Steel for tool holders

[DalboyParticipant @dalboy]

I have what I best describe as a button insert which I brought some time ago for another project but never got around to making a holder to fit into the lathe.

What would be the most useful steel type to use.

I have a piece that is approx 1/2" X 1/2" steel bar of unknown type but I have a very good idea that it is key steel as that is what I would of most likely had from my Plant mechanic days and it was in my toolbox with other square section pieces.

And as that would have been the only reason for having it in the first place. Now that I am doing model engineering all other material that I now own has been brought new and not square section.

Could that be used as a holder the button is only 6mm diameter. I know whatever I use will need to be machined to suit the insert.

Edited By Dalboy on 24/02/2023 12:22:00

[DalboyParticipant @dalboy]

[EmgeeParticipant @emgee]

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

[Martin ConnellyParticipant @martinconnelly55370]

Ø6 button tools are great for machining plastics where the forces are a lot lower than when machining metal.

Martin C

[JasonBModerator @jasonb]

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.

[DC31kParticipant @dc31k]

Posted by JasonB on 24/02/2023 15:04:15:

…even if a lesser quality steel it's likely to be as stiff as one with a 6x6mm shank like mine.

There are some fundamental misunderstandings of structural mechanics in the above statement, all of which have been discussed numerous times before on the forum.

The E value (Young's modulus) of steel has no correlation whatsoever with the "quality" of the steel.

The I value (second moment of area) of a rectangular cross section is proportional to the cube of its depth, so something twice as deep (12mm vs. 6mm) will be eight times as stiff for the same width.

[old martParticipant @oldmart]

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

[DalboyParticipant @dalboy]

Thank you all will give it a go with the square stock I have. It will only be used occasionally.

[Howard LewisParticipant @howardlewis46836]

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

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