# Triangle Jig



## DBateman (Feb 24, 2012)

I have been around woodworking since I was 9 years old and went with my dad on carpenter jobs with him. We did mostly remodeling jobs that included building cabinets and finish work.
I am beginning to put a shop together with several projects planned, including adding doors to some cabinets. Somewhere on the internet I saw where someone used a triangle base on a router to cut in a pattern that was parrallel to the sides, but at the corners created an arc. Since several of the cabinet doors already have this type of pattern I would be interested in finding out how to make and use this type of jig.


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## Gene Howe (Jul 10, 2007)

Sounds like you are wanting to groove a door panel already in a frame. 
A triangular base would be the way to go to achieve the arc in the corners. When the point of the triangle reaches the corner, you'd hold it in the corner and swivel the router so the opposite straight side of the triangle reaches the opposite rail/stile. 
Depending on the sizes of your doors, a trim router might be the best tool for this as the base would be smaller. The size of the triangle will have to be larger than the base of the router. 
You'll probable have to do some figuring and experimenting to get the point-to-bit relationship correct, in order to match your existing doors.


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## MEBCWD (Jan 14, 2012)

Hi Don,
Welcome to the router forums.

The base made for the router is an equilateral triangle (all 3 sides the same dimension). 

The size of the base is determined by the radius you want in the corners. The base is made using this radius as the distance from the center of the bit to one corner of the triangle.

The inside dimension of the frame/template that the base follows is determined buy the width and length of the cut you desire plus 2x the distance from the center of the bit to the center of one side of the triangle. The frame sides can also be curved so you can actually have a large radius, like at the top of the door panel, however any radius of the side of the frame/template has to curve away from the center of the panel.

Here is a link to a free triangle calculator.
If any input is 1 decimal the results will be one decimal so, I would input everything, angles and side dimensions, to 3 decimal places so you can round however you choose.

Triangle Calculator

An example:

You want a 2.00" radius in the corners 
In the top box of the calculator enter 30.000 (half of the angle of an equilateral triangle), in the right box enter 2.000 (the radius you want), in the bottom box on the right enter 60.000 (the complementary angle of the right triangle)
When you click the compute button it will show 1.732 for 1 side, 1.000 for the other side (this is your offset from the template), and 90.000 for the angle between the 2 sides.
Hope the picture helps. If you have any more questions I will attempt to answer them.

Mike


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## Gene Howe (Jul 10, 2007)

That's a pretty cool calculator, Mike. Much better than the trial and error method I envisioned.


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## MEBCWD (Jan 14, 2012)

Hi Gene,

I looked at a couple of other calculators before I made the post but one had the angles marked abc and the sides marked xyz, not how I learned it, and the other one had the angles and sides marked right but included a lot of information within the triangle that made it hard to tell what was going on. 

This one I like because you don't have to worry about which side or angle is which. All you have to worry about is having them in the right relationship to each other (angle/side/angle or side,angle/side). 

I like it's simplicity! *KISS*


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## DBateman (Feb 24, 2012)

Thanks Gene and Mike. I appreciate how quickley you answered my question. I have to finish setting up my shop in the next couple of weeks then I will be working on the project. I have a lot of 3/16 inch plastic from a local sign making company that I got years ago, and I'll be experimenting using that. Thanks again.


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## bobj3 (Jan 17, 2006)

Hi

I don't get it  can't you use a normal cir.jig (like a Jasper cir. jig) and put the pivot pin in the corner and just turn/spin the router and do the same thing ??? than you are not stuck with one size. ???


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## MEBCWD (Jan 14, 2012)

You're welcome Dom,

Good luck trying to set up and organize your shop, I know how exasperating it can be, I'm still working on mine.

If you really want to experiment try changing the lengths of the sides for the triangular base (2 sides the same length, all 3 sides different lengths), you have to go around the template 4 times to complete one full cut but you should get some interesting results. You can also change location of the router bit and get different results, 4 times around for 1 complete cut.

Remember if you have any questions we'll try to answer them as best we can.

.I made a mistake on how many times you go around the template and now it is correct!


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