How to Determine Screw Size Thread Count Step 1. Lay the screw down on a flat surface. Step 2. Place a steel rule down the axis of the screw . Step 3. Count the number of thread gaps within 1 inch of the screw . Step 4. Divide the count of thread gaps into the length. Step 5. If you have some stray screws and bolts (a.k.a. fasteners ) lying around and aren’t quite sure what size they are, or if you need to replace a missing bolt on a piece of machinery and need to know what size to get, here are some methods to easily figure that out. M2.5 Screws . For instance if you are measuring an M2x5 pan head screw the overall length will be 6.60mm but it will be listed under the M2x5 because a pan head is measured from underneath the head where as a standard flat head screw takes its size from the measurement taken from top to bottom.

If you have an identical screw , you can probably take it to Home Depot or Lowes and use the thread gauge mounted in the hardware section. (The HD in my area has one, but I'm not sure if all of them do.) This website also has several printable size gauges for screws … The 8 refers to the size (diameter) of the screw , and the 32 means it has 32 threads to the inch. The diameter is measured at the shank of the screw . Screws are sized by gauge number and length. Length . As a general rule, the length of fasteners is measured from the surface of the material, to the end of the fastener. For fasteners where the head usually sits above the surface such as hex bolts and pan head screws , the measurement is from directly under the head to the end of the fastener.

How to Size Machine Screws . Not only do you need to know the diameter and length of the screw , you also need to know the thread pitch, or number of threads per inch. Screws of the same diameter with a different thread pitch are not interchangeable, and may damage the tapped threads in a nut or hole if you try to force it to fit. To Determine the Size of a Bolt. First measure the diameter. Diameter is in either Inches ( not decimal ) or Millimeter. Second measure the pitch Pitch is threads / per unit. Inches are measured threads per inches . Metric are measured thread per millimeter. how to describe a wood screw . In the United States, a wood screw is sized by its. length, gauge, head style (for example, flat head), type of drive (for example, slotted or Phillips) and increasingly by style of screw .

How to Measure Bolt Size . Measure the length of the shank. The length of the shank is from the point where it meets the head to the opposite end. In the example, this is 4 inches . Determine the grade of the bolt. The grade describes the grade of metal or the type of material used to manufacture the bolt.