Wednesday, June 1, 2011

Dovetail Layout Part 1: Working The Angles.

I feel a little like I'm wading into shark infested waters wearing a suit made of meat. I hope I come out the other side with only a few bite marks and no missing limbs. If you have been reading along I have just started a series of posts based on dovetail layouts, no cutting dovetails, just a focus on the layouts. If you want to catch up on my introduction post you can read it HERE.

I am not a fan of putting dovetail joints up on a pedestal, but I will say that the different personalities they can display in different situations can make them a telling feature on a piece of furniture, and a mark of the woodworker who cut them. I admit that when my wife and I are out antiquing and I start looking at a piece of furniture, if there are drawers, the first thing I do is pull them out and have a look at the dovetails and i they tell me a lot.
Dovetails on an antique dresser we own. machine cut half blinds.

Are they perfectly even and production machine made or have they been hand cut? Are they through tails hidden by veneer or are they true half blinds? Are they crystal clear in their lines and meant to stand out or are they subdued and workmanlike? In the end I worry less about small gaps or less than absolutely perfect execution and more about the over all feeling I get from looking at it. I feel like these things will tell me a lot about what else went into the design and production of the piece. There are other things I look for to but inevitable past my first impression of the overall design and proportions, I learn a lot from the dovetails.

To my mind that makes my dovetail layout important to me, but you have to be smart enough to know where to use the correct layouts. If I looked at a drawer that was put together with half blind, hounds-tooth dovetails, that would probably put me off of the piece, because I would think, "what a waste."  I think that's what I dislike most about router made dovetails, off the template they are the same in any situation.There is a time and place for a "Hey Look At Me" set of pins and tails and a average, evenly spaced set both. Choosing when to use what is part of your own personal design conscience.

This is where you get into the chunky tails vs. skinny tails debate. Again this is not, as I see it, an issue of structure or strength, it is instead an issue of design. Cut whichever is most pleasing to your eye. Personally when I am designing the joint for looks, I tend to use a mix of both chunkier and narrower pins and tails spread out in a symmetrical pattern.

So what about the angles of those tails? How do you determine those? In the traditional joinery books I own there are two options and two options only. They are expressed as ratios of rise and run 1:6 and 1:8. If you've ever done any roofing work you'll recognize rise and run as the angle the pitch of a roof will follow. Expressed like this the angle is one inch of rise for every six or eight inches of length. You can measure and draw out this ratio every time, but if you plan to cut a lot of dovetails, I would suggest drawing the out on something a little more permanent than a scrap chunk of board.

I have chosen to draw them out on one end of my workbench, I have seen others have them drawn out on a bench hook. You can draw them on the ceiling of the ceiling of the shop if you want, but I have found it convenient to have them around so I can easily set my bevel marking gauge to them. Now the "rules" say that the 1:6 ratio is for use in soft woods, and the 1:8 ratio is for hardwoods. The thought is that dovetails in softwoods can be a little spongier and more forgiving and the more dramatic 1:6 angle gives them greater strength. I guess that thinking is sound but really there is a little bit of B.S. about it.

You should know how I feel about rules. I hate them. I have seen Roy Underhill on video talk about dovetail angles and finding them on antiques with angles of 1:3. Now that's a steep and dramatic slope. I think the "rules" are one of the things that make it difficult for dovetails to be an accessible joint for newer woodworkers. I understand the thinking behind them but seriously if we are creating different rules for angles in different woods then we are losing sight of what should be the real driving factor in the use of this joint. Strength and / or appearance.

I use the more dramatic 1:6 for dovetails that are going to be on the stage and super visible, like on the corners of a blanket chest. I use the slightly more relaxed 1:8 for dovetails that are blue collar and there to do a job, like on a drawer. I have found that 1:8 slope seems to make fitting easier when I cut half blind dovetails.
In the end there "rules" are more like guidelines. I never spend more than a few seconds setting up my bevel marking gauge, I never worry anymore about getting the angle "perfect" in fact that's why I continue to use a bevel marking gauge set by hand instead of a static dovetail marker. There is a little bit of irregularity, a little bit of humanity that gets introduced when I set the angle myself using the edge of my workbench and my hand drawn lines. When I cut my pins or tails (whichever I decide to start with) I cut one board first, then I use those cuts to mark the other board, this way I transfer any entropy I've picked up in the process and any off angle, miss cut, millimeter of intolerance, is transferred as well and doesn't stick out in the finished product.

I don't want to overload a post with too much information and lose anyone so I am going to call it there for the evening, Next time you'll hear a little more about paying attention to the big picture when it comes to laying out dovetails and I'll go over the tools I put to use. After that we'll get started going over the actual layouts themselves.

Cheers
Oldwolf

No comments:

Post a Comment