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Bow saw, turning saw, or frame saw

Bow saw, turning saw, or frame sawThis is a SketchUp model of a bow saw, also referred to as a turning or frame saw. (Although a frame saw can also be something completely different.) The bow saw cuts smooth curves and tight radii; the blade allows for long strokes that cut faster and more evenly than a coping saw.

This particular model is based on a mix of designs, especially Hasluck's The Handyman's Book (1854) and from plans in a 1920s issue of The Woodworker.

A hand made bow saw offers the ability to cut complex curves easily and quicklyOf course, no model is as good as its real-world execution, so I've posted images and text in the related project article.

About the SketchUp model itself: it looks deceptively simple. The arms, in particular, were quite difficult, especially for a SketchUp beginner. One of the images below is of just one of the arms, and a second links to a nifty image of the wireframe structure of the arm, which depicts the handle, pin and crosspiece that interact with it as solid object.

Creating an arm of uniform thickness but with the curved shapes did not take too long and wasn't too difficult. Create the basic outline, then "Push" it out to half the thickness of the arm.

Putting a taper on the upper arm was difficult, but then, I think I went about it wrong. I created a plane through the arm, intended to become the new tapered outer surface of the arm. Intersected the plane with the model. And yes, it should work - but it created a number of areas that simply did not fill. A model with many tricky holes, lines that weren't quite on-plane. Took forever to fix.

In retrospect, I'd try the Scale Tool, and drag only the one upper outer edge down to create the taper I'd want. I suspect that would work. Quickly and easily.

Next, the chamfer. I created a 45o triangle to subtract from all edges I wanted chamfered, and used the Follow Me tool. Same problem occurred: SketchUp couldn't create perfect-fit matches along an angled, curved edge. Some places didn't remove the chamfer. Others had holes where faces and edges ought to be. Again, these had to be fixed manually. Took a long time.

The rest of the arm was easy. I had a half-arm. I copied it, flipped it, joined the two halves into a whole. Added the mortise and the through-hole for the pins. And copied and flipped the arm, to make a second.

The crosspiece is as easy as it looks. Simple elongated rectangle, with short tenon protruded from either end, and a simple chamfer using the Follow Me tool that worked.

The handles are extremely easy - more about them, later. Pins and saw blade, easy. String, finicky but not hard.

Was it worth it? For me, yes. I enjoyed designing the thing. I had fun building it. And I love using it - the saw works beautifully.

- PD
 



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All Images

SketchUp model of a bow saw, also known as a turning saw or frame sawGoogle SketchUp model of wooden bow sawWire-frame model of wooden bow saw design done using Google SketchUpSketchUp model: bow saw arm or “cheek” detailSketchUp wireframe structure of bow saw arm, showing interactions with handle, pin and crosspiece
 

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