Shopsmith Forums

jsburger wrote:

ERLover wrote:For scrolling do the blades the MS sells fit the old scroll saws from the ER era?

They are actually jig saws not scroll saws but yes they fit I believe.

As well as 5" coping saw blades. Pins are removable.

Thanks Steve, you saved me from asking that question, which what I was going to do next.
Dont know what I will do with it as of the moment other then get it working, since I have band saws and hand held power jig saws. I know it can do what the others cant, but not into any of that, but nice to have in the repertoire.
The prize was the very clean ER with its SC.

So if a jig saw blade has a spring for blade tension, I am guessing/spitballing here, the spring has to have more tension on it then the resistance of the wood it is cutting.?

ERLover wrote:So if a jig saw blade has a spring for blade tension, I am guessing/spitballing here, the spring has to have more tension on it then the resistance of the wood it is cutting.?

I guess you could say that but the resistance is a function of feed rate.

The jig saw not only uses the spring for blade tension but the spring returns the blade to the up position. In other words the blade is only powered in the down stroke. Jig/scroll saw blades cut on the down stroke. There are blades that have a few up stroke teeth to help with chip out on the bottom side but the blades still cut on the down stroke.

A scroll saw powers the blade in both directions.

The spring is a 'return' spring. The saw pulls the blade down to cut. The spring pulls up on the blade as the saw is 'pushing' the blade up. The spring provides sufficient tension so the blade does not buckle. It also resists the pull down thereby providing tension.

On a scroll saw the frame provides tension equal in both directions.

Also the jig saw blade moves linearly up/down. The scroll saw blade moves in an elliptical motion advancing on the down stroke and retracting on the up stroke(slightly).

JPG wrote:The spring is a 'return' spring. The saw pulls the blade down to cut. The spring pulls up on the blade as the saw is 'pushing' the blade up. The spring provides sufficient tension so the blade does not buckle. It also resists the pull down thereby providing tension.

On a scroll saw the frame provides tension equal in both directions.

Also the jig saw blade moves linearly up/down. The scroll saw blade moves in an elliptical motion advancing on the down stroke and retracting on the up stroke(slightly).

Please explain how that happens. I have never heard of that. I know the newer hand held jig saws apparently have that feature.

How does the conventional scroll saw acomplish that?

The lower arm of the scroll saw is moved by a cam driven connecting rod.

The two arms pivot on bushings between the blade end and the back tensioned end. Since the blade and tensioning end essentially form a parallelogram, the two arms move in unison.

The blade end of each arm moves in it's own arc equidistant from their respective pivots.

As the arms descend(cutting stroke) the blade end of the arms move outward(towards the workpiece) on those arcs. As the arms ascend, the opposite occurs. The arc motion moves the blade away from the workpiece. The workpiece is located between the arm pivots so the arc is as described. The geometry of the arms is identical although they differ in other areas.

You can observe the blade appearing larger from the side as it runs. You can also observe it by cycling it manually.

The motion is slight, but it is there.

I'm not sure on the MotherShip's blades, but regular 5 inch jigsaw
blades work as well. They have a pin in the end, that needs to
be punched out. (Coping saw blades.)

steve

skou wrote:I'm not sure on the MotherShip's blades, but regular 5 inch jigsaw
blades work as well. They have a pin in the end, that needs to
be punched out. (Coping saw blades.)

steve

http://www.shopsmith.com/ss_forum/viewt ... 26#p197526

JPG wrote:

skou wrote:I'm not sure on the MotherShip's blades, but regular 5 inch jigsaw
blades work as well. They have a pin in the end, that needs to
be punched out. (Coping saw blades.)

steve

http://www.shopsmith.com/ss_forum/viewt ... 26#p197526

That is what I get for responding to something on page 1, without looking at page 2!

Thanks JPeG!

steve