Woodworker's Journal 2008-32-5, страница 68

Today's SHOP

Widely used by construction workers, tradespeople and DIYers, these are practical tools, subjected to job site conditions, designed for construction demands. One of the givens is reasonable expendability: Drop it off a roof or step on it and you shrug and just buy a new one. Their accuracy may be iffy and their scales a skosh coarse, but they work well.

A cast-iron head is essential for long-term accuracy, but it's more expensive to produce. The die-cast zinc head from a trade/consumer-grade square (right) is lighter weight and softer.

The heads usually are die-cast aluminum or zinc. The blades are stamped — graduations and all — from a blank, an operation that leaves burrs on the ends and even the edges. Typically, the graduations are 8ths and 16ths on one side of the

blade, 16ths and 32nds on the other. Having the most common scale on both sides obviates the need to turn the blade over.

There are variations at this level, but not accessories. If you want a longer blade, you can get a separate square with a 16"-long blade. But you can't buy just a blade.

The top category comprises premium combination squares manufactured primarily for metalworking. Brands include L.S. Starrett, Brown & Sharpe, Mitutoyo, PEC, SPI, and Fowler. Typical prices range from $75 for a two-piece square up to $170 or more for a four-piece set. Prices vary according to the specs of what you buy.

The high-end brands give you choices. Sure, you can buy a two-piece set off the shelf. But you can also specify the head (or heads) that you want, as well as the blade graduations, finish and length.

A square head can be cast-iron or forged-and-hardened steel. The latter is more durable and is often the preference of metalworkers. It's also more expensive — about $10 or so more. In a woodshop, the cast-iron head is just fine, and it'll be more durable than a die-cast metal head.

A lock bolt with a tabbed washer that slides onto flats ground onto the bolt and locks into the head is easiest to use. When the blade is removed, the bolt assembly drops — it won't fall completely out — and frees the tabs from the head, allowing the bolt to be rotated. You can do it without really looking. Lock bolts are used on Starrett and Rockier squares.

Depending on the woodworking you do, you can supplement the square head.

A center head is a V-shaped casting with ground reference faces inside the V. A slot for the blade aligns one edge directly in the vertex. A lock bolt allows you to adjust the head and lock it at any spot along the blade.

You use this head, as its name suggests, to locate the center of a round — a large dowel, for example, or a turned blank. Hold the reference faces against the round and scribe a line along the blade. Turn the round slightly and scribe a second line. The center is where the lines intersect.

Combo Squares:

Machine Tune-ups

You can check your table saw's table and blade alignment with a combination square. It's a two-step process.

Don't try woodworking without one!

Improve your productivity (and shop-time satisfaction) by keeping your woodworking machines properly aligned. A precision combination square is essential for periodic alignment checks and machinery tune-ups.

Check the flatness of your router tabletop with a long bladed combo square and a slip feeler gauge. This tabletop is dead flat.

Verify the set of your Jointer knives and the infeed and outfeed table alignment. Often overlooked, this task improves results.

68 October 2008 Woodworker's Journal