Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: Grade 8 bolt properties

[Subject Prev][Subject Next][Thread Prev][Thread Next]

On Nov 23, 2009, at 12:22 PM, Joseph R. Grill wrote:

I am working on a small project. Kind of a backwards design for some small steel brackets that are in the process of being detailed. The drawings the steel detailer call for Grade 8 1/4x20 bolts. I have found some information on the internet. What I think should be called out should be ASTM A354 Grade BD (it appears that it is in the same category as SAE J429 Grade 8). It has a yield strength of 130 ksi and a tensile strength of 150 ksi. Am I correct?
You're the only one who knows what should be called out for the project--what makes you believe the detailer called out the wrong bolts? ASTM A-354 gr BD is quenched and tempered alloy steel and grade 8 bolts are quenched and tempered medium carbon steel. That makes them different, even though the head markings are the same. The mechanical properties are the same for the grades you specified. If I were you I wouldn't consider them interchangeable until you find out why one was called out but not the other. Could be your detailer was just using he favorite throw-away designation, or perhaps there's a reason. Hard to tell from this distance.

In addition, the shop drawings that are in production, call for a ¼”-20 FH MSCR in another application on the project. I can see that it will be a ¼” flat head screw (the drawings show a countersunk part for the application and I believe the receiving part will be drilled and tapped. But what does the “MSCR” stand for? Sorry for the confusion here. And, what would the correct ASTM designation be? Same as above for the bolts as the table I found from American Fastener shows ASTM A#%$ Grade BD being for Bolts, Screws, and Studs.

I did a Google search for 'MSCR' and came up with one site that says it's a rarely used abbreviation for machine screw. It doesn't appear in either _Machinery's Handbook_ or my old drafting text. My drafting book references 'SCR' as a standard but dated abbreviation for 'screw,' and FH is an abbreviation for 'flat head.' So I'd guess that your detailer probably isn't a lot younger than I am and meant 'flat head machine screw' by FH MSCR. (Ref ASA Z32.13--1946)

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania 1864)

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at:
* * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to:
* Questions to seaint-ad(--nospam--at) Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: ******* ****** ****** ****** ******* ****** ****** ********