Also checkout my other upload here
[https://makerworld.com/en/models/1402600-metric-gauges](https://makerworld.com/en/models/1402600-metric-gauges)
I created a whole set from 3mm up to 9mm.
Hope you find them as useful as I do.

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I designed these simple tools using Onshape and printed them out on my BambuLab X1C with PLA+

I wanted something to test my heat inserts against, so that when designing new models I could get all the hole sizes correct.
They are all made using 0.1mm increments, so you can use them for anything from 3mm - 6mm

A web search shows these sizes as a rough guide, 

Threaded Insert Metric Size    A Insert Hole Diameter (mm)    B Insert Hole Depth (mm)
M3                                                            4.1                                           5.9
M4                                                            5.7                                           8.3
M4 short                                                  5.7                                          5.0