Small insert lathe tool (experiment)

[BillTodd]

I have a few boxes of small 10mm triangular turning inserts that I have not been able to use because I have no holder for them. Making the holder isn't too difficult but, because they only have a tiny 2mm hole, I been puzzling how to hold the insert securely (an M2 screw would be obvious, but not all that strong).

I pinched this idea from some larger  Iscar (?)  tool bars  and it seems to work well. The M5 grub screw has a eccentric 2mm pin turned on the end. The insert is locked down by 'undoing' the grub from underneath the tool thus both pulling the insert down and back.

It has the great advantage that the hex head does not get filled with swarf and there's no head to get in the way on top either.


[edit] The insert is sitting flat in the second photo - it's just the shadow that makes it look wonky

[Fredbare]

Hi Bill, I am am a bit thick, but is it only friction that holds the insert

John

[BillTodd]

Yes, friction is all that's needed. 

In all insert holder designs, the cutting forces should be opposed by support from the faces of the tool holder*. Very little force is required to hold the insert in place (this might sound like a contradiction to what I said above , but I really meant that a 2mm screw is too easy to break while doing and undoing it - BTDT)

*in my experimental one shown, the tip over hangs the edge by too much. The tip should really be supported directly underneath by the holder.

[BillTodd]

Aha!   The tool holders I have are not by Iscar but by a old British firm of Edward Hill's (HHM ?)

The patent is here:

http://www.google.com/patents?id=cwl1AAAAEBAJ&pg=PA1&dq=3097417&source=gbs_selected_pages&cad=2#v=onepage&q=3097417&f=false