Recently I had a problem with my Bosch mixer and in addressing it I learned something that other Bosch owners may find valuable.
I was starting to mix a favorite bread recipe of about 3kg of dough when the dough hook stopped turning even though the motor was running. No amount of coaxing would get the dough hook to turn. After finishing the dough by hand I turned my attention to the mixer.
Owners will know that the dough hook is activated by a spindle and the spindle turns because its splines fit down into the female splines of the motor/transmission. On inspection I noticed that the spindle’s splines were pretty chewed up. I thought I needed at least a new spindle. I called Bosch. The Service/Parts person listened to my description of the problem and replied that it was the transmission and that if I sent it in they would repair it for approximately half the cost of a new machine.
Now, like other Bosch owners, I bought the dang thing because of its reputation for having a transmission that could handle anything that was thrown at it. So ...
I knew the spindle splines were shot so I ordered a new Spindle at about US 25. When it came I got out my dental pick and high intensity light and looked at the transmission splines. They looked rounded but when I started probing I found that the base was full of gunk as hard as soft stone. After a thorough cleaning with the pick I fully restored the splines and the mixer now works perfectly.
Here is the takeaway ... one of the down sides of this mixer is that dough has a tendency to climb the center of the bowl and then go down the spindle. If it goes down the spindle it will settle in the bottom of the transmission splines eventually causing the spindle to rise up and get chewed up. Keep that transmission seat spotless by checking it carefully during cleanup.