The Incredibly Versatile Sweep Brace
Bob Smalser, Seabeck, WA
>[quote][b]Here's an article we�d like (for Gaff Rig)�how to use a brace with a long ship�s auger, for instance, to bore through a deep keel at a slight angle without the hole breaking through the side. For most of us, the problem is holding the brace and bit true so that our drilling is straight�a lot of folks would like to use hand tools, if only someone would show them how.[/b] Regards, Jim. [/quote]
My pleasure, Jim. I can�t think of a more multi-purpose tool than the ratcheting, reversible sweep brace, once present in almost every household�and because of that, nice ones are often under 10 dollars today complete with bits. Boring clean, accurate holes with ease, taper reaming those holes, screw driving and countersinking, cutting round tenons, and pointing spokes, the brace still holds a prominent place in the tool kits of chair makers and boatbuilders today because it still does some tasks much, much better than machines.
Braces came with different patented chuck designs and ratcheting mechanisms, and in different sizes and configurations. The most common sizes available have 6-inch sweeps, 8-inch, 10-inch, 12-inch and even 14-inch, the 10 being the most common. They are so inexpensive today, that there is no reason not to have two or more in play for a given task rather than bothering to change bits. In addition to an 8 or 10-inch, a larger 12 or 14-inch brace is handy for those occasions where more torque is required. So is the joist or right-angle brace for use in confined spaces.
Shown are some varieties of chucks commonly found, all of them with two spring-loaded jaws. The Stanley joist brace on the right has a chuck that comes off with a setscrew, but the others just screw off. The late model Miller Falls at center left is the beefiest design. The unmarked one to its right has lost its spring, and I�ve fabricated a replacement from music wire. The 2-jaw chucks are designed for 4-sided augers and accessories, but also work reasonably well with modern 8-sided screwdriver bits in longer lengths. Today, there are boatbuilder suppliers who carry magnetic bit extensions for the brace designed to hold those interchangeable, quarter-inch 8-sided bits.
The lead screw auger bit still has a place in modern shops. A low-friction design that pulls itself into its own hole, little pressure is required to bore even the deepest holes, and combined with the short joist brace offers options for tight spots not available elsewhere. It�s also the easiest tool to sharpen in the shop. A tapered auger file is used to put an edge on the inside (never the outside) lips that serve as nickers�
�and both main cutting edges of the bit.
I�d prefer to show Jim some examples of use in boatbuilding, but I don�t happen to have a boat in the shop this fall. I do have a custom concert stool of Bigleaf Maple I�m making for a choir director with a bad back, however, and if y�all don�t mind, it�ll demonstrate some capabilities of the brace even better.
Nothing out there bores an angled hole single-handedly as well as the brace, because it is slow enough to make corrections as you go and still result in a clean hole. Sure, I�ve also done plenty with long bell hanger�s bits in electric drills and a helper sighting from one side while I both drilled and sighted from the other, but like all conventional machine bits, there is always the risk of the bit wandering in inconsistent grain and the exit hole not being perfectly centered. That�s not as much of a problem with an auger, either used by hand or power�and the older, used Irwin and other maker�s bits designed for the brace and a bit extension are much easier on the wallet than a new ship�s auger. The bit extensions designed for the brace take some searching, as many antique tool dealers don�t know what they are�but because of that are equally inexpensive.
Here I�m using 8� and 12� bevel gages as indexes to bore a hole angled for 6 degrees of splay on one side and 11 degrees of rake on the other. I�m using the larger 12-inch brace for power. You can also see penciled sight lines based on the resultant angle of rake and splay� 5-dollar words that mean besides the bevels, I also align the centerline of the brace up with a separate line laid out on the work piece specifically for that purpose. You can do the same in other situations by tacking a batten or yardstick to the workpiece to serve as an index. I simply run the lead screw in my center-punched mark until the nicker lips bite, take my angles, and bore until the lead screw protrudes slightly from the opposite side of the work piece, sighting down my pencil line as I am boring and stopping occasionally to double check my accuracy using the bevels.
Then I flip the workpiece, circle my lead screw holes with a pencil so I don�t goof and begin in the wrong place, and counter bore using the bevels to achieve the same angles so as to make a perfectly clean hole with no chip out.
Next I use a tapered chair maker�s reamer to ream the holes for mating with the tapered, round, wedged tenons, using the same care to keep the angles correct as I used when boring the holes. These reamers generally have two identical cutting edges, and are used both clockwise and counter clockwise to even the wear on those cutting edges. These tapered and wedged round tenon joints are self tightening, allowing air-dried wood to be used for the legs so that cooked, dryer wood can be used for the stretchers�also self tightening as the air dried legs shrink when brought into central heating.
The tenon cutter acts as a rotary plane to quickly turn a spoke shaved stretcher end into a uniform round tenon that fits its bored mortise.
Continued�
