lower speed.
Here's a picture of the pen section right after turning and before sanding.
Seems to work best if I can get it pretty close to dead center middle.

That's pretty much what my ebonite looks like too after rough turning, very light ridging that is visible and can be felt. I found that I need pretty aggressive sanding (like minimum 180 grit) to remove the tool marks, and I'd prefer to have a smoother surface to minimize the sanding I need to do. This may just be the nature of the beast, but being pretty new to metal lathes and ebonite I was more concerned that there was something obvious that I was doing wrong or some fine tuning of the lathe I had to undertake.

 

[More4dan]

I'm out of town this weekend, next week I'll play with different rake angles and carbide shapes with some ebonite in my stash.

Thanks for sharing guys.


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[More4dan]

Here is my first shot at ebonite. My first guess is that a positive rake tool would perform better for a softer material similar to the way metals behave. Here I used the only positive rake cutter I have. It's a 10mm round with an insert from Korloy designed for aluminum. Positive rake and an almost sharp edge. I'll make a positive rake holder for a woodworking carbide next to see if I can get better results. I also got much better results with the feed starting at the headstock and feeding toward the tailstock. My guess is this stretches the material away from the hold point as it cuts vs the other direction where it compresses the material. I had some heavier banding going the other way. There is some very slight banding still but I should be able to go straight to micro mesh.


The first picture is as turned and the second is with some Meguiars Swirl Remover 2.0.

Turned about 1000 rpm using the power feed. Next I will make a positive rake holder for a square (2" radius) woodworking carbide insert and see the result.

Danny

 

[NT_2112]

That looks pretty close to what I get with Ebonite and your tool.

I wonder how a square bit might work.

 

[More4dan]

I'll see sometime later in the week as soon as I can find a few hours. Thanks for the feedback.


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[More4dan]

Made a positive rake square carbide holder. The resulting finish wasn't better and there was a lot of chatter when I tried cutting any deeper than about 0.003".

Here is the same result using the round carbide tool.

The round tool can also be used for rough cutting and for getting a near finished surface similar to making a finishing pass with a square carbide tool.

Danny

 

[magpens]

Thanks for doing this, Danny! . Good to know.