Welcome to another barbaric attempt at an Instructable! I am Steven, and I will be your host for today's woodworking shenanigans. Now, onto the subject of this tutorial: A bow saw, also called a frame saw. It is a type of saw popular in Europe, and can be seen being used in The Art of the Carpenter by Andre Roubo. It consists of a wooden frame held in tension by twine, and a thin blade.
Now, why would I want to make a bow saw? The advantage of the bow saw is it can be made cheaply, it's efficient, and allows you to swap out blades instead of swapping out saws. In addition, my hand saw stock right now is just the one Japanese crosscut saw, which is great for softwood crosscuts, but not so much rip cuts or with hardwoods. Plus, I find pushing is more natural and comfortable than pulling, and I am not flexible enough to use the Japanese saw in it's traditional way.
I hope that you may consider making a bow saw, if only a small coping saw version. It is a fun project.
Step 1: Materials and Tools
While many people make bow-saws from old bandsaw blades that snapped, I will be using 700mm blades available from Highland Woodworking in the US, or E.C.E Emmerich if you are in Europe. These blades are manufactured by Putsch, a German company. They are actually very cheap ($8.99 online for a joinery blade), which is why I choose to build this saw.
All wood for this saw will be red oak. It has very good strength and give; some people say the tannins will cause rusting, but put some oil on the blades and it should be good.
The two arms will be 19" long, and 1" by 1".
The stretcher shall be 26" 3/4".
I used two 3" nails with the tips cut off to hold the blade into place.
To tighten the saw, I use hemp twine. This breaks less than cotton garden twine, but still breaks. I am looking into bow string.
Step 2: Cut the Arms to 19" Long
I used a miter box because I'm not that skilled to freehand it yet. If you are using a Western handsaw, you should be good with oak. If you are using a disposable Japanese hand-saw like I am, go slow and don't force the saw if it gets caught. Unless specified, Japanese saws are optimized for softwood with long thing teeth. If your using machines, make sure to align the blade to ninety degrees.
Step 3: Make the Blade Slot
First, find the middle of your board's end, as shown in Picture A. This is easy by doing a trick I learned from a teacher: Draw a line diagonally from one corner to the other. Draw both diagonals. The intersection will be the middle. Of course, this is only perfect if the material is a rectangular prism, or another geometrical shape whose diagonals bisect each other.
Then, using a marking gauge, set it to the middle and scribe this distance on the front and back faces, along with the end. Try to fill in the cuts with pencil to enable better viewing.
Thirdly, find the depth of your blade; I sadly forgot to take a picture of this. Mark this distance with your gauge as well, with the throatplate of the gauge on the end grain and cutting cross-grain. Follow this line with your saw.
Step 4: Drill Holes
I marked the position of where the saw blade would go; this is documented in the first picture. I tested to make sure it fit in the second picture. This step is pretty darn simple, except you may get dust in the slot cut in the previous step; I cleared it out using the Japanese saw. Yew may find it better to buy or make some fancier hardware to hold the blade. To keep the blade in place, I used nails with their tips sawed off.
Step 5: I Tenon to Ramble On...
Sad attempts at puns out of the way (I don't know if puns are poplar on here or knot)...
First, I marked the halfway point on the arms at the 10" mark. I then made sure that the stretcher goes the proper distance.
To lay out the tenons, I set my marking gauge to one millimeter, and marked this from each face. Sadly, my moxon vise couldn't be used at the time, so I removed my shelf from my workbench and clamped the stretcher to the workbench. I then started cutting to the marked shoulder.
Step 6: Mortise That There Board
First, mark where the tenons are. This isn't a Fine Woodworking project here; I just center the tenon, mark it with a pencil, and then drill inside the pencil lines, making sure to have a depth stop on your drill press. Make sure you have wood to spare inside the lines. You can always remove more wood, but you can't put it back.
Sadly, I got a bit too aggressive on my first mortise, and now have a very loose joint. I found that cramming a shaving in there makes it nice and tight, however, and if I flip the arm around, the tenons fit much better. I then transferred the marks to the other arm. The second mortise was my best one yet, however.
Step 7: Shape the Arms and Stretcher.
To start with, I marked a 1mm wide notch 1mm from the top of the arm using a marking gauge. I then used my Japanese saw to cut slightly down, then polished my 1/4" chisel to cut out the notches. Even with all of this, the oak decided to be mean and crumbled on the top. I decided to make the tops into domes to hide this.
I then lightly chamfered the arms; Where my hand will be during use, I heavily chamfered the area with a block plane and rounded the chamfers with sandpaper. I used a smoothing plane on the stretcher, to get a more regular chamfer.
Step 8: The Toggle
To tighten a bow saw, you tie a loop of twine around the notches, then put a piece of wood (I call it the toggle) in the middle of this loop, and turn it until the blade sings. Man, I really butchered that description. Anyways, the toggle has to be long enough to hit the stretcher, which keeps it from unwinding itself. Apart from that, it doesn't really matter what shape it is, other than what you feel like is convenient. I made mine out of yet more scrap cherry, and decided to try my hand with inlay using some sweet-smelling wood I found in the scrap bin.
Step 9: First Cuts and Final Words
Thank you for reading this Instructable! I hope my mangled attempts at photography didn't mangle your comprehension of the steps, and I hope my descriptions didn't confuse you even more.
On the cuts: While I need to get a stronger type of twine (I used gardening twine which snapped quickly), the first rip cuts were very easy, especially compared to using a crosscut Japanese saw. I also need to practice using this saw; Overall, it works great and it feels much more natural to use than the small Japanese saw. I am glad I bought the crosscut blade as well: Bow saw for large crosscuts, Japanese saw for finer cuts.
After some use, I feel like I should make the tenons longer to make the saw more stable. Luckily, this is very easy, as I can use just make the mortises deeper and make a new stretcher. However, I might try this out on a pine prototype first. I also feel that I should make another bow saw, as having to change the blade can be a bit annoying.
One last note: How many puns did you find?
Edits: Edit One: 1/21/2015
Edit Two: 5/26/2015