MAKING A POLYCRYSTAL (CBN) INSERT TOOL HOLDER

[petcnc]

Sometime ago I watched in YouTube a guy machining a ball bearing using an insert that can machine the hardest metal (i.e. the bearing) like butter.
The inserts are called ELBOR, made in Russia and are cheap.



So I searched in ebay, found an auction I put a bet and I won it.



They arrived yesterday so tonight I had to make a holder to test it on the lathe.
First I made some measurements. They are 8mm X 14 mm cylindrical inserts with an unusual shape and negative rake angle.



I have some 14 X 14 mm steel bars that I think will be good for insert holders.



The guy in the video that used the inserts has a big lathe that can support large tool holders so he made a conventional tool holder.




For my mini lathe such a holder will protrude so much to the front that will be unusable.
A new approach needed.
I decided to fit the insert in the steel bar at the appropriate height to be exactly at the center of my lathe.



The bars were measured and marked



As the hole needed to be offset it would be impossible to drill it to the bar (part of it out of the bar). So I used another bar next to it, supported to a small viseand punched to the center of the required 8mm hole.



Then I drilled a 4mm pilot hole and the 8mm hole followed



Then I finished it with a 8mm end mill to flatten the bottom



Offset hole ready!



It looks OK



And the insert fits nicely



All I need now is a way to support it in place.
A small bolt on the top would be nice…
A hole to the back of the insert…




Threading the holder..



A small screw and my new lathe cutter is ready



Fits nicely to the tool holder



And lets try to machine some bearing… I decided to machine an old wheel bearing at 600 rpm without any lubricants or cutting oil



Piece of cake…



At 600 rpm without any oil or other lubricant it cuts the hard metal better than my carbide inserts cut steel. See the shavings!



I like the near mirror finish !!!



Thanks for reading.
Petros

 

[Tinman56]

Wow these look pretty impressive ! Nice job on the holder

 

[pontiac428]

Very cool! Are these tool bits designed to run at a negative rake, or can they do even better at a zero or positive rake? I recently tried to make a spindle mandrel out of an outer CV shaft and failed miserably when I found out how hard that steel was. This may be the solution, thanks for the post.

 

[petcnc]

Very cool! Are these tool bits designed to run at a negative rake, or can they do even better at a zero or positive rake? I recently tried to make a spindle mandrel out of an outer CV shaft and failed miserably when I found out how hard that steel was. This may be the solution, thanks for the post.

If you search at ebay for "ELBOR" there are some for sale!

 

[rwm]

That's way cool. Try it on some stainless and let us know how it works on that? Titanium maybe?
Robert

 

[Winegrower]

I just received two ELBOR inserts and you can see from the picture that there is only one edge on them. Maybe these are the runts of the litter? I'll have to grind another edge somehow.
Must it be a diamond wheel? Maybe I could do this on the Darex E80 some way? Opinions welcomed.

 

[petcnc]

I just received two ELBOR inserts and you can see from the picture that there is only one edge on them. Maybe these are the runts of the litter? I'll have to grind another edge somehow.

Must it be a diamond wheel? Maybe I could do this on the Darex E80 some way? Opinions welcomed.


View attachment 350384

Must be different flavors of ELBORS there! I'm not sure for what machining work each flavor is best. I thing that the ability to machine very hard metals would be fine though!
I never tested an ELBOR to a diamond grinding disk so I have no info on that!

 

[matthewsx]

I just got mine as well and it looks just like yours @Winegrower, let me know what you come up with.

John

 

[SLK001]

The problem with drilling a hole in the insert, is now you have to drill ALL of them, and the location of the hole must be fairly precise.

What's in that booklet? Anything interesting (like usage of an ELBOR insert)?

 

[Weldingrod1]

You can get regular style carbide inserts with one cbn corner. Cubic Boron Nitride. They gleefully eat hardened steel leaving an amazing finish! The chips look like fine steel wool and often burn... I mean literally combust on the lathe bed!

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