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Most nuts, bolts, washers and screws on Land-Rover, since Series 3, conform to a generic style part numbering system.
Prefixes:
AC = Screw, Self-tapping, Countersunk Head
AB = Screw, Self-tapping, Button Head
BH = Bolt, Hexagon Head
FB = Flanged Head Bolt
FS = Flanged Head Screw
ND = Nut, Domed
NH = Nut, Hexagon, Plain
NS = Nut, Square type
NY = Nut, Nyloc locking type
PS = Pin, Split Cotter
SH = Screw, Hexagon Head (Screws are fully threaded, bolts are partially threaded)
WA = Washer, Plain, Form A
WB = Washer, Plain, Form B
WC = Washer, Plain, Form C
WL = Washer, Locking
WP = Washer, Plain, Form A or special 'penny washer' size.
First digit:
1xxxxx = Metric threaded
4xxxxx = BSF threaded
5xxxxx = UNC threaded
6xxxxx = UNF threaded
Second and Third digits:
If Imperial thread, this indicates number of 1/16" of thread diameter.
On Metric threads indicates mm of thread diameter.
On self-tapping screws, this indicates the screw weight/size.
x03xxx = 3/16"
x04xxx = 4/16" = 2/8" = 1/4" or M4 or No. 4 size screw.
x05xxx = 5/16" or M5
x06xxx = 6/16" = 3/8" or M6 or No.6 size screw.
x07xxx = 7/16"
x08xxx = 8/16" = 4/8" = 2/4" = 1/2" or M8 or No. 8 size screw.
x09xxx = 9/16"
x10xxx = 10/16" = 5/8" or M10 or No.10 size screw.
x11xxx = 11/16"
x12xxx = 12/16" = 6/8" = 3/4" or M12
x14xxx = 14/16" = 7/8" or M14 or No.14 size screw.
Note how the metric dimensions are unrelated to the Imperial dimension.
Fourth and Fifth digits:
These indicate the length of the fastener.
On Imperial this is the multiple of the number of 1/8" long.
On Metric, the length is in millimetres for Set Screws, but in 5mm increments for Bolts.
xxx04x = 4/8" = 1/2"
xxx05x = 5/8" or 25mm long Bolt
xxx08x = 8/8" = 1" or 40mm long Bolt
xxx16x = 16/8" = 2" or 16mm long Set Screw or 80mm long Bolt
xxx20x = 20/8" = 2 1/2" or 20mm Set Screw or 100mm long Bolt
xxx24x = 24/8" = 3"
xxx25x = 25/8" = 3 1/8" or 25mm Set Screw
Note how the metric dimensions are unrelated to the Imperial dimension.
Last digit:
This is usually a 1 and may originally have been earmarked to specify a material or surface finish specification.
The 'L' suffix sometimes found just indicates 'Land-Rover'.
We use 'SS' to indicate Stainless Steel material.
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