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Pilot hole/Drill Pilot depth?

Pilot hole/Drill Pilot depth?

Pilot hole/Drill Pilot depth?


I had a question that I couldn’t get a clear answer online for, so there a tapped hole (thread portion & a portion deeper with no thread, then the cone shape of the drill at the bottom) [Please refer to picture]. And there’s a callout for a drill pilot depth, I’m curious because from what I’ve read, the drill pilot or pilot hole are used to ensure accuracy to the center when creating a feature, like a hole, or a hex; but I’ve never seen this called out before and I’ve also been asked to add a pilot hold onto a blueprint for a hex feature, so my main questions are:

1. Referring to the picture down below, is the “pilot hole depth” or “drill pilot depth” from the top to the red line (cone shape of the drill at the bottom of depth point) or the yellow line (normal depth)

2. Is there a standard for drill pilots/pilot holes?

Thank you!
Replies continue below

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RE: Pilot hole/Drill Pilot depth?

I think it depends in what type of equipment you are dealing with the tapped hole, if it is piping equioment if it is a vessel a tube sheet or an exchenger, ANSI,ASME, or TEMA.


RE: Pilot hole/Drill Pilot depth?

1) The drill hole depth would be the depth of the full pilot diameter.

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

RE: Pilot hole/Drill Pilot depth?

the tap drill (pilot) depth needs to be several pitches longer than the required full thread depth to allow use of a single plug tap for tapping and fewer issues with chip formation.
Changing to a bottoming tap just to complete the last few threads is a waste of time.

"Hard tapping" “rigid tapping” or “synchronous feed tapping.” doesn't care that much. Threads can be formed practically to the bottom of a blind hole.

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