Thread Pitch Gauge Tool - Why You Need It
How can a thread pitch gauge save you time and money when ordering British motorcycle parts? Let us explain. First off if you do not know what a thread pitch gauge is, a thread pitch gauge is a hand tool that allows you to measure a bolt or screws thread count per every inch. A thread pitch gauge usually comes in an assortment to allow you measure threads ranging from 10 T.P.I through 80 T.P.I. for example. Gauges come in many types to suit American thread forms, British, and even metric. The term T.P.I is short for "threads per inch". If you measure a bolt and it reads 26 T.P.I., that would mean that the bolt has a 26 threads per inch count.
Pictured above is my trusty 1960's thread pitch gauge made by "Union Tool Co".
When working on a British motorcycle (or any motorcycle), there are always some tools that you just have to have, a thread pitch gauge is one of them. Mainly because it is handy, and it is universal. As we all know British motorcycles which include Triumph, BSA, Norton, Matchless, etc, all have many different types of thread forms. It is not uncommon to see BSF, UNF, UNC, & CEI thread forms all on one British bike! Not to forget that the spark plug holes are metric... You typically see this on 1968 and later models when Triumph and BSA motorcycles where starting to introduce American threads.
Using the thread pitch gauge to measure a Triumph 650 crankcase bolt. Gauge states that this bolt has a thread pitch of 22 T.P.I.
Now to saving time and money. We have found that many times when ordering bolts, nuts, screws, studs, and anything with threads on it often times have been changed. For example, you own a 1970 Triumph T120R, you need the front axle nut. You call your local supplier (Classic British Spares of course) and you give us the part number that you need. We send you the nut. You attempt to install it but it will not thread because the thread pitch is wrong. Why? A previous owner installed an early axle with a different thread pitch. How would one know that? A thread pitch gauge. Basically a thread pitch gauge takes the time out of "assuming". Regardless if a motorcycle is all "original", when ever I have to replace anything that has threads on it, I get my thread pitch gauge out and measure first. We get calls throughout the month from customers buying 2 of everything because they are not sure if they have a UNF or CEI thread pitch. That could easily be avoided with a gauge. Ive seen gauges go from 10-50 dollars.