Although I designed, re-manufactured, and built CNC machine tools for decades, I did not set up myself with a nice Monarch lathe, or a Bridgeport milling machine with an indexing table and digital read outs...As much as I have tried to convince myself I need to buy them now, I do not think it would be a long term source of entertainment, I would have more fun with another SOHC Four, I can then harass eBay sellers for parts. Just ask smart ass questions.
I have found some really good guys out there, some of them know what they are selling.
I am experienced with buying and manufacturing power train components. I know what difference a few thousands of an inch can make to operational smoothness and life of the system.
I have never heard the term "topping" or "semi-topping" used before in a tooth generating process. I have used the terms ID finish, OD finish, Pitch, Pitch line, OD relief, Id relief, pitch diameter, bottom clearance, tooth profile, contact angle, lead relief, bottom relief, bottom clearance, AGMA quality number, hob harden and lap, hob harden and grind, hob and harden...I could drag out one of my old prints and be reminded of more.
I have drawn gear tooth profiles in excruciating detail to insure the gears we put in spindle drive trains ran smooth enough to allow a precision bore to be created...
Three of the machines we designed (I did the spindle power train) bore the connecting rods on that POS Harley Davidson V Twin, or at least they did in 1990. HD rods are probably made by communist slaves now...but who cares, besides me? I would not own one.
But I digress;
When shaping the tooth profile for a chain sprocket what effect does a topping or semi-toping hob have?