What is the hob cutting speed for gears?

A few weeks ago I tried to answer the question “what is the hob cutting time for gears?”, triggering (also in private messages) an array of different technical questions, one of which was rather common and referred to cutting parameters according to the tool and the material to be worked. What is, in other words,

the correct hob cutting speed for gears?

To try to clarify this further, I’ll start by publishing a fairly simple chart that I "borrowed" from the technical manual of a manufacturer (the Swiss company SMH AUTOMATION), highlighting the fact that the indicated limits are correlated to the diameter of the tools used by said manufacturer, given that the chart refers to its own product range.

A couple of remarks. The chart in question does not envisage variations due to any PVD coatings; it refers solely to the use of single start hobs; and only considers the number of standard cutting edges based on the hob diameter. 

These data are to be taken as an indicative reference, which is, in any case, very reliable.

Given that hobs are finishing tools and this is precisely what we are talking about, I underline the fact that the hobbing speeds can be significantly increased during pre-grinding roughing cycles.

Furthermore, at a practical level, the hobbing speed should also be adapted to suit other parameters such as the shape of the workpiece, the rigidity of the equipment, the power of the gear hobbing machine and, most importantly, the level of quality required by the technical specifications.