Overview
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!
Heat-set brass inserts are only as strong as the hole you melt them into: too tight and the insert cracks the surrounding plastic as it goes in, too loose and it spins freely under load instead of biting into the walls once it cools. The right diameter depends on the exact insert you are using, the filament, and even the specific printer, since real hole diameters rarely come out exactly as designed once shrinkage and extrusion width are factored in. Rather than guessing and ruining a finished print when you discover the hole was wrong, printing this test piece once tells you the right number to use from then on.
Available tests:
- M2 Brass threaded inserts
- M2.5 Brass threaded inserts
- M3 Brass threaded inserts
- more coming soon…
But wait, there’s more! For ultimate insert strength, adjust your printer settings to ensure at least three walls around the insert. This simple tip will lock your inserts in place, ready for even the toughest jobs.
Test procedure
Place the 8 threaded brass inserts into each of the eight test holes and find the ones that fit best
My M3 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 hole 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 ideal depth for the holes.
In this test with PLA filament for M3 inserts the hole with a diameter of 4.1 mm gave the best result.
A five-minute test that saves a lot of ruined prints down the line.
A small test piece that turns a guess into a known-good number.
Download
The model is free to download and print, licensed under the Standard Digital File License.