Machine Cut Through Dovetails

[Bob Smalser]

The lads I’m writing these for have been at it over a year now rehabilitating and using basic hand tools, and it’s time to develop mastery of the basic machines to increase efficiency. I can’t think of a better place to begin than some basic through dovetails. The dovetail is a utility joint for joining wood at right angles, one that will remain functional long after its glue has gone to dust, and remains the best joint out there for resisting tension stress like pulling on a heavy drawer. It is often a better joint for carcass corners than the mortise and tenon, especially in thin, Victorian frame and panel construction…

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…and is also one of the easier and faster joints to cut accurately once you master visualizing the joinery principles involved. Shucks, I even use them to join heavy gate frames like the two 7-foot gate leaves below:

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Drawers are their most common use, and I’ll begin a run of shallow utility drawers that will also double as tool trays for the shop on this fine rainy day.

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I prefer solid, crossgrain cedar bottoms on drawers, and also prefer thicker rough sawn stock as my starting point, as it makes for faster panel construction than planed stock. Crossgrain bottoms are sound, beautiful, classic joinery, can be done almost as fast as using plywood, and more importantly, are a great way to use up all that rip waste that normally goes into the stove. I lay them up above after jointing them so they lay edge grain up for minimum seasonal movement. So long as the bottom face remains flat against the bar clamps, the thickness planer will deal with any and all thickness variations easily. This cross grain bottom is 16 inches wide and 22 inches long. If you only own a 12” planer, simply omit glue in that center joint, plane them after curing, then lay the two halves up again, using a little more care in alignment. No dowels or biscuits are required, merely squarely jointed edges…the planer takes care of most of the alignment and the glue alone is more than sufficient strength. Trying to lay up the whole shebang at once and plane it across rather than with the grain remains a bad idea.

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I prepare the stock for the drawer front, back and sides sized to fit the carcass opening, and mark which faces I want to display based on any defects present in the wood. This stock is spalted holly from a small log that was unsuitable for cabin soles in boats, and there is a bit of grain runout and checking. I’ll wait until I glue the drawer up before gluing any checks and splits to save time, and also mark where I’ll have to move a dovetail a bit so any defects don’t fall on a tail or pin.

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Next I’ll groove all 4 pieces for the drawer bottom, cutting quarter-inch grooves, three-sixteenth’s deep using multiple passes on the table saw. Notice my blade insert is clearly marked on both sides at exact center of the saw’s arbor, and I’m careful to position a tooth on that mark before attempting to set the blade height to dado the grooves. As this drawer will also function as a tray, I’ve chosen to make all 4 pieces the same, 3/8” thickness.

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I set the marking gage to the thickness of the stock…

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…and deeply scribe all eight ends on both sides of the stock.

Continued…

[Bob Smalser]

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I grooved the stock as a first step to provide a myself a strong visual reference for joint layout and to insure I don’t goof and cut too close to the grooves by mistake. As the drawer front must resist the tension forces of pulling it open, that’s where the pins have to go, and I clamp the front and back pieces together for faster layout.

A common bevel and trysquare are the usual tools for laying out dovetails, but I find these shop-made dovetail squares much faster. They are simple to make from scrap sheet brass by drawing the conventional slopes…1:8 for hardwoods and 1:6 for softwoods…on graph paper. Then that graph paper can be contact cemented to the sheet brass and the blade cut out using a hack saw and files to the lines.

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If you make the blades a tight fit in one of your machine’s miter gage slots, that machine table can be used as the perfect gluing jig to epoxy the brass blades into their hardwood dado’s, followed by reinforcement with a couple brass box brads.

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I finish the layout by drawing out the entire joint and marking the waste to be removed. Were I cutting these by hand, I’d use the scratch awl for marking. But as today it will be the machine that does the work keeping the cuts square, the pencil alone is adequate. If I do enough of these joints in sequence, I can get to the point where once the grooves are cut as a reference, I don’t need to lay out the pins at all but can go straight to the machine for even more speed. But it’s been a while since I’ve cut one of these, and I’d just be setting myself up for a fall trying to be a showoff.

