Framing Square Octagon Table

How to use the Octagon Table found on a framing square.

The "Octagon Scale" found on a framing square, also referred to as the eight-square scale is found along the center of the framing square tongue as shown in our photo below. Using this \scale you can frame any eight-sided structure or polygon.

This article series explains how to make quick use of a framing square and its imprinted data to get some basic roof measurement data like roof pitch or slope, rafter lengths, and end cuts, stair

Octagon Scale on the Front of the Framing Square Tongue

Multiples of 5 on the octagon scale

The octagon scale on the front of the tongue of some framing squares (including the Empire Level framing square illustrated here) is used to lay out an eight sided shape or figure.

You will recognize this scale, if it's on your framing square, by noticing that it counts up in multiples of 5 with dots between the octagon scale markings.

Our photo below shows the unit-5 octagon scale on an Empire Level framing square.

Both entire homes and more-often towers or turrets are sometimes framed in an octagon shape while other structures use octagonal shaped timbers and beams that were cut out of square stock.

Interestingly Empire's own "Rafter Book" is silent on using the octagon scale.

We did find an explanation of using the octagon scale at free-ed.net from which we excerpt and paraphrase below.

SeeReferences or Citations for the full citation.

To use the octagon scale to lay out an octagon we start working from a rectangle whose equal sides are of length L.

Measure to the center of each side of the rectangle and place a center-mark there.

[Click to enlarge any image]

Draw a straight line through each pair of opposing center marks on your rectangle so that you have a cross dividing the large rectangle into four smaller squares.

How to Use the Framing Square to Cut Stock into an Octagon

To use the octagon scale on the framing square to cut stock into an octagon, use a pair of dividers whose ends are set apart a distance equal to the number of dots on the octagon scale that corresponds to the original length of the side of your starting rectangle.

One leg of the dividers is placed on the starting line on the octagon scale and the other leg of the dividers is placed on the nth dot that corresponds to the original rectangle side length.

1. The dividers are then used to lay out their spread distance on each side of the rectangle to give the cut points or marking points of an octagon as follow:
2. Place one point of the dividers on the end of the center line at the edge of the rectangle.
3. The other point of the dividers will mark the first octagon cut line.
4. Repeat this process for each of the other ends of the center lines of the rectangle to mark all of the other cut points of the octagon on the end of your timber or stock.
5. Repeat this entire process, steps 1-4 above, on the other end of the square stock
6. Draw lines along the sides of your square stock connecting the corresponding octagon cut marks that you made on the stock ends.

Because the octagon scale on the framing square does not extend past 16" (the length of the tongue), what good is it? It's used to mark the cut lines on square stock that you want to trim into an octagonal shape. Examples of octagonal stock appear as decorative posts and beams.

At the end of this article atReferences or Citations you'll find more texts and articles on using a framing square and written by other experts.

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Continue reading at FRAMING SQUARE USER'S GUIDE or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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