Greg's FAQs
Hex Bolts vs. Hex Cap Screws
What are the differences between a hex cap screw and a hex bolt?These terms are often incorrectly used interchangeably. The most basic difference between a cap screw and a bolt is the way in which these fasteners are installed. Technically, a bolt is installed by turning a nut to tighten the fastener, while a cap screw in installed by turning the head of the bolt to assemble... Read more
Lag Screw Shear Strength
How do I determine the shear capacity and strength of lag screws?Unfortunately, we have no specific data to answer this question. First, “standard” lag bolts that are readily available in the marketplace are ungraded, meaning they are not manufactured to any ASTM specification and have no verifiable mechanical requirements. Therefore, it is impossible to determine the strength characteristics of a lag screw unless they are custom... Read more
Grade 55 Steel Properties
Can I use ASTM 108 Round Bar, a CF-1018 round bar, for F1554 Grade 55?The problem with ASTM A108, 1018CF is that there are no mechanical requirements and typically the test reports that accompany this steel reflect the chemistry only and not the strength of the steel. Test reports will need to accompany this material that reflect all four of the values listed below, and these values will need... Read more
Malleable Iron Washer Details
What are the purposes for the different components in malleable iron washers (MIW)For many years a malleable iron washer has been a common component in heavy timber and marine construction. With a large bearing surface and thick cast design they help prevent the bolt head or nut from pulling through wood connections. There are two common types of MIW. One style of malleable washer is produced in... Read more
Grade C Eliminated From ASTM A307
What happened to ASTM A307 Grade C?One change with regard to specifications that will have a significant impact on the construction fastener industry is the August 2007 elimination of the grade C designation within the ASTM A307 specification. ASTM A307 is the standard specification for low carbon steel construction fasteners. Until recently, A307 had three grades A, B, and C. Grade... Read more
SAE Grade 8 vs ASTM A490
What are the differences in strength and application between SAE Grade 8 and ASTM A-490?In some respects SAE J429 grade 8 bolts and ASTM A490 bolts are similar, and in other respects they are different. The first thing to address is the fact that these specifications are covered by different organizations. SAE (Society of Automotive Engineers) covers bolts for automotive, equipment, and OEM applications, whereas ASTM (American Society for... Read more
Structural Bolt Length Tolerance
According to section 9 of the ASME B18.2.6 specification that covers fasteners for use in structural applications, an A325 structural bolt can actually be produced .12” to .25” less than the published length and still meet the specification.According to section 9 of the ASME B18.2.6 specification, which covers dimensional tolerances for hex bolts, A325 and A490 structural bolts can actually be produced between .12 to .25 of inch less than the published length and still meet the specification. This small difference isn’t much, but mass bolt producers save a significant amount of... Read more
How a Bolt Head is Formed
How is a bolt head formed?What many people do not realize is that the head of a bolt is formed by heating the end of a piece of steel round bar and then forging (reshaping) the heated end into a head. The head is not welded on or otherwise “attached” to the end of the round bar. For example, the... Read more
ASTM A193-B7 Thread Pitch
What bolts are available in ASTM A193-B7 and what is the appropriate thread pitch to specify?“My plant uses hex head cap screws, ASTM A193-B7 as standard. We typically stock the constant thread series 8 TPI fasteners above 1 inch diameter. However, many tapped items like expansion joints come with UNC thread counts, like 7 threads per inch (TPI) for 1-1/4″ diameter bolts. This causes a problem sometimes when fasteners don’t... Read more
ASTM F3125 Grade A325 Anchor Bolts
Can ASTM A325 bolts be used as anchor bolts?Engineers occasionally specify the use of F3125 Grade A325 heavy hex structural bolts as anchor bolts, but technically they are supposed to be used for structural steel connections only. Part of the problem is that the A325 specification is very specific as to the application and thread length. Because A325 bolts are typically used in... Read more