Fishtail Chisel - Useful?

[Derek Cohen]

Commercial skew- and fishtail chisels work differently. They are not equivalent.

The skew chisels I have from Blue Spruce are beautifully made and work very well. However, they require a different cutting action from a fishtail chisel (one can modify the to work in the same way as a fishtail. More in a moment).

Many years ago, when Dave at Blue Spruce was getting going with his dovetail/detail chisels, I bought some of the first he made. The 3/4" I have was the first he made, and in fact he remade mine to 1/8" thick steel on my request. I also purchased left- and right skews in 1/4". At this time he had no intention of making skews, not a value here, and we began corresponding about their virtues. These are the drawings I sent him ...

Skew chisels, with a 20 degree skew (equal to about 1:5 ratio), need to be used with a cutting action, as they cannot enter the corners ...



A fishtail chisel, however, can be pushed into the corner quite easily ...



This makes the clearing process much easier.

To modify a skew chisel to work as half a skew, the skew angle must be reduced to about 8 degrees (rough estimate).

Make your own. I used a grinder to transform a bench chisel into this ... using a handle I made for a marking knife (my first skew chisel). It worked extremely well ...



Regards from Perth

Derek

[Hilton Ralphs]

[Taylor Tools makes a kerf extender that's a bit less expensive than the Bontz or the Crosman. Like the Cosman, just available with the 0.025" blade.]

That size seems perfect for a saw plate of 0.015" thickness with a kerf of 0.003" each side (total 0.021").

[david charlesworth]

I prefer a pair of 1/4 inch home made skews.

The angle Derek shows for skew chisel seems much too acute to me.

Mine are ground at a fraction less than 1:6 which is the angle I use for single lap or secret mitre.

My skew slides easily along the side wall before nipping the corner waste off at the roots.

I find that a fishtail sticks into the side wall and is less friendly!

[Derek Cohen]

David, that the angle of commercial skews is too acute is the point I was attempting to make. We are in agreement.

Do you have a reason why your fishtail “sticks” along the side of the socket? Is it possible that the chisel sides/lands are tapered and sharp rather than flat?

Regards from Perth

Derek

[david charlesworth]

Derek,

Agreement is good ~;-)#

I would have to check. My fishtails are L-N, though I have one Japanese one as well.

Best wishes,
David

[Rob Luter]

Well, after much contemplation I ordered a fishtail from L-N. Starting to prep my drawer parts in anticipation. I should be able to get all my tails done this weekend and perhaps the through pins on the back. It's the time of year for yard work so shop time will begin to dwindle a bit.

[chris carter]

I've never used one for half-blinds and I've never found myself wanting one. I just use a 1/4" chisel to get into the corners. If I can't get that last crumb in the bottom corner, I can just knock off a corresponding crumb from the bottom corner of the tail. After all, it won't affect the strength of the joint one bit and nobody will ever see it. So what's the point?

[Tom Bussey]

I think they are useful and here are some pictures of mine. If one is not to brand conscience they can be picked up at a flea market- antique store for a buck or two.

DSC03633.JPG DSC03634.JPG DSC03635.JPG

[Mike Henderson]

I've never used one for half-blinds and I've never found myself wanting one. I just use a 1/4" chisel to get into the corners. If I can't get that last crumb in the bottom corner, I can just knock off a corresponding crumb from the bottom corner of the tail. After all, it won't affect the strength of the joint one bit and nobody will ever see it. So what's the point?

I believe that most people who do a lot of dovetails go this way. I certainly did.

If a 1/4" chisel is too big, use a 1/8".

Mike

[Derek Cohen]

I believe that most people who do a lot of dovetails go this way. I certainly did.

If a 1/4" chisel is too big, use a 1/8".

Mike

And almost all the people who say use a 1/8" chisel do not make "London" style dovetails (I have no idea why they are referred to as this) ... that is, very slim, pointy dovetails, where the sockets have little meat ...









Try using a 1/8" chisel into the corner of the sockets, and you will likely cause damage. Yes, you can use a 1/8", but really now ... the fishtail chisels excel at clearing the corners of sockets.

It's like using a chisel instead of a router plane to clear the waste in a dado. It can be done, but why not use a router plane?!

Regards from Perth

Derek

[Rob Luter]

Then there’s the consideration one must give to my meager (but improving) skill set. I’m sucking less and less at this the more I practice but I’m willing to invest in tools that will help me flatten the curve, if I may use a topical vernacular.