As my drawer front today is exceptionally thin, I’ll also use 1:6 as my dovetail slope instead of the usual 1:8 for hardwoods.

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I clamp a temporary face to the miter gage of sufficient height to keep my fingers a safe distance from the blade, and determine the miter gage angle equivalent to the 1:6 slope I’ll use. Turns out to be 9 degrees…

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…and I set my blade height just like I did making the grooves.

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Then indexing the face of the board vertically against the temporary face, I can use the miter gage to make the 9-degree cuts using multiple passes on one side of the pins.

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I do all four pin ends using one 9-degree miter gage setting…

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…then simply change the miter gage over to 9 degrees on the other side of zero to finish the pins.

Simple, fast and accurate. Moreover, you quickly can get to the point where these are so routine; you can lay them out with final saw cuts as opposed to layout tools. As the tail layout is taken directly from the finished pin sockets, the pencil lines are merely a guide. There are two additional techniques I use to avoid mistakes:

1) I always index the grooved side of the piece to the miter gage, insuring I’m always cutting with the widest side of the pin sockets facing forward.

2) Just to make sure I’m not cutting the wrong angle, my first cut is always taken at or near the center of the socket so I can lift the work piece and gander at it to make sure I haven’t lost track of where my brain is. Cut the wrong angle at the edge of the socket as opposed to the middle, and you get to make a new work piece.

Continued….

[Bob Smalser]

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Laying out the tails is simply a matter of indexing each corner together and scribing the inside edge of the pin sockets onto the drawer sides to mark the tails. Again, a pencil can be used, although an awl will do a cleaner job and might make accurate sawing of the tails easier for you than the sloppier pencil. Again, the grooves are very useful to insure I don’t get my ends mixed up, as the sockets all vary slightly, requiring each joint to be numbered before proceeding.

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The tails are freehanded on the bandsaw, with the center waste hogged out using multiple passes to line scribed by the marking gage. I cut to the outside edge of the pencil lines, using care not to touch them so I’ll have a tight, drive fit.

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Finally, the bandsaw miter gage is used to finish. With the tail cuts already made and the lines scribed by the marking gage on both faces, flipping the workpiece to cut the opposite edge is fast and easy.

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The drawer is glued and assembled on a dead-flat surface in preparation for getting out the bottom, and the glue is allowed to cure. The speed square is a useful staring point, but square is always taken from the diagonals. If you’ve cut the dovetails sufficiently tight, clamping isn’t required. Many folks use too much glue here…remember that end grain is never a gluing surface and using glue there is waste unless you have some minor gaps you’d like to close. Then if you use a glue with a long open time like urea resin, you can sand the joints into the wet glue prior to indexing the drawer to cure for an effective, one-step filler.

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As the solid, crossgrain bottom needs room to move with the seasons; after the glue has cured I rip the drawer back to the top of the groove. I could have done that before assembling the drawer, but having four uniform surfaces to index on the flat saw table during glueup is useful, and ripping the entire drawer as opposed to just the unassembled drawer back is just as fast.

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Now I saw out the planed, crossgrain bottom into a perfect rectangle sized to fit the grooves in an easy push fit. Here’s where beginners get into trouble squaring up large panels by relying on the accuracy of their machines and their squares instead of using diagonals. Even the best aftermarket fences and sliding tables require a perfect index surface to achieve their potential for square; one small irregularity or gob of sawdust can throw them off…and wood is never perfect. Large framing squares and T-squares simply aren’t cabinet tools for the same reason. Make a habit of using diagonals to square up large surfaces and spaces, and your unpleasant surprises will be elsewhere.

Getting the two long sides dead parallel is done easily enough on the jointer and table saw rip fence. End grain like in this example is jointed without splitting by nipping one end on the cutterhead, then reversing the work piece to complete the joint. Then I use the speed square and straight edge to mark square at the front edge of the drawer bottom, paring any irregularities close to the line with a block plane followed by a final pass through the jointer to the edge of the line. The rear edge is squared using diagonals to mark the ends, a line drawn, and the cuts made to the edge of the line using the bandsaw followed again by the jointer. Get those diagonals to within a 32nd of each other, and you are as square as can be done in wood.

