Measure once, cut twice
Hand Cut Dovetail Layout Tools
A new project means a new tool.
Which is not altogether true; building a Greene and Greene inspired cabinet may result in several new tools appearing in your shop. And if the design signaled a move from woodworking machines to the popular embrace of hand tools, that next project could be a large tool chest to hold them all. That was my experience with hand cut dovetails; it was my introduction to an array of new – but classic – methods, and a collection of old – but newly purchased – tools.
Hand cut dovetails require two immediate decisions; size and angle. Let’s dispense with the easy one – angle. The standard rule is either 1:8 for hardware, or 1:5 for softwood. Unless of course you dispense with the rules, some people do, in which case you’re on your own. You woodworking rebel. For me, I’ll stick with the rules, convenient because my Eagle America Dovetail Marker has both standard angles:
This sturdy, although small (for dovetails no more than one inch deep) marker is aluminum built (looks like plastic in pictures) and can be picked up at Amazon for around $12. Rumor is that the hole through the base could be used for fashioning some type of jig.
So what’s with this “1:8” stuff? My engineering background says that angles have numbers, like 10, 45, 90. A 1:8 simply means that if you draw a right triangle with a base of 1 inch, a height of 8 inches, you’ll arrive at the appropriate slope, in this case just over 7 degrees. The beauty of the 1:8 nomenclature is there’s no need for a protractor. Or math. Match a sliding bevel to the angle of the triangle and use it to lay out the dovetails. Of course using the Eagle America marker means completely skipping the triangle and bevel gauge exercise.
Determining the size of pins and tails can be simple, or not so simple. I struggled through one very looooong paragraph/essay on using dividers to precisely march across the end boards in order to exact perfectly measured lines. On the other end of the spectrum is an entertaining YouTube clip of master cabinetmaker Frank Klausze demonstrating his “no measure, no mark” dovetail. He eyeballs the wood, haphazardly flicks out the lines, and starts sawing an angle that feels right. Somewhere in between works for me; mark the middle of the board, loosely divide up each half, and wing it from there.
Shop made designs that include a square edge for marking the ends of the dovetail are handy; one marking tool can then be used for all the layout. With my Eagle guide I also rely on my excellent Lee Valley 4” double square (have I said how awesome that tool is?) to mark the ends. Check out Paul Sellers blog or YouTube video for his take on making your own dovetail marker, or as he refers to it, dovetail template.
Truth is straight lines don’t create straight dovetails. The more the blade wanders or tilts, the more work needed cleaning up the pins and tails. And the more gaps you’ll have to plug. This is where Dovetail Guides make their (ahem) mark. Their purpose is to prevent the saw from veering off course, positioning the blade so that it produces a true and level cut. Plenty of vendors offer dovetail guides, although a simple design from the June, 1992 issue of Woodsmith magazine (No. 81) is reasonably effective. A two-inch-long, 1 ¼” square piece of stable wood – I used maple – is mitered on each end to the desired 1:8 or 1:5 angle. Grooves are cut on three sides, the width based on the target width of the dovetailed board. For me, this was ½ in. So that you’re not running a short piece of wood over a dado blade, start with a longer piece of wood, say ten inches, cut the grooves, and then the miter cuts, creating several guides at the same time. As one final step I borrowed an excellent idea from UK woodworker David Barron and the dovetail guide he sells; on each end of my guide I used a forstner bit to cut a short recess for a round magnet:
This keeps my Gyokuchi saw (described in Dovetail Saws) held fairly tight against the guide. Also added a thin strip of sandpaper in the grooves to give it a bit more grip on the boards.
The primary disadvantage to this design is that it’s specific to the particular dovetail being cut – not only the angle, but the width of the board. My guide only works for boards ½ in. or less thick. Most of the guides offered for sale have the same limitation and offer multiple models to accommodate different needs. In the end it’s questionable on whether a guide truly trains your hand to cut straight. The best way of learning is doing, so I’ve reverted to free hand cuts using my excellent Lie-Nielsen dovetail saw, which I also discuss in Dovetail Saws.
