* Every geometric parameter of gear may be dimensioned in absolute freedom, without any necessity of follow standard values, up to operate even a difference in normal pressure angle of working and not-workimg flank, in order to improve stress strenght without overloading bushings.

This kind of freedom is already given by grinfding process too, so that couple milling + grinding offers a complete manufacturing process.

* Module value may be set very large, since milling tool dimensions are not very affected by module value (as happens in hobbing).

* Central gap in double-helical gears may be dimensioned only in reference to grinding and milling necessity, that are usually lower tha hobbing ones.

* Both milling and grinding operate in single-share mode, so that it is possible to machine partial toothing, also for pieces that have some volumes OVER root diameter.

Large gears may be machined by sectors, with proper milling paths.

* All design chances correspond to macxhining opportunities for gear manufacturers that work only for other firms, that may face any machining request without care about hobs availability.

* The machine, also if mainly used for toothing, still owns its performances, and may be used as an ordinary machining center over other kind of products or other surface on a gear.

* In case of fast table it is possible to operate turning machining.

* Machine may be used for a previous check of geametric conditions of gear, due to heat treatment for example.

* The same machine may operate , other than involute cut, also first rough machining and/or root fillet machining.

* With proper CNC software, it is possible to machine also large spur bevel gears, for any generating lenght.

(Available photos on request) * Machining of long pinions may be improved by using a rotary table with horizontal axe, with edge and intermediate counter-supports.

* Respect to hobbing machines, speed table in continous milling modes is very lower than in hobbing mode, with speed ratio about 60:1 - 80:1 and table is stopped in ulti-plane mode.

This means that CNC equipement is very cheaper (Don't forget that any supply offer of hobbing machine shows different prices according to required maximum table speed!).

* No tool rotation control is required.

* In case of machining of pinions with just a few teeth, there is non limit to cutting speed.

* In case of power failure , no damage occours in multi-plane mode and low damages occour in continous mode (Anyway less tha in hobbing mode, when both hob and gear have high speed at the momento of power failure).

* Machining center suppliers are quite numerous and behave in correct anti-trust mode.

* One only milling tool is good for machining a large range of modules on both right and left flanks, so that it is not necessary to buy a wide set of tools, and in double R/L execution too.

Although standard milling tools may be used successfully, it is possible to design some special cutters for gear milling; they would cost a little more than a standard tool, but would cost quite a little anyway.

I am personally sure that any milling tool supplier would be very happy to may develop such a new product !!.

* Delivery time of standard milling tool is very short.

* Milling tool is very cheap.

The whole tools set in milling mode has a cost enormously lower than corresponding hobs set, also if properly normalized and carefully handled and sharpened.

Don't forget that brazed skyving hobs must be re-sharpened and have a limited lifetime.

* Tools suplliers are a lot and operate in trade conditions, while hob suppliers are just a few.

* Milling tool is light, may be handled easily and also automatic tool change may be used.

* Milling tool diameter may be quite small since cutting speed is easily controlled by rotation speed.

* All cutting inserts move at the same speed, and in hobs cutting speed depends upon insert position over the hob.

* Milling tool usually takes one only type of insert.

* A lot of HM qualities and geometries are available.

* HM inserts for milling are standard, cheaper and offer a greater number of cutting edges available.

* It is possible and fast to change inserts on-board.

* Milling tool is not required to be as precise as an hob.

* Not necessary have R/L tools.

* No re-sharpening is necessary.

* Also hardened materials may be machined.

* Cutting action is immediately productive, without initial and final partial phases as it happens in hobbing.

No extra-streoke is required also for large helix angle.

* Centering of pre-existing surfaces is easy.

* Cutting speed is undependent and may be set according to HM performances.

* In case of use of 2 milling tools, machining time may reduce up to 50%.

* Stock removal is greater than in hob-skyving operation.

* It is possible to choose different scan policies, in both continuos and multi-plane mode.

* Feed and rotation may be stopped instantly without further problems.

* Crash consequences are less grave than while hobbing.

* Machining action is easily in sight.

* Low table speed permits an easy chips removal.

* It is not necessary to assure perfect position of gear on the rotary table; it is enough to know desplacement vector and consider it in additional offset position during machining.

In continous mode it is necessary to share the path and calculate a proper modified goal according to center desplacement.

In multi cut mode the table is stopped in a well known position during single cut and local offset modification is very easy.