saw vise design

[bugbear]

A neighbour was recently kind enough to give me his late father's saw vice.

This was a traditional "saw chops" where a pair of hardwood strips are pushed into a 'V' shaped jaw in the main frame. The frame is similar to this one:

http://www.cornishworkshop.co.uk/wwsawvice.html

A wrinkle in this design, which the donated vice showed me, is that the cross piece should be of a height to sit in your bench vice.

However, in the donated design, the jaw pieces had a tapered half lap, that fitted exactly in the 'V' of the stand's jaws. In this design, all the tapers must match exactly for the saw to be held nicely.

Further, the faces of the jaw pieces must be truly flat to hold the saw.

The lazy slob (or is that design genius) in me didn't like the notion of the all this precision being required, so this thought occurred to me:

The trad design is on the left. My "deskilled" version is on the right.

The curves are completely non critical, which is rather the point.

This design (almost) cannot help holding the saw tightly, right near the teeth.

Comments and suggestions are welcome.

BugBear

 

[Alan Smith]

Bugbear your thinking is fine however you will probably not be surprised to hear that someone else got there first. I'm not claiming the honour but I will say that some thick walled plastic tubing of about 1" dia ripped up the middle saves a lot of whittling with a spokeshave!!!

 

[bugbear]

Bugbear your thinking is fine however you will probably not be surprised to hear that someone else got there first. I'm not claiming the honour but I will say that some thick walled plastic tubing of about 1" dia ripped up the middle saves a lot of whittling with a spokeshave!!!

Very slick! The tubing would need to be very stiff, though.

Thinking further, if the external pivot (on the outer curved) is made asymmetic, so it's nearer the top, the clamping force will be unevenly distributed, with extra pressure at the top, which is desirable.

BugBear

 

[Alan Smith]

Nah, I think you'd find that if you asked an engineer that they would tell you that the force exerted would be equally distributed.

 

[bugbear]

Nah, I think you'd find that if you asked an engineer that they would tell you that the force exerted would be equally distributed.

No, it does vary, honest.

Consider a simpler clamping shape - a perfectly square 'u' section, upside down (is that an 'n' section?) sitting on a flat surface.

If a force is applied at the leftmost extreme, there is no moment at all to apply any force to the right leg of the 'n'.

If all the force were on the rightmost extreme, there would (similarly) be no force at the left.

Intermediate points are (obviously?) interpolations between these extremes.

BugBear

 

[Alan Smith]

I may be having second thoughts about my statement above!

 

[Joe]

Could you achieve a similar clamping effect with the simple vice that comprises two hinged boards by lining the jaw with strips of wood that are a little hollow in the middle? Or perhaps you could use thinnish (say 9mm) ply with several vertical ribs on the outside that are slightly hollowed out with stop shavings (on the face glued to the ply) to force the sheets into a curve? (Hope I've explained that clearly).

Joel

 

[bugbear]

Could you achieve a similar clamping effect with the simple vice that comprises two hinged boards by lining the jaw with strips of wood that are a little hollow in the middle? Or perhaps you could use thinnish (say 9mm) ply with several vertical ribs on the outside that are slightly hollowed out with stop shavings (on the face glued to the ply) to force the sheets into a curve? (Hope I've explained that clearly).

Joel

You need some way to ensure the force is effective over the full width of the saw; the other advantage of this design is that you can turn the saw by turning the entire vise, leaving the saw clamped. This renders the slightly crude clamping approach less of an issue.

I will point out at this stage that all this is "in my head", since I have a nice (although too small) Woden saw vise.

BugBear