The 1/4″ refers to the bolt diameter (in inches), the -20 refers to the threads per inch meaning that there are 20 threads per inch on this 

2-4 1/2 x 8 Hex Bolt. This bolt has a hex head, is 2 inches in diameter, has 4 1/2 threads to the inch, and is 8 inches long. Use a 2-4 1/2 nut with this bolt. Following are just some of the more popular sizes (diameter-threads per inch) of machine and caps screws and other fasteners Fastener Mart sells. Table 3.

DEFINITIONS. The diameter equal to the external diameter of the threads or the overall diameter of the part. (Nominal diameter is more of a label than a size. For example, a bolt and nut may be described as being ½" diameter. But neither the external threads of the bolt nor the internal threads of the nut are exactly .500 in diameter.

Hex bolts, also often called hexagon screw head bolts, hex cap bolts, hex-cap screws, or machine bolts, are a very common choice when it comes to construction and repair. 1/2"-13 x 1 1/2" Product Specifications

I will ship up to four lots in one small flat rate box for $5.95 shipping. HEX HEAD BOLTS WITH NUTS 1/2-13 X 1 1/4" LONG, PLATED (LOT OF 10) HEX HEAD BOLTS WITH NUTS 1/2-13 X approx. 1 1/4" LONG. PLATED, LOT OF 10 PIECES These bolts and nuts are mixed grades and classes. If you purchase more than one lot.

Metric Bolt Conversion. Metric bolt conversion data for industrial bolts/rods , machine screws and small diameter fasteners from Raaj Sagar Steels includes metric to standard bolt conversions. The chart below shows metric bolt conversions and DIN numbers for fasteners.

Other size measurements, such as screw, bolts, pin length, the outer diameters of nuts & washers, etc., appe the search result itself. A. Parts that 

Choose from our selection of 1/2"-13 nuts, including over 900 products in a wide range of styles and sizes. In stock and ready to ship. BROWSE CATALOG. Abrading & Polishing; Able to maintain their strength in high-pressure and high temperature environments, these nuts are used with ASTM A193 bolts to fasten pressure tanks, valves, and flanges.

Choose from our selection of 1"-8 bolts in a wide range of styles and sizes. In stock and ready to ship. BROWSE CATALOG. Abrading & Polishing; Building & Grounds; Electrical & Lighting; 1/2 "-13. 1/2 "-20. 1/2 "-28. 9/16 "-12. 9/16 "-16. 9/16 "-18. 9/16 "-20. 5/8 "-5. 5/8 "-6. 5/8 "-8. 5/8 "-10. 5/8 "-11. 5/8 "-14. 5/8 "-18. 11/16 "-18. 3/4

Hex Bolt Sizes and Thread Pitches Chart. *Length is measured from under the head to the end of the bolt. 3/8” - 16. 7/16” - 14. 1/2” - 13. 3/8” - 24.

1/2 " 13/16 " No. 4: RoHS (Restriction of Hazardous Substances) RoHS (Restriction of Hazardous Substances) Their high tensile strength means they can be used in demanding, high-stress Also known as pressure bolts, they meet the high-pressure, high-temperature regulations of ASTM A193 and are used to secure pressure tanks