What is the thread pitch of the mudguard eyelets from mid 90's Marin frames?

[Ugo51]

Hi guys, I just noticed that the thread pitch of the mudguard eyelets of my 1995 Marin Palisades Trail is not the same of the current industry standard. Or, at least, not the same of the bolts that are supplied with SKS Bluemels (M5 x 0.8mm).
Do you know what thread that is? I tried measuring it, and it looks like a M5 x 1.0mm, but that'd be odd...

Thanks.

 

[mdvineng]

American thread most likely UNF 3/16ths

 

[Ugo51]

Would that be 24TPI?

 

[mdvineng]

https://www.engineeringtoolbox.com/unified-screw-threads-unc-unf-d_1809.html

 

[mdvineng]

Could be UNC for 24tpi size #12

 

[Ugo51]

Mh... that's mildly annoying.
That bike is sending me a lot of very subtle signals to tell me not to keep it. And yet, I insist

 

[kermisking]

Will it tap out to an M5 standard that you are happy with or would that spoil the originality of the frame ?

 

[mdvineng]

Will it tap out to an M5 standard that you are happy with or would that spoil the originality of the frame ?

If it's 3/16 or the #12 unc the major dia is already 5.46mm

 

[kermisking]

I have not got a tapping conversion book to hand but I work in Engineering if possible going up to M6 ?. I have done plenty of filling holes with weld and re-drilling , tapping but that's not practical unless you can cope with a bit of localised paint loss ?.

 

[Tootyred]

As far as im aware all marin bolts are metric.

Ive just put bolts in the fork and rear eyelets along with the rack mounts on my 95 palisades and they are all m5 x 0.8.

This is also true of all my other marins

Are you sure the holes just aren't just paint filled or damaged in the past?