Radius Checker Finder

Update....07-09-2026....... This works great if you know the length of your 1/8 inch drill bit you use to measure the gap between the radius and the corner of the tool, and also the width of the printed part from the very corner and the flat top of the part. The idea is to subtract that from the length of the drill bit, and you know the length of the gap left.

The thing is that most printers will put a bit of a radius on that printed part corner, and you can not just caliper measure it. It needs to be as exact as possible if you want a precise measurement.

Find it by measuring a known diameter circle, like a 1-inch diameter bottle or circle. The gap should be .2071 inches. Knowing that, and then measuring with calipers the top part sticking out of the part, you will know the thickness of the printed part above the corner. Mark it on your printed part, and now all you have to do is measure the upper excess part of the drill bit sticking up on top. Measure it, subtract it, and the printed part thickness, and you have your measurement. Divide that by .414, and you have it.

This will measure radius from 1/8th inch up to over 3 inches. You can use calipers to measure either from the corner of the triangle or measure what is left on top of the 3/64 inch rod/drill bit. 1.5 inch rod minus .3421 (should be) corner width minus .5 left on top equals .6579. Then divide that by .414, and you've got your radius.

It will give an exact or very, very close measure of the radius.

Just use the whole numbers and the first 3, and sometimes the first 4 fraction digits will give the closest measurement.

Use a 10-24 threaded screw for the thumb set screw. It will cut threads in the plastic for itself.

Made strong to prevent warping of the triangle. Must be square. Slow printing for the top thumb screw boss, or print something taller while printing this.

Use calipers for the best measurement.

Enjoy, thanks, Rick.