Woodworker's Journal summer-2009, страница 55

Woodworking Math Geeks

"measure twice, cut once"...even in its traditional sayings, you see how important math is to woodworking.

Woodworker's Journal readers can

be counted on to show off their math skills.

Screw Sizes: The Easy Way

There's a very easy way to figure the outside diameter of all screw sizes. The magic number is 13. If you multiply the screw size by .013 and add .060, you get the outside diameter.

Example: the #4 screw is .112 diameter. By multiplying 4 x .013 = .052 + .060 = .112 diameter.

You can find out any size of screw by using this method.

Ron Pavelka, Orange, California

An Eye on the Golden Ratio

Aw, come on, Ian! Although I can't measure accurately from the pictures, doesn't your design

A reader thought Woodworker's Journal author Ian Kirby's "Wall-Hung Bookcase" involved more math than revealed.

of "A Wall-Hung Bookcase" approximate the Golden Ratio — rather than simply being a "shape" to accommodate cookbooks between two windows? If we approximate the top two areas as 4.5 units and the bottom area as 2.75 units - for a total of 7.25 units — the Golden Ratio would suggest 7.25, yielding 4.5 units and 4.5 units yielding 2.8 units. Aren't we really dealing here with the eye of a master woodworker not allowing himself to build to "bad" proportions, regardless of the space between the windows or the size of cookbooks?

Rich Donahue Huachuca City, Arizona

Striking a Plywood Nerve

A plywood manufacturer producing millions of sheets a year has strict controls and produces sheets which are deliberately 23/32" thick, not 3/4". I still want to know why!

Nigel Bond Getzville, New York

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60 Math Geeks