Here is my correspondence with Oregon Products regarding 72EXL chain sharpening:
To: Oregon Products Support <
oregon.support@oregontool.com>
Subject: 72EXL chain sharpening angles
Dear Sir,
 
Are the chain sharpening angles for 72EXL chain the same as 72LGX when sharpening on the Oregon 520-120 grinder?  If not what are the correct angles for the 72EXL chain?
 
Should the 10 degree down angle be used when sharpening the 72EXL chain?  
 
The 520-120 manual should be updated on page 12 "Grinding Angles Chart" to include the 72EXL chain.  
 
Thank you,
Their response:
From:
glenn.lovell@oregontool.com
Tue, Nov 28 at 2:09 PM
Hello, Thank you for your interest in the Oregon® brand.
 
The 72EXL uses the same sharpening angles as the 72LGX. The 10 degrees down angle is not a must have, it is a nice to have. When down angle is properly applied during sharpening it will get you 3 – 5% faster and more efficient cutting. Most chain users, other than professional loggers, will never notice the gain in cutting performance.
 
Grinder head tilt angle: 55 degrees.
Chain vise rotation angler: 25 degrees
Down Angle: 10 degrees (if you want to)
 
 
Kind Regards,
 
Glenn Lovell
Sr. Technical Services Technician
Forestry, Lawn, and Garden Division (FLAG)