The cutting edge – fitting the tines correctly
Generally you should make sure the cutting edge of your tines is at the front for forward rotating machines. It is usually easy to see which side off the blade this is.
However, some blades do fit on both ways, so always check your manual carefully.
Contra rotating Rear Tine Tillers and Cultivators will have blades that ‘scoop’ rather than ‘scratch’ and so will be fitted the other way around, cutting edge towards the back.