This month's topic is compasses, calipers & marking gauges. These handy tools can be as simple as a child's compass, or as complicated as a rosewood & brass multi purpose, marking gauge. Whether simple or complex they are all used for the same purpose, to transfer measurements. They also do this with less error than using a ruler or tape measure and marking pieces separately. A fine point leaves a much thinner line than a pencil, which means more accuracy.

Compasses can be used not only for drawing circles but also for transferring shapes & sizes as well as scribing. A simple pencil compass is very useful. They are great for marking any project where you want to round off the corners, or if you need to scribe a cupboard or counter top to a wall. In building log homes they are used to transfer the curve of the log in order to carve the saddles. If your kids are finished grade school, find their old pencil box and snitch the compass. You'll be surprised how much you end up using it.

Trammel points are closely related to compasses. They are made up of two clamps with sharp steel points, one of which is often removable to accept a pencil. They are usually clamped to a ruler, yardstick or any piece of wood, which is the right width but can be any length. They are best for marking large radius circles or transferring a measurement. A basic use would be round tables, but they are also essential for marking out curved cabinets or furniture. An often-overlooked use is checking the diagonal measurement of boxes and drawers. You set the points to one diagonal and then compare to the opposite. If they don't match your box is not square. This is much more accurate than using a tape measure because of trying to hold the tape to the corners evenly.

			Calipers are similar in looks to a compass but instead of a pencil, they only have steel points. They normally have three different arm shapes, curved inward (outside calipers), curved outward (inside calipers), or straight (dividers). They are not used so much in marking but mainly in transferring measurements. All three are very useful in woodturning, like laying out and sizing spindles and for checking the wall thickness of bowls, plates and vases.
Outside Caliper	Inside Caliper	Divider

Marking Gauges & Bevels

	Gauges and bevels can be made of plastic, wood & brass or steel. They will all do the same job but some can take more abuse and will last longer than others. The only advantage for the plastic ones, other than price, is that they will not rust if used outdoors. Marking gauges all have the same basic structure. They have a shaft with a sliding fence and a pin or blade set at one end. The shaft may or may not be graduated and the fence clamps to the shaft usually by a knob or screw. The majority of gauges use a sharp steel pin to make the mark but some have a sharpened steel blade. The blades tend to leave a cleaner mark as they cut the fibers instead of scratch them. They can also be used to cut thin veneer or even small rabbets in softer wood. A third version has a single point on one side and a two one the other. The single point is used as a standard marking gauge, the other side is used for laying out mortises. The outside point is fixed in place and the inside one slides to adjust to the mortise width. The fence knob locks both in place when set. One thing to keep in mind with marking gauges is that the points tend to follow the grain of the wood. Make sure you run the gauge so the direction of the grain is running away from the fence.

Sliding bevels have a body of plastic, wood or steel and an aluminum or steel blade. The blade has a slot in it and attaches to the body by a lock nut or knob. The blade pivots to any angle and is excellent for transferring angles, especially from existing furniture or material. They were also traditionally used in marking dovetail angles. When buying a bevel, check that the locking mechanism secures the blade snuggly. You don't want one, which will change angles with only slight pressure.