Super noob dovetail and wood movement questions

[DBeeson]

I'm literally just getting started with woodwork, so forgive me if I ask anything stupid

I've read a few books, but there are a few things I'm having trouble working out.

If you use corner joints like dovetails to make small things like boxes, but on say a table you have to have a 'loose' attachment to allow for wood movement, is there a certain size when you have to switch from one method to the other, or am I understanding things completely wrong? Could I make a desk with solid sides like a cabinet dovetailed to the top, or would it break with wood movement?

Do dovetails always have to be made with half pins? Could you have half tails?

Is there really any disadvantage to having fewer 'chunkier' pins and tails over lots of smaller ones?

If any of that didn't make any sense, please forgive me... it's 2AM :lol:

 

[SketchUp Guru]

Greetings and welcome.

I'm not quite sure I understand all of your questions but the ones I do, I'll try to answer. First of all, dovetails are done on the ends of boards so it you join two piece with them, the grain will effectively run over the corner. The wood movement that folks are mainly concerned about occurs across the width of the board, 90° to the direction of the grain. The pieces on either side of the dovetail joint, then, are moving in the same direction so there's no need to worry about movement.

The concern about wood movement for a desk or table top would come in when you have typical legs and aprons or skirting boards. The grain of the top usually runs from left to right as you are siting at the desk. the aprons on the ends of the desk or table would then have the grain running 90° to the grain on the top. Those aprons won't change much in length while the top will. So for that sort of assembly you need to make allowances for that movement so that you don't trap the wood. If it can't get wider it'll warp, cup or crown.

As to the half pins on the dovetail joint, you could use half tails but the half pins are traditional and they also make a great deal of sense. If the boards try to warp, the half pins confine the board nearer the ends than would half tails.

Dovetails are a joint that, in my opinion anyway, should have an aesthetic appeal. This of course is an eye of the beholder thing. It seems that most folks like narrow pins but they aren't always required. Also in my opinion, there's little point in cutting dovetail joints if they aren't going to be nice to look at. Today we have adhesives with incredible strength so there's no reason to make a fiddly joint like a dovetail joint purely for strength. there are plenty of other, easier joints you could make.

A dovetail joint is a design element so do what looks right for the piece you're building.

 

[DBeeson]

Now I read them during the daytime, I'm not sure even I totally understand my questions, but somehow you managed to answer them anyway :lol:

Thanks a lot