Make a kerfing chisel

[Derek Cohen]

In 2011 I posted an article (http://www.inthewoodshop.com/ShopMadeTools/KerfChisel.html) on a kerfing chisel, a tool used to deepen the kerf in half-blind dovetails.

http://www.inthewoodshop.com/ShopMadeTools/KerfChisel_html_m4d32909b.jpg



The idea for this came from a method used by Tage Frid, who used either a scraper blade or, as I viewed in a video, a section of bandsaw blade. The kerfing chisel was my effort at making a specific tool, rather than buggering up a prized scraper blade.


In the years since, I am aware of two similar tools, the first was by Ron Bontz and the second by Rob Cosman. Both are shaped like saws, complete with brass backs and scraper plates. They do the same thing.


Over the years I have received many queries how to make a kerfing chisel, and this posed a problem since I had made it from a steel gardening trowel/spatula. These can be difficult to find. I have been thinking of other ways to make this easier for anyone interested in rolling their own. This is what I came up with ...


At the moment I am testing out a few different sizes ...


https://i.postimg.cc/NfVQ1Ps9/K1.jpg


Top is Jarrah and bottom is Hard Maple.


A few others ...


https://i.postimg.cc/Fs19kQ4X/K2.jpg


The parts include a scraper blade (these are 0.03" thick). I was curious to see whether this would create a problem when dovetail saws have a 0.026" kerf (0.02" plate plus 0.003" set, which is considered "fine"). A ferrule is made from brass tube.


https://i.postimg.cc/QdThSkC6/K3.jpg


Turn the handle, and then saw the slot for the blade using a bandsaw. Place the handle on a V-jig to hold it steady. Ensure that the shaft matches the depth of the ferrule (so that is bottoms out against the end of the handle). Epoxy everything together.


So why is a kerfing tool so useful that it warrants being made into a specialised tool?


Here is a half-blind pin board socket being sawn. Note the diagonal angle, which leaves half the socket ...


https://i.postimg.cc/V6YwYxRT/K5.jpg


This is where the kerfing chisel is used: First clamp the ends of the pin board. The edge of the blade is squared (not bevelled like a chisel), but it has the potential to split or cleave a board. The clamp helps prevent this.


https://i.postimg.cc/bv08fyQk/K6.jpg


Tap the blade into the kerf, to full depth, moving towards the boundary line a little at a time - be especially careful with the outside kerfs, where there is less support.


https://i.postimg.cc/262D3095/K7.jpg


I have been doing this for a decade and may have had 2 or 3 splits in all this time, mainly from being careless.


When chopping into the socket, the deepened kerf will make it easier to split out the waste ...


https://i.postimg.cc/d33KCGgj/K8.jpg


The blue tape makes it easier for older eyes to see lines ...


https://i.postimg.cc/d3fcjLYP/K9.jpg


Cleaning out the waste is significantly easier ..


https://i.postimg.cc/fWqsNg02/K10.jpg


Removing waste leaves clean sides to the sockets ...


https://i.postimg.cc/2ynKsd9C/K13.jpg (https://postimages.org/)


This is saw-to-saw cut ...


https://i.postimg.cc/Dy26fK8r/K15.jpg (https://postimages.org/)


Regards from Perth


Derek

[Bill Carey]

In 2011 I posted an article (http://www.inthewoodshop.com/ShopMadeTools/KerfChisel.html) on a kerfing chisel, a tool used to deepen the kerf in half-blind dovetails.
............


In the years since, I am aware of two similar tools, the first was by Ron Bontz and the second by Rob Cosman. Both are shaped like saws, complete with brass backs and scraper plates. They do the same thing.

Regards from Perth
Derek

Crown Tools also makes one, which I bought on Amazon for 25 bucks a year ago, and it works great. But I like your chisel style and will probably make one some day.

449042

[Bob Jones 5443]

Bill, I can’t find the tool you describe. Do you have a link?

[Nathan Johnson]

Taylor Toolworks has it on their site for $19.99, though Sold Out.

https://www.amazon.com/Dovetail-Kerfing-Extender-Ground-468228/dp/B07H549F7C


Sorry to distract from Derek's post.

[Bob Jones 5443]

Nathan, I think something smells fishy about not being able to get the Tay Tools kerfer. Could there be patent problems somewhere? Seems unlikely when you consider it's like patenting a saw, but just when premium brands are gaining traction we no longer see the bargain basement tool. Sorry to foment rumors: I know how this sounds. But remember, just because you're paranoid doesn't mean the world ISN'T out to get you.

