Archive for the 'Metrology' Category

Dec 16 2015

Our Shooting Boards Make A Difference

When it comes to shooting boards, Traditional designs come with limitations that have to be accepted. The downside to this is that these limitations become part of the mental lexicon that woodworkers carry in their mind when they consider the capabilities of the shooting board. I’d like to take a moment or two and address how our shooting boards help overcome many of these limitations.

A Versatile Shooting Board

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Feb 05 2015

The Woodworking Accuracy Conundrum Part 1

There is a lot of information about wood movement on the information highway, and some of it has painted itself in a corner. That’s ok, We can help sort this out.

More often than I wish were true, I find myself reading generalizations about wood as a building material and woodworking methods that I wish were better understood, because they create incorrect impressions and misunderstandings. Some we may have seen are: “Wood moves, so being very accurate with it isn’t all that important”, “Wood has seasonal movement you know, so there is not too much concern for high accuracy”. “Just get it close” and “Wood moves, so you can’t really rely on it as an accurate or precision material”. Sound Familiar? It’s unfortunately not the best of advice.

There are many other statements often made along these lines, but they don’t even tell half the story. In fact, statements like these have influenced many who read them that wood is a terribly inaccurate material and is difficult to use for making fine things. Some go on to reiterate what they have heard: “Well you know, wood moves and so there is that accuracy issue”, or “Wood isn’t really a precision material”, without really understanding that this issue is really not nearly as big as they have been lead to believe. See, it looks a lot like what was said in the preceding paragraph, only paraphrased, and not at all any better understood. Understanding this is one of the most important things in woodworking. Sure, knowing how to use tools is great, but what good is that if we don’t understand the material the tools are used for?

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Jul 05 2014

Woodworking Squarely

Recently we have had some emails from woodworkers who have been having challenges with building their projects and having them come out square.

The biggest thing we need to realize about squareness is that we take it for granted, but when we really have to make something square, it is something that begins with wood selection, and evolves from meticulous prep work.

Our layout lines have to be drawn on stock that is already “right” in terms of squareness and dimension.

The joinery we cut and form into those boards must be as accurate as the stock itself.

Fitment will tell the tale. Errors when we make any become cumulative, and sometimes the only trick that works is to be right.

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Sep 14 2012

Golden Ratio Calculator for Woodworkers

One of the most important tools in a woodworkers design arsenal is the Golden Ratio. It is the ratio that balances the long sides of rectangles, with the short side of rectangles, and as a ratio it can be used for either interchangeably as long as one leg length is known.

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The Golden Ratio , or Phi as it is commonly called is a ratio that is described as:
Phi= 1 + the square root of 5 over 2. (approximately the ratio of 1 : 1.618)

It has been used in design work going back some 2,400 years. It is still commonly used today for design in Architecture, Engineering, Furniture, Art, Publishing, even Web Design. It has even been found in Nature. If you would like to know more, the Wikipedia Article on the Golden Ratio is very good. A search engine will turn up even more information. Continue Reading »

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Apr 04 2010

The Care and Feeding of Granite Surface Plates in the Shop

Published by under Metrology,Sharpening

Granite Surface Plates are the world standard for flatness in any shop. There are a number of places you can get them and the pricing on these tools varies widely. It is important to note that for most of us, they needn’t cost more than necessary.

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There are a lot of great things to know about them, but there is one thing that is really important to touch on first off.

The grading of Granite Surface Plates is of importance to the woodworker. Please have a look Continue Reading »

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Aug 19 2008

The Foibles of Tape Measures. The Best, and getting the most from one.

For the average user of a retractable tape, there can be some usages of a tape measure that unwittingly reduce its accuracy. Basically, many people are not even aware of these details. I did say usages, but there are also problems inherent with the way a tape measure is made, that for fine work, render it a tool which is not always the best tool for the job. When we ask a tool to wear too many hats, it fails to do as well by us as we may think it should. It is good to know what some of the weaknesses are so we can learn to accept what are and are not good practices for the tape measure.

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It may seem funny to have thought about tape measures as much as I have. As a life long woodworker, and over 25 years of civil construction and surveying experience, I have literally worn out a bunch of measuring equipment from using these tools all day every day. After using tapes in dirty environments where I took well over 100 measurements a day, daily and weekly, I have learned what I value and what has risen to be the best for me. I am just sharing what I have learned with you.

When you are buying a tape measure, there are several available features that you can consider. For shop use, furniture making and cabinet making, you will rarely need a long tape, but the long tapes have features that enhance accuracy. They come with 1-inch wide tapes, which are easier to read for eye relief, harder to distort and are more rigid. Often the 1-inch tapes include more rivets on the hook, which lend themselves to resistance to wear and stretch. Unless you need a shorter tape for handy reasons, I recommend the bigger tape just for its added stability. Continue Reading »

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May 03 2008

The Challenges to Squareness

Yup. The Challenges to Squareness.

