Lathe carbide toolholder with spacer?

I went to a school machinery auction a couple of months ago. I
purchased a small qty of Kenametal tool holders and each of them had a
spacer under the carbide. See link:
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My question is why, tool post too low on the lathe?
Reply to
aribert
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No, probably the insert puts too much force on the holder and eventually leaves dents in it. Then, the poorly-supported insert tends to crack. To give the best support under a positive-rake insert, you need something really strong there, so a cheap, flat piece of carbide is ideal.
Jon
Reply to
Jon Elson
That is the "anvil" -- and it is carbide too.
This provides a more rigid support surface than the steel of the tool holder, so it remains flat and protects the insert from breaking when it is supported only away from the edge where cutting occurs.
Also -- for insert threading tools, there are a series of these anvils available -- different side-to-side angles so you can tilt the insert to handle faster thread leads -- such as when you are cutting a multiple start thread where the thread angle is a lot steeper than normal. It changes the angle of the insert so the relief angles give adequate relief.
FWIW -- those are the *good* insert holders. The ones without the anvils are the cheaper one, and are to be avoided if possible.
These which you have are also negative rake inserts and holders, so you can flip a worn insert over after using all three of the upper corners. If the inserts have a groove, they may actually present a positive rake cutting edge, even with the negative rake mounting.
What is the shank size of these holders? 3/4" perhaps?
Enjoy, DoN.
Reply to
DoN. Nichols
Thanks for the replys - I learned something!
As to the shank size, I'm not sure - close enough that I could mill off excess if needed to use with my (relatively) low power Clausing 5914 and AXA holders. From memory, the school machine shop had Sharp Lathes, about 14 x 40, guessing 3 hp.
Reply to
aribert
Thanks for the replys - I learned something!
As to the shank size, I'm not sure - close enough that I could mill off excess if needed to use with my (relatively) low power Clausing 5914 and AXA holders. From memory, the school machine shop had Sharp Lathes, about 14 x 40, guessing 3 hp.
Your picture of the tool gives me the impression that you have to thick of a carbide shim under the insert.
It's doesn't take much power to make the tool shank thinner. You should only cut material off the bottom of the shank not the top. The reason for this is if you take material off the top and put it in your lathe the insert tip may be above center. You can shim a tool up to center, but you can't make it lower unless you mill off the bottom. I have seen tool holders with both the top and bottom milled off. Because the person who milled it the first time got it to fit the machine by milling off the top of the holder. But the tool tip was above center and had to go back and mill off the bottom to lower the tool tip to get it on center. I have even seen this with Aloris style drop in holders where they couldn't adjust the tool low enough to get it on center.
BTW Most of my lathe tool holders have the carbide shims under the insert. Only a few really small holders of mine don't have a shim under the insert.
Richard W.
Reply to
Richard W.
I did two things. One is that I milled one of my BXA toolpost holder to accept 3/4" shanks, and another was I milled some shanks to be smaller than they were.
On those Aloris type toolposts you have quite a bit of leeway with height.
i
Reply to
Ignoramus14389
I have seen that, and it's not a bad way to go.
You're right, but if the drop in holder goes down and sits on the compound and you're still above center. What are you gonna do? Mill off the top of the compound or the bottom of the tool holder?
I am not kidding I actually seen this done and by someone I thought would know better.
As for me I bought the largest drop in holder that would fit my lathe. CA size. I like 1" shank tool holders, but then my lathe has a 7 1/2 HP motor under it. I have some 1 1/4 holders, but I haven't needed them yet or I would have milled off the bottom of them already.
Richard W.
Reply to
Richard W.
Yes, given prevalence of 3/4" shanks on auctions and such, it is good to provide for them.
True
My lathe is 13" and I reasoned, possibly incorrectly, that I can only go with BXA.
i
Reply to
Ignoramus23517
BXA is probably correct.
For my Clausing 5914 I asked Aloris which size was best, and upon receiving the dimensions (like spindle center to top of compound) they said BXA. So that's what I got, and it does fit.
Joe Gwinn
Reply to
Joseph Gwinn

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