Just kidding here, but not entirely about the Tay Tools tool.

[Michael J Evans]

Bob
I did a little research and it is on Amazon but unavailable. It is being sold by Taytools.
I went directly to Taytools website and it is also unavailable but it lists for $20.

My other question is why couldn't you just use their 4" gents was to do the same thing?

[Bob Jones 5443]

In 2011 I posted an article (http://www.inthewoodshop.com/ShopMadeTools/KerfChisel.html) on a kerfing chisel, a tool used to deepen the kerf in half-blind dovetails.

http://www.inthewoodshop.com/ShopMadeTools/KerfChisel_html_m4d32909b.jpg



The idea for this came from a method used by Tage Frid, who used either a scraper blade or, as I viewed in a video, a section of bandsaw blade. The kerfing chisel was my effort at making a specific tool, rather than buggering up a prized scraper blade.


Regards from Perth


Derek

Derek, thanks again for your always-informative discussions. I'm not in a position to make one as you describe, so I'm going to hobble along with my scraper blade for a while and see where that leads me.

All the best,
Bob

[Michael J Evans]

Derek
How come you pictures cannot be clicked on / zoomed in on? I generally view from Mobile and can click on each picture to enlarge it, but yours are the exception.

[Bob Jones 5443]

Derek probably drags the photo file into the post instead of using SMC’s link feature. I’ve done that a few times and gotten results that resemble his. On your phone you can just enlarge his photos directly in the post without the need to tap on them.

[Jim Koepke]

Great post Derek, my only suggestion would be for people to try cutting a third kerf in the waste between the pins. Try it and you will find it makes popping out the waste so much easier.
This hasn't been tried with my Ron Bontz Kerf Maker but there have been those who say it can be used vertically.


Nathan, I think something smells fishy about not being able to get the Tay Tools kerfer. Could there be patent problems somewhere? Seems unlikely when you consider it's like patenting a saw, but just when premium brands are gaining traction we no longer see the bargain basement tool. Sorry to foment rumors: I know how this sounds. But remember, just because you're paranoid doesn't mean the world ISN'T out to get you.

Just kidding here, but not entirely about the Tay Tools tool.


Bob
I did a little research and it is on Amazon but unavailable. It is being sold by Taytools.
I went directly to Taytools website and it is also unavailable but it lists for $20.

My other question is why couldn't you just use their 4" gents was to do the same thing?

Bob, Michael, have you gone shopping of late? Many merchants are having supply problems. You will likely see the Tay Tools Kerfer in stock again. No telling when.

$19.99, $20 look the same to me.

A 4" Gents saw with the teeth filed down would likely be a useable alternative. If you search > 4 inch gents saw < you will see a Crown #187m listed at Walmart and on ebay for $19.94. Walmart may be online order only my interest ended with the search result.


Derek
How come you pictures cannot be clicked on / zoomed in on? I generally view from Mobile and can click on each picture to enlarge it, but yours are the exception.

Dereks images are hosted on his own site. Others do the same. Sadly if a member hosting their own images leaves us the images they have shared slowly leave with them. Others post them from internet storage firms. When some of them started charging rent for storage other images were lost.

jtk

[Bill Carey]

Bill, I can’t find the tool you describe. Do you have a link?


Just saw you question, but others have answered it. The only drawback to it is that it's a .025 plate, and my Bad Axe saw is .02. So it required a bit of time on a stone but it wasn't a big deal.

[Bob Jones 5443]

Bob, Michael, have you gone shopping of late? Many merchants are having supply problems. You will likely see the Tay Tools Kerfer in stock again. No telling when.

$19.99, $20 look the same to me.

A 4" Gents saw with the teeth filed down would likely be a useable alternative. If you search > 4 inch gents saw < you will see a Crown #187m listed at Walmart and on ebay for $19.94. Walmart may be online order only my interest ended with the search result.

jtk

Jim, as with so many times before, you are the go-to reference for stuff we need. Thanks for the note about the Crown. Trouble might be that its plate is 0.020", and I want to push down at the thickness of the saw's kerf. With the Cosman saw, that's 0.024". So I guess I'll still stick with my 0.025" scraper for now.

[Bob Jones 5443]

Just saw you question, but others have answered it. The only drawback to it is that it's a .025 plate, and my Bad Axe saw is .02. So it required a bit of time on a stone but it wasn't a big deal.

Bill, if yours was 0.025", I'd like to find another one if possible.

