This video is an accompaniment to my column in the Feb. 2009 issue of Popular Woodworking Magazine. The video focuses on using center lines to accurately locate hinge mortises. But the article goes into depth on a more general concept you have probably heard me mention before: relative dimensioning. The idea is simple: let the pre-existing parts of your project dictate the size of subsequent parts. And in many cases, this is much easier and far more accurate than measuring with a tape or ruler. I first learned about relative dimensioning way back in my WWA forum days from a guy named Dave Knipfer. Anyone heard from him lately? Anyway, he was an amazing craftsman and his work methods really resonated with me. And so relative dimensioning has been part of my work ever since.
Now some may think of this type of building as common sense. Others may say, “this is nothing new”. And for the most part, they would both be right. Ever hear of a story stick? Cabinet-makers and installers have been using them forever. But I know how much of an eye opening revelation this concept was to me when I was starting out, so I think its important that I pass it on to my fellow woodworkers who may not be familiar with it. So like the article says, “Throw Away Your Tape Measure”!
Download the PDF of the article, courtesy of Popular Woodworking.
I am curious how many of you use this system in your woodworking. Or are you purely a measure and mark type of woodworker?
Strangely I’ve developed this technique on my own kinda early on in my projects. At first everything was done by trying to make an exact mark repeatedly using a tape measure, but no go (usually). It was off regularly, but making parts using relative dimensioning was easier and more often more precise.
Excellent article Marc …… the ‘relative dimensioning’ method of work has always been a staple for me …… I suppose I’m just not smart enough to use a tape measure!
Many thanks for sharing the word about the power of this approach.
I’m enjoying looking at that little cabinet you are creating in the photo …… need to poke around your site and see if I can find a photo of the finished piece ….. looks lovely from here.
Be well in your WW adventures.
David Knipfer
Hey Dave! Long time my friend! Great to hear from you. If it wasn’t for your influence back at the WWA forum years ago, I wouldn’t have known anything about relative dimensioning. Now it an integral part of my workflow.
You can find a few more images in my little gallery slideshow here: http://www.thewoodwhisperer.com/gallery/ Just one of my little experiments in the Greene & Greeene gone gothic series, haha.
Well thanks for stopping by and I hope your are still making sawdust. Your boxes were quite inspirational to me in the early years. Well, they still are but I don’t get to see them anymore. :)
I saw relative dimensioning and immediately thought of Dave Knipfer. He did (does?) great work. I still have a small necklace box he gave me as a present on my dresser . He also had a lot of wonderfully useful info posted on the WWA board.
Anyways, very handy post.
I also appreciate the inlay post…I’ve always been horrible at it…but, that post cleared some things up…can’t wait to try.
Who needs to do it the old fashioned way when you can use this: http://www.leevalley.com/wood/.....3513,43516
You teased us about this many videos ago, I’m glad to see it’s finally here. Enjoyed the artice. Goes hand in hand with something I read a long time ago (some book club freebie) called “Measure Once, Cut Once” by Steve Shanesy.
I first began to use this type of thinking when I was a teenager working for my dad, who owned a plumbing company. I would try to perform relativly complex pipe layouts by adding the lengths of vaious fittings and pieces of pipe together to find out how long to cut the next piece. Then it was a revelation when I watched him lay each piece out on the floor and make marks, creating a plumbing story stick more or less. No measurements were needed. I try to do this with wood as much as possible now (when I remember).
It’s all relative…
I try to use relative dimensioning as much as possible, but find myself pulling out the tape measure or ruler even when I know I don’t need it. It’s a hard habit to break.
Never trust a tape measure.
I use it, because Marc Spagnuolo told me about it! The only dimensions I have been caring about are the overall dimensions of a project, like the cabinet I recently installed in our guest bathroom. After that was taken care of, everything else became a product of what I had established as the height and width depth of the cabinet. Including the doors, and the panels of the doors. It is important, however, that no matter how you do your dimensioning, tools have to be square and straight and sharp. I have some mortises that are slightly out of alignment (no big deal, as I can fix the results with sandpaper and planing) due to an abused mortising machine.
I have always used relative dimensioning. Nobody knows if the doors or drawers are not to the specs of the plan. They only know if it looks and fits right or not.
Exact dimensions become more critical as more people become involved in a project and parts are made at separate stations then assembled at another. Then everything has to be just right.
But in a small shop such as mine or any hobby woodworker’s shop, relative dimensioning is all that is needed – relatively speaking.
I recently took a class in woodworking and I was surprised that we took very few measurements throughout. I’m a little OCD so I found it difficult to resist the urge to break out the measuring tape, but the project turned out great, without taking obsessive measurements!
I know I need to do this more often!
In my first project, the Audio Cabinet I built in December, I measured nearly everything with my tape measure (or measuring tape). Most measurements were off by 1/16th as the tip on my tape is lose and sometimes pops forward adding a 1/16th. Thankfully the shelves were installed square as they were measured relatively but the top and sides have small proud surfaces.
The tip is supposed to be loose like that. If you hook your tape over the end of a board, your zero point is the inside surface of the hook. If you butt the tape end against the edge of a board, the zero point is the outside surface of the hook. Obviously both can’t be zero if the tip is fixed as they would not account for the thickness of the tip. So, the holes around the rivets that hold on the tip to the tape are oblong, allowing the tip to move the appropriate amount so zero is consistent relative to the rest of the tape.
This is why you should also never measure from a line to some other spot by placing the tip on the line. You don’t know if the tip is “in” or “out”. Instead, I place the 2″ mark of the tape on the line and measure that way, (usually) remembering to subtract 2″ from the measurement I read from the tape. This is known as “burning 2 inches” (or however many inches you used).
Having said all that…I use a combination of relative dimensioning and the tape measure, depending on what I’m doing.