How would you go about making a three fourths of an inch thick piece of pine wood 0.5 cm thick?

Answer 1

An inch is equivalent to 2.54cm. If a piece of wood is 3/4 of an inch thick, it is about 1.9cm (19mm) thick, therefore to create a 0.5cm (5mm) thick piece from this it would be necessary to cut the excess 14mm off.
The method to use for this will depend on the shape and size of the piece of wood.
For a small piece of wood, it could be marked around the edges, clamped in a work vice and hand sawn to give the desired thickness. Sanding the wood afterwards will bive a neat smooth finish.

When cutting, be careful not to place fingers in the path of the saw, and clamp the work-piece securely. You can put thin card or wood either side of the work-piece to prevent it being damaged by the clamp, but make sure these are clear of where you need to cut.

A small area could be cut down in thickness by using a router or a chisel. If you have not used either of these before, get some help and practice on scrap pieces first.

For a slightly larger piece, a very coarse sandpaper on a belt sander can quickly remove material or you could use a plane.

For large pieces use a thicknesser. If you do not have access to one of these, call joinery workshops and ask whether one would do this small job for you. This will give the neatest finish.