Cylinder Stud Thread Profile
- Thread starter ogrilp400
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I have had trouble with Stainless head nuts, Some try and pick up, Some are OK. Also cleaning up the threads in the cases, I have not found the right tap, In the finish, I put some saw cuts in an old head stud, To clean out the holes. Cheers Bill.
There is one definativ
The outcome is solidified in the VOC drawings held by the club and available to the Spares Company for manufacture
Guys, guys, you are missing the point. I know the specs for various threads, I have the books and can also access information on the web. What is in question is, Which thread form was used? Whitworth, CEI or BSCy? Prof Higgins piece is repeated below:
"The thought "Can there be a difference in CEI and BSCy threads?" came floating into my mind. I therefore went to my incomplete copy of B.S.811 which is titled CYCLE (BSC) THREADS with (FORMERLY KNOWN AS CEI THREADS) beneath it. This told me that the thread was first formulated by the Cycle Engineers' Institute in 1902, and was peculiar in that it included a series of threads applicable to any size of stock, rather than organised and progressive sizes. BS 811, issued in 1938, standardised a selection of the more commonly used sizes, and it was updated in 1950. The standard specifies a 60 deg thread angle, and a basic profile form with well truncated, radiused, root and crest. The truncation is defined as equal to the pitch divided by six, giving a more than usually shallow thread. Neither I norJanne Ostnas, who tried to help me, have been able to find a basic thread form for the original CEI thread. We know it had the same 60 deg angle, but experience with Vincent's head bolts and nuts makes me wonder if it had less truncation at the root and crest to produce a deeper thread. If this were the case, then a CEI nut would run freely on a BSC stud, but a BSC nut would suffer crest interference on a CEI stud, which seems to be what we are suffering from. Step forward please, all those engineers who can produce a basic thread form profile diagram for CEI - or a better alternative explanation!"
"The thought "Can there be a difference in CEI and BSCy threads?" came floating into my mind. I therefore went to my incomplete copy of B.S.811 which is titled CYCLE (BSC) THREADS with (FORMERLY KNOWN AS CEI THREADS) beneath it. This told me that the thread was first formulated by the Cycle Engineers' Institute in 1902, and was peculiar in that it included a series of threads applicable to any size of stock, rather than organised and progressive sizes. BS 811, issued in 1938, standardised a selection of the more commonly used sizes, and it was updated in 1950. The standard specifies a 60 deg thread angle, and a basic profile form with well truncated, radiused, root and crest. The truncation is defined as equal to the pitch divided by six, giving a more than usually shallow thread. Neither I norJanne Ostnas, who tried to help me, have been able to find a basic thread form for the original CEI thread. We know it had the same 60 deg angle, but experience with Vincent's head bolts and nuts makes me wonder if it had less truncation at the root and crest to produce a deeper thread. If this were the case, then a CEI nut would run freely on a BSC stud, but a BSC nut would suffer crest interference on a CEI stud, which seems to be what we are suffering from. Step forward please, all those engineers who can produce a basic thread form profile diagram for CEI - or a better alternative explanation!"
It is looking like we might have to employ the services of a medium, I am sure Phil Irving could simply give us a straightforward answer to the question.
If we are going to interview PCV, I think we could come up with a few more interesting questions....
Bill ThomasVincent H.R.D. Owners Club Member
I have had trouble with Stainless head nuts, Some try and pick up, Some are OK.
One of my interests is the manufacture of fibreglass domes for astronomical observatories, 4, 5 and 6.4 metre diameter. In each of these there are many (several hundred) stainless steel M10 x 30 mm nuts and bolts. Approximately 1 -2 % of these lock up and have to be broken off by hand once they weld up. I have tried very many types of lubricant and none so far has proved 100% successful. All nuts and bolts from the same material, same batch and same manufacturer so it is just something that most of us without a NASA sized budget have to learn to live with. Stainless on to mild steel as Bill refers to above should not do this but I know of at least one Club Member who tried so hard to tighten the nut on to the stud that he ripped a piece out of the top of the crank case. Mismatched thread forms were almost certainly the cause. Be warned. If they do not go down by hand they are not matched up.
I have had trouble with Stainless head nuts, Some try and pick up, Some are OK.
One of my interests is the manufacture of fibreglass domes for astronomical observatories, 4, 5 and 6.4 metre diameter. In each of these there are many (several hundred) stainless steel M10 x 30 mm nuts and bolts. Approximately 1 -2 % of these lock up and have to be broken off by hand once they weld up. I have tried very many types of lubricant and none so far has proved 100% successful. All nuts and bolts from the same material, same batch and same manufacturer so it is just something that most of us without a NASA sized budget have to learn to live with. Stainless on to mild steel as Bill refers to above should not do this but I know of at least one Club Member who tried so hard to tighten the nut on to the stud that he ripped a piece out of the top of the crank case. Mismatched thread forms were almost certainly the cause. Be warned. If they do not go down by hand they are not matched up.
Well I made it near enough 55 degrees so it is whitworth no? This was a stud made and fitted by you Trev to my B Rapide. I have the original2 part studs somewhere and I will dig them ou and measure them.