Sunday, September 26, 2010

#35 - RAS- choose the best blade

More of our on-going discussion about the Radial Arm Saw… Let’s see, where were we?... oh yes, we ended up talking about Positive and Negative blade hook angles.

My best description of how to check a sawblade’s hook angle was the ‘intersecting line method’ that I outlined last week. My second-most used visual to help understand this is that of a swimmer’s hand. If the hand is scooping the water, he is using a ‘positive hook angle’, but if the hand is laid back and just slapping water, it is a ‘negative hook angle’ effect. The swimmer won’t go anywhere using a ‘negative hook’ hand angle, but such is not the case with a spinning sawblade. It still cuts just fine when a negative hook angle is used, but because it is not digging or scooping, the operator has maximum control over the head and blade.

High-speed steel sawblades (those without carbide tips) are not really described in terms of ‘hook angles’ because a HSS blade truly cuts through the wood, whereas a carbide-tipped blade ‘scrapes’ its way thru.

Years ago, on any saw where the blade was suspended over the workpiece (ex: a miter saw; Delta’s “Sawbuck”, a sliding miter saw, or even a sliding compound miter saw) one would never see any blade on it, other than a negative hook. For some reason, that has changed. Now, one might see a 12 to 15degree positive hook blade installed on one of these saws, right out of the factory. While I am not going to speculate as to why the manufacturer’s decided that they could do this, I will say that I, personally, am not comfortable with it. As I told about in my example of testing, a negative hook blade offers the user so much more control over the sliding head, that to use any positive hook blade just invites ‘climb-cutting’.

On miter saws, where the head does not slide, a positive hook blade could be used and it still be as safe as using it in a table saw (which is another discussion entirely) because the head is ‘locked in’. There is no sliding movement as there is on a Radial Arm Saw or a sliding miter saw. With this in mind, I can understand it, but on a sliding miter saw? Not for me.

Hopefully, from our discussions, you have a better understanding of some of the techniques of a Radial Arm Saw’s blade needs. Next week, we’ll take a look at the different styles of RAS’s and get a tip or two about how to go about properly aligning a RAS

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