I searched the archives, but didn’t come up with anything directly on point, though I’m guessing this has been discussed before: My question concerns the orientation of dovetails at the corners of a carcase (as in a dresser or cabinet). I have seen many plans where the tails are in the top and bottom panels and mate to half blind pins in the sides (presumably to better resist racking). I have seen others – such as wall hung cabinets (where vertical forces are more in play) where the tails are in the sides. I guess I always thought it was really a toss up for free standing cabinets (especially where molding would hide the DT area), as forces from racking and forces from lifting (such as by the overhang of the top) will both come into play, but I thought I’d ask those with more experience whether tails in the top and bottom are superior to tails in the sides for free standing cases?
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Replies
Can't say if one orientation is superior to the other, but I always put the tails on the sides. I've seen too many pieces be moved about by lifting from the top panel to not want the additional mechanical re-enforcement running in that direction.
Jim
Hi Samson,
Use what looks good to your eye. I usually orient the tails so they are most visible.
Paul
I go tails on top, the way Moser does it. This way if you do put on a molding, the tails are visible on top (where the molding ain't). If you go without, I like the look of the even, parallel lines the pins make on the side.
Structurally it should not make a difference. DTs in this orientation that are properly cut and glued will not come apart when lifting a case by the top.
Tails on top, this locks the sides in, which is important for maintaining a good drawer fit.
John White
Yestermorrow School
Tails on top and bottom prevent or restrain cup in wide-board sides. Moving the piece is a red herring, IMHO.
Adam
I'm not trying to be smart, but why wouldn't tails in the sides prevent cupping of the top and bottom of the carcase too?
Thanks,
Sean
With tails in the sides, cupping is resisted by glue and friction. A cupped side may not pull up in a dry joint. The other way around, the dry joint resists the cup. The glue is extra.This might be something you need to try to fully comprehend.Keep in mind, the trick to cutting these joints is restraining the cupped side flat when transferring the tails to the end grain of the cupped board.Adam
Here's my confusion: 4 panels make up the carcase - in a sense, it is arbitrary which ones you call sides and which ones you call top and bottom (imagine a square carcase, for example). Any of these panels could cup. Any such cupping is better restrained by the mechanical pull of tails (as opposed topins) from the adjacent board. Is there a reason that cupping on the sides is inherently more pernicious than cupping on the top and bottom? - that we should make sure that those we situate as "sides" are the priority for anti-cuppng measures?
Samson,
You can tell me to go $hit in my hat but if you're asking a joint to correct a cupping problem, I think you're wishful thinking.
What's with the cupping issue? I'd correct that instead.
Regards,Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
Uh, Bob, it wasn't me who brought up cupping, but Adam.
That said, I can imagine that if a 16 or 18 inch wide panel had a slight cup, like 1/4 inch over its span, one could use battens to hold it flat while you marked the pins, and then the DT joint would mechanically do the job of the battens once assembled. I'm positing a slight cup across a wide panel.
And you never need ruin a hat on my account. ;-)
FWIW, I'm working on a project design where I'd like to make a carcase with through DTs and TAILS on the sides. I wanted to find out why this might be a dreadful mistake. Some have said, it's no difference. Some have said, tails in the side is better because these cabinets are inevitably lifted from the top at several points in their life. And some have said, tails in the top/bottom, because the most important thing is racking stability and to tame cupping in the sides. In other words, a typical Knots thread - all possible answers are provided! LOL
Ok, how big is this carcase/carcass?
Are there shelves? Give us a bit more detail.
Regards,Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
It's sort of typical sideboard size - maybe 18-20" top to bottom of carcase and 42-44" long (around 15" deep). There will be dividers and possibly shelves that would likely be hidden dadoes with a short sliding DT at the front. It will not have any doors or drawers (at least in the design at present).
Edited 9/29/2007 10:09 pm ET by Samson
You can't really correct a cup, Bob. Cups are caused by the rings seeking to straighten themselves out. If you plane off the high spots, you haven't solved the problem because you haven't addressed the root cause- the cup will be back.Period cabinetmakers probably figured this one out as the carcass DT joint, with its many small connections, is about perfect for restraining out a bit of cup and twist.I know some guys try to machine out cup and twist. If you use traditional tools, benches, and joints, this is unnecessary. I think that's a nice side benefit to sticking with our traditions.Adam
Adam,
because you haven't addressed the root cause- the cup will be back
Maybe I got lucky as I'm by no means what one would describe as a period cabinetmaker, but I have several assembled cherry panels, from boards that are 7/8"T X 21"W X 72+" long. They have been in my woodshop for nearly 1 year.
