Dovetail Problems

[Tom Winship]

I am cutting my first hand cut half blind dovetails in mesquite drawer fronts for a dresser. The drawer fronts are 3/4" thick and I am leaving 1/4" at the front side of the DT. So far about half of the dovetails have cracked (blown out) when I make the last parallel cut in the mesquite.
I have built two bedside tables using machine templates (I know, blasphemy) and understandably did not experience this problem. I know it is due to the many directional grain of the mesquite.

The only corrective I can see is to thicken the drawer front on future work, thereby being able to thicken the half blind, or to go back to using the power method (blasphemy).

I have been able to save all the drawer fronts. The pieces break out beautifully and I have glued them all back together with no detectable trace.

[Archie England]

If I'm understanding ....

What you're describing happens to me when I shave off grain that is beyond my inside chop line. I'm not very experienced with dovetails, but I've done enough to know that when I go beyond my saw line (or chop line) the chisel tends to follow the uncut grain beyond my intended point. Could the Mesquite be brittle enough to snap when paring along the grain, too?

Hopefully, the more experienced members will quickly weigh in. So, let's just consider this a "bump" for them to notice.

:)

[harry strasil]

Never done a half blind yet, but it sounds to me that you don't have the work piece clamped down tight to a nice flat surface to do your trimming. FWIW

[Tom Winship]

I will try to clamp it tighter, Harry, however, I think it is just the nature of mesquite. A straight grained piece doesn't give any problems, however if you see some swirls, get ready!

One of these that occurred, the grain was actually end grain when I started, but turned almost 90 degrees by the time I got to the bottom of the dt.

And as mentioned, it is brittle. When building a Maloof style rocker about a year ago, I dropped the chair on the end of a rocker from about 12-18". Broke the rocker at the adjacent rear leg. Strong, hard, but brittle. (And minute cracks are pretty common).

[Terry Beadle]

Sounds to me like you are getting a pressure wave in front of the cutting edge of the chisel that's causing the mayham and blowing out the blind area of the dove tail. David Charlesworth describes this pressure wave in his video on dovetailing. He uses extremely lite taps with the hammer and does not cut to the bottom of the dove tail socket in the first 1/4 inch or so of the socket.

I would suggest going to a liter hammer ( less than 4 oz ) and stopping the vertical cut shorter of the socket bottom. Use the horizontal paring technique recommended by Mr. Charlesworth more and less vertical cutting.

All that being said, wood is as wood does. That is to say even with the most careful craftsmanship wood is going to do unpredictable things. Case example for me is dove tailing in southern yellow pine. It's just not always predictable.

Also, check your chisel's sharpness and give it some extra stropping as you go.

Lite taps seem slower until you have to do repairs. A light wood hammer made from some scraps of rock maple will give you good service in difficult woods.

Best of luck !

[Casey Gooding]

Try using a backer board. It will help support the wood while you chop and should help prevent your problem.

[gary Zimmel]

Any time I do a half blind, which is probably 95% of the time, a backer board is used.
Here I just used another drawer face as a backer.

156065

I also will use a backer when I put the half blind joint together.
Any chunk I have laying around will do the job for this.

156066

Sharp tools, real sharp sure make the process easier.


.

[Tom Winship]

Okay, mentors. I cut another drawer this afternoon, with the half-blinds following some of your suggestions.

For instance:
1. After marking the pins and chalking them for better visibiility, I sawed along the lines.
2. I then clamped the boards to the workbench top and proceded to chop the waste.
3. I used smaller chisels (1/4" and 3/8") and started chopping about 1/8" from the end of the board. I would chop down until I was approx 1/8" above the bottom of the socket and kept moving back until I was at the end of the socket where the tail board bottoms.
4. This worked rather well and then I clamped the board in the vise with the backer board behind and continued to finish the socket.
5. After minimal trimming the joint did fit rather well.

One thing I did learn today is that I have a tendency to let the socket get thicker as I move toward the bottom. Not much, maybe 1/32-1/16". Of course then the tails are pushed further away from the socket and the joint becomes extremely tight. I compensated on one joint by beveling (with a plane) the end of the tail board on about a 5 degree. The fit was then beautiful! Do any of you use this trick or just cut the socket straighter to begin with.