What means '% diametric engagement'

Henk_de_Vlaam

Please, can somebody explain the option % diametric engagement in the hole feature. As a dutchman that is unclear to me and I cannot find the proper mechanical meaning on the Internet.

mahir

It looks like this option controls the tap drill diameter, and should maybe be called Thread Engagement instead of Diametric Engagement. If you have more engagement, more of your female thread engages your male thread. Also, your tap drill, and therefore your minimum thread diameter, will be smaller. Also, the tap itself will have more material to remove.

owen_sparks

Exactly so. 

The pointy ends of the thread contribute very little to the overall strength to the thread in operation but do massively increase the torque required to cut them in the manufacturing process. As such for hard materials a larger larger pilot hole may be used resulting in less thread engagement. 

For softer materials they're weaker and easier to cut we'll so take all the thread we can get so a smaller pilot hole is desirable.

Owen S

mahir

It looks like this option controls the tap drill diameter, and should maybe be called Thread Engagement instead of Diametric Engagement. If you have more engagement, more of your female thread engages your male thread. Also, your tap drill, and therefore your minimum thread diameter, will be smaller. Also, the tap itself will have more material to remove.

owen_sparks

Exactly so. 

The pointy ends of the thread contribute very little to the overall strength to the thread in operation but do massively increase the torque required to cut them in the manufacturing process. As such for hard materials a larger larger pilot hole may be used resulting in less thread engagement. 

For softer materials they're weaker and easier to cut we'll so take all the thread we can get so a smaller pilot hole is desirable.

Owen S

Henk_de_Vlaam

@mahir and @owen_sparks, now it is clear to me. I had to look after Thread engagement indeed. Now I'm attented to the drill diameter that changes automatically while changing % diametric engagement.

The only engagement that I knew (also via the dutch Google Translate) was the engagement between two people

owen_sparks

H_d_V said:

The only engagement that I knew (also via the dutch Google Translate) was the engagement between two people

That can lead to all sorts of bad things!