Torque and Chrome

Ford Bolts: #'s & Symbols-- What do they MEAN?

Ford (Lincoln, Mercury) bolts, screws & fasteners, in-general: Where can I locate / is it even possible to obtain, a chart or some-sort of magical decoder amulet that will tell me what the significance of the #'s & symbols on FMC's bolt-heads mean???!!! I had to do a bit o' guess-work figuring-out which (4) bolts to use on the "U"-brace/bracket on an alternator for a 1999 Crown Vic 4.6, V8..... , b/c I didn't have the old bolts to compare them to (MY car was missing the bracker & bolts, when I bought her). Anyway, near the area under the car where the bracket had been tossed-aside by the person(s) who pulled the alternator itself, I found 2 bolts that were both stamped on the head w/ an "M" inside a Hexagon (6 sided shape-- each side of equal length [just in-case some of us needed a geometry refresher[!]), & "9.8" below that. They seemed to thread perfectly into the hole(s) but I couldn't find 2 more like them HOWEVER, I did find two similar looking 1's, stamped w/ what looked like a small, waving flag, w/o a pole, above the #"9.8" . These 2 also threaded (seemingly) perfectly into the holes. The long-&-the-short of it is: I ended-up shearing one of each type (using a torque wrench, @ torque halfway between max and min, recommended by AllData FSM). Upon further research (& after extracting the sheared threaded-shafts), I found that there were several different types of bolts that had the VERY SAME markings as the ones I mention above, & there were 4 to 5 variations of shaft &/or head size, & even thread-configuration... But the VERY SAME stamp(!). Maybe there's some obvious "code" that I'm just not "getting" & I'm just showing that I'm still REALLY "wet behind the ears" w/ this DIY car stuff but, how the heck do ya' mark one bolt w/ one thing, & a completely different bolt w/ the SAME darn thing as the last 1???!!! And YES... I HAVE noticed that some of the stamps look the same @ 1st but, upon closer inspection, you might find a small dot, or a line under the #'s. What I'm speaking of are the stamps that are EXACTLY the same, on COMPLETELY DIFFERENT bolts! Thanks, for ANY leads! Louis T. Racker Atlanta, Ga PS If PPS Haynes manual (CV & MGM 1988-2002[???!!!]) gives SOME info, mostly speaking of how much torque-tension a particular bolt can withstand BUT, if that IS the case... How the heck are you (&/or the dealer) supposed to know if you've got the correct bolt/fastener for the component upon-which you're working???!!!. . . . . &, none of Haunes' pic's look anything like my bolts (prob from '88 yr model!) PPS I STILL DON'T KNOW WHAT 4 BOLTS I'M SUPPOSED TO BE USING IN THE UPPER ALT. BRACKET!!!

Public Comments

1. The markings on bolt heads have nothing to do with the size or thread configuration. These numbers and or markings indicate their minimum strength and/or "property class". Also, a lot of manufacturers will stamp their trademark on the head as well. For example, a hex bolt head that's stamped with 3 lines tells you that it's made from tempered medium carbon steel, has a tensile strength of 120,000psi and an SAE grade of 5.
2. the marks on the head bolt is the the tenstile strength of the bolt or how much torque you can put on the bolt.usually the higher #or more marks the harder the bolt is.but different manufactures have different marks.