[davidthefat]

Originally Posted by Joe G.

Bevel gears require extreme precision in three dimensions. Both the top and side must be precisely machined, and you must have some way to precisely locate the bevel gears on the shaft. Definitely a job for machine tools. As a mental exercise, picture the number of ways a bevel gear's alignment can be "off," versus spur gear alignment.

Selection of bevel gears is another hurdle. Choosing an appropriate pitch, pressure angle, size, etc. is critical for good performance. Again, I'll let those with experience with these things elaborate further.

And even if you get it all right, bevel gears still create a noticeable drop in efficiency when compared to spur gears. Another argument for the self-contained approach.

From what I have read, helical gears are more efficient than bevel gears, that is why they are using in car transmissions. But they do cost more than bevel gears.