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To finish the panel drawer bottom, I bevel the sides to 10 degrees…

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…and rabbet the sides and front edge to fit the groove with a snug, sliding fit.

Continued….

[Bob Smalser]

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I install the drawer bottom. Usually, the bottom is held in by one slotted screw through the bottom of the drawer back that allows for seasonal expansion, but as my drawer back is only 3/8” thick in this application, I elect to glue the front of the drawer bottom to the drawer face groove. This isn’t as easily repaired as a screw-mounted bottom, but is still repairable when the time comes.

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The drawer bottom was made slightly over long to accommodate shrinkage and a future repair…

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…and the dovetailing job is will serve for a long time without repair.

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The flat, square drawer is finished by easing a few edges using the block plane followed by a coat of boat soup (60-40 linseed-turps with pine tar and drier) applied hot.

[Dan Stuewe]

Bob, thank you very much for taking the time to post this. I may never use this method to make dovetails, but I can say that I will be a better woodworker for reading this article.

Thanks,

[Michael Stafford]

Very well presented article, Bob.

Thanks for teaching the right way...

[Kurt Aebi]

Bob,

Another fine article! Thanks for sharing with us and helping each of actually "See" what the written word can't clearly show us.

Keep 'em coming!

[Ken Fitzgerald]

Excellent article Bob! Well written and illustrated! Thanks!

[Mark Singer]

Bob,

Excellent! I have used made them using the bandsaw ..combimed with hand work but never the tablesaw... Very nice article.

[Jerry Olexa]

Bob EXCELLENT article! Thanks for taking the time to do so... I've learned a lot! Appreciate your effort!!!

[Scott Parks]

Bob, thanks for the articles, I thouroughly enjoy your knowledge. I'm always looking forward for your next post.

My question though, What is the purpose of using a "raised" panel for the drawer bottoms? Is it to accomodate a thicker bottom?
Also, this is the way I've always machine cut DT's. Like Bob said, fast and easy and accurate. Although, I use my dado blade so it doesn't take as long to nibble away the pins.

[Zahid Naqvi]

Bob,
thanks once again for taking the time and putting in the effort to transfer your immense knowledge.

[Bob Smalser]

My question though, What is the purpose of using a "raised" panel for the drawer bottoms? Is it to accomodate a thicker bottom?


Stiffer bottom and less planing required.

Quarter-inch cedar is a bit springy.

Half-inch cedar weighs no more to speak of than quarter-inch DF ply, either.

Wonderful way to use up all that narrow rip waste...nuthin wrong with mixing species for variety, either.

[Wes Newman]

Very nice write up Bob. I propose that this be moved to the Articles Forum for later use. I definitely will be coming back to read this article again.
Thanks again Bob.

Wes

[Bob Smalser]

Q&A and Feedback



:
For the drawer bottoms-what kind of cedar are you using? Spanish cedar, aromatic cedar, western red cedar? It also appears to be quartersawn (which makes sense). Can I just use some left over fencing if I put it in my kiln first?

Any cedar or other scraps I happen to have on hand. I also alternate cedar and other woods if I don’t have enuf of any one species…..makes interesting color contrasts. The cedar you are looking at had just come in from out in the rain….the construction allows for shrinkage sufficiently that wet wood isn’t a big problem.


:
Great tutorial, Bob. Do you ever have problems with the tooth set on the ts blade?

Some fellas grind the set off of their blades for a dead flat surface….if I’m gonna be that fussy on a particular project, I’ll either cut them by hand or cut short and pare the sawmarks with a chisel. Changing blades is something I generally avoid unless I have to…..when I get into a larger shop, I’ll simply use two TS’s….one with a permanent stack dado mounted.


:
Seems like if you were going to use a "machine" anyway, a dovetail jig would be the way to go. If cost is an issue, a fine dovetail jig can be made for very low cost using the stots template.

