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I’m looking for ‘proportions’ for dovetail joints, or a standard proportion if there is such a thing. I am designing some cabinetry on CAD, and have the luxury of creating dovetail slots in solid models of cabinet parts. The slot feature needs a depth, a width (top or bottom of pin or tail), and an angle. The system can then create a dovetail joint of my choice. I seem to remember reading about the proper proportions for a dovetail, is there such a thing? What about the dovetail router bits?
Thanks for the info while I browse my tooling catalogs…
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Most dovetails are between 6 and 8 degrees.
*Thanks! I was using a total of 15 degrees, (7-1/2 per side) and it looked OK to me. I also found a proportion listed in an older woodworking book that listed different angles between hardwood and softwood. If anyone is interested, I'll post it...
*Lee Valley sells Veritas dovetail markers. They have one for hardwoods and one for softwoods. The angles they use for the pins is stated in ratios: 1:8 for hardwood and 1:6 for softwood.
*Marino is correct: dovetails are normally prescribed as a ratio. 6 degrees is not the same as 6:1. As for CAD, I always design my dt's on CAD and usually arrive at proportions that please my eye. The beauty of CAD is that when I am satisfied with the size, placement and spacing, I plot the joint out 1:1 and tape to my workpiece to use as a template for sawing the joints.
*In hand carcass or box dovetailing a rise between 1 in 5 and 1 in 9 is quite typical. For softwoods and carcase construction a rise of @ 1 in 6 is usually used. For fine work, such as small boxes and lap dovetails in drawer sides, and for hardwoods, a rise of 1 in 8 or 1 in 9 is within the normal range, although I've seen and cut them as delicate as 1 in 11 or 1 in 12, which requires well developed hand skills.To put some degrees on these rises to compare with the way dovetail cutters are sold out of the catalogues, a rise of 1 in 4 = approximately 14 degrees, which is, as I said before, really considered too steep an angle for box corner dovetails because of the weak short grain formed. A rise of 1 in 10 = about 6.5 degrees.Sliding dovetails can be worked by hand. I've done it many a time, especially in restoration work and the like, where getting in with a router is difficult, and it's important to retain integrity and that sort of thing. However, for most new work a dovetail cutter in a router is the norm. They are available with rises from 7 degrees to 14 degrees, (Amana catalogue.) This means they come with rises between 1 in 4 and about 1 in 9. I said that a rise of 14 degrees is normally considered too steep because of the weak short grain, but in truth I've never had a problem with a sliding dovetail shearing off, and it's probably due to the whole mass of the sliding dovetail as compared to corner box dovetails.As to how deep a sliding dovetail should be cut, I cut a slot no more than 9 mm in an 18 mm cabinet side or divider. In other words, half or a tad less to retain strength in the side. I remove the smallest amount possible from the shelf that fits into the slot, i.e., I'll use a 16 mm diameter cutter for an 18 mm thick shelf. As before, this is to retain as much of the wood as possible. Naturally, you cut the slot in the side first with the cutter and tailor the shelf to fit. If the slot in the side is 9 mm deep, then the dovetail should be fashioned no more than 8.75 mm long to prevent bottoming out. (Please, don't anybody whine about it being too hard for you to understand the metric system. If you can tell that you've just been short changed in a shop, you understand it just fine!!)I have to say that I wouln't use a 14 degree cutter with a dovetailing jig to make boxes for two reasons. 1. The short grain problems. 2. Machine cut dovetails are coarse and ugly enough as it is without deliberately making them uglier. In my high end work there is no place for a machine cut drawer dovetail, far too unsightly. But I have no qualms about using them in economy work, and in hidden carcase construction because they can be cut in a fraction of the time required for hand work.
*I see that many of you have touched upon some of the issues I continue to wrestle with. It's nice that someone has elaborated more eloquently than I. Since I am so used to the flexibility that CAD offers (I teach this stuff, what can I say?), I find myself moving toward proportions that are not 'standard'. Not to mention, if you really want to do it right, it requires hand-cut joinery.I appreciate all the input, and now I just have to take the time to perfect cutting more dovetails until I get it right the first time...Thanks!
