We have a kitchen aid mixer with one of the attachments stuck on. We can’t get it off the motor.
I think what happened was that the kids made something, didn’t clean it well, and it dried on. I was fooled because they cleaned the bowl.
We’ve tried soaking, heat, WD-40, pliers, big fuckin’ hammer, pretty much anything we can think of. The next step is dismantling the housing, but I wondered if anyone had any other suggestions.
One of the in-bowl things like a paddle or whisk, or something on the front PTO fitting like a slicer, grinder or sausage stuffer?
Go here,
and there’s a free phone line, 1-800-334-6889, and a couple of on-line ways to find help. They’ll probably want your model number, so find that first.
PTO!? You can drive a mower, tiller or baler off one of these? 
The on top vertical kind, to attach the bread kneader, whisk, etc.
Looks like this.
It might be bad for the motor depending, but I just made a cup of coffee after reading this, and it occurred to me that if you put a kettle under it and plugged it in, the steam might loosen the rock-hard sugar (or whatever).
What the heck were they mixing, and how did they get it up there?? I’ve used KA mixers for so long, taking things on and off is almost muscle memory, so I had to go look at the thing for a bit.
On mine, the paddle (or whip or dough hook) is a loose fit on the shaft, and to take it off, it pushes up about an eighth-inch, rotates a bit clockwise, then just drops off once the peg on the shaft lines up with the slot in the paddle.
Unless they were mixing plaster or royal icing, I can’t think of what they could have done to jam it up so badly. I’m guessing you’ve got a tilt-head “Artisan” model as it’s nearly impossible to get the bowl off a bowl-lift mixer without taking the paddle off first. But that shouldn’t affect how the thing comes off.
I hear what you are saying, and I completely agree. (I think it might have been my husband, but he’s doing the “not me” right along with them.)The motor runs just fine, and I’m pretty sure the spring still pushes in and out.
It is just stuck. I’ve tried soaking, WD40, pounding on it with a hammer and chisel, trying a piece of metal rod widthwise to lever it to rotate, steamed it. We owned it for probably 5 years before this, I know how it operates. Screw it, I’m going to try to dismantle the housing, approach it from that way.
Looking at my KA mixer the shaft is steel, and the wire whip is another metal. I suspect that corrosion has set in between the two metals.
Before you tear it apart try this.
Get some good rust penetrant (not WD-40) PB blaster or something similar. Spray the shaft. Spray in the little key way hole.
Let it sit over night.
Turn the mixer over and have someone hold it. take a punch and a small hammer and see if you can get the beater to move up the shaft. As gotpasswords said it has to move up before it can turn. Once you get it up, spray the shaft again and work on moving it to release.
Good Luck
Just in case ya need it, here’s a link to a KitchenAid Service Manual (PDF), so you can break it down without breaking it 
!
CMC +fnord!
What about a couple of good solid whacks at the bottom of the attachment (upwards towards the machine) with a rubber mallet.