Sunday, December 28, 2008

Half Blind Dovetails

I believe the two most important skills in handcutting dovetails are careful layout and the ability to saw a straight line.

Regarding the feather-ruffling question: Pins or Tails?

My answer is: Yes.

For a box or drawer that will have fat pins, I cut tails first. Cutting the tails first allows you to saw the two tail boards at one time. Plus, transferring layout lines from tails to pins is easier than vice versa.

For a delicate project with skinny, English-style dovetails, I cut pins first. With thin pins, it's very difficult (and in some cases, impossible) to transfer layout lines from tails to pins, so cutting pins first makes sense.

That being said, I'm cutting tails first for the drawer on the sawbuck table, with through dovetails at the back and half blind at the front.

The drawer will have angled sides, so the width at the top is 15" and the width at the bottom is 13". I believe I've mentioned my geometry-challenged brain before.*

My tool arsenal includes: dovetail saw, jeweler's saw, various chisels, guide block, plane blade, pencil, ruler, dovetail marker, clamps, marking gauge, mallet, and tiny square.

I call the technique: Dovetails with Training Wheels.

The training wheels are in the form of a guide block that's used to keep the chisel perpendicular to the workpiece. This ensures that the area that's removed between tails & pins will be flat. Some people like to undercut this area so pins and tails seat exactly to the guide lines, but a guide block removes this potential problem.

Once I've cut the tails, I use a bevel-edged pencil to transfer the outlines to the adjoining board, but you can also use a marking knife. Take care to make precise marks when you transfer these lines. When you saw the waste, cut right to the line (the line will just barely be sawn away when you've finished cutting). The more accurate the layout and cut, the less paring (if any) you'll have to do to fit the boards together.

*A friend accused me of never posting anything that I've screwed up. So here it is. Because I'm missing a math gene, my boards are not aligned along the top and bottom edges.

To transfer the tails' outlines to the front board, I aligned the top and bottom edges as I would with a square project. But bevelled sides require that the boards be offset when you transfer your marks.

I still don't know the equation to figure out the measurement for the offset, but fortunately the depth doesn't matter in this project, so I can plane the top and bottom edges to match.

There's also a gap in the top pin. But it's nothing that a little well-crammed wax can't fix once the project is finished.


Dave said...

Great post, I surely try some of your suggestions.

Anonymous said...

I love the step x step photo instructions on your method of dovetailing!

Anonymous said...

Measure once,
Cut twice,
Plane thrice.

Anonymous said...

Cool, Kari! My next stop along the journey :)

Handi said...

I have been following your blog for sometime now, and I have to say I admire your work and all.

This one here, The "Half Blind Dovetails" Instructions was GREAT.

I've seen many Videos, Instructions, etc, and I think your Set of instructions "Including Mishaps" Was Great, This show the woodworker in you, it shows you arn't affraid to make a Mistake and let people know, Both Learn from it, and learn how to omit the mistake as they get better.

Thanks for the Instructions, I will definatly be trying this out, as I've not had the pleasure of giving Dovetails a chance just yet.


Anonymous said...

Hi Kari,

Nice set of instructions. By the way what brand of saw and size of blades are you using to cut out your waste in your first section of pictures?


Kari Hultman said...

Thanks guys. :o)

Luke, if that's the case, then I've been doing it right all these years! haha

Steve, I used a Lie-Nielsen dovetail saw with a 9" blade and 15 ppi for all the sawing in this post.

Tom T. said...

hi Kari, I had a question about the choice to cope saw the waste - I have seen some woodworkers chisel all the waste out by chiseling horizontally - looks like you are using cherry? a hard wood to chisel cross grain - I have tried your method and just get crushed fibers - maybe my chisel is not sharp enough - I like how clean the final result looks. Do you use a hammer to chisel or just hand pressure on the chisel- Tom

Kari Hultman said...

Tom, if you are getting crushed fibers, then I'm guessing you are trying to chisel off too much at one time and/or your chisel is not sharp enough.

I use a pretty beefy Japanese chisel (with a mallet) and have even used a mortising chisel to chip away the waste. You can try chopping the majority away with a mortising chisel and then switch to a very sharp paring chisel for the final few passes.

I chop away about 1/16" at a time (once I've removed most of the waste with the jeweler's saw). The closer I get to the final pass, the thinner the shavings I'll take.

If you prefer to use a chisel to remove all the waste, then you can take bigger pieces at the beginning and lighten up as you get closer to the gauge line.

