Cutting Clearance for PCB stamping

[Kevinoh]

HI there,
I have just taken on a nice little job to make a tool for releasing multiple component assemblies from a PCB (printed circuit board) and was wondering if anyone had any advice on the cutting clearances for optimal tool life?
The PCB is 1.2mm thick and uncoated.
I did a test piece in an other tool with 0.025/side clearance and the edge was pretty clean but I have no idea how long the edge will hold up, wether PCB is abrasive etc etc. I have spent a few hours trawling the net but can't find any data whatsoever.

Any ideas or experience would be great...

[RomanLini]

I don't have any experience with punching shapes out of PCB, but if it is fibreglass PCB it is very abrasive to tools. Carbide tools last longer although I doubt you can machine your punch and die from carbide!

I have a hand-nibbler tool for PCBs and it is steel, but the steel has been hardened.

Maybe you can use high carbon steel and then have it hardened?

[Kevinoh]

Thanks RomanLini,
We make a lot of carbide tooling here, but unfortunately we only quoted for tool steel. I was intending to use D2 hardened to 60-62 HRc, and get it TiCN coated, but now I know it is abrasive I might upgrade to ASP23 or some other sintered steel, maybe even CrN coat it too...
That still leaves me with the issue regarding cutting clearance though, I'm guesstimating about 6-7% per side at the moment.

Cheers for your input anyway

Kev