Friday, January 26, 2018

Half-blind dovetails

I have written about my lack of enthusiasm for through dovetails for many, certainly not all, applications.  I only use through dovetails in applications where maximum strength is the highest priority, like my travelling toolbox,  but I don't think they look that great, especially on the off-side.  My understanding is that this was the consensus historically.

However, my opinion doesn't apply to half-blind dovetails.  They seem to me like an ideal way to get both great appearance and strength in many more applications than just drawer fronts.  Half-blind dovetails block the "box joint" side of through dovetails while preserving their strength.

This appreciation of half-blind dovetails led me to see if I couldn't become more proficient in making them.  I decided to make at least one every day for a week as a start.  I don't presume to offer a guide to making them because there are plenty from experts but will instead describe my experience and offer some supplemental observations.  If you prefer tips from an expert, try this and this.

Before I get into the details, an observation.  I have always thought of half-blind dovetails as more difficult to make than their through cousins, but it doesn't seem to be the case.  They take longer, but that's about it.  Maybe it's me, but slight gaps don't seem to look as bad as they do on through dovetails.  There are probably multiple reasons, but one is that you only see one side of the tails.  It's true that you can only saw out half of the pins but that doesn't seem to be a big deal.  Chiseling out the waste in the pin board isn't much more difficult than it is for through dovetails.

There is nothing different about the tail board except that the tails are shorter, so there's no need to discuss it.  The usual considerations apply.

For some reason, marking out the pin board has been a real struggle for me and, now that my sawing has improved, this is the major source of inaccuracy in my work.  It's the reason some my first attempts this week were poor.  Perhaps it is declining eyesight, but just using a marking knife hasn't worked for me.  Pencil hasn't worked for me either.  Sawing a bit away from the line and paring to fit is extremely time consuming and tedious.

After my poor first attempts, I used the masking tape trick and it worked better, but it is time consuming.  This was the method used for the test joints you see here and, despite the improvement, I believe it is the primary cause of the remaining inaccuracy.

For some reason, sawing the pin board for a half-blind dovetail seems much more difficult to me than for a through dovetail, but it isn't.  I've puzzled about this.  It may have to do with the fact that it sort of forces you to start at the front, create a kerf across the top and then saw down the line.  The mistake I make the most is sawing a bit beyond the gauge line into the web.

Chopping out the waste isn't all that difficult.  It can be a bit challenging if the grain dives.  One thing I've done in the past if I was making a lot of joints is use a forstner bit in the drill press to remove waste down to depth, which creates a reference, but I am not doing that for this exercise.  I do think that using the drill press the way Rousseau does in the video link above speeds things up a lot if you are making a number of joints.

My first effort:

Notice the gap at the front of the tails.  On my second effort I was careful to make sure the tail board was up tight when marking out the pins and to make sure I didn't move the scribed line when chiseling out the waste:

There is one significant gap and I don't know why it's there.  It could be a sawing error but my guess is that it has to do with marking out and cutting to the blue tape.

More later.


  1. Andy,

    Both sets would be serviceable, a little pooky in the gaps and only another wood worker would notice. The top one looks like there is a little "nasty bit" left in one or more corner of the tail board and you made a slight booboo on a couple of the pin board's base line. I've never had it happen to me :-).

    I'm not a fan of the blue tape, maybe because I haven't tried it enough times, it just seems like too much work for too little help. I am a fan of the the 140 trick but something I thought of the other night after reading about (I can't remember who did it) clamping a fence on the base line of the tail board is to use light CA glue to hold the fence. I haven't tried either yet but I expect when I make the drawers for the kitchen cart I'll have a chance if I don't forget. Old timers dontchknow.


  2. I see an improvement in your second set. As much as it is tedious to chop etc etc, I think it is better to stick to one method until you are proficient and then try something else.