Those with router jigs should cut a couple drawer sets over long by an inch or more so you don’t waste stock tuning the jig. Tune the jig using the actual stock then trim the stock to length when you are satisfied with the joint.

Personally, I find the better ones excellent for large runs of blind-dovetail cabinet drawers of identical thickness….for through dovetails or small runs of mixed size and thickness blind-dovetail drawers I find them fussy, tedious and often slower.

An interesting contest would be a couple sets of roll top desk drawers. 3 or 4 pedestal drawers in two thicknesses of drawer front and two drawer depths…a wide center drawer…. and 4 top drawers of a third thickness with two separate depths….all blind dovetails.

With a standard of zero stock waste, forcing you to mill separate scrap stock to set up the jig….I wonder how far I’d get cutting them by hand in a race with the jig? If we used through dovetails instead of blind dovetails and I could use the machines above…I might even spot you a drawer.

I’m not picking on you, your comment is valid; I’m just pointing out that all methods have their plusses and minuses.



My question though, What is the purpose of using a "raised" panel for the drawer bottoms? Is it to accomodate a thicker bottom?

Stiffer bottom and less planing required.
Quarter-inch cedar is a bit springy.
Half-inch cedar weighs no more to speak of than quarter-inch hardwood ply, either.
Wonderful way to use up all that narrow rip waste...nuthin wrong with mixing species for variety, either. So unlike quarter-inch plywood….these drawer bottoms are free.



Do you use drawer slides?

Expensive ball bearing steel slides?

The biggest of all the needless gizmos for most applications, IMHO. Given their considerable expense, I don’t understand their popularity, as they require the same construction tolerances as traditional joinery.

Make the drawer and carcass traditionally, and neither weight nor full extension require anything but oak-on-oak and paraffin wax. Even for big file drawers full of books or tools.

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Do you recommend drawer slips to support the bottom?

http://www.amgron.clara.net/drawers/slips.jpg

I've repaired them on old furniture.

A fancy touch that can reinforce a thin side, but still generally a factory shortcut to avoid using a raised panel and one more glue joint to fail and require repair.


Who are you writing these for?

My descendants. These are book chapters I post for y’all to review, provide feedback for clarity revisions, and in return, use as you see fit. Most have been on hand tools, as I believe that’s the best way to start and there is a big gap there among today’s most popular woodworking teachers.

I worked for the tradesmen in my family extensively but reluctantly as a kid, as it didn't help my baseball or hunting/fishing careers. I didn't really get interested in what they did for a living until I was older and they were dead.

I held up the ends of their planks and sharpened their slicks and Disstons long before "The Great Craft Revival" and its "rediscovery" of hand tools and figured I ought to start writing this stuff down, as there's a lot of really poor hand tool information out there by well-meaning folks who fiddle with them as hobbyists but never actually met anybody who derived the bulk of their living from hand tools.


:
I've got 2 minor differences, you may find them useful, maybe not.

1. I've got a ball bearing guided router bit that cuts the groove for me in the dry assembled case,1/4" x 1/4" or deeper if I change the bearing. I use it on a table then remove the small scrap in the corner with a chisel.

2.I keep a special blade for cutting out the tails 12 tpi with the set dressed off.....very smooth job.


:
I've been using the table saw to cut the pins for dovetails for years now, but I clean out the waste with a chisel. Why? Cleaner joints. No machine can get as picky close as a good sharp chisel. I used to use a "Zona" saw for cutting the kerfs,(and I still do on stock thinner than 1/2") But in real life time is money, and a good jig on the table saw gives me good cuts in a fraction of the time. I also leave the blade just a red hair shy of the base line, and pare to the line when I'm chopping out the waste.
There was an article in FWW a few years back, by Steve Latta, on cutting the tails with the table saw with a blade ground to a 7 degree angle, but I can't see sacrificing 2 perfectly good blades for such a committed use. Of course if I made hundreds of DT drawers or carcasses a year, I might...