#34- Radial Arm Saw- How’s your Hook?

Last week, we started a discussion about the Radial Arm Saw and I covered a couple of the reasons as to why I am a member of the ‘pull the blade through the workpiece’ camp. We’ll continue the discussion this week with reason #3.

Third, IF the proper negative-hook sawblade is used, the operator has complete control over the force of the blade thru the wood. Now, IF a positive-hook blade is used, the blade will try to ‘climb’ thru the workpiece and make the operator push back against it. ALWAYS use a negative-hook sawblade on your Radial Arm Saw.

I did some testing years ago and it really is true. Using the ‘pull-through’ method, with a 20 degree positive-hook blade, I had to push back against the saw head slightly to keep the blade from trying to ‘run’ towards me. On the other hand (again using the pull-through method), when I used a 15 degree negative-hook blade, I could use one finger to pull the blade thru the wood and it did not try to climb at all. In fact, I would let the head stop every couple of inches and just let it sit there…and it wouldn’t move, even though the blade was spinning at 3450rpm and buried in the wood.

This might be a good place for a talk about negative and positive blade “hook angles” because they do have an effect on how smoothly a RAS blade can pass thru a workpiece. For this discussion, we are talking about carbide tipped blades. Picture, if you will, a circle. On that circle, we draw a straight line vertically and a straight line horizontally - with the intersection of the two lines dead center in the middle of the blade’s hole. Now, we give that circle some blade teeth and let’s say that the ‘blade’ is going to rotate, and cut, counter-clockwise. Align one particular tooth right on the vertical line.

With that picture firmly in mind, here are your three ‘hook angle’ definitions:
If the flat of a tooth is exactly aligned with the vertical line, that blade is a ‘zero hook angle’ blade.
If the flat of the tooth has its upper tip tilted in the cutting direction (in our example, that would be counter-clockwise) this blade is a ’Positive hook angle’ blade.
If the flat of the tooth has its upper tip tilted AWAY from the cutting direction (in our example, that would be counter-clockwise) this blade is a ’Negative hook angle’ blade.

We’ll pick up here, next week.

Send your questions or comments to:
Toolsmartz@bellsouth.net and we’ll see what we can do to help you.
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