Making a Rob Cosman kerf extender

[SteveMP]

Like the idea of Cosman’s x10 after doing several half blind dovetails on the travel chest. But its a little pricey for what it is: https://robcosman.com/products/rob-cosmans-kerf-x-10
The guy that sharpened my saws threw in some scrap plate and brass back. Had some free time on my lunch break. To be continued after i get my lathe out and set up.

 

[HOJ]

I came across one of these a few years ago when I visited Classic Hand tools, I was starting on a project to make a few drawers for an Oak storage case, but being frugal decided to make my own version from a gentleman’s saw I had knocking about, works really well, maybe not as refined as Mr Cosman’s version, or yours, but cost me nothing.

 

[SteveMP]

I came across one of these a few years ago when I visited Classic Hand tools, I was starting on a project to make a few drawers for an Oak storage case, but being frugal decided to make my own version from a gentleman’s saw I had knocking about, works really well, maybe not as refined as Mr Cosman’s version, or yours, but cost me nothing.

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Thats great! I would have probably done that too if i had an extra gents saw. I was looking for a way to make one as cheap as possible and kind of got lucky with these scraps. Otherwise was going to use a card scraper. The only problem is the card scrapers i have are too thick and i ended up splitting one of the dovetails i was working on.

 

[SteveMP]

Small update. Getting too hot to work in the garage now so atopping here. Turned a handle from a chunk of scrap cherry.
Did some more file work and sanding. Handle needs a couple more coats of finish and the brass some finer sanding and polish and remove the bluing.

 

[Mike G]

I cut the end off an old bone-handled table knife. I've since come to the conclusion that any form of this technique is too brutal, and liable to cause more damage than it's worth, so I stick with chopping with a bevel-edged chisel.

 

[Woodbloke]

I cut the end off an old bone-handled table knife. I've since come to the conclusion that any form of this technique is too brutal, and liable to cause more damage than it's worth, so I stick with chopping with a bevel-edged chisel.

Tend to agree with you Mike. I can't see how it'll work with very thin plate Japanese saws either so I think I do as you suggest and stick to a bevel edged chisel to pare away the offending material - Rob

 

[SteveMP]

I cut the end off an old bone-handled table knife. I've since come to the conclusion that any form of this technique is too brutal, and liable to cause more damage than it's worth, so I stick with chopping with a bevel-edged chisel.

I initially thought it was brutal as well as it split a piece i was working on. Then rewatched the Lie Nielsen video and noted he said to clamp it or put in vise. Once ai did that had zero issues.

 

[HOJ]

clamp it or put in vise

As I did:

 

[SteveMP]

One down. Will send this to the guy that gave me the scraps. Starting on a second one.

 

[SteveMP]

Tend to agree with you Mike. I can't see how it'll work with very thin plate Japanese saws either so I think I do as you suggest and stick to a bevel edged chisel to pare away the offending material - Rob

I'll try it an report back. I have a full array of japanese saws. some probably thinner than what you have seen.

 

[Woodbloke]

I'll try it an report back. I have a full array of japanese saws. some probably thinner than what you have seen.

You may well find that with a very thing plate (made say, from an old Japanese saw blade) on the extender you make, it'll buckle n'bend as you start to hit it with tapometer. The ones that RC uses for Western saws use much thicker steel - Rob