November 3, 2009

Hinge recess jig


I designed and built a simple jig today to create those pesky little recesses, otherwise known as mortises, that the door and window hinges drop down into. They are so easy to mess up trying to guide the tools by hand. Too wide, too deep, too long, crooked, I have made all those errors before and I was tired of fighting the task.


My jig is made from  leftover pieces of material that were donated from Don's workshop. He has a real treasure trove of metal odds and ends and fasteners too. I used 90 degree aluminum angle. The larger of the two pieces was 1.5" x 1.5" by .125" thick. It is long enough and wide enough to allow me to clamp stop blocks to it and also the clamp the pieces I am going to attach hinges to.


The hinges I will be using are just under 3/8" in length, they are the standard dollhouse door hinges you purchase from stores. To create a guide notch in the angle I used a 3/8" end mill cutter, I could have used a 3/8 straight cutting router bit instead. The bit created a little too long of an opening so I glued in a brass shim to shorten the length. (Note that I don't always get these things right on the first try) Or you could use a narrower bit and take two passes to make the opening.

My chisel is guided down against the three edges of the opening. Hand pressure is all that is needed to make these shallow cuts.

The second piece of 90 degree angle was epoxy glued to the first piece. It is used to control how deep the bottom of the recess will be cut and to guide the chisel in so it is level for a perfect flat bottom for the hinge to rest on.

My chisel rest on the smaller angle as I push in to remove the waste piece. All  you need is light hand pressure to pare out the waste. A very sharp chisel is required for the task, my chisel is .25" wide.

I hope this post inspires you to make jigs to improve the quality of your work and also to make it much less stressful. I made mine for both reasons as I hate to mess up windows and doors I have spent a lot of time making. I was dreading the hinging task so I motivated myself to do something to make it easy for all the miniature houses I want to build in the future.

The secret to designing jigs is to think about the motions you need to make for the task and how you can control those motions for accuracy and repetition in the simplest way possible.

 How will you guide the tools you use to make cuts and how will you hold the piece you are trying to cut in the correct position?

You can build a hinge recessing jig out of hardwoods, just be careful not to allow the chisel to cut into the guiding surfaces. It will last a good long time. Or you can glue thin brass to those surfaces to give them an even longer lifetime of use. If you use a jig often and it gets a lot of wear then metal is a good choice.
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