Hammerknife

The other day I was cutting some slices from a block of cheese, as I have many times before, and once again painfully noticed the quite large amount of force necessary to push the knife through the cheese.

To solve this, I propose a knife with a mechanism built into the handle to apply repeated blows through the blade, in the cutting direction. (To achieve this from the handle, the blows must have a rotational component, I think.) You would just press down lightly, and the mechanism would either use an electric motor to hammer the knife through the thing to be cut, or would operate like an automatic center punch (but repeating) to harvest energy from your continuous light pushing and concentrate it into short sharp blows.

This would be useful for cutting many things other than cheese. With a sufficiently strong and hard blade (not necessarily a contradiction—see composite metal swords), it should be possible to cut metals, which would be useful for harvesting components from appliances found dumpster diving, for example.

An advanced version could have a sagitally split blade similar to that of an electric carving knife. One side of the blade would hammer down at a time, cutting a little further, while the other would remain in place, stuck to one side of the kerf either through friction or using barbs, as an anchor for the blow and/or energy harvesting.