Pull Tooth Kerfing Saws.

[Stewie Simpson]

Attached are some Pull Tooth Kerfing Saws I am working on. The handle wood is Bubinga, 0.020 saw plate gauge, the toothed length will be 120mm, and the hang angle 45* to the tooth line.

The handle has only had 2 coat of Garnet Shellac. I am looking at filing the saw teeth 15tpi; 8* rake; with crosscut fleam.

These 2 Kerfing Saws are designed for cutting out the shallow wedge abutments on wooden bench planes, so no tooth set will be applied. Their design could be easily modified to suit deeper kerfing work where some set would be a requirement.

Stewie;

[Kees Heiden]

They certainly look very nice!

I don't really understand why you put the handle on an angle? Does it make the sawing of abutments somehow easier?

[Stewie Simpson]

Kees. Re the hang angle at 45*; when the wrist is in a straight or neutral position, the controlling forearm is in parallel alignment to the tooth line.

Stewie;

[Derek Cohen]

Stewie

I would imagine that this pull handle is the opposite of what is desired, both in ergonomics and physics - for example, a pull Japanese saw creates plate strength through coplanar/in-line tension. A handle at 45 degrees moves well away from this. Do you have references/information that supports your design decisions?

Regards from Perth

Derek

[James Waldron]

Stewie

I would imagine that this pull handle is the opposite of what is desired, both in ergonomics and physics - for example, a pull Japanese saw creates plate strength through coplanar/in-line tension. A handle at 45 degrees moves well away from this. Do you have references/information that supports your design decisions?

Regards from Perth

Derek

After truly exhaustive research (looking at the pictures of Japanese saws in the most recent Japan Woodworker catalog), it appears that:

Japanese traditional backsaws have handles coaxial with the back.

Saws with no back have handles coaxial with the centerline of the blade.

Very modern saws with molded handles sometimes have curved handles with hang angles that vary quite a bit.

It appears to me that Stewie's saw plate 'sees' the force applied at the junction of the handle and blade and can't 'see' the presence or absence of a coaxial handle. But then my engineering expertise is fully as pathetic and shallow as my research.

Consider the pot stirred.

[Kees Heiden]

Not ALL japanese pullsaws have the handle in line with the plate. The ones for resawing (I forgot their name) are at an angle too. Those big rippers are for really rough work of course.

[Pat Barry]

I trust that Stewie has experimented with various hand angles in the intended usage for this saw and found the hang angle he implemented to be comfortable for the user and controllable. I think the ergonomics of the saw is driven by the manner in which it is used however and if a different user likes to work higher or lower or with a bit of an angle of tilt to the workpiece they can adapt or choose a different tool. One interesting thing would be to see the saw in action because that would answer most of the questions.

[Stewie Simpson]

Not ALL japanese pullsaws have the handle in line with the plate. The ones for resawing (I forgot their name) are at an angle too. Those big rippers are for really rough work of course.

maebiki oga



http://lumberjocks.com/fissionchips/blog/36555

[Stewie Simpson]

I trust that Stewie has experimented with various hand angles in the intended usage for this saw and found the hang angle he implemented to be comfortable for the user and controllable. I think the ergonomics of the saw is driven by the manner in which it is used however and if a different user likes to work higher or lower or with a bit of an angle of tilt to the workpiece they can adapt or choose a different tool. One interesting thing would be to see the saw in action because that would answer most of the questions.

Thanks Pat. I appreciate the vote of confidence.

Stewie;

[Stewie Simpson]

The kerfing saws have been sharpened 14 tpi ; 10 degree rake angle ; 5 degree fleam ; 0 set applied.

They were then tested out on softwood; hardwood ; and some gnarly Blackwood Burl. All clean cuts; close together ; straight and consistent within depth of cut ; no noticeable rocking motion by the saw blade ; and the handle grip accompanied by the 45 degree hang angle felt quite natural within use.

Stewie;

[Stewie Simpson]

Achieving the correct rake angle was a critical key to insuring a smooth start within the cutting stroke. In this case the rake angle was tested at 0*; then 5*; then 8*; before settling on 10*. All done using traditional hand filing.

[george wilson]

No offence intended,Stewie, but I'd find it easier to judge the angle I'm sawing at with a straight handle. Especially critical when sawing down in the escapement of a plane. The "fishtail you put at the end of the handle would give enough of a grip to use them in a straight line with the blade.

[Stewie Simpson]

No offence taken George.

[george wilson]

I dunno. Maybe it's no different from having a Western style handle on a brass backed dovetail saw, Your hand is at about the same angle. But,I can get used to anything myself.

[Stewie Simpson]

As I mentioned in my opening post with some set applied these Kerfing Saws were capable of far deeper cuts.

Stewie;