Originally Posted by
IanW
Paul, in my opinion (& I'm quite prepared to be shouted down) the relationship between grip angle & rake angle is very tenuous, and any effect of a more aggressive tooth angle for a given grip angle can be swamped by other factors, especially sharpness. A sharp saw with a relaxed rake will feel more aggressive than a dull saw with a higher rake angle; soft woods allow the saw to bite harder at any rake angle, & so on. I think we are getting into very esoteric territory adjusting grip angle for specific tooth rakes!
To me, the most noticeable effect of grip angle is on comfort in sawing, having your wrist twisted up or down in an attempt to keep the tooth line horizontal, as we often want it to be, can be uncomfortable & makes control of the saw less intuitive. We all use saws in odd situations at times, and manage it, but for accurate sawing, having the work & my body in a comfortable position that minimises physical effort helps a lot (I like to minimise expenditure of effort! :; ).
Spine/back weights are as variable a feast as grip angles. Again, I think it's pure preference & what you get used to. You could over-think this too, & work out what cross-sections of steel or brass provide x amount of stiffness for a given length of blade & then decide on what minimum stiffness is required (a decision which is likely to be quite arbitrary). Then you decide what weight is optimal to give just the right 'bite' for a given rake angle, which again would be an arbitrary decision due to the difference in sawyer technique, woods sawn, etc. Which would achieve precisely what? Just about every person I watch using one of my saws puts too much pressure on it regardless of spine weight. We all add a bit, despite what we may think, but there is a sweet spot that allows the saw to cut freely & quickly, which comes with experience & practice. My favourite D/T saw has a light 3/16" thick spine, which I find just right, but I make some saws with 1/4" spines. I've noticed the majority of people, when given the choice, go for the slightly heavier saw. This surprises me because I find the lighter saw so much easier to control as I flip it right & left cutting tails, but the customer pays their money & makes their choice.
You could argue that a heavy spine on a mitre saw does help with holding it vertical - the heavy weight makes it more easily felt if the saw leans to left or right, but I think spine weights are also arbitrary and not based on any exhaustive empirical study. The difference in average spine weights between Britain & the U.S. supports my contention that it has much to do with tradition & perhaps the cost of metal in the days before the colony produced its own on a large scale....
:U
Cheers,