Shredder Tuning for no friction, shims & alignment

Precious Plastic Machine Development
#1

Does anyone who has completed a shredder have any advice for eliminating friction in the arrangement?

considerations are:
1. shims between blade seat pieces so they bolt together tightly and effectively with the box sides.
2. collars on the ends of the axle so blade pieces dont come loose onto the round milled ends of the shaft
3. spacing between the blades and spacers on the shaft. you can perfectly tighten the blade seat pieces to the box with a shim. But how to ensure that the blades sit perfectly apart with no friction?

The only way I can think of is to lathe the shaft more than the recommended size in the schematic, reduce the number of blades and use collars to fix the blade positions, avoiding side loading the bearings when you bolt the box together.

What are peoples experiences with this stage of ‘shredder tuning’?

Many thanks in advance for responses

#2

I’m not really following what you’re going after?

Remember the spacers and the cutting teeth are different thicknesses of metal to allow for clearance between them. In my design the cutting teeth were 1/4″, and the spacers were 5/16″, so you have 1/16″ (or about 1.5mm) total clearance between the teeth. So when everything is put together you won’t have any metal-on-metal contact. Also remember that if you want things to fit together tightly like that, you’re going to have to make the parts more accurately (which increases cost).

Personally I think it’s OK if the teeth on the shaft can float a little bit. Everything goes together pretty easy and tends to self-align…

When I put mine together, everything spun freely on the first go.