Hardinge C10 holder Question

[Lanso]

Does anyone know the purpose of the concave sides as seen in photo? (they look factory)
It's an unmarked C10

 

[FredC]

Does anyone know the purpose of the concave sides as seen in photo? (they look factory)
It's an unmarked C10

I am going to say yours is shop made. I just looked that one up in my catalog and the inside surfaces are flat as expected. If I am correct, it is hard to guess why the builder did it that way.
All my Hardinge tool holders have the "Hardinge" logo as well as the model number. A few tool holders that were purchased from Hardinge were actually made by Brown and Sharpe and had B&S numbers and logo.

 

[Lanso]

I always thought the unmarked holders I have were aftermarket and the only purpose I could ever think of was ease of broaching - if that was the way that rectangle was cut?
I have other unmarked with straight sides. The Quality and hardness are same as Hardinge.

 

[FredC]

It has been 45 years since I had one in my hand. Back then wire EDM was not a thing so they would have been cut with a broach or a shaper. No clue how they are cut today. I see EDM cuts on collets today so it is possible they could use that technology on other stuff now.

Today I have Omniturns and a Hardinge GT, so the C10 is not appropriate for either type machine. We do use Hardinge holders on both types of machines exclusively.

On your C10 copies, the radius reliefs maybe for limited contact to enhance squareness when tightening the tools? Or the guy building them may have been quirky.

 

[Lanso]

FredC wrote
“On your C10 copies, the radius reliefs maybe for limited contact to enhance squareness when tightening the tools? Or the guy building them may have been quirky”

Two good thoughts.

 

[Jonathan Smith]

Maybe the center was hogged out with a drill then finished with a broach.

 

[stephen thomas]

Maybe the builder wanted to be able to hold round bar located one edge & centered under the SS?