Paddle mixer

From DIYWiki

Paddle mixers are used for plaster, paint, resins, lime mortar, papercrete and occasionally other things.


Small paddle

Small cheap mixing paddles are intended to be used in a regular drill. Typically these have a hexagonal shaft, and are often painted orange.

Standard Paddle

These are intended for a mixer drill only. They have a threaded end, and are larger & heavier duty than the above types.

Home made paddle

They're easy to make if you have a welder.

A few people have tried a short length of chain welded to the end of a rod, and report better results than a rigid bar.

Paddles for plaster

For plaster mixing, it's important to be able to clean the paddle of all plaster between batches. Many commercial designs fail in this respect, with corners and traps in the design which are difficult to clean out. (Completely set plaster doesn't matter providing it doesn't come off into your new mix, but partially set plaster from the previous mix causes the new mix to go off faster.)

Mixer drill

These run at around 500rpm with about 1kW, and are designed to be used for longer under load than a standard mains drill. They have a threaded socket to take standard paddles.

There are also bigger versions that drive 2 mixing paddles.

Standard drill

Not designed for paddle mixing, prone to overheat in this application, and they run too fast with too low torque. Paddle mixing with them tends to void any warranty. They remain popular because only a paddle need be bought, but work throughput is poor compared to a purpose designed paddle mixer. Pick a drill with a 2 speed gearbox on low gear.

SDS drill

These run at lower rpm than traditional drills, a real advantage. Still not as well suited as a purpose designed mixer drill.

Paddles can be held in a Jacob's chuck adaptor, or SDS shanked paddles also exist.

Self contained paddle mixer

If you do a lot of plaster mixing, one of these might suit. They can be left running, enabling other work to be done.

They generally consist of a large bowl and an overhead motor & paddle, but other patterns exist too.

Horrible hybrids

Paddle modded 6272.jpg

Paddles can be modified to better suit the task and the motor in use. Here a 500rpm paint mixing paddle was modified to pulp paper at 800rpm:

  • one of the 2 rotors was cut off to increase the ideal working speed of the paddle
  • the blunt rotor edges were sharpened to improve pulping
  • the threaded top end was evenly ground down to fit a mains drill with 2 speed gearbox. (this is far from ideal, but we needed it right away and couldn't find a mixer drill within driving range).

If tempted to grind a threaded paddle to go into a jacob's chuck, the hexagon must have accurately straight sides or the chuck can't keep hold of it. This is impossible to achieve freehand. It should be accurately symmetrical to avoid wobble and heavy vibration.


See also

Cement mixing