A carpenter is only as good as his scribing tool.
Scribing is an important part of any installation job and one that requires precision. After being frustrated with inconsistent results from using a standard compass and pencil, I thought that I must be able to make a better scribing tool. Read the following tips to complete the perfect scribe or learn how to make your own scribing tool.
The scribing tool must be accurate
The device that I came up with is made from a few pieces of scrap maple and some brass fittings from the hardware store. My shop-made scribing tool uses a short Sharpie marker that friction fits into a 3/8” diameter hole. The broad face of the reference leg allows you to follow the wall, ceiling or floor and maintain the marker perpendicular to the reference surface. That was one of the major shortcomings that I found with a standard compass as it tends to wander from perpendicular giving you inconsistent results. My scribing tool also features two pivot points which gives you greater flexibility in adjusting it and allows you to offset the marking plane from the reference plane if need be. The reason for using a marker rather than a pencil is twofold. A marker never needs sharpening so it will always mark consistently unlike a pencil that changes as the lead wears down. The second reason is that it is permanent and won’t rub off or smear like pencil will.
Scribe on the tape
I use green painters tape along where the scribe line will be marked. Using tape prevents unwanted marks on the finished surface as well as giving a cleaner cut in some materials. The green color provides a good contrast with the red marker making it easier to see your cut line. A scribe line that is barely visible is a hard thing to follow accurately with your saw.
Cut & tune the scribe line
Cutting the scribe line with a back bevel makes it faster and easier to make any adjustments that are necessary after fitting the piece. Staying to the waste side of the scribe line when cutting gives you some extra material to work with when fine-tuning the fit. A block plane set for a fine cut makes short work of this. Staying to the waste side of the scribe line also keeps your line intact so you can see where you are. If you remove the line completely you no longer have any reference. Once the piece has been fine-tuned, remove the masking tape and you have a clean, crisp scribe that is a perfect fit.