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MG MGA - Rear Arch Front Splash Plate Fastener

Waiting for the snow to melt, I'm trying to fill in a few long-missing bits. I've so far been defeated by one of the two screws used to mount the forward splash plate of the rear arch, which I've not been able to identify from the BMC fastener code document. According to 1600 Service Parts List, 5th ed., 4 screws are required for each plate. Two are given as part number HZS0405, which translates as zinc-plated hex-head set screws, UNF 1/4" x 5/8". But identifying the other two leaves me stumped. The part number is given as PTZ604, but I've never been able to figure out what this screw is. It's not in the fastener code list. The closest I can come is the picture in the Anglo Parts catalogue (designated there as 162.588), which appears to show a sheet metal screw of some sort, but I can't tell more than that. Does anyone know, by chance? Failing that, is there a source that I may have overlooked for deciphering the Service Parts List part number? Any help appreciated.

Cheers!
Ken
Ken Korey

HZS0405
Hex head, Zinc, Screw (UNF), 1/4-28 x 5/8 long
"Screw" means full thread.

PTZ604
Phillips, Pan head, Tapping, Zinc, #10 x 1/4" long
It's a self-tapping screw, but a sheet metal screw will work as well.
Barney Gaylord

Thanks much, Barney! I couldn't have done it without help. PTZ604 almost makes sense, in BMC part-number-speak, except for the "6'; no screw in my fastener code book has just three numerical digits.
Ken Korey

Barney,
My list shows PTZ604 as a #6 screw and that is what was in my cars. Which is correct? Have a good day!

John












John Progess

Oops, you're right, PT604 is #6 x 1/4". I was thinking 3/32 = #10. Should have looked at my car first. (#10 is a BIG sheet metal screw).
Barney Gaylord

OK, I'm with the program now--at least for this screw. Thanks, John! What's the list that you're using, Barney and John? I have the usual downloaded BMC Fastener Decoder Booklet, but it's obviously not comprehensive. I also tried searching the identity of the dipper switch screw, AJD1243Z, and struck out completely. I do better with Sudoku.

Ken
Ken Korey

Combination of the BMC book plus some appendices to the Moss UK catalog usually works for me. Todd Clarke can also help - he has an encyclopedic knowledge of fasteners. FYI three areas where the fastener codes are either inaccurate or incomplete are (1) cone points - where there's a letter code for cone point fasteners, and the catalog won't specify it even though the fastener is indeed cone point, almost always because it threads into a weld nut. (2) pozi vs. phillips isn't distinguished by fastener code. (3) plating doesn't always appear to be zinc even when the code says it is. A number of fasteners on my MGA and BGT were originally cad plated even though they have zinc plate codes (I don't think there even is a cad plate code).
Mark Lambert

Thanks, Mark! I did just download the Moss UK catalog, and it's a really good supplement to the BMC Fastener Guide, especially for stock hardware parts beyond screws, nuts, and washers. However, there's still a number of fastener codes in the MGA Service Parts list that I can't find in eithe (AJD1243Z and PTZ604, for example, although the latter is in Barney's and John's secret codebook).

Re. your other points, (1) cone-point screws turn up in the BMC Fastener Guide with P in the second place (e.g., HPN, HPZ, HPP for hex heads of various finishes). As you point out, these are most frequently screws associated with weld nuts. All of the fastener sets I've received from Todd Clarke have had cone points where specified by the Service Parts List. (2) Pozi ISN'T distinguished by code, as you note, but the ones most commonly used are fairly well known; Todd stocks a good selection for those fastidious enough to care. (3) I've never been able to figure out the logic by which some fasteners rated cadmium plating, but it sure isn't coded.

I know that I can pester Todd about these pressing fastener issues, and I do when I have an order for him (yesterday, in fact.) But it would be nice to be a bit more independent, especially if figuring out the codes meant that I could pick up a few stock fasteners at the local auto parts emporium when needed. I much appreciate your help in this.

Ken
Ken Korey

This thread was discussed between 28/02/2010 and 05/03/2010

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