Layout Basics I Ne

Layout Basics

By James D. Thompson

December, 2005

I. Connecting two points .................................................................................2 II. Erecting a perpendicular .............................................................................5 III. Compasses and lead .................................................................................10

IV. Bisecting a line ...........................................................................................12

V. Constructing a hexagon ...........................................................................13

VI. Making equal parts..................................................................................15

VII. Constructing 4 or 8 parts of a circle..................................................18

VIII. Centering Stock for Turning................................................................21

© www.OldToolsShop.com 1 January 14, 2006

I. Connecting two points

Remember as you read this that I make no claim to be an expert. I am simply a competent journeyman, and the methods I use are my own. Others may use different methods, and those are probably as good as mine.

I was taught most of my basic layout in the late 1950’s by a journeyman Millwright who was dirty, smelled badly, and was constantly spitting tobacco juice on everything and everybody near him. He was almost illiterate, and spoke like an illiterate, and cursed constantly. His only saving grace was that he knew what there was to know about layout, and was willing to teach me. I will always be grateful to him for the knowledge he imparted to me. His teaching was the basis for me learning more advanced layout later and earning my living doing layout work. A good portion of the pipe in the mammoth California Water Project was laid out by me.

Layout is accomplished using one or both basic methods: Centerline layout and/or baseline layout.

In centerline layout the center of the object is found and a line is drawn through it, usually vertically. A horizontal centerline is also often used in conjunction with the vertical line, or alone. Measurements are mostly made from these 2 lines.

In baseline layout a base line is established, usually on or along one edge of the object. Another baseline can be established, usually at the end of the object, and this line is usually perpendicular to the first baseline. Measurements are mostly made from these 2 lines.

Notice that I said, “mostly made” from these lines. You can use any combination of base lines and center lines to get the job done. There are no hard and fast rules, just guidelines that you may or may not choose to follow.

Lets take a look at a few simple layout methods.

One of the first things I always tried to teach my apprentices was how to connect 2 points with a straight line. Here they are points A and B.


The first thing to do is put your pencil point on one of the points as shown below.

Bring the straightedge up to the pencil, and then use the pencil (or scribe) as a pivot point to move the straightedge to the second point.


Then draw the line.

I have watched many apprentices trying to align the straightedge with both points at the same time, without using the pencil for a pivot, and it is always a struggle. This way is quick and accurate.


II. Erecting a perpendicular

Here is how I establish a square line at the end of a line without using a square. I learned this when I was laying out large steel plate. The ends of a large steel plate are rarely square, so a square line has to be established near the end. A framing square is not large enough to draw a line all the way across a 12’ wide plate.

You, of course, are not going to lay out any large plate using this method. And on most of your work you will simply use a square. But you can impress people at parties by showing them how to do this. It is pretty cool, and if you can do this you can say that you can do your entire layout without a square.

Draw a line parallel to the side of the plate or other work.

Set your compass or divider at any convenient distance. Usually this will be slightly less than half the distance across the plate. Swing an arc back across the line.


Here is the arc.

Using the same setting on the compass, swing an arc to intersect the first arc.


Draw a line of indeterminate length through the 2 points. Indeterminate length means longer than necessary.

Still using the same setting on the compass set off another point on the line.


Draw a line from the starting point up through the last point you established. This line is square with the base line.

PS

I received a post from John Lederer showing me another way to erect a perpendicular at the end of a line. Take a line A--B.

Place your compass center above the line, and draw a circle that intersects the line at A and at arbitrary point D. Now draw a line from D, through the center of the circle, till it intersects the circle again at point E. From E to A will be a line at right angles to A-B.


Just goes to show that you are never too old to learn something new.


III. Compasses and lead

A word about compasses and lead. This probably should have been the first page of the series.

There are a great many different types of compasses and dividers. This picture shows one of my sets. The tool at the bottom right is for making very small circles.

Lead comes in packages as shown above. It is available in a wide variety of hardness’s. I use HB which is pretty soft. I break off a piece about an inch long and put it in the compass.


The convention is to sharpen the lead on the inside only. A piece of sandpaper on a flat surface works great. It is necessary to sharpen the lead quite often for best results.

If you always sharpen the lead on the inside you will always be able to come back to your layout after sharpening without having to readjust your compass. It is just a timesaver.


IV. Bisecting a line

One of the most basic things in layout is bisecting a line. This simply is a way to find the center of a line, or anything else for that matter.

