Just ran across my old compass. I thought they were called proportional spacers, but I guess not.
It is a drafting tool. Has no pencil, just two metal sharp pointed ends.
Anyway, when I taught fly tying, I suggested the new tiers might get one to check the proportions of their flies. It is great for setting to the size of the shank, for example, and then checking wing length, tail length, etc.
Aren’t they also handy for splitting feather barbules…
not to be critical, but with a degree in mechanical design, thought I’d point out those are actually called “Dividers” the ones with a pencil on one end, are called compass. I use my old drafting tools for fly tying too they do come in handy 
Mike
Mike,
Weren’t they used in Naval navigation back in the day? To calculate distances after setting the device to a distance on the map legend?
that could be. but I know in drafting they always referred to them as dividers. But that was over 30 years ago too.
Mike
I knew they were “proportional” somethings…Looked it up. They are called “proportional dividers”.
Anyway, they work well for what I used them for as they maintained the setting for comparison purposes.
Ah yes! … that’s right. that rings a bell now.
Mike
I beg to differ folks. The ones shown in this post is a divider. Proportional dividers has points on both ends and a mechinisim in the center to set the proportion between the two ends of the dividers. I have both. Most drafting instrument sets do not come with proportional dividers.
Jerry
Here is a photo of a proportional divider to show what Jerry is describing.
So for those of you confused about needing either a divider, compass, or a proportional divider, fear not. Just use your scissors to compare sizes and proportions. Of course, you really only need to do this for a short time, and then you’ll develop your own judgement.
If one’s hands are steady enough.
I just use a hook in a hackle plier.
I need to know how this works. It looks so old school.
That’s why I said I used it in my fly tying classes. It was a way the new tiers could check their material proportions.
Hi Sandfly,
I’m intrigued by your device. Is it available? I tried a Google but no luck yet.
Thanks,
Mike
I am trying to get a hold of the guy again where I got them. I had them for sale last year in my shop…
I like the thompson wing former for wing sizes… Multiple wings from 1 feather, all equal in size to each other with no guesswork…
The tool that Byron showed looks like what I used in Mechanical drawing classes back in the late 50’s/early 60’s. You loosen one of the screws and replace it with a draftsmans (draughtsmans) lead, voila a compass for drawing circles.
Adios Philip
If you get one of the “spring bow” kind, with split legs that the screw goes through to clamp the points you can remove the points and insert the ends of a razor blade. When you tighten the main adjustment screw the blade will bend into a nice curve. Makes a great handle for the blade when trimming deer hair.
Cheers,
A.
if u try this, use caution… different blade brands have different stress allowances. great idea, in fact i think i may give that a try… just dont over tighten, shattering a razor blade hurts!
