A Simple Beam Compass

Made at 173

With no major projects being accomplished at 173 this year, and work continuing on its all-consuming course, I've enjoyed a year of stealing.  That's right - stealing.  For, you see, I have found a nice pattern of stealing time in the workshop - 5 minutes here, 10 there, a day here, another a week or two later.  In those stolen moments I find myself making small tools, goofy, but useful little baubles. 

Beam Compass

Before we get any further, here's a fun little explanation of a beam compass:

A beam compass is used for drawing larger circles or curves larger than what would be possible with small compass sets. A scaled beam is required to carry two trammels found inside small casement. The beam can be of either wood or steel, depending on the workshop where the beam compass is being used.  

To operate, the central trammel pivot pin is fastened to one end of the beam, with outer scribing trammel point connected where required along the beam to suit the desired radius being drawn. The trammels can be adjusted by sliding along the beam, making it simple to draw a whole series of different sized circles. The trammels are locked to the beam by side-mounted set screws, and it is important to ensure that the trammels are securely locked to prevent sliding while drawing the circles. - Ernest Amor

What ol' Ernest is talking about here is a precision tool used to draw a circle.  I think it looks something like this:

And that's cool, I mean really nice!  I suppose if I was making circles every day for a living, or if I was an architect or engineer or something, I'd probably invest in something like this.  But, alas, I am none of these - nay nay.  What I had in mind for 173 is much, much simpler!

The Inspiration

Right before Christmas I made a little bird feeder, that needed a plate-like base.  I didn't have a compass big enough to properly draw a circle on the board, so I ended up getting a circle cutting jig for my router - and all turned out perfect:

I got the design from a book by John Perkins uniquely titled, Build Your Own Birdhouses.  While looking through the book, I noticed this little callout box at the bottom of a page...

And that's where the thought of stolen moments came in...hey - tinker around with one of these, ya never know when you'll need one!  So I did!

Design and Build

Pretty fancy subtitle for making what has to be almost the simplest possible beam compass, but here we go.  Because it's such a thing for me, I searched through some scraps and found the perfect piece!

I started by scribing the center line using - you guessed it - the center line scribe I made from scraps back in November of 2019.  Weren't they heady days!

I just locked the scribe into my vise and ran it over the scribe point a few times.

Then laid out points at 1 inch intervals.

From there, I got set up and drilled holes at the 1" intervals.  These are the holes where the panel nail will go, and form the pivot point.  

Having more than one spot for the nail panel makes the compass adjustable for varying radius lengths.  Then I drilled a hole at the other end just slighter smaller than a standard pencil circumference to help the pencil stay firmly in place.


With that done, that could simply be the end of the project.  But I thought I'd give it at least a little bit of a finished look.  I started by using a washer to mark out a  radius on the ends of the beam.

After that, I cut of the bulk of the waste, then took the beam to my benchtop belt/disc sander and rounded the ends.


Somehow, pretty much since I first started making homemade tools (which isn't really that long ago), I've been drawn to Minwax Gunstock stain for the "signature" color.  

Maybe because it works so well with amber shellac, which I also like.  Either way, that's what went on the beam.  Here's a first shot at the completed beam compass:

A little more of an overhead view...

And one last beauty shot.

A few of the hand tools made right here at 173! 
The small center line scribe
The wide center line scribe
The large marking gauge
The 45 degree marking tool
You might also like some articles about the 173 workshop!

The Collection

And with that, the beam compass is added to the collection of tools made right here at 173!  Once again, writing this post took waaay more time to write than it took to make the tool!

Stay safe out there!
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