Author Topic: Fork leg Stud  (Read 417 times)

Offline Angus

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Fork leg Stud
« on: 14.01. 2018 14:43 »
As many of you will know I am prone to disasters so before I make things worse  *smile*
During the summer I noticed the top nut that holds the 'Y' piece that holds the mudguard to the fork leg kept coming lose. Eventual realised it had wrung off. I found a nut that fitted and did up tight enough (probably the wrong thread 1/4 BSF) and that had lasted the summer. Now trying to fix it properly.
I have tried two nuts method, bottom one a correct one top one the one that lasted the summer and they dont move it just undo together
I assume this is a stud and can be removed. If so would it be ok to get a friend who can weld to tac weld the nut to the stud and try that or is it an proper engineering job.

 
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1961 A7 since 1976
1960 A10 Gold Flash Super Profile Bike
1958 Matchless G80 Project
1952 Norton Model 7 Plunger
1950 T100

Offline RoyC

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Re: Fork leg Stud
« Reply #1 on: 14.01. 2018 15:29 »
Can you use some thread lock on it ?
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My bike is a 1958 A7SS
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Online JulianS

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Re: Fork leg Stud
« Reply #2 on: 14.01. 2018 16:38 »
It is not a stud you cannot remove it.

Takes a 5/16 BS Cycle nut originally.

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Offline Angus

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Re: Fork leg Stud
« Reply #3 on: 14.01. 2018 16:52 »
Thanks Julian (Well for the reply anyway), So I take it that it needs to go to an engineer to drill out and replace or are we saying the leg is junk. Unless I bodge it.
ps all four of mine take 1/4 cycle tread nuts
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1961 A7 since 1976
1960 A10 Gold Flash Super Profile Bike
1958 Matchless G80 Project
1952 Norton Model 7 Plunger
1950 T100

Online Greybeard

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Re: Fork leg Stud
« Reply #4 on: 14.01. 2018 18:14 »
Is it worth retapping with a smaller suitable die; maybe metric?
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Online JulianS

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Re: Fork leg Stud
« Reply #5 on: 14.01. 2018 18:55 »
I would avoid any bodge job.

The forks have very little bracing to resist twisting under braking - just the "y" piece and fairly thin supports which are welded to the mudguard. The mudguard often splits at the edge by the support due to vibration and/or twisting. Even less bracing with 1/4 inch studs.

Sometimes the threads are damaged by cross threading or corrosion.

Welded repairs need care to avoid distortion of the thin walls.

I would look for a sound pair of bottoms.

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Online terryg

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Re: Fork leg Stud
« Reply #6 on: 15.01. 2018 08:14 »
I had a similar problem, with the need to replace a boss and 'stud'.
After welding a surrogate boss in place it was necessary to ream the fork leg, owing to distortion of the inner tube surface.
With hindsight (the tool that's never in the box when you need it) brazing on the boss might have avoided or reduced the amount of distortion.
Nevertheless, worth taking recovery action, in my opinion.
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Terry
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Offline Angus

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Re: Fork leg Stud
« Reply #7 on: 15.01. 2018 09:13 »
Thanks Terryg
So an engineering repair is possible. I have been looking out for a spare set since I found the problem in the summer and have not seen any. I am accumulating a spares supply for my 2 A's and will keep looking but at least this means that if I find the right person the leg can be repaired.
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1961 A7 since 1976
1960 A10 Gold Flash Super Profile Bike
1958 Matchless G80 Project
1952 Norton Model 7 Plunger
1950 T100

Offline chaterlea25

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Re: Fork leg Stud
« Reply #8 on: 15.01. 2018 16:52 »
Hi Angus,
There's enough metal in the stud boss to drill into and locate a turned up stud or a cycle thread  bolt with the head turned down,
Some chamfering on the boss and stud head will leave room for either a TIG weld or braze

A while ago I rescued a set of legs by re threading the studs to 7mm and making some "bastard" 7mm x 1/4W hex nuts
 *work*

John
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Offline Angus

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Re: Fork leg Stud
« Reply #9 on: 15.01. 2018 17:00 »
Thank you John (chaterlea) that is much more hopeful and what I was thinking of getting done. I have found some studding 1/4 cycle bar online and have someone who could cut, drill and thread (they may not let me use the studding as they may want to create the stud themselves). If they then TIG weld or braze will I need to plan on get the leg reamed ie could it go out of shape.
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1961 A7 since 1976
1960 A10 Gold Flash Super Profile Bike
1958 Matchless G80 Project
1952 Norton Model 7 Plunger
1950 T100

Offline chaterlea25

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Re: Fork leg Stud
« Reply #10 on: 15.01. 2018 19:09 »
Hi Angus
The bolts should be 5/16in.
TIG would be better as the heat is kept very localised
Having a "head" on the bolt will give a larger weld radius so stronger

John
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1961 Super Rocket
1963 RGS (ongoing)