This handy tool takes the guesswork out of choosing the right hole size for brass threaded inserts.

Simply push your insert into one of the labeled holes, and you'll instantly know if it's a snug fit. No more wasted time or materials!

But wait, there's more! For ultimate insert strength, don't forget to adjust your printer settings to ensure at least 3 walls around the insert. This simple tip will lock your inserts in place, ready for even the toughest jobs.

Test procedure

Place 8 threaded brass inserts in correspondence with each of the eight test holes and search for the ones that better fit them

My brass insert, for example, did not fit 3.9, 4.0, and 4.1 holes.

Turn on the iron welder, and set the temperature to 300°-350°.

Push down each brass insert into its holes by using the edge of the welder until the top surface is parallel to the test piece's top surface.

Now you can compare the result for all hole sizes from the top and bottom perspective. The bottom view allows you to get an idea of how well the insert fits into the inside of the hole and it is also useful to estimate the better depth for the holes.

In this test with PLA filament the hole with a diameter of 4.1 mm gave the best result.