Posted by
Easy WoodCraft on
Mar 14, 2016
Trammel points (also called a beam compass) come in handy when you need to draw a large diameter circle or arc. Trammel points are a set of steel points that can be mounted on virtually any length beam, as long as it's straight. The heads are held in place by tightening a knurled knob on top of each trammel point. Some versions include an accessory head that accepts a standard pencil, in case you'd prefer a pencil line to a scribed line. Bridge City Tool Works (
www.bridgecitytools.com) manufactures a gorgeous tool (
inset) that features a beam with a built in metal rule.
Basic use
Just like the panel gauge, trammel points require two hands for use. One hand holds one trammel at the pivot point, while the other hand moves the opposite head in a graceful arc or circle to mark the work piece. Keep the points razor sharp and you'll need to apply only light pressure to mark your work piece.
Stick trick
If you don't own a set of trammel points and need to draw a large diameter arc or circle, try this crude but effective substitute. Simply drill a pair of small holes the desired distance apart in a thin stick. Use an awl or a brad to temporarily hold one end at the pivot point, and insert a pencil or awl in the other hole to scribe or mark the arc or circle. Naturally this isn't anywhere near as accurate as a good set of trammel points, but it'll do in a pinch.
LARGE ARCS WITHOUT TRAMMELS
Sometimes, you may find that you need to draw a large arc that exceeds the ability of your trammel points, or that would require a really long beam, or you just don't have trammel points. In cases like these, try one of the variations of the old "bent stick" trick described below.
Bent stick
The boat builder adage "If it looks fair, it is fair" certainly applies here. Just grab a thin strip of wood that's long enough to create the desired arc, and have a helper flex the stick from start point to finish. Once the desired arc is obtained, draw along the wood strip with a pencil to mark it on the work piece.
Plexiglass strip
One disadvantage to using a wood strip is the grain of the wood can and will affect how the strip flexes often in an uneven arc. You can get around this if you've got some thin plexiglass handy. Since the plastic doesn't have any grain, any arc you flex in it will be perfectly smooth.
Clamp trick
It never seems to fail that whenever I need to use a bent stick to draw an arc, there's nobody around to help. When this occurs (and the arc is small enough), you can use a pipe clamp or bar clamp to flex the stick. This leaves your other hand free to transfer the arc to the work piece.
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