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Comment by JKCalhoun | Hacker News Reader

My KitchenAid mixer ate a gear many years ago. They would lead you to believe they are a high quality brand, no?

After disassembly, it turned out to be perhaps the only plastic gear in the thing. It occurred to me that it was perhaps designed to fail rather than the mixer continuing to break the bones of the person who got their hand caught in the paddle.

So, I throw the engineer a bone for that one. I was bummed though to have to order a replacement gear from some obscure place in Florida for like $75 or whatever.

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I had the same gear fail. It's called a worm gear and is, indeed, intended to fail before damaging the other gears. They're much cheaper if you buy a non-oem part. I bought one from amazon for ~10 USD.

Yeah, this was a time when Amazon was in its infancy. :-(

A worm gear! It is indeed designed to take the fall so the entire machine doesn't shred itself.

I bought an official replacement from KitchenAid for $12 including shipping.

> It occurred to me that it was perhaps designed to fail rather than the mixer continuing to break the bones of the person who got their hand caught in the paddle.

This is a good call out of potential other reasons an engineer team might make something cheaper & easier to break. It would be awesome to read a summary of the trade-offs the teams discuss in their process.

Yeah, sometimes there are plastic gears designed in specifically for this, in blenders and kitchen appliances, some lathes even have a set of several copies of one plastic safety gear. But sintered metal gears in planetary gearbox of a cordless screwdriver which fails faster than it's battery (Einhell) - not acceptable.

The real crime is that there are only like 5 appliance parts companies that stock parts and they each seem to look at the other companies for what to stock. Meaning, if someone else has it they won’t. But what ever they do stock ends up selling for 500% or more of the wholesale price.

For those who want to see a teardown, AvE has one on his channel here; https://www.youtube.com/watch?v=0qKp-0h9P18

Interesting — it is the "Professional" version and appears to have different internals than my consumer-grade one.

My Electrolux Assistent N8, from 1978, also has a worm drive. Not plastic though, instead it has an electromechanical stall detector that shuts down the motor if it stalls. No need for sacrificial parts!

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