The problem with the saw-set is that it looks so simple. I mean, basically it looks like a pliers-like affair with a hand operated punch that forces the tooth against an anvil. A dial type knob is provided with numbers from say, 4 - 16, which allows you to set the thing for the # of saw teeth per inch (tpi). So, can't be that difficult; just dial in the # of teeth and away you go...... Well, not quite. Some of us, led by Steve, had noticed that most saw-sets had a second knob or 'adjustable bar' on the lower side, directly below the punch. He posed the question in rec.norm as to what this was for. Judging by the underwhelming response we obtained, it wasn't clear to a lot of others either. What followed was a week long barrage of humor, insults (most at O'Deen's expense) and argument between the four of us. Before we began this discussion, the impression the four of us had (except O'Deen, who was purposedly vague :^] ) was that rotating the indexed knob to a lower number (as in tpi) exposed more 'bevel' on the anvil and thus produced more 'set', and vice versa. This was how we thought one controlled the amount of set, ie., a 6 tpi saw would have more set than a 12 tpi saw. We are now fairly certain this is not the intent of this knob. While one can control 'set' this way, we believe the intent of this knob is to control the point at which the tooth is bent. That is, the anvil provides a fulcrum over which the tooth is bent; the function of the knob is to move the fulcrum up or down the tooth and thus define the bending point.
So....how does one control the set of the teeth? Well, imagine we have the saw blade clamped in front of us and we slip the saw set down over the teeth. One will immediately notice that the saw-set has a certain amount of slop, or wobble. If one lifts the handles slightly, it will be noticed that the anvil moves away from the blade by a corresponding amount, so that squeezing the handles now gives more 'set' than before. Rotating the saw set downwards by lowering the handles slightly produces the opposite effect, since the anvil is now closer to the saw blade. Once you've experienced this 'slop' or 'wobble' it becomes obvious that some indexing mechanism is needed to hold the saw set in a constant position, so that your setting job doesn't start to look like bad dental work.
Hence the screw on the underside of the saw set; with it contacting the saw blade it provides a constant reference point. Screwing, or otherwise moving it in towards the saw blade rotates the saw set up and the anvil is moved further from the teeth, producing more set, while screwing it out allows the saw set to rotate downwards, producing the opposite effect.
One thing that we haven't settled on yet is a reliable way to translate the initial setting of this indexing screw or bar to the actual amount of 'set' produced. Since there are so many different saw- sets out there, there's probably no one rule that fits all of them. So, initially it might be good to try just a slight amount of set; you can always add more later....it's harder to go the other way though... :^)
So... to summarize, (in Steve's words) "Top knob's for *location* of bend, bottom knob's for *amount* of bend".
So simple I'm not sure how it evaded us for so long, huh?
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