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Oz34
United Kingdom
2541 Posts |
 Posted - 08/04/2019 : 22:51:24
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Michael, it would appear that you have not read my post above. I am using Sports & Vintage track rods & ends, but original locking nuts. As these original locking nuts are working perfectly that suggests to me that Mike has the correct thread on his parts.
Dave
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NeilF
United Kingdom
66 Posts |
Posted - 08/04/2019 : 23:09:53
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The magnifying device you refer to is a Profile Projector or Shadowgraph see Mitutoyo catalogue or search on Wikipedia. These optical instruments are still used today for inspecting the form or shape of small parts which cannot be measured with mechanical instruments. I am sure that any specialist bolt/nut/stud manufacturer will have one in their inspection department.
Neil |
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rustcollector
United Kingdom
410 Posts |
Posted - 08/04/2019 : 23:27:19
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| Dave, just throwing stuff around. With all respect just because a nut fits a thread doesn’t make it right, I too have some nuts and they are a very loose fit, so could be 55 or 60 thread angle. This thread ( pun intended) goes to show that the more you know the more you worry. When I was looking into this myself, I remember some old posts where it was gone into, on searching I couldn’t find what I had previously read, but I think there was some talk of a metric thread. As I said my recollection is very vague. I would add more, but I fear I may alienate people on here and stop them contributing in future, all information is valuable. |
Edited by - rustcollector on 08/04/2019 23:36:19 |
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rustcollector
United Kingdom
410 Posts |
Posted - 08/04/2019 : 23:31:40
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| Thanks Neil, used one when I worked as a mechanical engineer but didn’t know the name, the one I used had a large round screen probably 10 or 12” dia. This device enabled you to make very accurate comparisons. |
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John Libbert
USA
211 Posts |
Posted - 09/04/2019 : 11:41:21
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An optical comparator is what I've heard them referred to. There was one in the tool room at a previous employer.
As far as bicycle thread form being used on M.G.s, look no further than the studs on the TC windscreen pivot and quadrant. These are British Standard Cycle 5/16 X 26 TPI form. They have 60 degree thread angle and usually 26 TPI although 7/16 & 1/2 also come in 20 & 24 TPI options. I got new studs several year ago from Roger Furneaux and a tap & die from someplace I can't recall at the moment. Perhaps Tracy Tools. I wonder if this same thread form was used on earlier M.G.s such as P Types.
Best regards,
John |
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rustcollector
United Kingdom
410 Posts |
Posted - 09/04/2019 : 13:31:24
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| Hi John, or are they BSB (brass) very similar to BSC |
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John Libbert
USA
211 Posts |
Posted - 10/04/2019 : 11:18:00
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Michael,
The tap & die I bought to use on the studs and tapped holes in the windscreen frame were BSC and worked very well. I'm not sure how similar that BSC is to BSB. I'll have to look into that at a later time.
John |
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rustcollector
United Kingdom
410 Posts |
Posted - 11/04/2019 : 21:53:06
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As I mentioned earlier I seem to remember reading an old thread on this subject and there was mention of metric thread, I cannot find the original post.
Metric thread of 1.25mm pitch
or converted to English
0.3149 x 20.32 tpi which is very close to 20 tpi but 60 degrees.
I have tried anew repro track rod end on an original thread and it does get tight the further it is screwed on , which could suggest the tpi is slightly out.
Also a 55 degree track rod end would fit a 60 degree external thread.
So more to add to the confusion. |
Edited by - rustcollector on 11/04/2019 21:56:08 |
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coracle
United Kingdom
1937 Posts |
Posted - 11/04/2019 : 23:47:57
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| Perhaps a further degree (or five) of confusion? |
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rustcollector
United Kingdom
410 Posts |
Posted - 15/04/2019 : 11:27:14
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| Richard are you sorted on this now? |
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rustcollector
United Kingdom
410 Posts |
Posted - 21/04/2019 : 16:13:32
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| Ok, I guess so and you don’t want to borrow the dies I’ve found? |
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Richard Hardy
United Kingdom
2159 Posts |
Posted - 21/04/2019 : 23:29:24
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Hi Michael
Apologies for the delay in responding, I have been away from the forum for a few days.
Thanks for the offer although with the limited initial success in my request, I wend down the screw cutting route and using correct thread chasers, the result were A1, so I am now all sorted. Thanks all the same, this was appreciated
Kind regards
Rich
Vintage MG Parts |
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Roger Furneaux
United Kingdom
88 Posts |
Posted - 24/04/2019 : 23:07:20
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hi Richard - that's good, but you don't say what thread angle you used...
As a further twist to this mystery, some of the repro. cock nut appear to be far too loose, and as they are only 1/4" thick, are at risk of stripping. I can only guess that they are not the correct thread, yet they come from a well-known maker. I don't know if S&V nuts are better. So bad in fact that they were rejected by at least one restorer.
As a result, I am having a batch made, 5/8" x 20tpi, 55deg. angle, and they fit perfectly on all the rods tried on so far.
ocTagonally
Roger |
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AVBowden
United Kingdom
68 Posts |
Posted - 25/04/2019 : 13:22:45
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Hi All
All this talk of Optical Comparators, Profile Projectors or Shadowgraphs is making me feel quite nostalgic so I decided to make one as nobody seems to have actually measured a thread. It's easy, just use an old slide projector, the garage wall and a protractor.
The piccies show a P type track rod thread.
My money is on 55 degrees but please feel free to disagree!
Andrew
NA0256 |
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rustcollector
United Kingdom
410 Posts |
Posted - 25/04/2019 : 21:47:50
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Andrew,
Fantastic, what a good idea.
I would concur with you that the thread is in fact 55 degrees. I feel much better having it confirmed and demonstrated rather than someone stating they are 55. Now what thread form #128514; |
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