June, 2009

Finding Center the First Time

Problem solving with construction calculators. Part 2.

By Gary Katz

When I was a kid people used to say: “If I had a nickel for every time I’ve….” Today it’s a dollar. And every dollar counts, especially in a recession. Builders spend countless hours on layout tasks, from decorative walls and ceilings, to stairs and built-ins. Using construction calculators not only cuts layout time to a fraction, they ensure precision, which eliminates corrective work down the road. Construction calculators also protect attitude—a critical component to any well-run operation.

In the last article on Conquering Cumulative Error, we looked at wainscoting layout. With wainscoting, there’s always one more stile than there are panels—that’s because wainscoting always starts with a stile and ends with a stile. But for bookshelves, because we determine layout by the inside dimension of the bookcase, there’s always one more space than there are shelves. And subtracting a space doesn’t help solve the problem. The solution is adding a shelf.

For a bookcase that has an interior opening measuring 785⁄8 in., add 3/4 in. before calculating the shelving layout. Enter 793⁄8 INCH into the calculator, then press the M+ button. If you want the shelves landing close to 12 in. on center, press the ÷ key, enter 12 INCHES, and then press the = key. The quotient, or result, is 6.614583. Well, you can’t have  a fractional number of shelves—they only come in even numbers. To guarantee 12-in. spacing, round that number down to 5; if having 12 in. between shelves isn’t as important as gaining one more shelf, round that number up to 7. Do the math by pressing the clear button once (On/C), then press Rcl and M+. That will bring up the original inside dimension of the bookcase, including the additional shelf. (To clear the memory, you must press the RCL key twice!)

For a closer look at the exact spacing, it’s easy to run the numbers. Hit the ÷, then press 5 and the = key. The result is 157⁄8. That’s significantly more than 12 in. o.c. Clear the display and press Rcl and M+, then enter 7 and press =. The result is 115⁄16. Remember, the 3/4 in. shelf is included in that dimension, so the spacing between shelves would be 109⁄16 in.

To layout the shelves, hook a tape measure on the outside of the bottom shelf. Mark the first shelf location at 115⁄16 in. (if the tape measure is hooked on the bottom of the bottom shelf, the layout marks will always be at the bottom of each shelf).

Direct the calculator to add the quotient to itself by pressing the + key once, then press the = key. The second layout location is 2211⁄16. From that point, don’t press the + key again, just keep pressing the = key for each succeeding shelf location. All of the shelves will be laid out precisely the same distance from each other—the first time. Think of all the time and frustration you’ll save by not having to draw little circles around your layout marks, then squares, then triangles, then….

In the next article, I’ll cover laying out stair balusters, which can save you some serious money.

GARY KATZ, with nearly 40 years experience in the industry, has been a frequent contributor to leading trade journals for more than a decade. He produces the Katz Roadshow- Carpentry Clinics at lumberyards all over America, and publishes THISisCarpentry.com— an E-magazine for carpenters and craftsman. To learn more, visit: www.GaryMKatz.com