I picked up a nearly new Mikron gear hob at a car boot sale last week (amazing what turns up at these places sometimes). No markings, but It looked to be a useful model engineering size, so worth risking a couple of pounds I thought.
However, the hob form baffles me. The circular pitch, as well as I can measure it, is about 98 thou, which seems to stack up with 32 DP. Fine. However the tooth depth is only 40 thou.
From my Machinery's Handbook a 32 DP, 20 degree PA, standard involute tooth should be 62.5 Working Depth, or 67.4 thou Whole Depth.
Is it perhaps a stub form? Again from my Machinery's Handbook, 32 DP,20 degree PA, standard stub form Working Depth would be 50 thou. Still not right.
Can someone with better knowledge of gears than me throw some light on this (before the hob ends up being thrown)