How To Figure Out Thread Size Of A Screw

How to Tell the Size of a Threaded Bolt

by Dan Ferrell

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The most common method to fasten components to engines, appliances, article of furniture and many other types of equipment is to use bolts. They come up in unlike sizes and configurations, depending on the specific part they demand to hold in place. Therefore, it is important to supplant a worn out, damaged or lost bolt with the same type used by the manufacturer. However, earlier you go out to buy a replacement, y'all demand to know exactly what commodities size and blazon y'all demand.

Pace 1

Make up one's mind the bolt forcefulness. On a standard (U.s.) bolt, lines or slash marks on the caput indicate grade or strength. The more than lines information technology has, the stronger the bolt. Metric bolts may have numbers on their heads for the same purpose. This code tells you how much torque (tightening) the bolt tin can withstand, and the vehicle service transmission for your particular make and model will indicate the exact torque to utilise. If you lot buy a bolt of lesser strength, information technology might break when you attempt to spike it.

Step two

Measure the exterior diameter of the bolt threads using a vernier caliper. The thread diameter is what is referred to every bit the commodities'due south size on the product package. Use inches for standard bolts and millimeters for metric bolts.

Step 3

Measure the distance across the flat sides of the bolt head using the vernier caliper. This measurement will requite the size of wrench y'all would demand to unfasten or tighten this bolt. Employ inches for standard bolts and millimeters for metric bolts.

Step four

Measure the distance betwixt the bottom of the commodities head and the opposite end of the commodities using the vernier caliper. This will requite you the bolt length. Use inches for standard bolts and millimeters for metric bolts.

Footstep five

Measure the bolt thread pitch using a thread pitch approximate, which you can buy in most tool or auto parts stores. This will give you the number of threads per inch, if yous are measuring a standard bolt or the distance between each thread for metric bolts.

Determine the type of thread, if you are measuring a standard bolt. You volition find two types of threads: Coarse thread (Unified National Coarse, or UNC) and fine thread (Unified National Fine, or UNF). Coarse threads have a wider altitude between each thread than fine threads.

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