You didn’t actually think this was going to be easy did you? Well, it isn’t always, but I think the endeavor of overcoming some of these challenges can make things better, especially if you like taking good to great. Knowing what some of the issues can be, and how to overcome them when and if they arise, can help our results better match our desires.

We learned in The Constructs of Squareness article that geometrically speaking, a right angle is 90 degrees, and if it isn’t 90, then it isn’t a right angle. Everything can be represented perfectly on paper, in CAD drawings and in theory, but in building, milling, and manufacturing there are a number of factors, which can affect the quality of accuracy. Some we have to accept, some we can learn to work with, and knowing the difference is how we approach closer to fine, if fine is the goal.

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Things that affect the accuracy we use to build do vary. Goals, philosophy, materials and tooling all play a part.

Goals affecting accuracy are often production oriented, cost oriented, or what the intended use of a final product is. If the Goal is to build a doghouse, it needs done quickly, and the price of materials and labor needs kept low, then, the accuracy of squareness need only be relative. If the goal is to make a jewelry box, where scale is small and appearances will be highly scrutinized, then the accuracy of squareness becomes much more important, because the philosophy behind jewelry boxes is seeing how far craftsmanship can be taken. Close tolerance fit and finish is a very large part of how this type of work will be evaluated. Continue Reading »

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Apr 29 2008

The Constructs of Squareness

Published by under Layout Strategy,Metrology

The prevalence of the right angle in engineered structure is probably second only to the straight line in order of importance. Engineered structures in wood are often using plane geometry to help describe and document what they are and how to build them.

Much of the way we think about civil engineering, architecture, woodworking, and even some metalworking, call it flat work if you like, is based on previously understood, maybe even taken for granted, notions about geometry.

Every line that goes in a given direction without variance to that direction is straight, all points that lie upon a line, line segment, or ray can be thought of as congruent. At any point on a line, another line, line segment or ray can intersect, begin sharing a common end point, and create an angle.

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There are four ways we look at angles… The most basic angle is the right angle, the angle of 90 degrees, which when measured, corresponds to a quarter of the 360 degrees in a circle, or some thing other than a circle that circuitously begins and ends at the same point. The other ways we describe angles are of angles smaller than 90 degrees which are “acute” and angles larger than 90 yet smaller than 180 degrees, which we call obtuse. If the angle is greater than 180 and less than 360 degrees we call it a reflex angle. When working in terms of squareness, we are only concerned with the 90 degree, or right angle. Continue Reading »

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Apr 06 2008

The Utility of the Straightedge

Precision refers to the amount of dimensional accuracy or incremental refinement used when something is made, and can be attributed to the quality of the layout, workmanship, or machine set up.

Accuracy refers to the confirmation of dimensional tolerances.

Dimensional tolerances differ with the various types of projects a woodworker will commonly undertake. The set up of shop machines and precision hand tools often requires the precision of accuracy to be at the thousandth of an inch level, however most woodworking projects require accuracy at a level which is commonly referred to by fractions, and is often referred to in the 1/32nd (.031) to 1/64th (.016) range.

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The quality in our craftsmanship is inherent in our understanding of these constructs, and our personal stake in setting for ourselves, a level of tolerances. These tolerances are the differences between woodworking, and fine woodworking. Continue Reading »

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Mar 31 2008

Understanding Fractions, The Key to High Accuracy When Measuring.

Published by under Metrology,Skill Development

I want to have that little talk with you about, Fractions. Yeah. But the plan is, if all goes well, that it won’t hurt – as much as it did last time. Working in sub inch territory usually involves the use of little buggers. The problem many people have when working with fractions, is that they relate the use of the common fraction to their math education experience when they were in school as children.

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Our school systems scared the bejeezus out of everyone by forcing us all to learn a series of mathematical exercises, which evolved around fractions that we would never use again in our entire lifetimes. For many, this often created mental blocks to the entire notion of fractions, even the simple useful ones, because after that harrowing experience, it seemed that nothing pleasant could possibly come from the manipulation of fractions at all. In fact, when people are faced with dealing with fractions, they generally feel some panic along with it. A panic that rates up there with the sound of high speed dental drills and root canals, and it is most likely from their harrowing experience in math class. Folks remember what all the wonky practice of solving mismatched fractions was really like, and relate that it was way, way too similar, and maybe even the diabolical preparation, for diagramming English sentences later on during their high school education.

I hope I can help make this a lot more user friendly! Continue Reading »

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