Razor-fine layout lines
Buying a Marking Knife
Does it make sense to measure to 1/64", and then mark a line with a pencil point that's twice that width? Even a fine mechanical pencil proves no match for the precision of a marking knife. Here's what you need to know before buying one.
- We show a dedicated marking knife in these photos, but you can, in most cases, get good results using a utility or craft knife. However, beware that those knives' thin blades might flex and stray from your intended layout.
- You can buy individual left- and right-handed knives, as shown top right, or a knife with a dual-bevel blade below right. All have a flat face on the blade opposite the bevel, letting you place it tightly against a straightedge or mating workpiece for a precise mark. The left- and right-handed knives tend to have larger handles, making them easier to grasp if you have large hands.
Learn the basics first
•: Sharpen your knives on a fine-grit stone or sandpaper by simply pressing the bevel against the surface and dragging back and forth a few times. Remove the burr from the flat side by making a couple of passes on the abrasive. It won't take long to put a keen edge on the knife.
•: You don't need to score deeply, just enough that a chisel or handsaw will seat in the kerf. With coarse-grained woods, such as oak or ash, the marking knife might follow the grain rather than your straightedge. To avoid this, make the first scoring pass lightly, and follow with successively greater pressure, deepening the kerf.
Here are some examples of when a keen marking knife will leave a pencil looking dull.
A mortise-and-tenon joint requires a precise fit to be strong and attractive. To lay out a mortise, as shown on the table legs above right, first mark the mortise sides with a marking gauge. Next, mark the top and bottom of the mortise with a marking knife and a square. Once you've got a mortise located on one table leg, use it to lay out the mortise ends for the other legs. Simply clamp the legs together and grab a square to transfer the lines. You can also use your marking gauge or knife to mark the shoulders for the tenons on the mating workpieces.
Sizing up project parts
Marking knives help you precisely transfer measurements when marking parts to size. For example, marking a piece of solid-wood edging to match a veneered panel, as shown right, gives you an exact fit. You can do this with any project part that must be cut to fit an existing opening or when making story sticks, templates used for marking and transferring measurements.
After scoring the pin-socket depth with a marking gauge, use a knife to define the tails.
Use your already-cut tail board to now mark the locations for the mating pins.
You enjoy two advantages when laying out dovetails with a marking knife, as shown right. First, you get the greater precision of the knife's keen edge, resulting in a better fit. And when you begin cutting the pins and tails, your chisel or handsaw slips into the knife-cut kerf for straighter, cleaner cuts.
Single-bevel marking knives: part #33N07.01 (right-hand bevel); #33N07.02 (left-hand bevel); $31.50 each, Lee Valley, 800-871-8158, leevalley.com.
Dual-bevel marking knife: part #885-2154, $50, Traditional Woodworker, 800-509-0081, traditionalwoodworker.com.
Dovetail markers: part #05N61.04 (6); #05N61.05 (8); #05N61.08 (14); $12.95 each, Lee Valley, 800-871-8158, leevalley.com.
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