Sunday, September 26, 2010

#36- RAS-styles & alignment

Radial Arm Saws (RAS) are best known for being used to perform repetitive cutoffs on wider, or longer, boards. I have seen extension tables that would allow someone to lay up 30-foot boards and cut them shorter. This would be very hard to do on a table saw. A RAS can do that very easy because the head moves, not the actual workpiece.

Speaking of the head moving, there are two types of RAS’s. The first and most economical is the “regular style”. I call it that because I don’t believe there is an actual name for it. This RAS simply has an upright column at the rear and that has an arm attached to it that is sticking out from it towards the user. That arm has a grooved track built into it and the head’s roller bearings ride along those grooves to allow it to slide fore & aft. This saw is the one most seen in home shops and it is very fussy about aligning properly. At the outer end of the track, arm flex can be an issue.

The more professional design is the “turret-arm” RAS. The rear column is still there, as is the arm coming towards the user…but that arm is only ½ as long and it has a pivot point for the actual arm that has the track in it. The track arm- picture an upside down T, with the track being in the crossbar of the T and the stem being the pivot point- contains the grooves for the head’s roller bearings. This type RAS is far easier to align and has much less flex than the ‘regular’ design.

With a turret-arm RAS, achieving proper saw alignment is easier because having the track pivot in the middle allows the adjustment to better control the track arm. With the regular style, when the head is at the end closest to the user, there is always some flex. Maybe not much, but some…and the user has to factor that in when making their cuts.

Aligning a RAS is not all that complicated. I always suggest that the user get a piece of stock that is as wide as their saw can handle, lay it on the table, make a cutoff pass and check it with a framing square. Note: I don’t like using framing squares under normal conditions, but it’s about the only thing that has the capacity to check a wide-cutting RAS. Once the cutoff is checked, then the adjustments can be made. On a regular RAS, the alignment screws are located at the rear junction of the track arm and the column. On a turret-arm, the adjustment is made at the centered pivot point.

Follow your owner’s manual, check your adjustment results by making another cut off of the wide board and you’ll have your saw cutting straight in no time.

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