If you go onto Youtube and type in "Myfordboy", scroll down and go to the video which says "how to make involute gear cutters".  Have a look at this video it might shed some light.  I have made 1 of these following the directions on the video.  However, I hardened it but I had trouble getting the cutter sharp.  I  ended up sending it to a sharpenning place and they did it for me.  It works ok.  Still need to do some fine tuning on it to work properly though.  Hope this helps.  Here is a pic of the 1 I made.  Don't worry about those holes, they are only mounting holes to mount onto the arbor I made for it.

Here is a pic of the cutter on the arbor.

That is the gear profile you can see (which is a "silver" colour).  The gear next to it was not cut from that cutter.

Mtw fdu.