I just managed to get my shooting board working after having it collect dust for a year and then decided it was time to get a mitre jig. I make a lot of boxes and I've never been able to get mitres with hand tools....until now! Its a fairly simple build but does require a lot of accuracy to get it to work properly.
Step 1: Marking and Cutting the 45 Degree Pieces
These cuts are probably the most important of the whole build, if they're not cut straight then your mitre cuts on the shooting board will be off. If the mitred angles are even slightly off it ruins the final product.
I did this the simplest way I know how; to make a square and then divide it diagonally.
So I took a piece of plywood and measured a 10cm X 10cm square and divided it diagonally, making sure to square down the thickness of the board too. I then clamped down a piece of wood to guide my saw as straight as possible to make the cuts.
After the pieces were cut I clamped them next to each other in the vice and planed them a little to get rid of any fuzziness.
Step 2: Making and Attaching the Top Platform
After cutting a piece that was 15cm long and 14cm wide from the same 1cm thick plywood I held the long side of the angled pieces against it. Holding my speed square up against it I could then transfer the 45 degree angle onto the top platform.
It's not 100% crucial to get this angle perfect but it will help the jig seat properly if you can get it as close as possible. After that all I needed to do was glue the angled pieces onto the top platform, I did try to screw them on but it was moving the pieces around too much, so the glue helped me get it glued more accurately.
To help get the jig as flat as possible on the bottom you could place some sandpaper on a known flat surface and take it back and forth until you reach the desired flatness.
Step 3: Making and Attaching the Back Piece
A 15cm by 10cm piece (from the same 1cm thick plywood) is what I cut for the back panel. I'm not sure if this piece is 100% essential but it felt to me like it would hold the pieces more square and make the whole jig more solid.
After cutting the piece I held the previous pieces on top of it and marked the inner line of the sides. I then used my finger as a guide to draw the rough centre of the piece by eye and marked up and drilled four pilot holes for screws.
I then put the screws through the back piece until they were just about poking out of the other side and used the points of the screws to mark the pilot holes onto the angled pieces.
After that it was just a case of screwing the back onto the angled pieces.
Step 4: Making and Attaching the Stop
I cut a 1cm width piece from the 1cm thick plywood and made it around 14cm long. It's very important to get this piece flush with the side of the jig so that it's at a right angle to the plane iron. If you're even a little bit off the mitres will be off too. I drilled and screwed this onto the top platform.
Step 5: Using the Mitre Jig
Obviously the mitre jig is best used with an existing shooting board. Holding it firmly against the shooting board stop and pushing against the piece to be mitred with one hand, you then use the plane with your other hand and make purposeful strokes to remove the angle. The wood your using also has to be square for it to work at its best.
You may need to tweak the angle of the iron a little bit to get it to work properly, it's worth doing a test with a piece of scrap wood before using it on your final project.
Step 6: The Results!
I decided to use some chunky Sapele and some thin pieces of Pine to test out the effectiveness of the jig with different materials. As you can see they both worked very well and I've already made a box from oak using this very jig.
There are many different ways to achieve these results, this isn't the perfect jig by any means but it does work well for me.
I really hope you enjoyed this Instructable, please if you have any comments feel free to post them below and check out my YouTube channel and Twitch channel, where I live stream woodworking 5 days a week!