Clarification-Bolt markings

[Mick Conde]

MG Group: For years I have wondered about the bolt markings and how they relate to the "grade" if any. As an example, the rocker tower bolts, 8 & 10 mm, are marked AUTO D and R. If grade were correct, which is the proper one? If this info is in print, please advise. THANKS Mick Keystone Classic Cars LTD. PS: Merry Christmas to all. _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp.

[Mick Conde]

Bob- Thanks for your reply. I think the 8 & 10 mm was a bad example to use, as I this is the only place metric was used. Most common bolt suppliers were Sparts/Bax/CSR and a few others, some of these suppliers also used the D & R (grade?) markings. I spoke with Don Lawson (tech editor for Sacred Octogon & long time personal friend) and he didn't have a clue. I was hoping one of our group from across the pond could straighten us yanks up proper! Mick Keystone Classic Cars, LTD.

>From: "Robert Johnson" rjdirect@earthlink.net> >To: "Mick Conde" mick_conde@hotmail.com> >Subject: Re: [mg-tabc] Clarification-Bolt markings >Date: Mon, 24 Dec 2001 21:54:50 -0800 > >Hello Mick: > >I have in my auto library a recent book entitled "Hot Rod Hardware" by >Timothy Remus, published in 2000 by Wolfgang Publications, Inc., 1310 Sunny >Slope Lane, Stillwater MN 55082 USA. The first few chapters assume the >reader knows nothing about fasteners and describes in great thoroughness >the >grading and markings of bolts made of different materials with >illustrations >in considerable detail for Metric and Inch hardware (and some comments >regarding Whitworth). I have found it to be a very useful reference. > >Grading markings on metric bolts consist of either 2 or 3 numbers, the most >common being 8.8 (roughly an SAE Grade 5), 9.8, and 10.9 (roughly an SAE >Grade 8). The "AUTO R and D" you mention do not appear among the listings >of >markings used either historically or currently so what you have is a bit of >a mystery to me. Perhaps these markings are specific to some other marking >system which might have been considered too obscure to have been included >in >this otherwise very good book. > >Bob Johnson - '46 TC 1450 >Crescent City, California > >

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[Chip Old]

On our T-Types the metric bolts used in the engine and gearbox weren't made to the prevailing DIN metric specifications, much less to modern ISO metric specifications. Just like the BSF, BSW and BA bolts, the heads usually (not always) have letter grade markings (D, R, S, etc). I've never found anything definitive about these markings, but a table in a very old Metric & Multistandard Componants Corporation catalog provides the following rough equivalences. Emphasis on "rough". British US DIN ISO ------- -- --- --- R 3 6S 6.8 S 5 8G 8.8 V 8 10K 10.9 X 12K 12.9 The "D" isn't included in the table. I may be very wrong here, but if I remember correctly the "D" occurs only only on bolt heads also marked "AUTO", as in "AUTO D". Maybe "AUTO D" is some other grading system, or could be it is simply a brand name, or perhaps it's something else. Anybody know?

On Tue, 25 Dec 2001, Mick Conde wrote: > Bob- Thanks for your reply. I think the 8 & 10 mm was a bad example to use, > as I this is the only place metric was used. Most common bolt suppliers > were Sparts/Bax/CSR and a few others, some of these suppliers also used the > D & R (grade?) markings. I spoke with Don Lawson (tech editor for Sacred > Octogon & long time personal friend) and he didn't have a clue. I was > hoping one of our group from across the pond could straighten us yanks up > proper! -- Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271 Cub Hill, Maryland 1962 Triumph TR4 CT3154LO CT3479E fold@bcpl.net

[Chip Old]

Dug around some more and found the following comparison table: Grade Designation Tensile Strength in PSI ----------------- ----------------------- BS A & B 62,720 DIN 5D, ISO 5.6 71,160 SAE 0, 1, 2 74,000 SAE 3 100,000 BS S 112,000 DIN 8G, ISO 8.8 113,800 SAE 5 120,000 BS T 123,200 DIN 10K, ISO 10.9 142,000 BS V 145,600 SAE 8 150,000 DIN 12K, ISO 12.9 170,674 BS grade R is missing

On Tue, 25 Dec 2001, Chip Old wrote: > On our T-Types the metric bolts used in the engine and gearbox weren't > made to the prevailing DIN metric specifications, much less to modern ISO > metric specifications. Just like the BSF, BSW and BA bolts, the heads > usually (not always) have letter grade markings (D, R, S, etc). I've > never found anything definitive about these markings, but a table in a > very old Metric & Multistandard Componants Corporation catalog provides > the following rough equivalences. Emphasis on "rough". > > British US DIN ISO > ------- -- --- --- > R 3 6S 6.8 > S 5 8G 8.8 > V 8 10K 10.9 > X 12K 12.9 > > The "D" isn't included in the table. I may be very wrong here, but if I > remember correctly the "D" occurs only only on bolt heads also marked > "AUTO", as in "AUTO D". Maybe "AUTO D" is some other grading system, or > could be it is simply a brand name, or perhaps it's something else. > Anybody know? -- Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271 Cub Hill, Maryland 1962 Triumph TR4 CT3154LO CT3479E fold@bcpl.net