Posted by BillS on January 05, 2010 at 15:41:30:

In Reply to: hobbing machine posted by bilal on January 05, 2010 at 08:01:42:

Hob table feed rate is translated from number of cutter gashes, cutter rotation speed, hob type material/coating, and work material type.

If you start with the material and a chip load (chip thickness) and speed (inches/minute), then you can do the math to calculate what the table feed and rotation speed would need to be to get chip load and speed.

Normally, books showing tables of speeds and feeds are available showing suggested values by material and machine operation. There you would also find the formulas to account for teeth/gashes per rotation and inches/minute to rotation RPM for tooling diameter.

I think these are the formulas you are asking about:

Cutter speed (inch/minute) = pi x Hob Diameter x RPM

Table Feed Rate (inch/revolution)

Chip load (inch/tooth) = ---------------------------------------

Number of Hob Gashes

This is usually a starting point since coolant, machine rigidity, and tool life all play a part in your
final choices.