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MG MGA - Steering column thread.

Could someone kindly give me the screw thread details for the top of the steering column (and the big nut) which secures the steering wheel boss to the column. I have a damaged column thread and need to find a die to run down it to clean up the threads. Presumably it’s the same for my Twin Cam as a pushrod MGA?
Bruce.
Bruce Mayo

Hi Bruce

I had a similar problem. I bought a new nut and cut it in two to make two half dies. Put them on the undamaged part of the thread, clamped together with my Mole wrench and very carefully worked the improvised die off to the end of the thread.

It worked!

If the thread is badly damaged it would be good to file the worst off locally before trying the split die. I did not have to do that.

Hope you are enjoying life on the IOW.

Cheers
Dave
Bolney Coupe

May be easier to try on a Mini forum, it uses the same thread
Dominic Clancy

Thread file would be the go-- The problem with running a die down it is getting it started in the right spot to align with the thread when it gets there instead of cutting a new thread and wrecking it---a thread file will sort it out--OR if you've got plenty of length just cut the damaged end off

A thread file is a good tool to have in your kit,

https://www.ebay.co.uk/itm/234270670096?hash=item368b9ebd10:g:5rAAAOSwn6Fhg-CB
William Revit

Thanks Dave, Dominic and Willy. Both good ideas worth trying. So, Willy it’s UNF then?
Bruce.
Bruce Mayo

Bruce. The unified national thread system uses a 60 degree thread. Hence, the notion that there is any difference between a thread file used for a coarse thread vs a fine thread does not make sense to me. Both are 60 degree threads and, depending on the size of the work piece, a 20 TPI thread could be considered either coarse or fine. Sounds more like poorly written advertising copy than useful information in that advertisement.

Les
Les Bengtson

Thanks guys for all your comments. Panic over! I think I can close this thread now - a bit of careful miniature triangular filing here and there and the threads became useable again. Fixed!
Bruce.
Bruce Mayo

9/16 UNF x 24 TPI
P Draycott

If the thread is 9/16-24, it is not Unified National and is some system predating the introduction of the Unified National system which was introduced in the late 1940s. MGs contained a number of older thread systems, especially in the T series and MGA period. Some of the parts on the MGB were still using non-Unified Standard threads when the vehicle went out of production in 1980.

This is worth knowning and considering for two reasons. First, it may be difficult to find a nut or bolt to fit some of the older systems in today's metric UK. Especially if you cannot identify the correct size of the bolt or nut.

Second, many of the older systems used something other than a 60 degree V thread when the threads were formed/cut. Whitworth, for instance, used a 55 degree thread. Thus, the standard "re-threading file", or a 60 degree triangular file, is less than ideal for cleaning up damaged threads.

Les
Les Bengtson

There was a March 2019 thread in Autoshrine entitled “Steering wheel nut thread size and pitch” in which Cecelia Bruce said that the thread is 11/16-28TPI. Unfortunately it will not load here for me.
Bolney Coupe

Correction. 11/16 UNEF X 24. Unified National Extra Fine
P Draycott

This thread was discussed between 05/11/2021 and 09/11/2021

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