March 11, 2010

Tutorial: hand-cut half-blind dovetails

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Duration: 21:41 minutes

One of the readers of the blog recently posted the following Comment to the earlier article on More great drawers:

Could you add ‘Cutting Pins by Hand for Half-Blind Dovetails’ to the list of topics to cover? I fully get how to cut pins and tails for through dovetails, but half-blind pins I can’t seem to wrap my mind around. Is it all chisel work? Is there a sawing technique I don’t know of to cut 80% through the thickness of a board?

Torch, this article and video are my response to your request – perfect timing!

Although today it is considered the hallmark of a woodworking craftsman, the dovetail was not always held in such high esteem. In fact, dovetails used to be buried behind trim, as they were strictly a utilitarian joint; but they were used for their holding strength. Today we make dovetails by hand and with dovetail jigs, to get beautiful results; and they are beautiful!

In this episode I show in detail how to cut one half-blind dovetail on a narrow board. Although I managed to damage the fit on the first attempt, I recovered to shoot the chopping of the pins for this episode in its entirety. In the video I show in high speed the details of chopping the waste, from start to finish:

  1. Very light chiseling at the baseline, to ensure that it stays nice and clean.
  2. Once the baseline is established, more aggressive chopping can take place.
  3. But care must be taken at the half-pins, to prevent splitting of the wood; typically, a narrower chisel, and lighter chisel action are required, or the board will split.
  4. Slight undercutting at the baseline, about 1° to 2°, will result in better and easier fit of the tails in their sockets.
  5. However, too much undercutting will result in a weak joint – as a result, avoid too much undercutting. Practice, practice…
  6. Chop the bulk of the waste with the board supported by the workbench; then place the work piece in the vise, to finish with light paring cuts.
  7. Cut a very small chamfer on the back of the dovetails, to easy entry into their respective sockets in the pins board.

Gary Rogowski is a great advocate of the 5-minute dovetail, a practice session to get ready for the real job of cutting the joinery on a real project. And although the exercise is typically for through dovetails, I believe it applies just as well to half-blind dovetails. In fact, I always do a similar warm-up when I use the Leigh dovetail jig – I never start cutting dovetails cold, regardless the method. Click on this link to see the Inlaid Dovetails Tutorial videos I posted on the blog in March 2008, using the Leigh D4 dovetail jig.

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Hand-cut dovetails: “Cutting to the line”

This one is for Betsy, at Lumberjocks.com.

Betsy has had trouble cutting to the line when hand-cutting dovetails. Therefore, she would like to improve the fit, by making sure to better cut to the line. I promised I would try to document how I do it.

I found that using either the index-finger fingernail, or the thumb fingernail, to create a “fence” for the saw, works best for me. Therefore, I first place the fingernail exactly on the line, and then I place the saw on the board (click on the images to enlarge):

Once the saw is on the board, I sight down the cheek of the saw to the extent I can – the back gets in the way, as it is considerably thicker than the saw blade. By sighting down the cheek I get the best feel for the angle at which to hold the saw, thus giving me a good chance at being able to get the angle correctly. Note that the saw appears to be quite a distance to the right of the mark in this photo – THIS is exactly what it should look like:

Keeping my finger nail “fence” in place, and using a very light touch, I start the cut on the push motion (if using a Japanese saw, you must start the cut using a pull motion). Some people refer to this light touch as de-weighting the saw (I think this is the most-used term). This “light touch” also means that you are exerting on the saw *only* the force required to push and pull the saw on the board – no more, and no less.

Once the kerf is established, I remove my finger “fence” and complete the cut while sighting down the cheek of the saw. If the saw is not following the line, I do not try to correct it by steering the saw. It is impossible to do so with a dovetail saw, and it is also not recommended. The best thing to do: Start over.

I am certain that when I first started my hand-cut dovetails practice sessions I was tense, and therefore it was difficult to start the cut on the push motion. And I was amazed at how easy it was once I used as light a touch as possible.

It took me a while to realize this *is* the proper way to be to best cut to the line. With very minor adjustments it is possible to even “split the line” – provided, of course, that the line is wide enough to be “split”.

Edit to add: Dan, at WoodNet, said: The thumb is most definitely the rough cut fence and the index finger for accuracy.

During the Dovetails session at Woodworking in America (Parts 1, 2, and 3), Frank Klausz recommended to “…split the line when cutting the pins; and cut on the waste side of the line – the pins side – when cutting the tails…” Of course, Klausz cuts pins first.

So, Betsy, keep up your practice. And please let us know when you can cut to the line precisely. That will be your AHA! moment.

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Practice should make perfect: Hand-cut dovetails

The cat’s out of the bag: I have started practicing hand-cut dovetails.

I started my practice sessions with this gent’s saw; in retrospect, I should have practiced starting the cuts with a much lighter touch than I used, as I could see a curve in some of the kerfs as the cut went deeper:

I am certain ignorance on my part played a big role, but I just could not get comfortable with the grip on the gent’s saw. As a result, I ordered an E.T. Roberts & Lee Dorchester 8-inch, 21 ppi rip dovetail saw. As soon as the saw arrived I started practice sessions, cutting parallel lines marked on the end grain of the board:

Problem: At first I was unable to remove the protective coating from the steel – Grr! It turned out that this company uses lacquer on their steel, to minimize the risk of corrosion between manufacture and delivery; a few drops of lacquer thinner removed the coating completely, and made a huge difference in performance! My bad, of course. Isn’t ignorance bliss? I understand that most (?) American manufacturers use a wax coating, which is easily removed with mineral spirits.

As I started using the new saw, it seemed somewhat difficult to get the cut started. My intent was to make practice cuts, targetting 1) a pre-set depth, and 2) perfectly parallel cuts. I noticed, as my practice session got longer and longer, it became much easier to start the cuts. And toward the end of the session I was able to start a cut and finish it in seconds. I have read somewhere that this is normal behavior for this type of saw.

However, I will have to practice a lot more, for I noticed two serious problems:

  1. I have a tendency to overshoot the depth, and
  2. I can cut better parallel lines when the saw is tilting to the left, as in the last photo.

Next step: Cutting to a line.

I hope I can get better when cutting with the saw tilting to the right. Practice should make perfect – I hope!

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