A gift as precise as the work.
The trammel head without the cursor is always the pivot point (the point you use as a center for your arc), this is the pivot trammel. The trammel with the cursor is always the scribing point, called the scribing trammel. Loosen both trammel points. Lock the scribing trammel head at exactly four inches on the trammel bar rule. Place the scribing trammel point at the FIVE INCH mark on your six inch pocket rule. Now slide the pivot trammel point to exactly the ONE INCH mark on your 6" rule and lock in place. You have just calibrated the PT-1 Precision Trammel Set to exactly four inches. (This technique avoids using the end of the rule, which is bad practice.) As long as you do not change the pivot trammel setting, all future settings of the scribing trammel are accurate. Anytime you sharpen the points, use a pencil, or change the pivot point setting, you will need to recalibrate the scribing point ifyou wish to use the trammel rule. For those of you using the metric side, repeat the above process using a 10cm spread of the points.
For extremely accurate work, you will need to minutely adjust the scribing trammel. Because the tool is calibrated to the trammel bar rule, simply adjust the scribing point using the rule as a guide. It is very easy to adjust this head in 1/64" increments. Loosen the scribing trammel slightly and nudge the trammel head forward with your thumb until the scribing point is exactly where you want it. Unless you are working on the Hubble Space Telescope, you will never need this kind of accuracy in wood. We had a design for an adjustable point, but rejected it because this design is simpler and easier to use. Plus, you always have the satisfaction of knowing the exact radius of your arc or circle.
Tables, chairs, wheels, graphics, geometry development, including pentagons, hexagons, and octagons, are all vastly easier with a trammel set. Add a second scribing trammel to layout precise parallel lines (arched window frames, for example). You can also use a trammel to check the accuracy of a glued-up carcase. Remember, measurements across diagonal corners in any square or rectangular shape will be the same only if the corners are square. The PT-1 Precision Trammel Set can be a very effective way to accurately determine case squareness during assembly. Other uses include accurate step measurements where you need an index mark repeated evenly along a straight line.
This item is no longer in production and is not available for purchase. It is listed here for reference purposes only. The last known published price is listed below.