130712-2006 EDT
Elektrotechnik:
Your description implies that you want to dissipate 2 W at the interface of the point contact with the bulk piece of steel, and that both the point contact, and bulk material are steel, and not stainless.
This is a lot of power in a very small area, and that means a lot of heat that will change the character of the interface contact.
Without doing a controlled experiment, and only a two terminal ohmmeter instead of a 4 terminal test, I get about possibly 0.1 ohms with square shank screwdriver, and a scribe with a tip diameter of about 0.01".
For 2 W at 12 V you need a resistance of 72 ohms. You won't get 2 W dissipation at the interface without an extremely small contact area and/or controlled contact force. If you just want 0.167 A of current, then use external current limiting. Power dissipation of 0.167 A in 0.1 ohms is about 0.003 W.
If the contact resistance is 0.2 ohms, then to get 2 W dissipation in 0.2 ohms requires a current of 3.16 A. And 0.1 ohm requires 4.47 A.
What is your goal and do you really want 2 W at the interface? The surface of a 2 W resistor dissipating 2 W will burn your finger. A 2 W resistor is fairly large compared to a point contact. I suspect 2 W dissipation at the tip end of my scriber would probably fuse it to the other piece (weld).
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