AJS & Matchless Owners Club

I purchased a set of badge screws as mine were not correct, they were brass coloured and appeared not to screw in cleanly the new ones appear too big although I'm assured they are correct, they will not even pass cleanly through the badge holes.
Question is what is the correct thread size for that tank, I know it should a BA size but what size should the tank be I can clean the threads out with a tap but am wary, I don't want to create a leak or end up with an incompatible thread.

Ian

Hi Ian, I guess you saw from your parts List the pt. no. for the screw is 000152 this is an old standard fitting. However, giving thread sizes in parts lists for standard fittings stopped approx. 1951 Onwards. So you need to refer to an older parts list for the size. I recommend the 1954 old to new part number conversion book for this purpose. I have quite recently compiled a PDF file containing most of the standard fitting pt no's
( old & new ) of those standard fittings, those being ones you can buy from many outlets. Best to by the best from club spares. Other suppliers fittings may have for example letters etc on bolt heads. Save the PDF file I mentioned, for future reference also to see the thread size for your bikes badge screws. 5/16" 3 BA. bronze head 000153 has chrome head, I assume for Matchless. If the screw is 3 BA so the tank should be. Holes can get blocked with paint. Assuming you have the correct thickness badge and rubber backing, the screw should screw in fully OK. If this is not be case you may need to shorten the screw a bit. If so put a nut on the screw first. When you have finnished the shortening job remove it cleaning up the thread on the way off.