Sunbeam Mixmaster 12 (vintage 1950s) 12 speed stand mixer runs a little rough at low speeds, and when you turn up the speed it revs up and down. If you turn the dial it does not increase speed from settings 8 through 12.
If this unit needs oil, what kind of oil should I use, and where do I apply it?
Part 1. Oiling the model 12:
Anyone can do this part.
On the top of the motor are four places where oil should be applied.
Starting from the speed finder dial and working forward-
There is a small hole on the top of the motor, just in front of the speed dial. Using a wooden skewer or a match, clean the hole out, and apply two drops of good quality sewing machine oil.
On top of the motor, and near and behind the juicer attaching cone is another hole, sort of key-hole shaped. Clean it out and put in one drop of oil only.
Three drops of oil go into the juicer cone. Let them run down the side of the hole.
Next to the juicer cone is another round hole. You may need to turn the handle as in removing the beaters to uncover it. Clean this hole too, and apply another three drops of oil.
Do not apply more oil than specified. It will get into the works where it shouldn't.
The following proceedures assume some mechanical ability. Read first to assess whether you are competent before starting.
After all these years, the gears in the front of the motor housing probably need fresh grease. This is a fibre based food grade grease that can be obtained from most bearing sellers. (I used a non-food grade grease, but I have to watch that the motor doesn't get too hot, and the grease run down the beaters, which can happen in extreme conditions.)
Prepare to get greasy during this proceedure. Latex gloves are an asset for doing this job.
Remove the cover plate in the centre of the front, and then the central screw from the front and pull away the front housing cover and handle. Don't loose the coil spring inside. It goes over the screw you just undid.
Unclip the return spring on the beater ejector, and remove ejector and spring together, slide the ejector down and off the beater spindles, then up and out of the guides..
There are four screws that retain the gear cover. The lower right hand one also retains a wire. Remove the screws, and gently bend the wire so the cover can be removed. There is a gasket underneath. Take care not to break it, it's brittle.
Once the cover is away, the gears and worm shaft are visible. Using a pop stick or old screw driver, remove the grease around the under side of each gear. A square headed set-screw retains each gear. When you find each screw, remove it completely. Turning the worm shaft will make the gears rotate.
Once both screws are out, pull the beater drive shafts downwards and out of the housing, and lift out the gears.
Using pop sticks, paper towels etc, but NOT solvents, clean out the gear space. Remove all the grease possible. A toothbrush is good for cleaning the worm thread. Use someone elses.
Wash the gears and shafts in petrol, kerosene or similar and dry thoroughly.
Reassembly is the above in reverse order, first filling the gear housing with fresh grease.
Grease each drive shaft lightly before refitting. Note the holes for the set screws in the shafts.
The nylon gear goes on the left, brass under the juicer cone.
Fit the nylon gear first, working the shaft upwards until the locating hole in the shaft can be seen through the screw hole in the gear. Fit and tighten the set screw.
Align the brass gear so both screws face forwards at the same time when engaged with the motor worm, to prevent the beaters clashing. You may have to put the brass gear in and out a few times to get the right teeth engaged with the worm shaft. Then slide the shaft in, once again observing the alignment of holes to ensure the set screw locks the gear securely.
Put everything else back in reverse order. Apply a smear of grease for the beater ejector where it slides, and don't forget to put the wire back under it's screw.
Part 2, speed control.
The jerky operation at low speed is probably due to dirty points in the governer. Addressing this involves disassembling the rear end of the motor.
DON'T pull the motor armature out of the housing without first removing the brushes during this proceedure. There's no need to remove the armature, but if you're curious....
Remove the chrome cap from the centre of the speed finder dial. Remove the lock nut from the thrust control screw under the cap. Remove the dial, catching the washer that goes under the nut.
There is a resistor, usually green, and a capacitor, a small aluminium cannister under the dial. Gently pry the retaining legs away from one end of each and remove them. Note which one goes where so you can put them back correctly. Marking with a felt pen is a good idea.
Now are visible two slotted screws. Remove these screws and pull the governer housing back and away from the motor. Note the pin with a plastic head, and remember to put it back when reassembling the same way around.
Locate and clean the points with a slip of soft wood and metal polish. Clean away the polish thoroughly. Do not use emery paper, it will make the points arc, and speed control will be worse than now.
Put everything back the way it came off.
To reset the governer, leave the locknut on the thrust controling screw loose. Set the speed control to position 1. Whilst pressing the dial home with one hand, screw the thrust screw in or outwards until the motor just starts to run, and lock the screw by tightening the nut. Test the control for full range, and tweak by slightly altering the thrust screw position as required. Getting the speeds just right first go is usually a fluke.
Replace the chrome cap and you're done.
Thank you for such a well written and detailed instructional how to answer. Very helpful to me when working on my grandmothers Mixmaster.
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