Gas Tank Mounting Bolt OEM Size?

hobageeba said:

Can anyone tell me what the correct nut would be that screws into the mounting bolts on a MKII Roaster tank? The PO has 1/2" Standard nuts barely screwed on there but that's definitely not right. 1/4" Whitworth?

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hobageeba said:

My current tank came pretty much unmounted so I'm not totally sure of the setup, but looking at the exploded diagram from the parts manual, it looks like it gets a rubber pad under the front and back, with a bunch of rubber washers stacked on the mounting bolts. Is that about it? I'm guessing the rubber washers can be anything that fits that I can pick up from my local hardware store?

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L.A.B. said:

[Use nyloc nuts. Make sure the front tunnel pad is thick enough to support the tank and use the 063121 Roadster strap at the rear.

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L.A.B. said:

"Whitworth" is a coarse thread, so you are more likely to encounter Whitworth threads where fasteners screw into alloy (but not carbs), however, many coarse threads will be UNC on a Commando (mostly the same thread pitch as Whitworth but UNC has 60 degree thread angle instead of Whitworth's 55) although there are a few BSF, so don't automatically assume all fasteners into alloy are Whitworth.

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hobageeba said:

L.A.B. said:

[Use nyloc nuts. Make sure the front tunnel pad is thick enough to support the tank and use the 063121 Roadster strap at the rear.

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Looks like these should do the trick then: http://britishfasteners.com/index.p...nf-nuts/unf-5-16-24-nylock-nut-thin-3625.html

L.A.B. said:

"Whitworth" is a coarse thread, so you are more likely to encounter Whitworth threads where fasteners screw into alloy (but not carbs), however, many coarse threads will be UNC on a Commando (mostly the same thread pitch as Whitworth but UNC has 60 degree thread angle instead of Whitworth's 55) although there are a few BSF, so don't automatically assume all fasteners into alloy are Whitworth.

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Great info, thanks man!

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illf8ed said:

Don't you have a local hardware store? 5/16" NF nyloc nuts are readily available at my ACE hardware. That's one of the nice things about Commandos, mostly American standard fasteners.

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hobageeba said:

illf8ed said:

Don't you have a local hardware store? 5/16" NF nyloc nuts are readily available at my ACE hardware. That's one of the nice things about Commandos, mostly American standard fasteners.

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Haha, yeah I did some more research and found out the UNF is synonymous to American Standard "fine thread".

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HISTORY
The origin of the standardized screw thread began in the mid 1800's through the efforts of William Sellers in the United States and Sir Joseph Whitworth in the United Kingdom. Both men in their separate countries had their screw thread designs standardized. Sellers' design was known by several names: Sellers; Franklin Institute; US Standard; and ultimately standardized as the American National Standard Series. Whitworth's design was standardized as: Whitworth Series. Discussing the differences between the two series is not in the scope of this discussion.

The “UN” thread form was developed after World War II by representatives of Great Britain, Canada, and the United States of America, to prevent recurrence of the wartime difficulties in supplying fasteners and tools in both British Standard Whitworth and US Standard configurations when and where needed. In 1949, after years of committee meetings between Canada, England and United States of America the American National Standard Series was replaced with the Unified Inch Standard Series. In the end there were three base reasons identified for the change. The first reason was to provide interchangeability with Canada and United Kingdom. The second reason was to allow for interchangeability in the growing global marketplace. The third reason was to correct certain thread production difficulties. The jointly-developed thread form was named the Unified Thread Form. the Unified Thread is also referred to in the B1.1-2003 as Unified Inch Screw Thread. This Unified Inch Screw Thread both superseded the previous British, Canadian and American national standards, and later served as a prototype multi-national thread form standard that was eventually metricified to become the ISO Metric Screw Thread (the M-series).

Some confusion over the UN designation exists. Some people think it means Unified National based on the fact that three national entities came together to unify their thread standards; thus: Unified National Screw Thread Form. By reading the B1.1 this is not supported; rather UN is the abbreviation for UNIFIED. In the B1.1 the thread is called either Unified Inch Screw Thread or Unified Screw Thread with the preference being Unified Inch Screw Thread to indicate the unit of measure used in the screw thread series.

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United States Standard thread (USS thread), also known as Sellers Standard thread,[1] Franklin Institute thread[1] and American Standard thread,[2] is a standard for inch based threaded fasteners and washers.

The USS standard is no longer supported. It, together with the SAE fastener standard, was incorporated into the Unified Thread Standard. However, the term, USS, continues to be used occasionally today to describe inch based threaded fasteners with a coarse thread pitch and inch based washers that are a little bit larger than the corresponding SAE washer. The Unified Thread Standard uses the term UNC (Unified National Coarse) to describe a fastener that previously would have been designated USS and the Unified Thread Standard uses the term UNF (Unified National Fine) to describe a fastener that would have previously been designated SAE.

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