*A suggestion for cutting the dovetails. I've spent lots of time practicing doing it by hand and get pretty good results (plus a lot of satisfaction). But I also designed and built a jig for my bandsaw that is much more involved than the one in this month's American Woodworker. It slides in the bandsaw's miter guage and guaranties perfectly straight cuts and uniform angles. However, you still chop out the waste with a chisel to get that "sharp" edge.By the way, Lee Valley Tools sells simple little devices for drawing the angles. I think they're at about 7% for hardwood but I'm not sure.
*Can through dovetails be made to join 1/2" plywood sides and back with a 3/4" ply front? Instructions with a low-cost jig I just bought suggest this can't be done. I've already worked all my wood for ten drawers for a large entertainment center I am building and am reluctant to start over with any of the drawer pieces. If my question is answered no, please suggest an alternative way to join up these drawers. Note, I've already slotted all boards to receive the bottoms, which will be 1/4" ply. As is obvious, I have never built any furniture before.
*Runrig,I was interested to read that you do 9mm sliding dovetails in 18mm stock. I have always used 5-6 mm, ie., about a third rather than a half. The article that got me going using SDs (in FWW, way, way back) used 4mm tails for that thickness. I must admit, one of the main reasons I've settled on 5-6mm is that it seems easier to get a good fit, the shallower they are. Is that just perception on my part? Seems that strength of the joint is not an issue, here, with that much wood nestling in the housing, but I'd be a bit nervous taking out half the side of a large case-piece. Probably unwarranted, since once the joint is assembled, there shouldn't be much in the way of forces liable to cause any damage. Just interesting that there are different thoughts on these things, and they all seem to work! I use SDs a lot, not only are they esthetically pleasing, they are structurally sound, and quick and easy to make, with nothing more than a router and a couple of very simple jigs. I always use them for any fixed shelves inside cabinets that have to hold up heavy loads like bookshelves - have seen a lot of less carefully constructed old pieces with bulging sides after serving long years in that role. I hope a few details like this will keep my 'heirlooms' standing up straight long after I'm gone.IW
*Rick, I'm sure what you suggest can be done; in woodworking, just about anything can be done if you put your mind to it and figure it out. One thought is to add a 1/4" spacer piece to the 1/2" sides when you cut the side pieces, then saw and sand off the excess 1/4" of the pins after the joint is cut. (That's probably more trouble then it's worth.) I'm not at all a purist when it comes to woodworking-- I use plywood, MDF, etc., all the time. But when I see dovetails cut in plywood drawer sides, it always gives me a feeling of revulsion. Sort of the same feeling I used to get a couple of years ago when Dennis Rodman was popular and TV would show him prancing around in nylon stockings. Would you consider using another type of joinery to join the sides to front and back? What about a rabbet and dado joint? In this, you rabbet off the ends of the front and back leaving about a 1/4" tongue; then cut matching dados in the sides-- the tongues fit into the dados. This makes a plenty strong joint, especially if you are using drawer slides. Reinforce it with finishing or air driven nails. Hope this helps. Good luck with your project. GPW
*I want to switch to metric measurement. Can someone suggest a source for reasonably priced measuring instruments? Thank you.
*Hah, Ian! You found one of my other aliases. Runrig is now retired, and I've taken over the franchise. Quoting from the original post,i "As to how deep a sliding dovetail should be cut, I cut a slot no more than 9 mm in an 18 mm cabinet side or divider. In other words, half or a tad less to retain strength in the side."Then, as now, I sometimes think in shorthand, and don't cover all the angles. It perhaps would have carried better emphasis if it had read,i "I cut a slotb no more i than 9 mm, etc.," and if I'd added the rider, i "but it's not always necessary to go this deep," the description would have encompassed more options to account for different circumstances. You are quite right, for it isn't always necessary to house nearly half the thickness of the cabinet side. I tend to make sliding dovetails about 7-8 mm deep in an 18 mm side, but I have gone 9mm, and as little as 5mm. One reason I prefer a slightly longer dovetail is that I find it a bit easier to work, particularly if there is a little hand fitting required. It's a bit easier to balance a chisel on a longer flat surface for example. In a perfect world, no hand fitting should be needed of course, but there might be a bit of warp or twist in the timber that can throw either (or perhaps both) the housing or the dovetail out during machining. Now, if Scotland can beat the All Blacks tonight (US time) my day will be perfect, even though the Texas Gulf Coast weather sucks all year round, with the exception of December and January that is! Sliante, and G'day mate.
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