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Nuts, Bolts, and Washers

Courtesy of John Kipping Spares , submitted by Bill Kelly,

Triumph used a system of part numbers which defines the specification of a particular nut, bolt and washer.


Prefix gives type of nut.

Last 2 digits give size & thread

Thus a YN2912 is a 9/16" UNF nyloc


Prefix gives type of bolt

First digit (s) defines thread size as per nuts above, but the thread type is always UNF unless the second digit from the right is 5 in which case the thread will be UNC. The last two digits give the length in eighths of an inch (up to 49). Thus a KT504 is a No. 10 UNF, a countersunk slotted head 1/2" screw.


Washers prefix gives type

The last two digits give the size as per the chart above for the nuts (03 to 13).


That's it! Now you'll be able to find the right nuts, bolts and washers for your Triumph!



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