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Comment by sgtnoodle | Hacker News Reader

A coffee grinder will quickly make a lot of really fine salt. I do that when I need to heat treat 3D printed parts to improve their material strength. You pack the part into fine salt, bake it at the original extrusion temperature, then slowly let it cool down. The plastic liquefies, and the packed salt holds its shape.

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That'll probably really fuck up a coffee grinder, so make sure you don't use it for coffee.

I would assume they are talking about a blade "coffee" grinder, which is ironically terrible for coffee.

If you want a really fine grind in a hurry you can use one and get ok results. You have to let it rest every 30s or so to cool down or it heats the grounds too much. I liked to shake it while grinding too. It isn't quite Turkish grind and there are a few large pieces that won't get full extraction, but if you want really fast extraction (or fast intentional over extraction) it works.

Yeah, a blade coffee grinder. For sure don't run salt through your expensive burr grinder!

why would it fuck up a coffee grinder?

Salt corrodes stuff

And salt is a lot harder than a coffee bean. Blade is probably a really weak/soft metal. Might be harder than salt on the Mohs scale, but that just buys you time.

Blade also gets kicked around more going around the salt instead of grinding through, more bending = shorter lifespan.

Nice method, what infill do you need for that to work? 100% or is less possible?

You do need 100%, otherwise you'll end up with a void at the top once the plastic melts. You could experiment with intentionally designing in a "sprue" of extra material to melt and control where the void is, but I haven't tried it yet.

I've successfully used this method on a sun gear for a planetary gear box designed for a low speed, high torque application. Due to mechanical constraints, the gear only had about 1.2mm of wall thickness at a 5mm radius, and it was prone to shearing off. Remelting it in salt solved the shearing, without having to redesign anything else.

A good blender works too.

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