How do I choose the right size of a nut or washer?

First, it is important to understand that the size of a nut or washer is based on the diameter of the threaded stud or bolt it is used with. Follow these steps:

• Measure the outside diameter of the threaded stud or bolt with a ruler or caliper. This gives you the M thread pitch size - a standard measurement for bolts and nuts. For example, an M10 means a diameter of 10 mm.
• To select the correct nut, the inner diameter should match the diameter of the threaded stud or bolt. For example, if you have an M10 bolt, you need an M10 nut.
• To select the correct washer, the inner diameter of the washer and the outer diameter of the bolt or threaded stud should match so that the washer fits securely.

Also note the thread profile (usually metric or imperial) and make sure that the nut, bolt, and washer are made of the same material to avoid corrosion. Still unsure? Do not hesitate to consult a DIY expert.