|Project by Peter Oxley||posted 12-10-2010 09:49 PM||11762 views||41 times favorited||23 comments|
This jig is based on the box joint jig designed by Matthias Wandel at www.woodgears.ca . If you haven’t seen his site, you should check it out – a ton of great ideas for shop machinery you can build yourself.I made a few modifications to the original design to fit my work style:
- I moved the crank mechanism to the right and oriented the primary gear vertically, which I thought would make it more comfortable for me to use.
- I use fractional inches in most of my work, so I designed the system with that in mind. The screw pitch is 16 TPI, so one turn advances the jig 1/16”. The primary gear is four times the size of the drive gear, so a full turn on the crank gives me 1/4” advance. I designed the primary gear assembly so it could be changed to different size gears, but so far I’ve only used the one size.
- I didn’t trust myself to always turn the crank exactly a full turn (and I’m the sort of guy who can lose count between one and three), so I added a scale to the fixed fence and an indicator on the carriage. For additional accuracy, I added an indicator by the drive gear and colored the indicator and “zero” tooth red. This also gives me the flexibility to make joints in increments that are a multiples of 1/8” and even multiples of 1/16” without building additional primary gears, but would require making partial turns on the primary gear. However, the smallest joints I have made are 1/8”, which requires 1/4” advance – one full turn of the crank.
- The carriage rides on two sliding dovetails. I’m a little fixated on sliding dovetails, and even make full-extension drawer slides out of them sometimes. The carriage is tight enough between the dovetails that there is no noticable movement.
- In an effort to save a couple of dollars, I used a seamless sleeve instead of a bearing for the screw. That was a mistake, as the side load on the gear creates quite a bit of friction. I’ll replace it with a bearing soon.
The last two pictures are the largest and smallest boxes I’ve made with the jig so far. The big box is a book-return drawer for our local library with ½” x ¾” box joints. Yes, I cleaned up the glue before installing it! The little box is for my dial calipers and has 1/8” x ¼” joints.