On line A-B, set the compass to any distance greater than half the length of the line. Then using both A and B as centers, swing intersecting arcs above and below the line.

A line drawn through the intersections will cut line A-B exactly in half.


V. Constructing a hexagon

Another basic layout procedure is laying out a hexagon.

Draw a circle of the desired size and then draw a centerline. With the compass set to the radius of the circle, swing arcs both ways from both the top and bottom intersection.


Now connect all the points on the circle and the result is a hexagon.

If the centerline is drawn vertically, then the hexagon will have a point on top. If the centerline is drawn horizontally, then the hexagon will have a flat on top.


VI. Making equal parts

Another basic layout technique is dividing things into a number of equal parts. This can be quite frustrating when done any other way.

Let’s say that I want to divide this page into 6 equal parts. I ask myself what numbers can be divided by 6. And the answers are 6, 12, 18, 24, and so on. So now I check to see which of these numbers of inches will fit diagonally across the page. In this case 12 inches works. So I divide 12 by 6 and get 2. That means that the equal divisions are 2” apart on the measuring rule. So I mark every 2 inches.


Now I use a square to draw lines through each tick mark I made along the rule. Thus the page is divided into 6 equal parts. No fuss, no muss, no bother! :>) (This is one of the few times when a square is essential.) Ah, but what if the number of divisions is an odd number? Well, then you are just out of luck! No! Just kidding! If you want 5 equal spaces, just ask what numbers are divisible by 5. They are 5, 10, 15, and so on. Use the one that will fit across the page on a diagonal. If 10” will fit, then the marks will be 2” apart on the rule. If 15” will fit, then the marks will be 3” apart on the rule. December, 2005

The numbers don’t have to come out as even numbers. Here I want to divide the width of the page into 10 equal parts. But 20 inches will not fit in the distance across the page.


Oh, me! Oh, my! What will I do? I cannot spin the straw into gold! Oh, yes I can! 1 1/2 inches times 10 equals 15 inches, and 15 inches will fit diagonally across the page. Sometimes you have to put on the thinking cap, but this method always works. Measuring using metrics makes this method even easier.


VII. Constructing 4 or 8 parts of a circle

This one is a double feature because one leads into the other. A couple of years back I read in the Tips and Tricks page of a magazine a tip from a reader who had discovered a very complicated way to lay out 12 equal spaces on a circle. He was using 2 framing squares to accomplish this. His ultimate reason for doing this was that he wanted to make a clock face. I was flabbergasted at the complexity of the process, so I wrote in with my solution which is shown below. I received a check for $100 for my effort.

Draw a circle of the required size and draw a centerline through it. Set your compass at a distance approximately the diameter of the circle.


Swing intersecting arcs from both intersections in both directions.

Draw the line which is now the horizontal centerline. The circle has now been quartered. That is the first part of the solution.


Now set your compass to the radius of the circle. Swing arcs on both sides of each intersection. The result is a circle divided into 12 equal parts. Logic tells you that if the radius can be used to lay out a 6-sided figure, that it must also be able to describe a 12-sided figure. So what would be the result if you were to divide the circle into 8 parts?

(Old trick for getting the apprentices to do something for themselves.)


VIII. Centering Stock for Turning

There are several devices for sale which are supposed to help you find the center of a piece of stock that you want to turn in your wood lathe. And they work just fine, as long as the stock is round or square. But usually the piece I want to turn is NOT square or round. It is likely to be almost any shape. Like the piece shown below.

So how do I find then center of irregularly shaped stock? I use a pair of dividers.

I set the dividers to an approximate size and put one leg on the approximate center.


Then swing the divider to another side. Then check all 4 sides and adjust the divider until you have found the largest circle you can draw. Push the divider leg into the wood to mark the center.


Now draw the circle. I do this on both ends of the piece. If there is a defect or damage to the wood I can often move the center on one end to avoid it, particularly on a handle where one end is going to be small anyway.

Now I double check to make sure the stock is big enough for its intended use.


I use a center drill on the tailstock end where I normally use a live center. (A live center is one which has bearings inside and spins with the stock. A dead center does not turn. ) On the drive end of the wood the mounting method depends on how I intend to drive the piece, but I always have to have at least a small, shallow hole drilled for reference. I bought and made several different devices for this, but in the end I found that my trusty dividers are easier and more certain than any other method. As always, your mileage may vary.

January, 2006

© James D. Thompson

© James D. Thompson


Layout Basics I Ne

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