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MG TD TF 1500 - Pivot studs on windshield support memebers

The shorter of the two pivot studs on the TF windshield support stanchions need to be changed, as the threads are badly worn.

I have been informed that the original studs were pinned into the frame prior to being chrome plated. The strong advise was NOT to attempt removing them!

Brown & Gammons sell replacement studs, both pinned and unpinned, implying that it is a client's choice.

Has anyone attempted this task? I wonder what options are available to someone in this predicament?
P Pichler

I have not done this personally but since the support stanchions are much softer than the pins it's going to be very difficult if not impossible to remove them unless you have a very special setup I would believe.

Perhaps drilling out the studs to 90% of their width incrementally and then chipping away at the remainder with a dremel tool might work.

I would see if you can find a damaged one to practice with.

It will be interesting to see who had done this.
Christopher Couper

I would drill them out BUT you need to be very careful to drill concentric to the stud.

NO Guessing.

I would machine a bushing which was a very tight fit on the OD of the stud and would accept a "Drill Jig Bushing"

Like this one.

https://www.victornet.com/detail/ZHB9/64-1-3/8.html


Aluminum is OK for this outer locating bushing. This outer bushing slips on the stud on one end, and the Hardened drill jig bushing goes into a tight fitting hole on the other end. This keeps the drill bit concentric wit the stud.


These should be available from any good Machine tool supplier.

These are made from Hardened steel and the drill will not cut them.
The one I show is 1/4" OD. You may need to have two bushings made as you might need an assortment going up to just below the diameter of the stud.
Criss mentioned 0.010 below. You could stop. somewhat short of that.
I looked at some pictures I took of my wind-screen during rebuild and I am guessing 5/16 studs. The 5/16 BSF stud has a pitch of 22 TPI. The single depth of the threads is in the range of 0.028" so I would think going 1/32 under the 5/16 would be enough to allow you to "un-peal" the remains thread like a helix.

I am no sure what the pin would do, however.

To preserve the plating I would not try to re-pin. Green Locktite will hold it just as well.

These are just my thoughts on how I would go about it.

Jim B.
JA Benjamin


Be carefull on these, I am pretty sure that the threads on these studs are British Cycle thread, 5/16 26 TPI


Ralph.
R E J Stewart

Peter,
sorry I did not reply to your email (touring in Greece,I could receive mail but I could not send?).

There has been a debate about the pivot thread. It could be either Standard Cycle or Standard Brass. both are 26TPI but different thread form angles. Over my years of British motorcycle maintenance I have found that they interchange OK.

If you are going to drill out and clean up the thread you must be VERY careful.
The TF stanchion is NOT the same as the TD and as they only made around 10,000 TF's the parts are not easily found.
Ray
Ray Lee

Thank you all for the replies to my problem. And a problem it is!

Jim, I especially liked your detailed response but I would be compelled to find a very good machine shop to perform this work, which Ray seems to have perform in the past, given his cautionary note.

There was one other suggestion and that was to repair the stud by cutting away the worn portion and TIG welding on a replacement portion, seeing that I have a replacement stud handy.
I am unsure where the cut would have to be enacted as it would have to be somewhere in the threaded portion of the stud, avoiding the unthreaded portion used for the actual pivot hole in the cowl brace casting.

I do have a British Brass 5/16" 26 TPI die that could be run after the TIG welding but am unsure about he efficacy of such a solution.

I am open to additional comments on this aspect.

Thank you again to all.

Peter
P Pichler

There is one alternative method which does not require a lot of machining.

Find a good metal filled two part epoxy.
DECVON is a good supplier here.

Carefully clean the buggered threads. Degrease and wire brush with a brass wire brush.

Fill the threads with the epoxy, just to a 5/16 diameter. If you could find or make a cardboard sleeve to constrain the epoxy to 5.16 this would be good. Leave a little of the outer end of the thread exposed so you can start your die and pick up the existing thread.

Let the epoxy set for at least 1 day.

Carefully cut new threads, picking up the old ones to start.

We have repaired worn threads on the half nuts on lathes using this kind epoxy and a similar, but not exact, method and they have lasted for years.

Jim B.
JA Benjamin

Peter, over 40 years ago I wrecked mine while removing it. Luckily I had access to a lathe and machined a bullnose stud. 5/16 cycle one end and I think 7/16 BSF the other.
Ray TF 2884
Ray Lee

Thank you for the alternative solutions and dire warnings.
It is a challenge indeed.

Peter
P Pichler

This thread was discussed between 14/09/2019 and 17/09/2019

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