There are a number of choices when it comes to bolts for fixing wood. Each woodworker has a preference and bolts are not something that is normally used very much during DIY work, so it should not be necessary to buy in large quantities.
The coach bolt has a square collar, or neck and a dome shaped head. The collar locks itself into the wood as the nut on the end of the bolt is tightened, so only one spanner is needed to fix it. There is no need to hold the head of the bolt as the nut is turned. Putting a washer under the nut will stop it from sinking into the surface of the wood. These coach bolts come in a whole range of sizes and go up to twenty inches in length and up to three quarters of an inch in diameter.
Machine bolts have flat heads and will not lock into the wood so two spanners are needed to tighten them up and a washer should be used at both ends. These go up to twenty inches in length and three quarters of an inch in diameter.
For smaller woodworking jobs machine screws are suitable. The heads are slotted and can be tightened with a screwdriver while the nut is held with a spanner. A washer should be used beneath the nut but there is no need for one under the screw head. These come with a variety of different heads including counter sunk, round and pan heads and are available up to two inches long and a quarter of an inch in diameter.
Nuts come in different types too but they are commonly hexagonal. Wing nuts are useful because they can be tightened by hand. The main thing to check is that the nut and bolt have the same kind of threads because they are made in metric measurements and in various types of imperial thread. Whitworth (BSW), British Standard Fine (BSF), British Association (BA), Unified Coarse (UC) and Unified Fine (UNC) are all available in DIY and woodworking shops.
