Shop Tips & Tricks #29: Large Format Compass & Layout Tools

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Blog entry by GnarlyErik posted 10-08-2021 06:46 PM 570 reads 0 times favorited 4 comments Add to Favorites Watch
« Part 28: Pencil Nub Therapy Part 29 of Shop Tips & Tricks series no next part

Anyone who spends much time working with wood projects will eventually find themselves making small jigs, tooling and fixtures to do certain jobs, or make them easier or more precise. That’s because it’s easier, quicker or less expensive than finding something to buy for the job, which usually isn’t available anyway.

Years ago I made a large compass for laying out some work requiring radii. You can buy ‘beam’ compasses but they are fuzty to work with, and the beam itself can interfere with making the radius at times. My solution was to make my own down and dirty large format divider style compass pictured here. The arms are stable hardwood (white oak) and the radius bar is mahogany or cherry, I don’t recall which. The connections are copper rivets but small bolts could also be used. I like the rivets because those allow the compass to lie flat without damaging anything underneath.

It’s surprising how often I pull this thing off the wall to use. This one will do a radius of about 18” but a compass for any size is easily made. I think my pictures are self-explanatory.

(I just recently put the radius arm clamp on the compass. Previously I merely used a spring clamp, but that was imprecise and sometimes interfered with my layout work. I probably should make a curved radius arm, but it works just fine as is.)

Furthermore, I am a big fan of ‘Inside Reading Folding Rules’. There are a lot of little tricks you can use with a folding rule and although I have several steel tapes, I probably don’t use one more than once or twice a year. A folding rule is also handy for making a large radius. My method is to drill a small hole precisely on the 1” mark of the wooden rule. Then, driving a small nail through the hole and into whatever centerpoint your radius needs, it’s easy to strike any number of different radii by holding a pencil at the proper point along the rule as you swing the arc. Just don’t forget to allow for that 1” deduction on the nether end!

Along with folding rules I also have a collection of aluminum straightedges from 12” to 48” and a regular drafting T-square, all of which come in very handy for layout work.

Lead weights are very handy for holding ‘the other end’ of straightedges, T-squares, whatever, and for making graduating curves with battens (bendy strips of thin, straight-grained woods). I have a collection of mismatched lead drafting ‘whales’ (also called ‘ducks’) which have a cast-in point for holding battens in place. These have felt glued to the bottom so they can be used with drawings on paper, and they come in handy for all sorts of things besides. These are very handy for holding down the far end of a straightedge, or for holding parts together while glue dries, etc. Bean bags filled with lead shot also work very well.

I just priced a single one of these drafting whales on eBay at $55 + $9.20 shipping! But, you can also make your own with simple equipment around the shop. Here is a humorous blog about making your own whales for your reading pleasure:

I will add one thing to this excellent piece about casting hot lead into a wooden mold. The author of this piece had issues with the wooden mold charring when the hot lead is poured. It is easy to avoid that by simply spraying the inside of the mold with a couple coats of hi-temperature reflective paint which is sold in auto parts stores for use on engines and manifolds.

-- "Never let your dogma be run over by your karma!"

4 comments so far

View Madmark2's profile


3096 posts in 1831 days

#1 posted 10-08-2021 08:43 PM

Good tip on the high temp paint. They don’t hardly sell drafting tables any more. :(

CAD is great, but there is something about an E size drafting table that is so … cozy?

-- The hump with the stump and the pump!

View Sylvain's profile


1399 posts in 3743 days

#2 posted 10-10-2021 01:03 PM

As many software, if one doesn’t uses it regularly, CAD will not save time. And one has first to learn how to use it.

Drafting tables with drafting machine are still available ( about 2200£ for an A0 [1 m²] size).
Quite an investment if one doesn’t uses it regularly.

Although a thick MDF board with two side straight and square and a good T-square would do if needed.

-- Sylvain, Brussels, Belgium, Europe - The more I learn, the more there is to learn

View GnarlyErik's profile


366 posts in 3377 days

#3 posted 10-10-2021 03:31 PM

I have a full-sized architectural drafting table equipped with a ‘drafting machine’ in my office. I bought it cheaply from an architect’s office who was selling off such things. I also have a 36” x 48” drafting board with steel edges in my workshop which I use with a T-square. However, I find myself more often simply using a smaller piece of 3/4” cabinet grade plywood because of its smaller size. With a T-square can be used with anything with one straight edge no matter the shape of the piece.

I am of an age now that I’ve decided to leave CAD to the younger set, even in the face of its obvious advantages.

-- "Never let your dogma be run over by your karma!"

View davidkanedv's profile


1 post in 9 days

#4 posted 10-12-2021 08:41 AM

I thoroughly enjoyed reading your content, and it was quite beneficial to me. If you have time, you are welcome to join me in playing five nights at freddy's.

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