These are the sizes you need to know. Sometimes, metric fasteners appear alike but don’t fit. There can be a few tenths of a millimeter difference between bolts that strip out or hold, That’s one of those things you notice once your parts is mounted. Having something as a quick reference helps make those decisions quicker and more safeley.
This might involve using newer hardware on an old piece of equipment or sourcing from multiple company. The “M” means metric, and the 8 is its size (an M8 bolt will be 8 millimeters at its major diameter). A single number conveys all that information. It tells you how big of a wrench to use, what the thread pitch is, and how much torque the bolt can absorbs before it breaks.
Why You Need This Reference Chart
That last part is very important, as we’ll see below. Knowing all that will help you avoid overdoing it with a fastener that can’t stand your best effort anyway but more importantly it helps keep you from grabbing the wrong tool. The chart lays out all the relationships in one place. This means you don’t have to go back and forth flipping different tables or memorizing everything while time ticks away on a project.
It displays wrench sizes, torque values, property classes, thread data, bolt head styles, nut styles, etc., in one convenient place. Details is important here, too: Which class of property do you choose? If it’s light furniture or brackets, a 4.6 bolt will work; for structural connections (or any item prone to vibration), you’ll need at least 8.8 or 10.9. While the latter have higher tensile strengths they also require tighter torque control.
You can over-tighten a 10.9 as easy as you can under-tighten and leave it loose, a stretched bolt beyond its yield point isn’t good either. The reference table show recommended values for both 8.8 and 10.9 bolts. This lets you find the proper grade based off the work required different than guesswork.
The same goes for wrenches. The chart lists each bolt size along with correct wrench size. This prevents you from chewing up corner of a bolt or rounding its head if your wrench fits too tight. It may not seem like that big of a deal but a mangled bolt turns what should of been an easy removal into a tedious struggle later on.
This holds true as well if you convert from inches (SAE) to metric. If you’re working on an old machine that has a mix of different fasteners, such as an imported piece of equipment, this conversion table will help. It gives you the metric equivalents for popular inch sizes so you can replace them. Typically using the nearest metric equivalent is fine, although again do check lengths and threads as the two systems weren’t intended to be used one for the other directly.
Don’t forget washers. The flat washer at the top distributes the load and protects the finish. The lock washer at the bottom left or the serrated washer at the bottom right prevents loosening. Refer to the chart for standard sizes to get the proper outer diameter. Avoid one that is too small and does not cover enough. Also, avoid one that is too large and interferes with surrounding components.
In truth though, what’s valuable about such a reference (whether online or otherwise) is that it brings all those random rules of thumb into one coherent image. Once you know where to look, for example, your decision on whether to use an M8 or an M6, a nyloc or a hex nut, etc., ceases to be a crapshoot, you have a fast yet solid answer.
