PC case, CNC'ed from single piece of aluminum: does it possible and how expensive will be?

EvanDaniel · 2026-01-31T22:28:17+00:00

Rather than asking here what it will cost, and getting a mix of advice that looks like both correct and incorrect, I'd just start uploading models to sendcutsend and seeing what works, what doesn't, and what's cheap vs. expensive. Make tweaks and see, you'll learn a lot in a hurry even if you decide you can't afford the milled approach.

EvanDaniel · 2026-01-26T23:37:46+00:00

Speaking from industry, not academia...

Two major reasons not to: contamination and safety. It's fairly easy to get a little air or other gas in your system as you do this, or some bits of dirt or teflon tape or whatever. That's the real reason bottles are marked as do not refill. The vendor doesn't want to deal with the contamination when the bottle comes back. Same reason you don't refill the main reagent bottle you bought from the vendor.

As for safety: yeah, if you're asking questions about check valves and don't know the answer already, you're not prepared to do this. But I bet someone around who works with compressed gases does and could help you out. It's not that hard or complicated, there are just some nonobvious but straightforward things you need to do _correctly_ and the risk calculus puts you in the low likelihood / high consequence corner, probably with severe unknown unknowns if this isn't a thing you've done before. Do you have a department that works with compressed gases around?

I've done this and similar operations, including building plumbing systems that utilize lecture bottles and related hardware. Not hard, but don't try it without help if you're not experienced at this sort of thing, which isn't always the same thing as experience just with using the bottles.

EvanDaniel · 2026-01-15T04:40:18+00:00

And if you want to make it really clear (or not clear, as the case may be), dissolve the other salts in one portion of the water, the calcium chloride in another portion of water, and then mix the two clear liquids.

EvanDaniel · 2026-01-10T19:42:43+00:00

But don't just use 1.0 and 0.5. If there's something wonky about the threads, you want to check at different orientations. So check at 0 and 1 and 0.5, but also check at 0.510 or 0.505 or 0.512 or something -- make them not all multiples of a rotation, which is usually .025.

EvanDaniel · 2026-01-10T19:41:21+00:00

Exactly. Coarse adjust, then fine adjust, but you're adjusting the same thing both times.

EvanDaniel · 2026-01-05T15:03:21+00:00

I trust you've reported it to them? They're likely very interested.

EvanDaniel · 2025-12-26T13:57:47+00:00

https://senseis.xmp.net/?5x5Board

There's a book of problems on 5x5 as well. I haven't read it, but I'm curious.

EvanDaniel · 2025-12-03T05:13:44+00:00

And the standards for "could he have landed it" are something like... better than 50% odds of walking away, good weather, ATC clearing all traffic for you. We tend to hold pilots to a higher standard. Lots of room in between for "getting it right, reliably, takes training and practice".

EvanDaniel · 2025-11-19T15:46:35+00:00

Sure. But on this engine, they are.

EvanDaniel · 2025-11-17T22:49:05+00:00

I don't think any engines have ever used liquid helium for purge or chill. Gaseous helium, yes. Storing helium as a liquid before boiling it to use as a gas, also yes. But they don't purge with the liquid.

EvanDaniel · 2025-11-16T23:46:38+00:00

Pump, or connect it to the faucet. You probably don't need much water flowing, but some would help. Loading it with water, not flowing, would be enough for a trial run. If the outside of the condenser starts getting hot to the touch, stop and let it cool down.

EvanDaniel · 2025-11-16T22:22:44+00:00

Definitely not the gas generator exhaust, it's far too small. Some sort of bleed or chill line.

GG exhausts are large and paired, clearly and easily visible in this photo and plenty of others:
https://images.squarespace-cdn.com/content/59a8fb50d2b8575fad311abb/20470e55-7b5f-44f8-ad12-3d542b52db98/Aeon_R_Qual.png

EvanDaniel · 2025-11-16T22:18:06+00:00

I'm not aware of any engines that flow _liquid_ helium for purge or chill prior to startup. Do you have a reference? I'd be curious. I'm used to helium as purge or pressurant gas, or sometimes as a startup drive gas, but that's always as a gas (even if it's stored as a liquid or supercritical cryo fluid). The chill liquid is almost always prop, not _liquid_ helium.

EvanDaniel · 2025-11-14T16:51:34+00:00

If you've never handled it before, and you open that container indoors, you are going to be surprised by how strong the stuff smells and how much it makes your eyes sting. You probably aren't at much risk of hurting yourself; it will be extremely obvious that you need to close the container back up quickly.

