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Pocket Hole Drilling Fixture

Senior VP of Engineering, Carl Calabria, describes the design and 3D printing of a pocket hold drilling fixture using the Markforged Mark One 3D printer

[This post was written by Carl Calabria, our Senior Vice President of Engineering]

Traditional woodworkers enjoy using dovetail and mortise and tenon joints to fasten pieces of wood together when glue alone will not suffice. I count myself among them. When it comes to non-critical projects where speed trumps elegance, I will reach for my pocket hole jig every time.

This jig guides a specialized drill bit into the wood at a prescribed angle and to a specific depth. Next the pieces of wood to be joined are temporarily clamped together while a screw is driven through the pocket hole and into the other piece. The pocket hole jig I designed more than 15 years ago used components sourced from the Kreg Tool Company. It employs a pneumatic cylinder with a foot activated valve to clamp the work piece and a pneumatic drill to drive the bit. The jig clamped into my woodworking vise and was designed to work with stock in the 3/4”-1” range or the 1 1/2”-2” range. Switching between ranges involved unscrewing and repositioning the pneumatic cylinder, a tedious operation. I recently decided to upgrade the fixture so that it could quickly be adjusted and handle stock up to 4” thick. I also added switchable magnetic clamps so that the jig can be quickly mounted on my tablesaw making it much easier to handle long work pieces.

The newly imagined fixture is a great example of mixed material engineering. I used MDF (medium density fiberboard) for the base, extruded aluminum for the guides, a 3D printed bracket for the pneumatic cylinder using a Nylon substrate with embedded carbon fiber, and a pair of 3D printed Nylon knobs. Printing the bracket allowed me to integrate several features (right angle support for the pneumatic cylinder, guides for the aluminum rail, and provisions for securing the bracket at an arbitrary position along the rail) that greatly simplified the design process.

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