Dovetail Question

Dave Richards

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Machine Cut vs Hand Cut

I've been pondering this subject for a while and would like your thoughts. Why is that most machine cut dovetail joints look like zipper teeth (OK, box joints) while hand cut dovetail joints don't? The typical machine cut dovetails have pins and tails that are the same width. I've never seen a hand cut dovetail joint cut that way. Generally the width of the pins is but a small fraction of the width of the tails in a hand cut joint and there are usually a small number of pins relative to the machine cut cousins.

Yes, I'll grant that with a jig such as the Leigh, the spacing can be more like you would do with a hand cut joint but it seems that even with the Leigh jig, many woodworkers shoot for getting as many pins and tails as they can in the joint.

With the common comb-type jigs and router table-based jigs such as the Incra, zippers are the rule.

Is it that those who hand cut dovetails are just plain old too lazy to cut a lot of them in a run? No, I don't really think that.

I realize that there is more gluing surface area in the zipper-like joint but I don't think that is a valid reason when you can look around any antique store and find a bunch of old, hand cut joints that have yet to fail. And with the sorts of adhesives we have these days, there really isn't a need for the larger surface area.

In my opinion, the typical comb jig type dovetails are not aesthetically pleasing. surely I'm not the only one who thinks that.

So what say ye? Anyone?
 
Yup. Agreed.

Still, I think that these days, the hand-cut crowd often tend to make some pins as teeny-tiny-thin as possible, just to blatantly show that it is NOT a machine-cut joint.

...art

ps: but in all honesty, I have not seen that many Leigh joints to say if they are mostly done zipper style or not.
 
The biggest thing that limits machine cut dovetails IMHO is the router bit itself. The bits don't last too long on shanks smaller than 1/4" - so that really defines the thickness of your pins. That's one of the biggest distinctions between hand cut and machined - the distance between pins is "analog" in that you aren't limited to some overly symmetrical layout due to the width of your bit or the comb fingers. But, the saw and chisels I use are the bottom-end of my limitations - they set how small I can go - and a saw kerf is teeny compared to a 1/4" router bit's shank.

The other VERY limiting factor in a router bit is the bevel angle. There are only really a handful of angles - 10, 14 and i think sometimes you'll see a 12 degree. When I hand cut, I'm not sure what the angles are but i work in 1:7 or 1:8 ratios. I'm told that's nowhere near a 14 degree router bit - i think it's closer to ten, though. That really distinguishes the hand-cut dovetail from a machined one, too. That angle really seems to scream machine cut for some reason. Maybe it's mathamatical instinct like the golden mean or the fibonacci sequence.
 
Dave,

I am right there with you. I really appreciate the craftsmanship of the hand cut dovetails. I find myself taking a peek at the sides of drawers and construction of furniture to see how they were made. Without changing the focus of the discussion, I guess I just love the hand work whether it is dovetails, mortise/tenoning, carving ... I guess that's why I like making the joinery for my dovetail boxes with my dovetail saw and chisels.
 
I've been re-practising my dovetail technique, for the past weeks and apart from what has been said already I find it much more flexible in relation to proportions of pins and tails, slope angles, separation between them than router cut dovetails.

The fact of needing a jig to cut them makes almost impossible to make different spacing on the same drawer joint for instance. What about different length pins on the same joint as well. ? Try to make any of these three with a router.
 
Dave, with the modern invention of the internet I think you will see more and more of a rift between machine cut and hand cut dovetails. Let me explain...

As others have said, machines require a certain amount of mass, remaining wood and cutterheads to perform safely. Hand cut dovetails do not. At the same time the ingenuity of man has no limits, and with the modern internet now, unmillable dovetails such as hounds teeth, micro-pins and tails, and even odd shaped dovetails like Lovetails and Pistoltails are on the web. More and morepeople are seeing these hand cut dovetails and the more they are seen,the more the machine cut dovetails look kind of stagnant, bland and crappy.

Myself the first thing I do when I open a drawers look for dovetails...then I look for the tell-tale nick of a handsaw. When I do my own dovetails, I strive to keep that nick to only one spot...but I leave at least one so that there no question they were cut by hand!!
 
