A friend is a neurosurgeon and they use some special saw that stops as soon as there's no hard tissue providing resistance. So you press it hard into the skull, and when it's done chewing through the bone, it immediately stops.

Apparently the scariest bit for the junior doctors to learn to use, somehow.

That is known as the perforator drill bit - https://www.reddit.com/r/toolgifs/comments/z2zikm/cranial_pe...

Used to make burr holes so that the dura can be stripped away from the skull using the Penfield 3 instrument.

Then what's used is what's known as the B1 with footplate to create the bone flap - https://www.researchgate.net/publication/323134344_Exposure_...

Here is an example of the drill system - Midas Rex MR8 - https://www.ebay.com/itm/125960633809

Here's a video of a surgeon performing the pterional craniotomy, probably the most common craniotomy for things like aneurysms, - https://www.neurosurgicalatlas.com/volumes/cranial-approache...

Same or very similar stuff is used to cut plaster casts for broken bones. You see that small circle rotating next to your veins in legs and there is suddenly some tension in the room. Especially when saw seems to keep stopping when cutting through plaster for no good reason, causing some confusion for the doctor and making him lean more heavily into it.

Afterwards they realize that harder resin casing was layered with soft fabric by previous orthopedic surgeon in previous hospital, so the thing actually worked as intended (but if you keep pressing power button and leaning into it it will keep cutting). Talking about hospital equipment in Switzerland, 2 weeks ago after a nasty paraglider crash landing.

Cast saws are different, they don't affect skin as demonstrated by this youtuber with a high speed camera:

https://youtube.com/watch?v=Bx1AiQdMQro

edit: though actually I googled the skull saws which I wasn't familiar with and they might work on a similar principle, found someone talking about using them in autopsies anyway.

That's strange. Cast saws don't need to stop like that; they can't cut skin even running at full speed. Your grey matter is not as tough as your skin and you wouldn't want to touch it with even a gentle power tool, though, so it makes sense that brain-surgery saws would be different.

I'm forever grateful to the doc who actually pressed the running sawblade into his hand to prove that it's harmless, instead of just saying "don't worry, it's safe" while going to town on my leg with a power tool.

You mean the bonesaw-through-the-chest scene in Reanimator was not accurate?

What would the difference be in your mind?

As long as the blade is suitable for cutting bone and it's all sterilized, what would make it medical grade over carpenter grade?

My Dad was the manager of a tool store for decades. He has had a lot of knee problems and he has a funny story about his knee surgeon coming into the store looking for a drill bit to drill out a stripped screw. He jokingly asked if the stripped screw was in someone's knee, and sure enough it was.

My woodworking equipment has a certain amount of jitter and give. It seems to have precision to about 1-1.5mm. I imagine medical grade machine cutting would have higher precision?

Probably, but when you're watching these surgeries as a layman for the first time it's surprising how much fumbling around they seem to do. I have a few pieces of metal inside me so took more of an interest at some point, and even those surgeons admit their job is mostly carpentry on hard mode.

My grandfather was an orthopod and an amateur carpenter. The skills really do transfer.

Next time you go under ask your surgeon to take pictures and videos. Very interesting to see inside your body!

I even kept the metal rods they had in my leg in between surgeries that would otherwise be thrown out!

A friend of mine got a hip replacement, and asked for the old hip.

They refused to give it to him. They said it was "medical waste," and they weren't allowed to deal with it, except in whatever federal manner was required.

It would need to be survive an autoclave, for one thing. It would need to be possible to actually clean it, not shed bits of paint and plastic into the patient's skull, material compatibility with antiseptics, etc.

If I thought about it for a few minutes, I'm sure I could create a long list of requirements for a suitable saw.

> what would make it medical grade over carpenter grade?

In my experience, about $50000.

As long as it survives an autoclave and doesn't leave behind any debris in the site, it seems fine.

You will have a very hard time sterilizing a carpenter grade saw.

Nah… that was a joke.

But their tools look surprisingly like standard hardware.

Lot more pricey, though.

'x grade' stuff is usually just about testing & certification, it's not that it is actually necessarily any different from the 'standard' model.