Food mixers and blenders are two of the most labour-saving appliances available for the kitchen. There is a wide range of models and your choice will be determined — apart from appearance and price — by the number of jobs the appliance can perform using the variety of attachments available with each model.
Some food mixers may be uneconomical to repair if the motor fails; many manufacturers, however, have service agents who carry spare parts and in most cases a replacement motor can be fitted at a reasonable cost. Always check to see if a repair is possible and worthwhile.
Mixers can be divided into two groups — large food preparation machines and hand mixers; blenders are either an attachment to a mixer or a separate unit. Food preparation machines are large and powerful; they can tackle a wide variety of cookery tasks and will cope easily with large quantities and heavy mixtures. They usually have a wide range of optional attachments, including primarily a blender, which are for specialized food preparation.
Hand mixers are smaller and less powerful than food preparation machines; they are also less expensive and more commonly used. They can tackle most of the tasks performed by the larger type of machine, but in smaller quantities and with lighter mixtures; they are flexible since you can use them in a saucepan or mixing bowl.
This type of mixer should be used only for light work; it tends to become overloaded if used for heavy work such as making dough. When choosing a mixer decide to which uses it will most often be put; if you have to overload a hand mixer, you really require a food preparation machine.
Replacing gears One of the results of overloading the mixer is damage to the gears which drive the two beaters. The gears are normally made of plastic or nylon; in the event of overloading they are designed to strip and lose the drive from the motor, preventing the motor seizing up and burning itself out. To renew the gears, separate the two halves of the mixer body; these are usually held together with nuts and bolts. Once you can see the gears. You will find they are held in position by a frame, which also connects the motor drive shaft to the gears.
Determine whether the gears are different from each other (that is moving to the left or right); some mixers use identical gears and some use opposites. Note which type you have and how they fit together before you remove them. Ensure you buy the correct replacement gears and ask the supplier which grease you should use with them; the gears must be coated with the recommended grease before you reassemble them inside the appliance.
Once greased and replaced, insert the two beaters in place and slowly rotate the motor shaft by hand. This will turn the beaters; if they scrape against one another, you will have to reposition the gears so the inserts for the beaters are in the correct relative positions. Beaters knocking against one another while the appliance is running will cause serious damage and could be dangerous.
Food preparation machines
These machines may at first sight appear very enclosed and sealed ; there are, however, several small repairs and simple maintenance jobs you can perform.
Belt and pulleys
If the drive belt needs to be replaced because it has frayed, cracked or stretched, you can do this yourself. Remove the mixing bowl and take off the top cover, usually held with three screws. This cover will usually have an anti-vibration seal on the front of the gearbox assembly; this should also be removed. You can now remove the drive belt; check whether the large pulley is metal or nylon since each type requires a different belt. The correct replacement belt can be obtained from the supplier of the mixer. The small pulley is held to the motor shaft by a pin driven through it. If it should need replacing, remove the pin by lifting off the loose sleeve and tapping it out with a drift. Support the back of the pulley with one hand to avoid damage to the motor shaft or motor as you tap the drift. Once the pin is out you can remove the pulley and replace it with the correct component.
To replace the large pulley you have to remove the clutch dog which holds it in place; this is screwed to a drive pinion assembly. Hold the gear inside the slow speed connection as you remove the dog with the correct size spanner. Be very careful not to damage the gear mechanism. You may be able to borrow or hire the correct removing tool from the manufacturer; if not, try to lock the gear with a large flat-bladed screwdriver.
Planet hub and gear
Inside the moving hub gear is a smaller gear, which may be metal or nylon. This gear may fail, therefore nylon versions are now replaced with their metal counterpart since it is much stronger. You will have to remove the planet hub to replace the gear; lift the head of the mixer backwards and secure it in position. The hub is held by a nut and washer; once removed you can free the hub by tapping the spindle with a mallet. With the hub free you should see the gear attached to its drive shaft with a push-on clip. If the gear is broken, you will see the pieces loose inside the hub. Prise off the hub clip with two small flat-bladed screwdrivers and fit a replacement gear; it is worth fitting a new hub clip to ensure the new gear is completely secure on the drive shaft.
A blender or liquidizer may be an attachment to a food mixer or a separate self-contained unit. These machines vary in power, design and price.
Drive coupling wear
If you disregard the correct quantities and thicknesses to use in the blender, the drive coupling inside its base will tend to wear very quickly. The coupling is made of a flimsy material so if the blender seizes up during use, the coupling will break or melt. This prevents the motor stopping and causing greater damage to the appliance.
Another reason the blender may seize up is if the bronze bearing in which the cutter blade rotates dries up because of lack of lubrication; in this case heat is created which will cause the shaft to seize. When lubricating this bearing, grip the nut securing the cutter blades with pliers and unscrew the drive coupling; on some blenders the blades spin in a clockwise direction while on others they spin anti-clockwise. Lubricate the bearing with vegetable oil and clean the shaft so there is a smooth running fit. Replace the cutter blade in the reverse order of removal.
Adjustment to the speed variation control and the motor of these appliances should be left to your local service agent; they are complex and require fine adjustment.