You have access to a lot of metric fasteners today. If you're looking to specifically hold materials together, then metric bolts are what you'll need to invest in. There are many choices, but if you stick to this guide, you'll be able to find the right set without struggling.
Make Sure Bolt Strength is Appropriate
In order to put complete faith into a particular variety of metric bolts, it needs to have the appropriate strength levels. Only then will it support materials being joined together for a long time, as well as holding up to the environment it's exposed to.
Think carefully about strength properties until you can find the perfect metric bolt match. You should account for what the bolt is made of, the protective coatings it might have, and the specific tolerances the manufacturer put in place. Just try to match strength levels with how these bolts are being used in projects coming up.
Carefully Review Diameter Sizes
You'll need to figure out what diameter size is appropriate for your metric bolts. The options may seem endless, but if you study how you plan on using these metric fasteners, you can easily narrow your choices down to one diameter size in particular. It just takes some sound assessments, such as what materials you're driving the bolts into and how much strength you need. For instance, if you plan on supporting heavy materials like steel, you might be better with a thicker diameter because it will improve this fastener's tensile strength.
Consider Varieties With Built-on Washers
If your metric bolts will be exposed to a lot of force when connecting materials together, you might want to consider a variety that has built-on washers. The washers will help distribute the force evenly to ensure the bolts don't break down under pressure.
Built-on washers are also going to save you material costs because you're just paying for one type of fastener, as opposed to two if you purchased washers separately from metric bolts. Ultimately, this design is going to help your metric bolts perform better with different materials.
If you're planning to join materials together like wood or steel, you can use metric bolts and get great fastening results. Just make a point to get a variety that has advantageous properties, so that once you start working with metric fasteners, you have nothing but positive experiences every step of the way.