hobbing helical gear

look at my book pfauter with the calculation formulas for the helicoidal

sorry it's in german

yes, the machine can do it originally, but when I bought it, the parts were missing to make the helical

A standard conventional pfauter hobbing machine has two sets of change gears. One to set the number of teeth and one to set the lead of the helical gears. For axial feed there is another set of gears.

When hobbing helical gears, you require additional rotation of the gear blank that is linked to the axial axis movement in order to produce the helix. On my pfauter, it is the z axis. On Andy's machine it is the X axis.

So basically, there needs to be a set ratio between the gear being cut and the hob + another ratio between z axis movement and the gear being cut. The latter is controlled by the lead of the gear being cut.

Axial feed is not necessary for cutting a helical gear on a small scale. At my workplace, we hob large gears sometimes over 10 tons. Sometimes the hob will get blunt before the cut can be completed. In this case it is convenient to shift the hob axially in order to spread the action over the entire length of the hob. This can be done without stopping the cutting process, but generally we don't do that.

Henk

If the hob is long enough to complete the generating of the involute profile it will work. I can't see how axial feed will help at all unless the face width is small.

60 Deg seems unusual. Are these crossed helical gears? I don't have experience with those...