A question about thread sizes in a parts catalogue

Singles built before the Lambertini era
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Parker3865
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A question about thread sizes in a parts catalogue

Post by Parker3865 »

I have been translating a parts manual into English (MS word online does the translation!) for a friend with a Morini 175 GT (a very early one I believe). The Machine screw sizes are MA. I guess the M is metric, I wondered what the A stood for?
Morini 250 2c rebuilt from a box of bits.
Morini Jen
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Re: A question about thread sizes in a parts catalogue

Post by Morini Jen »

Hi Richard.

The following is a Google translation of a snippet from the Sapienza University of Rome website...

"The unification of the threads underwent a notable increase after 1964 transformation. Before that date, the threads, despite being metric, did distinguished into 5 series: MA, MB, MC, MD, ME.

The MA thread has been replaced by the coarse thread,the other 4 (MB, MC, MD, ME) in a single fine pitch thread series".


So it would appear that 'MA' is an obsolete designation for a common or garden Metric Coarse thread. The letter 'A' doesn't really stand for anything.
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Parker3865
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Re: A question about thread sizes in a parts catalogue

Post by Parker3865 »

Many thanks for that. Your Googling abilities have surpassed mine!
Morini 250 2c rebuilt from a box of bits.
Morini Jen
Posts: 104
Joined: 12 Jun 2022 18:49
Location: Warwickshire U.K.

Re: A question about thread sizes in a parts catalogue

Post by Morini Jen »

Thanks Richard. Although I think I probably need to get out more.
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