Hi Tim,
I am pretty certain when I swapped some out on one of mine ('82), I just used the 61/266 etc ones. IIRC they were the same part numbers. I know some vendors were trying to sell the front ones using the rear part numbers. The fronts have that sort of scalloped profile.
Thanks Cory. I assume they are the coarse cutting threads for plastic. I could have pulled it apart and taken them out but I have a few saws apart now that I have just got the parts I need to get them back together.
I'm going to run that 630 against my 036 to see how it compares.
I've been cutting some dead white ash this week. It is so dry that the dust flies and walking on the chips sounds like you're walking on Rice Krispies.
It keeps the air filter busy. Splits when it sees the axe so it's easy to process.