Using a plane to smooth wood is not a simple task and it takes considerable practice to be able to get an even, smooth finish. There is always a tendency to hold the plane too tight, put too much pressure on it and try to force it through the wood.
For a plane to do a perfect job every time without too much effort from the woodworker, it should be very sharp and set at the correct angle. A plane with a dull edge will just chew the wood up and may also be awkward to use because it will slip as you try to force it through the wood. Where woodwork is concerned everything should be careful, precise and gentle but firm. Never try to force things or it is guaranteed that sooner, or later, you will slip and make an error that you cannot correct, or injure yourself.
A metal wedge holds the blade in the right position and keeps the angle optimized for cutting. The old wooden planes that are still around have wooden wedges and were often made for special jobs by a particular carpenter. To remove the blade from the plane just lift the lever on a metal wedge, or simply pull out a wooden one. If there are holding screws in the metal blade release these. The blade will then come out easily.
Modern planes often come with a pack of replacement cutting blades, a bit like craft knives and it is very simple to replace a blade when it loses its edge. A plane without this facility needs to be sharpened just like the cutting edge on a chisel. A fine oilstone is ideal for this and the angle of the cutting blade should be 30 degrees. Some DIY or woodworking shops offer a sharpening service for plane blades.
The biggest problem encountered when planing recycled wood is often old nails and other metal fixings which may be embedded in the wood and not easily seen until the plane blade hits them and chips. This takes a long time to repair and may sometimes ruin the blade completely. Always remove paint from wood before planing because it will come off and block up the blade and make it blunt very quickly.
Plane blades need to be looked after carefully and kept very sharp and honed to the correct angle, which is thirty degrees. The time spent doing this is well worth it when you come to use the tool and see how easily it glides through the wood.