Half Blind Dovetail Problem

[alan west]

IMG_1760.jpg

About every 7-10 sets of half blind dovetails I end up with one like this. Any ideas what I did wrong? The tails look a little ragged because I tried to chisel them some to see if that would help which it did not.

[Mike Henderson]

I'm guessing those are hand cut dovetails from the scribe line on the board. It looks like the sockets are not cleaned out well, keeping the tails from fitting into the sockets properly.

Mike

[Many people (most) would make the space between the tails smaller. That's just an aesthetic issue and has nothing with the fitting. I'd do four tails and space them closer together.]

[Derek Cohen]

Mike's observation is a good one - that the inside end of the socket may not be vertical. That would push the tail board away from the baseline.

The other possibility is that you are creeping over the baseline when paring out the waste.

Lastly, you have set the pins slightly too deep, and the tails do not flush out.

Regards from Perth

Derek

[Matthew Hills]

How hard was the joint to assemble? Almost looks like the fit is too loose

[Patrick Chase]

IMG_1760.jpg

About every 7-10 sets of half blind dovetails I end up with one like this. Any ideas what I did wrong? The tails look a little ragged because I tried to chisel them some to see if that would help which it did not.

As others have said, it looks as though the back wall of the socket (the surface that mates with the tops of the tails) isn't very well cleaned. It may even be tapered such that the socket becomes shallower as you move away from the joint.

The interface between the top of the tail and the back of the socket is long grain to end grain, so it isn't buying you much of anything in terms of glue strength. It's also completely hidden (both from inside and out) except for the edge shown in your picture. If you're having problems like this on a recurring basis then you might want to undercut the back of the socket a bit, such that the shallowest part is at the cosmetic interface.

[Robert Engel]

Looking closely you will see some debris in the corners of the sockets. I would check the shoulders using a router plane.

But its not always debris. When this happens to me its usually because I sawed the sockets oversized.

I would also make the sockets just a bit deeper.

The problem now is even if you correct everything, once you've pounded a DT joint flush, the fibers are compressed and don't expect a perfect fit on the second try.

[Prashun Patel]

"The problem now is even if you correct everything, once you've pounded a DT joint flush, the fibers are compressed"...

I haven't found this to be the case. I find subsequent fittings to go together more easily, but not sloppy.

I agree with the others that the pin sockets need to be cleaned up. A skew chisel or fishtail chisel is fantastic for this. In addition, clean your tail sockets. A dirty trick here is to use the saw to cut into the corner, going just below the base line on the inside face.

[James Waldron]

From the photo, it's hard to tell what's shadow and what's gap. That being said, it appears possible that the tail board may have developed a bit of cupping that's holding the pins up. Not as likely as the other suggestions here, but one that may be worth checking.

Good luck and let us know what you find.

[David Eisenhauer]

I agree with the need to clean out the corners, perhaps shave a couple of side walls, but also wondered about a slight cupping issue. The top line does not look 100% flat to me, in the photo anyway.

[alan west]

Thanks for all of the great comments. It was the back wall of the socket. I ended up making a new drawer as all of the other six drawers were perfect and this one bothered me

The joint did initially go together tight.

[Patrick Chase]

Thanks for all of the great comments. It was the back wall of the socket. I ended up making a new drawer as all of the other six drawers were perfect and this one bothered me

The joint did initially go together tight.

Is it possible that it initially went together tight at some angle other than 90 deg? That would be consistent with the back wall of the socket being sloped, and that's one reason why test-assembling dovetails in isolation can mislead you (unless you constrain them to be square).

[Mike Henderson]

Thanks for all of the great comments. It was the back wall of the socket. I ended up making a new drawer as all of the other six drawers were perfect and this one bothered me

The joint did initially go together tight.

To check your work before assembly, use a square (I like the double square) and check the depth of your socket. It should be flat to slightly dipping toward the back. Use the square to check the back side of the socket and make sure it is flat to slightly inward so you tail will fit tight against the top of the socket.

Mike