IMO keysteel would suffice for single point cutting tools but with a button tool you are more likely to have a wider cutting area so greater force on the tool holder so even with small DOC you could get some deflection/chatter, you will not lose much if you you machine the 12×12 to suit the insert and give it a try, may work out OK for you.

Emgee

If you keep the 12mm depth of the tool blank it should be OK, even if a lesser quality steel it's likely to be as stiff as one with a 6x6mm shank like mine.

I have used keysteel for making toolholders, en19t or en24t would also work well. The only disadvantage of using mild steel is that the insert pockets will be softer and more prone to damage than harder grades of steel. If you normally shim for height, or there is room, then the custom tool shanks can be made deeper which makes them stiffer. All the tools used in the museum's Smart & Brown sit at 17.53mm height and are milled down from 20mm shank tools which reduces greatly the need for shimming as all 3 toolposts are matching heights.

Edited By old mart on 24/02/2023 15:29:20

Edited By old mart on 24/02/2023 15:31:50

FWIW

I have made several tool holders from plain Mild Steel.

As already said the tool holder shank whould be as deep and as wide as reasonably possible.

The stiffness depends on the cube of the depth, so a 12 mm shank is eight times as stiff as a 6 mm.

(The formula is BD^3 / 12 )

The object is to ensure that the shank is as rigid as possible. If it flexes, chatter is more likely, and accuracey reduced.

Howard.

Edited By Howard Lewis on 25/02/2023 17:13:27