decoding fastener part numbers

Austin Healer

Austin Healer

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This is the first post in a series dealing with decoding Rootes factory fastener part numbers. This section will deal with sheet metal (tapping screws) only. A typical sheet metal screw part number is 9731046. I worked it out with the exception of the finish/drive number correlation, any input will be gratefully received!

This would be broken down thusly. 97/3/1/04/6

97 sheet metal screw
3 head type.
1 diameter simple progression with 1 being #4, 2 being #6, etc
04 length in 1/16" increments
6 finish type drive type

so this is a #4 pan or truss head screw 1/4" long

codes for head type are
1 flat head
2 oval head
3 pan or truss head
6 raised (oval) head
7 Phillips flat head

finish codes

2 chrome slotted
3 ?
4 zinc phillips ?
5 zinc slotted
6 ?
8 chrome phillips
 
Here's the method for decoding the machine screw part numbers. This category does not include hex head screws, Rootes considered those to be bolts.

An example is 39313081 Broken down as follows. 39/3/1/3/08/1

39 machine thread screw
3 head type and thread pitch
1 drive type slotted, phillips, pozi
3 diameter starting with "0" which is a #4 screw
08 length in multiples of 1/16"
1 finish type

So this is a #10 slotted pan head screw, 1/2" long in zinc plate

codes for head type are
0 BA thread these include 00-03 which includes the drive type (00 is a slotted flat head screw, 01 is an oval head slotted screw)
1 or 2 countersunk (Flat head) UNF (SAE to Americans) usually listed with the drive types 10/11 or 20/21
2 Oval head could be 22 or 23
3 Pan head Could be 30,31, or 33
3 Binding head (truss head) when followed by a 2 (The trunk hinge screws are Truss head/slotted)
4 Fillister head could be 40 or 41
6 Round head UNC thread
7 Flat/oval head UNC thread
8 Pan head UNC thread

codes for drive type are
0 phillips
1 slotted
2 ??
3 pozi ??

Finish codes are
0 ??
1 zinc
2 chrome
5 stainless
 
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Set screws and bolts

typical part # 19052045 broken down 19/05/2/04/5

This is a 2BA set screw 1/2" long

19 bolt or set screw
05 thread pitch and type of fastener (set screw or bolt)
2 diameter (#3 would be a #10 bolt or set screw)
04 length in 1/8" increments
5 finish type

codes for thread and fastener type

00 BSF
05 BA
10 UNF bolt (SAE, fine thread)
40 UNC set screw (coarse)
50 UNF set screw
60 UNC set screw
70 UNC set screw
80 UNF set screw

Finish codes
1 black oxide ?
2 zinc
3 ?
5 ?
 
These would be a great addition to the next revision of the shop notes. Thanks, Sean.
 
Here's how to decode part numbers for nuts.

Typical nut part number 9600521 broken down as 9/6/00/52/1

This is a 2BA plain nut

9 nut
6 English thread system
00 type of nut
52 diameter only BA fasteners have the "5" prefix
1 ??

Thread system
5 unified threads (UNF/UNC)
6 English threads (BA/BSF)

Nut types

00 plain nut for BA or BSF thread standard thickness
10 plain nut UNF
20 jamb type nut UNF (half thickness)
40 slotted (castle) nut UNF
50 plain UNC
51/52/71 Nyloc UNF
53/53 Philidas nut UNF A philidas nut has a welded ring at the top of the nut
57/64 square nut UNF
58 square nut UNC
55/56 Oddie nut also called a Dzus fastener
62 domed (acorn) nut

Diameter

BA nuts only come in #2 and #4 and are called out with "52" for 2 BA and "54" for 4 BA. BSF nuts use the UNC/UNF size method. You can tell it's a BSF fastener because of the thread system designator. (6)

UNF and UNC nuts start at "01" for a #6 nut. Size progression in 1/16" increments starts at #4 for a 1/4" nut

Last digit finish or material?
0-4 ??
6,7 ??

There are nut part numbers with a "90" and "52" prefix which cannot be decoded... or I just haven't figured it out yet! "52" prefixed fastener part numbers are part of the old (pre Tiger) Rootes part numbering system. I have found set screws that are also prefixed with "52".

Studs are prefixed "19". There are studs which are UNF/UNF and UNF/UNC. They have equal lengths on both ends. A full schedule is in the Alpine parts list.

Lock washers are prefixed "96" and there are several different types. Most lock washers on Tigers are internal tooth type. Exceptions include the lock washers under the screws in the door pillar strikers which are beveled and external tooth. (Same as TR4, I buy these from Moss Motors). There are some square section single coil lock washers and some of the conventional split washer type. Most of these are on mechanical assemblies, and not body or suspension, parts.

Flat washers are prefixed "90" and come in a number of different i.d's and o.d's as well as different thicknesses. The Alpine parts list has a full schedule of these. Most British flat washers have a smaller O.D. than a normal SAE flat washer. British dimensioned washers can be purchased from Clarke Spares and Restorations. (An MGA parts vendor) He can also supply some Pozi-driv screws that were used on these cars post 1965.
 
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Is there a way to determine what screw size, type and head style is used in specific locations, such as front and rear turn signal lens fasteners?
Thanks! The above data is all indicative of a LOT of research.
Chris...
 
GearHead_66 said:
Is there a way to determine what screw size, type and head style is used in specific locations, such as front and rear turn signal lens fasteners?
Thanks! The above data is all indicative of a LOT of research.
Chris...
Click to expand...
Yes, I spent quite some time.!! the correct sized washers can be bought from Clarke Spares and restorations as British washers have a smaller OD that US SAE washers. they also have #10 fine thread pozi drive screws. There is also a page that I submitted with both sheet metal and threaded screws...
 
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