Matching a replacement screw or bolt can be a headache given the number of sizes and threading pitches you can find in even a modest hardware store. Mate the old and new for a perfect match.
Lifehacker reader KamWrex shares a great tip for finding a replacement screw sans guesswork.
Looking to replace a screw or bolt and don't know which to pick? If you use screws with different threading you can end up stripping or cross-threading your screw holes and ruining your project. An easy way to find a replacement is to take your original to the hardware store, place the threads of your original screw and potential new screw together, and compare the threads against a light source.
If the screws have the same threading they should "mesh" perfectly and should have the same pitch and angle of threading. Also, roll the two screws together back and forth in your hand with the threads still meshed. The threads should move smoothly against each other and if you hold one stationary while turning the other, it should screw and unscrew with ease.
You also need to consider length and thickness of the screw when matching but as a general rule if one screw is thicker than another you should still be able to tell by comparing the threads. As a side note, wood screws typically have coarser threads than metal screws (pictured) so that should narrow your search considerably.
Assuming you have a screw or bolt on hand to take with you, this is an excellent way to find a perfect match when you don't know the specifics of the screw or bolt in question. Have a handy tip for making DIY projects more fun and less frustration? Let's hear about it in the comments.