Lotus Elan

Hub Thread Size?

PostPost by: JGeezer » Thu Jul 02, 2015 11:09 am

Would anyone know the correct thread size for the wheel hubs (I would guess knock off or federal nut is the same). Bunged up one a bit and I would like to clean that up. It HAS to be on the left (off) side, of course, just to make finding one so much easier.
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PostPost by: rcraven » Thu Jul 02, 2015 11:25 am

I assume you mean the large thread the spinner screws onto.
When I was making a hub puller I measured the thread as 2.048? inside (i.e. minor diameter), 2.17 (2.168)? outside (i.e. major) & 10 TPI, and the puller fits, but as far as I'm aware those measurements don't correspond with any standard thread.
Anyway, how do you propose cleaning it up? A suitable die nut will be hard to find. In a lathe you could either take the settings off whatever good thread remains or the spinner / nut.
Or have I misunderstood your question?
Robert
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PostPost by: JGeezer » Thu Jul 02, 2015 12:39 pm

rcraven wrote:I assume you mean the large thread the spinner screws onto.
When I was making a hub puller I measured the thread as 2.048? inside (i.e. minor diameter), 2.17 (2.168)? outside (i.e. major) & 10 TPI, and the puller fits, but as far as I'm aware those measurements don't correspond with any standard thread.
Anyway, how do you propose cleaning it up? A suitable die nut will be hard to find. In a lathe you could either take the settings off whatever good thread remains or the spinner / nut.
Or have I misunderstood your question?


Yes, you have it. I would like the standard thread measurement to obtain a die, rather than replacing the hub. The threads were accidentially damaged a bit from a jackstand. You can get almost anything these days - cheap! - if you are willing to wait for the mail from China.
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PostPost by: rgh0 » Thu Jul 02, 2015 12:58 pm

It is probably some standard British thread form ( BSF?) for maybe a 2 3/16 diameter. I am travelling currently so dont have my reference books to look it up. You will need an angle of the thread to work it out in combination with the pitch and diameter also . You will not get a die for it I suspect very easily but you can set up a lathe with the right tool angle and thread cutting pitch to clean it up or you can get an old knock on and cut some grooves in it to act as a thread cutting die to clean it up.

If its not to bad just running up an old knock on onto the hub with some extreme pressure grease lube may move the threads back into shape

cheers
Rohan
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PostPost by: Craven » Thu Jul 02, 2015 1:51 pm

Hi,
Check the internal roundness of the of the hub, it may not be an issue at the moment but I found a hub that had the thread reshaped, when I came to replace the front bearings the outer of the race would not come out pass a distortion in the bore.
FWIW
Ron.
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PostPost by: RichardHawkins » Thu Jul 02, 2015 9:06 pm

If the threads are only slightly damaged you may be able to clean them up with a triangular file. The work takes a while, but with such a large thread at least you can see what you are doing. Otherwise a lathe seems the sensible solution.

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PostPost by: JGeezer » Thu Jul 02, 2015 9:30 pm

Thanks, guys! I will check the roundness and probably resign mydelf to doing a lot of delicate file work.
J Geezer
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PostPost by: ort » Thu Jul 02, 2015 9:44 pm

I'd use a thread file, these are available in both 55 and 60 deg thread form, some also have the internal form as well

thread.jpg
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PostPost by: Quart Meg Miles » Thu Jul 02, 2015 10:49 pm

Nearest British thread in my Zeus charts is BSP but 11 TPI covers size 2" (actual 2.347" OD), size 1?" (actual 2.116" OD) and all the way down to size 1". No mention of 10 TPI and no other thread close.
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PostPost by: CBUEB1771 » Sat Jul 04, 2015 4:36 am

I checked the knock-on nut thread on my new +2 rear hubs from TTR and got essentially the same result as did Robert, 2.17" X 10 TPI. The thread crests are pretty heavily truncated so I am sure the nominal major diameter is larger, although perhaps not quite 2-3/16". It is hard to determine the included angle of the thread without having an optical comparator but against my pitch gage it looks a bit tighter than 60 degrees, so 55 degrees might be right. As with Meg I could not find a match with a standard thread in any reference I have, either on paper or online. I did have one really curious result though. I Googled on "2-3/16 X 10 thread" and up came replacement parts for Hardinge lathes, specifically backplates for mounting chucks to head spindles. Now I am having visions of Ron Hickman walking through a machine shop and having a "what's this then" moment when seeing a lathe with the chuck taken off. Pure fantasy but at least I know an approximately equivalent thread has been in use elsewhere in industry.
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PostPost by: Chancer » Sat Jul 04, 2015 7:37 am

If you can identify the thread but not find a die then mounting the hub in a lathe and using a thread chaser would be the best approach, I have recovered several damaged threads in this way, as long as the pitch and form is standard you will find a chaser.
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PostPost by: billwill » Sat Jul 04, 2015 3:27 pm

CBUEB1771 wrote:I checked the knock-on nut thread on my new +2 rear hubs from TTR and got essentially the same result as did Robert, 2.17" X 10 TPI. The thread crests are pretty heavily truncated so I am sure the nominal major diameter is larger, although perhaps not quite 2-3/16". It is hard to determine the included angle of the thread without having an optical comparator but against my pitch gage it looks a bit tighter than 60 degrees, so 55 degrees might be right. As with Meg I could not find a match with a standard thread in any reference I have, either on paper or online. I did have one really curious result though. I Googled on "2-3/16 X 10 thread" and up came replacement parts for Hardinge lathes, specifically backplates for mounting chucks to head spindles. Now I am having visions of Ron Hickman walking through a machine shop and having a "what's this then" moment when seeing a lathe with the chuck taken off. Pure fantasy but at least I know an approximately equivalent thread has been in use elsewhere in industry.


Ah, your message comes two weeks too late. As mentioned elsewhere, I have taken our big antique Holbrook Lathe up to Gayle Mill in Yorkshire. A few weeks ago I could have tried one of my Elan spinners on the main shaft of the lathe. By memory it is indeed a similar size.
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PostPost by: alan.barker » Sat Jul 04, 2015 7:00 pm

ort wrote:I'd use a thread file, these are available in both 55 and 60 deg thread form, some also have the internal form as well

thread.jpg

+1 i agree 100% for this type of situation use a thread file :mrgreen:
Alan
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PostPost by: oldchieft » Sat Jul 04, 2015 7:57 pm

I would use a knife edge swiss file on a thread this big

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PostPost by: alan.barker » Sat Jul 04, 2015 8:54 pm

sorry but with a thread file there is no problem with the angle of the thread and the pitch. Or at least that is what i learned during my apprenticeship in H M Dockyard Portsmouth :wink:
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