[Bob Jones 5443]

You can buy the Crown 187m on Amazon right now, but the descriptions available on eBay, copied apparently from Hartville Tool's copy, are confusing: plate 0.020" but kerf 0.037"??? What, the teeth have a 0.085" set on both sides? In any case, the plate is all I need for this purpose, and it's too narrow.

[Derek Cohen]

Just saw you question, but others have answered it. The only drawback to it is that it's a .025 plate, and my Bad Axe saw is .02. So it required a bit of time on a stone but it wasn't a big deal.

I have been doing a little experimenting with plate thickness, and so far it seems that this does not make any significant difference.

Most saw plates are 0.02” thick. Then add 0.003 - 0.004” each side for the set of the saw, and you end up with something closer to 0.03” than 0.025”.

Then there is the accuracy of sawing to the line - how close can you get? Are you within 0.003 of the line, or less. In other words, are you changing the socket size? I do not think so.

Plate thickness will affect how easily it cuts into the wood. However, this is affected by how big a bite one takes. That also is determined by the hardness, and brittleness, of the wood.

I measured some of the cabinet scrapers in my collection. They were mostly greater than 0.03”. Paint scrapers from the big box were greater than this, and some have used these successfully.

Bottom line: at this time I would argue that a blade up to 0.03” is fine.

Regards from Perth

Derek

[Derek Cohen]

You can buy the Crown 187m on Amazon right now, but the descriptions available on eBay, copied apparently from Hartville Tool's copy, are confusing: plate 0.020" but kerf 0.037"??? What, the teeth have a 0.085" set on both sides? In any case, the plate is all I need for this purpose, and it's too narrow.

The main issue I have with modifying and using a Crown gent saw is that the brass back is very light. Ideally, when striking the kerfing tool, saw or chisel style, you want to use a steel hammer. The energy from one is better focussed than a wooden mallet. I doubt that the Crown would survive very long.

Regards from Perth

Derek

[Bob Jones 5443]

I have been doing a little experimenting with plate thickness, and so far it seems that this does not make any significant difference.

Most saw plates are 0.02” thick. Then add 0.003 - 0.004” each side for the set of the saw, and you end up with something closer to 0.03” than 0.025”.

Then there is the accuracy of sawing to the line - how close can you get? Are you within 0.003 of the line, or less. In other words, are you changing the socket size? I do not think so.

Plate thickness will affect how easily it cuts into the wood. However, this is affected by how big a bite one takes. That also is determined by the hardness, and brittleness, of the wood.

I measured some of the cabinet scrapers in my collection. They were mostly greater than 0.03”. Paint scrapers from the big box were greater than this, and some have used these successfully.

Bottom line: at this time I would argue that a blade up to 0.03” is fine.

Regards from Perth

Derek

Derek, I want to make sure not to split the wood. My push saw is a Cosman, 0.020" plate, but only 0.002" set on either side, for a kerf of 0.024". Rob sells his little kerf tool at 0.025" width, I suppose to shave down the sides smooth, but no more. Quite fortunately the scraper I found lying around is exactly 0.025, so I think I'm set, albeit crudely because I only have the rectangular scraper to work with. But I think I'll be alright.

Your comments make sense, depending on one's saw's kerf width.

[Bill Carey]

I have been doing a little experimenting with plate thickness, and so far it seems that this does not make any significant difference.

Most saw plates are 0.02” thick. Then add 0.003 - 0.004” each side for the set of the saw, and you end up with something closer to 0.03” than 0.025”.

Then there is the accuracy of sawing to the line - how close can you get? Are you within 0.003 of the line, or less. In other words, are you changing the socket size? I do not think so.

Plate thickness will affect how easily it cuts into the wood. However, this is affected by how big a bite one takes. That also is determined by the hardness, and brittleness, of the wood.

I measured some of the cabinet scrapers in my collection. They were mostly greater than 0.03”. Paint scrapers from the big box were greater than this, and some have used these successfully.

Bottom line: at this time I would argue that a blade up to 0.03” is fine.

Regards from Perth

Derek


Probably right Derek. When I first got it and started some blind DT's I could not force the Crown into the kerf, so I took off enough that I could push it into the kerf with some slight resistance. Never did measure it before or after hitting the stones, so it could have been .035 for all I know. I suspect Crown has better tolerances than that but who knows. After using it for a year - on maybe 100 to 150 BDT's it's still pristine and functions well. If it was getting beat on every day not sure how long it would last, but for my use it's fine. If I did BDT's every day I would go to a Bontz tool.