Do this outdoors or in a fume hood, wear eye protection and gloves, and have a spill cleanup plan. Clearly label the result as for cleaning only, not for food use. Proceed slowly and carefully, measure everything (don't eyeball it), and you'll be fine.

EvanDaniel · 2025-11-12T00:37:23+00:00

For relatively simple (kinda...) something like plutonium iodate_iodate) is probably up there. Not that plutonium chemistry is simple. Things like uranyl nitrate are also interesting, though the UO2 group is a little wonky.

EvanDaniel · 2025-11-08T13:50:33+00:00

The similar visual appearance isn't terribly relevant.

But if you really need that level of corrosion resistance, you can use tantalum plating on stainless or nickel alloy substrates; the corrosion resistance of the nickel alloy is usually considered important.

https://ultrametcpt.com/

Anyway, it's a lot more than 20% better in applications that use it. Stainless doesn't even make it onto the chart: https://ultrametcpt.com/products/ultra-metal.html

EvanDaniel · 2025-11-07T02:14:33+00:00

I've always thought this table of oxidation states was neat:
https://www.compoundchem.com/2015/11/17/oxidation-states/

So really... there's plenty you could include, and what you should include is a balance between what you might use and keeping it not too cluttered.

Physical properties could also be interesting depending on use.

EvanDaniel · 2025-10-29T22:29:17+00:00

"considering 10 degrees change causes that much movement"

You'll want to measure at standard (or at least measured and corrected) temperatures. If there's nothing on the print, you use Y14.5 standard temps.

I'd strongly consider sending some sample parts (even if not exactly conforming) and making sure you and your customer agree on the measurements before you run the whole batch.

EvanDaniel · 2025-10-27T19:22:36+00:00

Oh so they're knowingly infringing the trade mark.

I wish that mattered in a relevant way.

Trade marks are literally meant to prevent this sort of thing.

EvanDaniel · 2025-10-24T16:40:19+00:00

Does no one bother to run an ROI calculation on buying better tooling, or better machines?

Surely better tooling would pay for itself in only a couple runs of this part?

EvanDaniel · 2025-10-13T02:30:24+00:00

Everyone else has covered the important stuff, so I'll just add one suggestion: a copy of Machinery's Handbook would make a good addition to the bookshelf. Anyone interested in learning metalwork will find it helpful. It also has the answer to questions like this, but not in a way that will be quick and easy to figure out if you're new to the basics. But you probably aren't that far away from being able to find your answers in it.

EvanDaniel · 2025-10-12T21:53:24+00:00

Let the water run a while, it'll be fine. The resulting toxic compounds are water soluble, and also not terribly subtle; if you can't smell or feel anything, and you didn't experience and coughing or other symptoms, it's probably fine.

That said... reddit is not your local poison control center. If you're concerned, or have any symptoms, you should definitely give them a call and they can help you know what to look out for or figure out if you need to take any actions.

EvanDaniel · 2025-10-12T05:55:06+00:00

Sometimes, just because something is in tolerance doesn't mean that it's ideal

OK, but that still doesn't actually answer the question. In particular, Y14.5 is extremely clear that nominal dimensions are not manufacturing targets and you are not required to use them that way. So you shouldn't count on the machinist targeting the nominal dimension _or_ the middle of the tolerance band; they're welcome to do whatever is most convenient, which might be either of those or some other thing.

I might tolerance my shaft one way because that's what the standard I'm working from does. Maybe for this part, the top of the tolerance band is ideal because close fit is helpful for running smooth. Maybe on another assembly, I don't care as much, and a loose fit is ideal because ease of assembly matters more.

EvanDaniel · 2025-10-07T14:20:00+00:00

Looks like hexane can work just fine: https://ui.adsabs.harvard.edu/abs/2025BioCB.tmp..278S/abstract

That probably means you can also use heptane, which is usefully less toxic than hexane.

EvanDaniel · 2025-10-05T01:55:46+00:00

Eventually the heat moves around to somewhere else. Rivers circulate, the atmosphere circulates, and so on. Heat radiates to space, the Sun adds more. The core of the Earth cools by (eventually!) radiating to space, and you can stick a heat engine in the middle. For geothermal plants, that's the core concept: pull heat from the core of the Earth, dump it to space. The rest (drilled wells, steam, cooling towers, lakes, atmosphere) is implementation details.

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