A pen or pencil can be used to make the actual markings in the wood. A mechanical pencil works well since it produces such a nice thin line. For an even thinner, more accurate line, a Marking Knife can be used. Knives produce somewhat of a kerf that a saw can follow, and since they’re necessary for so many other woodworking tasks, might as well get one. My preference is the Paul Sellers recommended Stanley 10-049 Pocket Knife:
Bought mine from Amazon for a whopping $5.11, and added ten of the 11-041 blades (fine cutting at 0.024” thick) for $21.58. I’ve been using the same blade for a year now and expect these ten blades to last a good while. Both sides of the blade are beveled – a departure from “true” marking knives with a single bevel – so care must be taken to angle the knife slightly to keep the point tight in the corner when running it up against the inside of a joint. If you don’t then that bevel could push the point of the knife away from the edge, throwing the mark off. Speaking of which, pencils have the added advantage that mistakes can be erased. Tricky to do with knife lines.
The depth of the dovetail is marked on the ends of all the boards. This is just the width of the joining board, and so the board itself can be used as a guide. Balance the board upright at the end and use pencil or knife to make the mark. A quicker and probably more accurate method is to use a Marking Gauge. When ready to buy you’ll be faced with two styles; pins and cutting wheels. I own both, to try out the different styles, and for the convenience of having more than one gauge handy when multiple settings are needed for the same project. Lee Valley’s Veritas Wheel Marking Gauge is a solid little tool for a reasonable $34.50:
Options include metric or imperial graduated (mine has imperial) and a micro-adjust feature (skipped that one). In the end haven’t found a need for the graduated marks – my eyesight just isn’t that good with those little marks. Replacement blades can be picked up for $4.90. Have heard some folks complain that the fence doesn’t register enough surface area (just over ¾ in.) for a stable cut. I’ve found it sufficient, although it’s interesting to note that the Veritas Mortise gauge – which I also own and recommend – has a larger fence.
My second (as well as third) marking gauge is actually a combination gauge, a tool that serves as both marking and mortise gauge. It is also a pin style. The sliding stem has a single pin on one side for marking, and double pins on the opposite side for mortises. Took a bit of a gamble with the purchase of a Robert Larson Co. 605-1250 Beechwood Mortise/Marking Gauge for $26.40 (Amazon). The construction is quite nice…until reaching for the toy like thumbscrew:
How much money could Robert Larson have possibly saved using plastic instead of brass? Baffling. It seems to meet the need for locking down the sliding stem while keeping the fence perpendicular. Hope its sturdy plastic. Apparently the reasonable price also meant foregoing equal height mortise pins. The near pin is about 1/16 in. too tall and will need to be filed down:
If you just like to have parts for building your own combination gauge, then Harbor Freight provides them. Their largely worthless combination guide retails for $9.99, but with their standard 20% off coupon you’ll only be wasting $7.99. Disassemble it and at least you’ll have a brass thumbscrew. Shopping at HF is like watching the ponies run; sometimes you win, sometimes you lose. Too much slop in the fence; on the left the solidly constructed Robert Larson, the right Harbor Freight:
With enough pressure on the thumbscrew the sliding stem holds, but the fence wobbles and is far from perpendicular. I’ve seen shop made mortise gauges based on designs from the 18th century that dispensed with the screw entirely, using a thin wedge tapped in to tighten the fit. I suppose the same could be done here if I really wanted to use it. I don’t.
My preference is to cut the tails first, then the pins. Not to say this is the best way, just the way I learned. Once the tails are marked and cut, the matching joint will be cut to fit. Which means the boards need to be lined up to allow a pencil or knife to run along the inside recesses and transfer the marks for the matching pins. This alignment needs to be accurate with no movement to the boards while the joint is being marked. Do so and bad things happen. Or good things don’t happen. Hard to believe how many sources actually spell out aligning the two boards by balancing one on a hand plane. Not a stack of wood, or perhaps the box my hand plane came in, or even a copy of War and Peace. I’d rather use an Alignment Board, a simple and quick jig that’s nothing more than two pieces of plywood fastened together with narrow vertical and horizontal fences that line up the edges of the two dovetailed boards:
The wood to be marked is clamped vertically and flush with the top of the alignment board:
The second board, in this example the already cut tails, is then aligned over the first board:
This jig gives a very stable hold and allows me to easily mark the corresponding joint, especially important if a knife is being used. A careless bump halfway through the marking process won’t provoke a long stream of obscenities. My alignment board of construction grade wood and techniques (screws and glue) won’t garner awards; I’ve seen much more photogenic models featuring beautiful hardwoods and, of course, a dovetail joint (first you’ll need to build an alignment board…). Someday I too will build such a version. Some day.
For today I’m focused on creating a decent dovetail that perhaps in some small way will justify all my newly collected tools.