version 2.24 online

[ArtF]

Hi All:

 I managed today to cut my second good bevel, a match for the first and they run perfectly together. ( Of course they ARE styrofoam), but they dont take any pressure and you cannot feel any binding in the roll.
I had a lot of trouble getting to this point. Much of it was my own misunderstanding or wrong assumptions on the math required. Turns out the process is fairly easy, but any wrongheadedness in cutting can make you think your wrong in many ways. As a result I ran down many wrong alleys.

  Zeroing the blank is very important in this. One thing I did that looked OK, but screwed me every time
is the zeroing. When cutting a bevel you tilt the 4th axis to the pitch angle. This means the when you look
at the top of the balnk is will always tilt very slightly downwards from the chuck, it should not be straight
in the X axis. The amount of tilt is the addendum angle. This tilting means you can do bevel as low as 1 degree in pitch angle. Zero degrees is impossible, the teeth never change tangental relationship.

Anyway, you tilt to the pitch angle and you now have a face that is tilted down by the addendum angle as a result. SO far so good. Now when I cut a blank, I dont cut the back face, I do that post cutting by dropping the tool in back of the first tooth and running A axis 360 degrees..makes a nice bevel angle.

This means that when cutting Im presenting with a tooth face that is longer than required..I had been starting the cut approximately where I figured the tooth shoudl start...this will hose you everytime. :) .. The reason of course is that the gear is tilted, so any move in the X changes the blanks effective diameter. This means you MUST be zeroed properly in the X..( assuming a the chuck is on the X axis).

 If you start with a blank of proper size this will not happen to you.

Zero the tool so tool center is exacly over the top of the tooth closest to the chuck. If you have a premade blank, then this means due to the tilt the zero will be very obvious, the rear cone of the  gear will be the highest point , just zero directly above that point with the point in the center of the tool.


 Let me know if you do a test, I need to see the result if you can photo it, if not please let me know how it runs or anything you note in the process.

 The code is made to always cut upwards and nver plunge cut. I havent as yet corrected for the slight tool gouge at root clearing due to the dedendum angle. It wont affect you very much, but will be taken into accoutn as I turn on helicals and zerols..

 Clearing is done on every first involute shave. The code is programmed to produce complete teeth rolling towards you as the gear progresses.

 Ive only cut my 45 degree bevels, but have checked the math from 1 degree to 89.9999 degrees so pretty much any bevel should be able to be done provided you can tilt that amount.

Good luck,

Art