Screw length & thread engagement
Too short and it pulls out. Too long and it bottoms out or punches through. This gives you the minimum bite and a length to buy.
Screw size
Threads into
Minimum bite
3.0 mm of thread
Total screw length needed: about 5 mm (round up to the next size you can buy, then check it does not bottom out).
One diameter of thread is plenty.
Two things that catch people out
- A blind hole is often deeper than the threaded part of it. Test with the screw dry first.
- In a countersunk hole the head sinks in, so the thickness you type here should be the part below the cone, not the whole panel.
Gear for this job
Affiliate links — they cost you nothing extra and keep this database free.
Threaded insert kit for plastic
Adds real thread depth to thin plastic
Longer screw assortment
When you simply need more engagement