That is cherry and the front is curly cherry, which is rather hard.

Hope that helps!

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Vic Hubbard said...

Finally! I asked you for a dovetail tutorial ages ago. Geesh, Kari:-D You do the best tutorials, so the wait was worth it. Btw, which Photoshop do you use? Is it the professional version or one of the Element versions? I want to figure out how to do a photo layout like you're doing.
Oh yeah, I was watching one of my videos yesterday (or the day before) and I believe it was Frank Klaus who was adjusting a Krenov style plane with his little metal hammer.

Kari Hultman said...

Sorry Vic! I thought I'd get to this project before now...

I use photoshop CS2 for Mac. I don't know if they have it for PCs or not. The layout is nothing more than a blank page in photoshop where I drop in the photos and key in the type. Nothing fancy.

Thanks for letting me know about Frank!

mdhills said...

Nice photos of the work in progress. Wonder if "Comic Life" would make the assembly even easier, or do you live in PhotoShop for your paying work?

I wasn't clear how a math error resulted in the alignment issue -- wasn't the layout done by aligning the parts, without any special measurements, geometry, trigonometry, or calculus?

For comparison, saw my first half-blind tutorial by Phil Low, who did cut pins first (although he cheated by using pine for the sides):

Metalworker Mike said...

Really nice half-blind dovetail tutorial! And I must compliment you on your choice of dovetail gauge. :)
The result was lovely, as well. I'm starting a project where I have to decide whether to do half-blind dovetails or use a separate drawer face. I'm leaning towards the latter. :)

Kari Hultman said...

mdhills, I use photoshop for work (never heard of Comic Life and will check it out).

Heavens no I didn't use any calculations for this project--my brain would be fried! haha I did align all the pieces to transfer my marks, but because the sides of the drawer are angled, it didn't come out right. I'm waiting for some geometry whiz to let me know what I did wrong. ; )

Thanks Mike--good luck with your project!

mdhills said...
This comment has been removed by the author.
mdhills said...

Heh. Guess I fall under the "reading comprehension challenged" category -- missing the bit about angled sides.

Now that I caught that, I wasn't clear from the step-by-step if it described cutting the joint for the angled sides. I believe that you need to either cut the sides of your tails at an angle, or adjust the angle on the pins. Very similar to angled mortise&tenon. I'd probably try this at step#4 -- where your strike across the ends of the sides is done parallel to the edges, rather than perpendicular to the faces. Not sure if you can still gang them up -- my mind boggles at that.

Kari Hultman said...

mdhills--or better yet, I could just make drawers with square sides from now on. ; )

Ethan said...

Oh, don't get boring on us, Kari!

Everyone makes their drawers with square sides! :)

Lovely tutorial! You're always so inspirational in how easy you make everything look.

Anonymous said...

A guide block to keep the chisel at 90 degrees! That is so simply brilliant! It's so very North Bennett Street School of you that it makes me think that more than likely it is what cabinet shops of the 18th century probably did as well. Love the tutorial and the layout as always.

Kari Hultman said...

Ethan, it's easy to make things look easy in photos. ; )

Shannon, it's actually College of the Redwoods (although they may also teach this at NBSS). I learned this technique from David Finck, who learned it from Krenov. But I'm sure it's been around a lot longer than either of those two men.

Anonymous said...

Kari, I believe if you were to butt the tails board up to the face board with the outside face of the tails flush with the edge of the face board you could then mark the top of the first tail. Then you would strike a line and use this to line up the tail to when you placed it over the face board to mark the pins.

Hope you can make heads and tails LOL out of this convoluted explanation.

Kari Hultman said...

Ace, I THINK I understand, but would that set the tails board higher than the pins board when you mark your pins? If so, then you would want to do the opposite of what you suggest--mark the bottom tail instead--because with the way I did it, when put together, the tails board sits higher than the pins board.

If I understand you, your suggestion would put the tails board even higher. But if you did the opposite, I think it might work. Thanks!

Glen said...

I like how you used the plane blade. Very nicely done. Thanks.

Jay @ Wood Plans Projects said...

The traditional method of creating half blind dovetails doesn't differ much from the method of creating through dovetails, but there are some points to keep in mind:

The section of the pin board that is not to be cut (thus forming the blind portion of the joint), is called the lap. The lap on the board should never be less than 1/8" thick, yet should never exceed 1/3 of the pin board's thickness, to ensure the