In my opinion, the typical comb jig type dovetails are not aesthetically pleasing. surely I'm not the only one who thinks that.

I agree but the variable position jigs make that a choice not a requirement. The other thing that makes machine cut tails stand out to me is the width. You can only get so narrow and still allow the bit through, eh?
 

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Jason's post got me wondering about those angles. Coulda dug out the trig tables but instead I opened SketchUp, drew a couple lines, marked off the ratios, then used the protractor tool to measure. 7:1 is about 8 degrees, 8:1 is about 7 degrees off of perpendicular.

I think aesthetics has a lot to do with why DT router bits have such higher angles than the tried and true traditional ratios. Until the advent of A&C furniture, one seldom saw the joinery used in making a piece of furniture. Other than in more utilitarian pieces, dovetails and the like were most often covered over with molding or another part of the piece.

With dovetails and other joinery becoming part of the "look" of the piece, the higher angles make it more obvious that there is an angle there.

Of course these higher angles further detract from the ability to make more petite sized pins or tails.
 
. . .although dovetail joinery is not a focus with A&C, and most often either mortise and tenon or finger joints were used.

That is correct, but till the A&C revolution, the M&Ts and other joinery used were generally of the non-through type and invisible, basically, when viewing the piece. Prior to that, drawbores on M&Ts were usually done from the back faces so they were not seen. A&C was a lot about honesty, as in the early days of the industrial revolution, much joinery was replaced by metal fasteners and A&C was a move toward making it obvious that the joinery was there. Since then, and particularly within the last couple decades, joinery has become an even greater design element with quality often being assigned to that visible joinery. And with design elements often being emphasized, using those higher angles makes it more obvious that you are looking at a DT, even from a distance.
 
Thank you all for your input. So far we haven't had anyone say they like the zipper tooth look of dovetails cut with the comb type jigs or positioning tools such as the Incra. If I may read between the lines, the consensus seems to be that carbide dovetail bits make fat dovetails out a neccessity. Narrow pins are more desirable and more pleasing to look at than the chunky pins required to fit sockets cut by carbide router bits.

I think you would all agree that dovetail joints are a bit fussy to cut no matter whether by hand or by machine. There are a lot of faces that need to be cut so they align properly. Certainly compared to a joint such as a lock rabbet, a dovetail joint is much more difficult to get right.

Now, for something like a drawer box, we could use a lock rabbet to join the corners and with adhesives such as Titebond or better, epoxy, the drawer box would be as strong if not stronger than a dovetailed drawer. This with less fussing around to get the joint to fit correctly thus with less time invested in that part of the project.

So considering all that, why would someone choose to cut a joint that isn't pleasant to look at? But we see it all the time. Salespeople at kitchen cabinet shops can't wait to prove to you that the cabinets they sell are of the highest quality by showing the dovetails in their MDF drawer boxes.

By the way, I'm just asking questions and trying to understand how things go. I'm not criticizing anyone's work.

When I lay out dovetails with my router, I use essentially the same process as anyone who is hand cutting them does, marking out the wood.

FWIW, there are router bits that will do much nicer looking dovetail sockets than we are accustomed to seeing. I have a set of 8° bits starting at 3/16" diameter and going to 1/2" diameter in 1/16" steps. the cutting depth is exactly twice the diameter. The smallest one which has a cutting depth of 3/8" makes a socket with the narrow end at about 5/64" wide. Still wider than a saw kerf but pretty narrow. By contrast, CMT offer an 8° carbide bit with a 3/8" cutting depth but the diameter is an 1/8" larger.

My reason for starting this discussion wasn't about these bits but I thought I would throw out the info on them anyway.
 
Interesting conversation. I would have liked to use DT's on a couple drawer units I am building, but time material and $ have precluded such. I really enjoy the look and satisfaction I get when I get a set of hand cut DT's to fit properly, however if I was making a piece for a client that spec'd DT's or was spending the money to warrant them I would probably go to the jig and rout them in the interest of time. On a personal project, I'd probably hand cut them just to prove I can!
 
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