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I use a set of tweezers as part of my toolkit, and they have a hole in one arm and a corresponding spike in the other. Why?

Tweezer Example

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I think it's funny how quickly a non-electronic design question will get down voted and closed unless people say to themselves "huh, I was curious about the same thing..." – Samuel Dec 17 '13 at 22:08
It should be noted that these kind of tweezers were around far before people even thought about SMD parts or had anything in electronics could remotely be lifted with one of these. – PlasmaHH Mar 25 '15 at 16:30

The spike is called an "alignment pin" and is useful for very fine tweezers that might twist or bend slightly, causing the tips to misalign.

Here's an example at Aventools:

Tweezers with alignment pin

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I have never hear a good explanation, but this is my personal thought:

If the tweezers have sharp ends (like the ones in the figure) they can mechanically twist slightly so that the ends of the arms do not meet perfectly. This in turn makes it difficult to hold the smallest SMD components. The spike and the hole force the ends of the arms to be aligned.

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Google suggests this answer might be correct and that it is called an "alignment pin". – David Dec 17 '13 at 16:53

Aside from the alignment purpose, it also allows you feedback. That is to say, it lets you know when the tips have pressed together, and how much.

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Silly argument: my fingers' muscles know how much they are pressed together. – The Resistance Dec 20 '13 at 16:00
@TheResistance Congrats, the world doesn't revolve around just you. – Passerby Dec 20 '13 at 16:25
You mean there are people who don't know how hard they press, unless they feel the pin? Bring them on! – The Resistance Dec 20 '13 at 16:33
@TheResistance and there are people who can't see without magnifying glasses, can't hear without hearing aids, and can't bend their hands or fingers without pain. – Passerby Dec 20 '13 at 16:36

In all my years of working in a lab, I have yet to find out what the pin and the hole are for. I have finally resorted to explaining that that part of the tweezers has been placed there to keep the researcher and students awake, because if you aren't paying attention that spike can go right into your finger. I am even in a position to remove them from the student classrooms because it is a safety hazard.

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