Not a trace of cupping, dead flat. The pieces were milled with machines. Granted they have been clamped and stickered flat the whole time. I am in no way trying to refute what you say.
I just don't think you can take any piece of wood and make it do what you want it to do. You can however select the right wood to shape it as you want it to be. Probably not saying this right.
I mill my wood and then let it settle for a time, acclimate to it's surroundings. Do some boards , let them sit. Joint edges, flatten faces, let them sit. Patience, I'm an old fart. The wood tells me what to do next.
The point I'm trying to make is that with proper stock choice and preparation, one doesn't have to worry about flatness and square, no matter what tools are used to get the desired result. I don't want to rely on the joinery to fix it for me.
Am I wrong?
Regards,
Bob @ Kidderville Acres
P.S. All exposed surfaces receive finish.
A Woodworkers mind should be the sharpest tool in the shop!
Edited 9/29/2007 11:30 pm ET by KiddervilleAcres
Edited 9/29/2007 11:32 pm ET by KiddervilleAcres
Edited 9/29/2007 11:38 pm ET by KiddervilleAcres
Edited 9/29/2007 11:44 pm ET by KiddervilleAcres
Sampson,
The sides are usually more visible than the top or bottom, cup would be more noticeable. The top and bottom would probably be covered with moldings so cup would be less noticeable. If your carcass had drawers, they would run smoother and be easier to fit with true sides. The backboards would srengthen the carcass vertically.
Paul Dzioba
Thanks, Paul. That all makes perfect sense. I'm beginning to think that this question defies generalization, as the details of the piece and design will make a difference. I understand that hald blind dts - tails in the top is likely optimal for things like dressers. I'm thinking that for what I'm building it's six 'o one and half dozen of the other.
Sam,
JohnWW and Adam have both mentioned the importance of keeping case ends flat so that drawers aren't bound up by case sides that bow inward. And most period cases have their tails on top and bottom. There was an 18th century school of thought that joinery ought be hidden, and many period English and some American case pieces are assembled in such a way as to minimise the visibility of the construction. The phrase for this aesthetic was "neat and plain", and it would dictate that evidence of dovetailing be hidden, by using the "secret (full-blind) dovetail" or, a half-blind dovetail with the pins and tails covered by molding. In this style, a chest might be joined with the case ends having half-blind pins at the bottom, where the pins and tails are on the underside of the case, and the top having half-blind pins on its ends, where the pins and tails are covered by a top molding. Another alternative, a top with overhang is applied over two or three top rails, (at front, center and back) dovetailed into pins worked on the ends.
The effect of drying of slabsawn (plainsawn) wood is that of the growth rings straightening out, as Adam describes. Wood shrinks more parallel to the rings, than it does across them. Once the wood is dry, ( has reached equilibrium with its environment), and any cupping has been removed by dressing to thickness, it will remain flat, unless moisture is re-introduced, or further drying takes place. Now, seasonal changes in humidity may, in extreme instances, cause some tendency for wide panels to cup. Good construction will allow for swelling/ shrinkage to take place, while restraining tendency to warp. Most often, cupping of thoroughly dried wood is caused by unequal moisture uptake or loss, to or from only one side of the panel. This may be caused by leaving the panel flat on a surface like a benchtop, during which time a change in weather takes place, or by applying finish to one side only of an unrestrained surface. Cupping caused by unequal moisture loss will not necessarily be in the direction of the growth rings' straightening, but in the direction of the surface with the least moisture.
Ray
Thanks for the detailed explanation, Ray. It helps.
Samson,
I'm not that experienced, but a few months ago I built a 42"x36"x8" case using 1/4 sawn white oak and dovetails on all four corners. To offset any cup or bow I dadoed the shelves into the sides. The top and base helped keep those pieces in line. My big concern was getting the doors to fit well..it all worked.
If I had to do it over I'd be more careful with my dovetail clean up. I guess I was too aggressive with the smoother and lost square on the outside dimensions...needed to shim at the base.
So what did you write and delete?
Feel free to ridicule (at least anything I've written) at will. You won't hurt my feelings and maybe I'll learn something.
By the way, I prefer to cut tails first, though I can see the attraction of pins first if you like your pins narrow (easier to mark the corresponding board).
Relax.
No anxiety in my question, just curiousity.
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