Topic: TAPS AND Dies

[DickL]

I bought a new rear fender from  Partzilla for my 1970 cb750K0. I'm trying to match the threads to fattach fender to the frame where the rear light blinkers are. Honda chromed the holes. ANY IDEA WHAT  tap to use to chase the threads? I tried my metric taps but no luck. I SUPPOSE THEY ARE JIS. What size? Any help?

Dickl

[calj737]

What size fastener do you believe goes there? If its 10mm, it may be one of the rare instances where they used 10mmx1.0 fine thread. 10mmx1.25 occurs in other places, and modern pitch is 1.5. So you may have the correct size wrong pitch?

[greenjeans]

Pretty sure it's an 8mm x 1.25

[Bodi]

All CB750 threads are ISO metric. Honda switched from JIS during - some say at the start of - the 1967 models. 6mm and 8mm screws did not change for "standard" pitches, the fine pitch (not used on our bikes) did, I think. Smaller fasteners did change and it's a bugger when working with bike models that spanned the 67 change and you don't know that a part was replaced with a newer/older one.
Chrome is not going to tap easily.
Try to measure the thread pitch. It isn't easy with that small a hole but I've stuck paper in a hole and run something down against it, then measured the marks left on the paper.
These ones are 8mm on all bikes I remember. I doubt the K0 is different?
8mm can be 0.75mm, 1.0mm, or 1.25mm pitch. ISO Honda bike ones have all been 1.0mm - at least I think so.

[mrbreeze]

I have a set of Craftsman thread chasers that come in handy for checking thread sizes and it seems to me that I ran into threads on my bike here and there that didn't fit. The set I have doesn't have every pitch for every size but when you come across a thread that the kit doesn't fit you can do a little research and figure out which one to buy or you can see if you have a regular tap or die of that size. I also like having the chasers just to clean up existing threads. Sometimes a regular tap/die is too aggressive and leaves you with a sloppy fit.

[greenjeans]

I can confirm,on a few fenders I have, the bolts are 8mm x 1.25
Both are later fenders (73 & 74)    I know the early fenders have different mounts for the tail lights, but I believe that bolt is the same size and pitch, just shorter.

[DickL]

Thanks guys. It Was an 8x1.25. Worked like a charm. Now I have to find the caps.

Dickl