Accuracy & Precision in Woodworking

[Beave2012]

I will say this, the idea behind precision is relative as stated in the article. Some may go for perfection and will never achieve, others go for practicality and may have gaps or worse. No matter what you strive for the project should give you your tolerances. A waterproof box needs very tight tolerances while a shoe rack needs less.

For me, my precision, or lack of can add value. If I want exact I'll go laser or CNC, and take the soul out of the project. If I want functional or prep work I go power tools. However if I want magnificent, I'll go hand tools and watch those shavings come off like butter, eyeing my joint cuts if needed, and letting the wood tell me what to do by the way it moves.

There is always a need for some precision (a 30" board can't span a 35" gap) but precision is relative to the project.

And yes I'm bias to hand tools because no matter how much I love using my power tools, I am never as satisfied with a project than when I complete it by hand. I am proud of those moments of precision as much as I am the flaws that make it imperfect. Most likely that's due to CNC and lasers making perfect easy, and I'm not a fan of trying to match a computer's accuracy, instead I want a computer to match my projects character.

[Hobbyman2]

I think you guys nailed that one.

[Gene Howe]

I think you guys nailed that one.

Absolutely agree.

[sehast]

I grouped accuracy and precision together but they are really two different measures of excellence as shown below. While absolute accuracy is important for woodworking I feel precision or repeatability is most important.

Targets.png (120.65 KiB) Viewed 10674 times

[Gene Howe]

Very nice visual explanation. You hit the target, with that one.

[john_001]

Someone (I forget who right now) talked about first, second and third class sawing. But I think the idea applies to most woodworking operations. Third class is when neither accuracy nor appearance are important. An example would be breaking stock down to rough size. Second class is where accuracy is important but appearance isn't. An example would be tenon cheeks. First class is when both are important. An example would be tenon shoulders.

Also, many measurements are relative: for example, it may be OK if one leg of a table differs from the plan by 1/4", as long as the other three are the same size.

[JPG]

I cannot say that I agree with the target analogy. Like most analogies it is flawed and prone to misinterpretation.

Accuracy is getting all legs of a table to the same length as intended and measured the same.

Precision is the resolution of the measuring device.

I know, another analogy! Just ignore the table leg part.

[Gene Howe]

Practicality dictates that the same length legs also all meet the floor equally.

[JPG]

Practicality dictates that the same length legs also all meet the floor equally.

Only if the floor is 'precisely' flat.

[masonsailor2]

I think a table saw or miter saw are capable of accurate cuts that are acceptable for a certain level of woodworking. The same goes for a router table. To produce joints that are at a very high level hand fitting is usually required. I think that is where woodworking becomes an art form and leaves the craft level behind.
Paul