Derek Cohen
03-22-2022, 8:36 PM
The topic of a kerfing tool for half-blind dovetail sockets came up again in another thread. Rather than adding to this thread, where these details risk being lost, I offer them in a thread of their own.
I documented making the first dedicated kerfing tool in 2011. This is different from the ones made by Ron Bonz and Rob Cosman, who began posting theirs about 3 years ago. I believe that Ron may have made his before Rob (although Rob would never admit this). Theirs is patterned after a backsaw, while mine is chisel-shaped.
In developing the latest generation (in January 2021), making it easier for others to build one for themselves, this is the design that resulted. At the time I made up a few extra, which have long since been sold …
https://i.postimg.cc/632prB3T/FS1.jpg
https://i.postimg.cc/sXkDKbQm/FS2.jpg
The build article and details is here: http://www.inthewoodshop.com/ShopMadeTools/MakeKerfingChisel2.html
This includes advice on how it is used.
What I will add is that you need to resist using any old scraper blade or piece of saw plate in its construction. If the plate used is too wide, it will leave a wider-than-desired kerf, and this will can lead to gaps in the final fit. For example, most dovetail saws today use a 0.020” wide plate. Add 0.003” set on each side, and you have a kerf 0.026”. Some older dovetail saws have plates 0.025” and tenon saws may have plates that start at 0.030”. These are just within acceptable limits. A putty knife generally has a blade 0.035” and thicker. That is too thick.
A thinner plate is better than a thicker plate. The “cutting” end is squared off rather than wedged like a chisel bevel. A wedge would cleave or split the wood. A thinner plate will experience less resistance and require less force to push away the wood fibres.
In the article I used putty knives and ground the blades down to 0.020” using a belt sander. Recently I discovered that an old replaceable Z-Saw dozuki plate was the perfect 0.020” thickness. Use one of these if you have an old saw with broken teeth.
https://i.postimg.cc/BQ8jc2NL/13.jpg
Regards from Perth
Derek
I documented making the first dedicated kerfing tool in 2011. This is different from the ones made by Ron Bonz and Rob Cosman, who began posting theirs about 3 years ago. I believe that Ron may have made his before Rob (although Rob would never admit this). Theirs is patterned after a backsaw, while mine is chisel-shaped.
In developing the latest generation (in January 2021), making it easier for others to build one for themselves, this is the design that resulted. At the time I made up a few extra, which have long since been sold …
https://i.postimg.cc/632prB3T/FS1.jpg
https://i.postimg.cc/sXkDKbQm/FS2.jpg
The build article and details is here: http://www.inthewoodshop.com/ShopMadeTools/MakeKerfingChisel2.html
This includes advice on how it is used.
What I will add is that you need to resist using any old scraper blade or piece of saw plate in its construction. If the plate used is too wide, it will leave a wider-than-desired kerf, and this will can lead to gaps in the final fit. For example, most dovetail saws today use a 0.020” wide plate. Add 0.003” set on each side, and you have a kerf 0.026”. Some older dovetail saws have plates 0.025” and tenon saws may have plates that start at 0.030”. These are just within acceptable limits. A putty knife generally has a blade 0.035” and thicker. That is too thick.
A thinner plate is better than a thicker plate. The “cutting” end is squared off rather than wedged like a chisel bevel. A wedge would cleave or split the wood. A thinner plate will experience less resistance and require less force to push away the wood fibres.
In the article I used putty knives and ground the blades down to 0.020” using a belt sander. Recently I discovered that an old replaceable Z-Saw dozuki plate was the perfect 0.020” thickness. Use one of these if you have an old saw with broken teeth.
https://i.postimg.cc/BQ8jc2NL/13.jpg
Regards from Perth
Derek