Got some scrap wood? Need a marking gauge? This instructable will describe the process of making one from the other. Which is which is left as an exercise for the reader.
"What is a marking gauge?", you ask. Well, gentle reader, a marking gauge is a tool that woodworkers use to put nasty lines all over their projects so that other woodworkers can see them and nod in appreciation of the fine craftsmanship. If you find that you need to scribe a line parallel with an edge, such as when cutting joinery, dimensioning stock to thickness, or showing off to your neighbor, then a marking gauge is the tool to use.
Step 1: What You Need
I'd like nothing more than to wax philosophical about our metaphysical properties, but this is an Instructable, and, as such, requires "stuff". Here are the thing you'll need.
- Safety glasses
- Two dowel scraps of different diameters. I chose an oak dowel at 3/4" and a poplar dowel at 3/8"
- A scrap block of wood
- A Scrappy-Doo coloring book. Just kidding
- A drilling tool, such as a drill press, bit brace, oil derrick, or electric drill
- Drill bits the same diameter as your dowels
- A clamp
- A sharp chisel
- A pencil
- A nail (not pictured)
- Sandpaper (not pictured)
Step 2: Anatomy of a Marking Gauge
Before building a tool, it helps to know what the parts are and how they work. Nothing is more embarrassing than building something and then realizing "Hey, that's supposed to move!" Examine the image and follow along with this narrative and we'll explore this tool together.
The longish part (which we will make from the 3/4" dowel) is called the "stem". The scrap block of wood will be transformed, by your skilled hands, into the "stock". The stem goes through the stock, perpendicular to the broad face of the stock. At one end of the stem is the "spur". Giddyap! The spur is the bit that will make the mark on the wood.
This marking gauge employs a dowel with a bit of a inclined plane carved into it. This dowel locks the stem in place when the position has been satisfactorily set. In fact, it will lock it into place even if the stem is NOT satisfactorily set. This design not only allows the marking gauge to be made with simple tools and parts, but it also makes for a micro adjustable tool; just bang it against the bench until you get the desired dimension. Try doing that with a $60 marking gauge!
Step 3: Marking the Stock for the Locking Dowel
You need to make some marks on the stock. It would be handy to have a marking gauge for this, but you would probably be building this because you don't have a marking gauge. What a predicament! It's like the whole "which came first, the chicken or the barber that cuts the town's hair" thing or something.
First thing to do is get your scrap wood for the stock pretty square and flat. There are several ways to do this. Because the piece I had was small, I used a jack plane to get everything set. It probably took me about a minute. Doesn't have to be perfect. If you use power tools to face the stock, then please use appropriate clamps and push sticks.
First, let's mark the line that will define where our locking dowel will go. Use your combination square and a pencil to scribe a line across the face, slightly more toward the "top" of the stock than to the bottom. Use your combination square to transfer the line across all faces and edges.
Step 4: Drill the Holes
You might have guessed it. You need to drill some holes now. The first hole to drill is the one the goes from edge to edge. The 3/8" dowel will go into this hole. I would recommend drilling a test hole to see how well the dowel fits. Sometimes the tolerance on store bought dowels isn't as accurate as you may need, so you may need to sand the dowel or choose a different bit.
I used the drill press for this. Drill on the line, about right in the middle of the edge, all the way through. If you're off the line, it's not a big deal. Just be sure that if you're posting instructions online on how to make this device, remember to make fun of the fact that you goofed a bit so people don't realize you have no idea what you're doing.
Once that hole has been drilled, change bits to the one you will need for the larger dowel (in my case 3/4" Forstner bit) and drill through the face of the stock. You don't want to drill right on the witness line, because it's against the bylaws of your homeowner's association. Instead, drill about 1/4" away from the line. Drill straight through. It is important that this hole is perpendicular to the face. If it's not, the gauge will operate a little funny, which may be a quirk you're willing to deal with, but really this shouldn't take long to do over.
Step 5: Cut the Tensioning Dowel
Okay, place the smaller dowel in the hole and push it through until about a half inch sticks out the other end. Use a pencil and mark the edge of the large hole onto the exposed part of the dowel. Cut out a notch the side of the marks. Don't worry about making it round. Just the the sides cut and the notch to the proper depth.
After cutting the notch, put an incline on one side using a chisel, preferably the side that has more material. There is no particular angle to use. I think this was at about 20 degrees.
Replace the tension dowel into the stock and put the stem through the stock. Make sure it fits. Don't force it through or you'll blow out the back. So I've hear *ahem*. Once it's in, push the tension dowel so the incline engages the stem. It should get a pretty good hold of the stem at this point. You're almost done! Huzzah!
Go ahead and cut the dowels to length at this point. The stem I cut to about 8", the tension dowel is about 3", give or take 3.74 centifudgeits.
Step 6: Refuel the Manufacturing Machine
Mount a standard sized bowl of ice cream to the workbench and apply to the main manufacturing machine in the typical style. THIS STEP IS CRITICAL! Failure to refuel at this point may result in complaining of fatigue and snarky comments from a spouse.
Step 7: Adding the Spur
Drill a small hole in the end of the stem. This hole should snugly accommodate a nail of your choosing. Use a file to bring the nail to a very fine point and drive it into the hole in the stem. Cut the head off the nail and file it. This is your spur.
I've read that point spurs like this are good for going with the grain, but a knife-like cutter should be used when going against the grain to reduce tear-out. If you're so inclined, file the other side of the nail to a nice edge. Now you've got a two-fer!
Step 8: Finish
Assemble the gauge and make sure all parts move as expected. Sand to your liking and finish with a nice oil to preserve the wood. Do not do anything that would change the geometry of the holes. That would be a total bummer, dude.
Once you've made one of these, you'll find that you could crank out another one in a few minutes. This essential tool is very easy to make and I welcome any and all comments about the technique.