Coburn cutting crown angle formula

**ioptic** · 07-23-2011, 06:47 AM

Hi all optic gurus !

Does anyone remember the formula which determines the cross base power to be cut- to an angle - which is used to set the Coburn generator head ? :)

From memory the formula has the cutting crown size in it eg 100mm, the:- n' of the lens material and power of the cross curve - to be cut- in mm radius- but it has been 30 something years since I saw this formula - so rather than trying to work it out from first principle - I am pinning my hope on the collective brain power of Optiboard Gurus :)

...or if everyone's memory fails - does anyone still have a coburn generator head angle chart ?

thanks to all in advance

Rob -o-o-

**lensgrinder** · 07-23-2011, 10:20 PM

$sin \alpha = \frac{d}{2(r - e)}$

Where
$\alpha$ is the angle
d is the diameter of the wheel
r is the radius of the surface
e is the radius of the wheel edge

**ioptic** · 07-24-2011, 10:56 PM

Originally Posted by lensgrinder

$sin \alpha = \frac{d}{2(r - e)}$

Where
$\alpha$ is the angle
d is the diameter of the wheel
r is the radius of the surface
e is the radius of the wheel edge

super - thanks - forgot completely about the wheel edge radius in the formula :)

At this stage the question had over 70 viewings and one reply - yours!

Hence tip me hat' and award you 1 place !

congrats and many thanks !! :)

-o-o-