Repairing a stripped stud's thread.

[ajlelectronics]

M8 thread on a stud may be partially stripped half way down. Is there a "Helicoil" type sleeve that can screw down over say an M6 thread, to restore the M8?

This is on an expensive shock absorber that didn't like the BMW stiff nut, threads probably made of chocolate.

 

[Bullet2012]

is room available to just use a spacer over the damaged section so the nut tightens onto a good piece of the remaining thread ?

 

[ajlelectronics]

is room available to just use a spacer over the damaged section so the nut tightens onto a good piece of the remaining thread ?

No, the top of the thread is where it is damaged. I was thinking (once I confirm my suspicion) of an M8 stud with an M6 tapped hole through it. I know that the dimensions are a bit close though.

 

[Agroshield]

is room available to just use a spacer over the damaged section...

The opposite might be an option - make a longer nut so the part of it that engages the male thread is lower down.

Potentially that part could be 'inside' the item being secured.

Think of an allthread coupling nut. Turn the hex off the lower half of it so it is cylindrical and make the hole in the component being secured larger to suit.

 

[BrokenBiker]

Im going to ask, knowing the answer is probably no, but can the stud not be removed and replaced?

 

[ajlelectronics]

Im going to ask, knowing the answer is probably no, but can the stud not be removed and replaced?

I don't believe so, but it is conjecture until I have another look at it tomorrow.

 

[8ob]

M8 to M6 sleeves are available, cutting a straight thread that small over any distance would be the challenge.

Pardon our interruption...

Bob

 

[BrokenBiker]

I don't believe so, but it is conjecture until I have another look at it tomorrow.

No problem, only asked as we all have times when we can't see the simple answers.

M6-m8 'adapters' are a thing though. I've seen them advertised whilst looking for other things...turning your duff m8 into an m6 may be fidly though

 

[tom2207]

Ive cut them off the bottom of laand rover shocks and welded a section of a bolt on , .... [ gac handed apprentice tried to put the wrong nut on with an ugga dugga gun ]

 

[Agroshield]

M8 to M6 sleeves are available, cutting a straight thread that small over any distance would be the challenge.

The specific one to which you link is a bit vague on the pitch of the M8 thread. It notes 1mm pitch but it is not clear if that is just the internal M6 thread or both internal and external threads.

This one is explicit on the details:

Pardon our interruption...

As you say, it would be quite a challenge to reduce the M8 thread to a 6mm diameter cylinder before die-cutting a new thread. On a shock absorber, it could be done on a mill with a boring head, with the tool facing inwards.

 

[Barking Mat]

Could you weld an M8 nut on the knackered thread, and when the shock dies, cut it off and replace the entire unit ?

 

[ajlelectronics]

Could you weld an M8 nut on the knackered thread, and when the shock dies, cut it off and replace the entire unit ?

It is brand new.

 

[tom2207]

Id cut and weld that and not get excited by it ,,, use a wet rag round the top of the shock , and / or a bit of steel plate , both probably

 

[mr haynes]

Couple dabs of weld and run a die down

 

[BrokenBiker]

It is brand new.

View attachment 496115

What's the reason for not simply returning it as faulty?

 

[8ob]

How about running a thread chaser down it and using a long nut? Should catch enough good thread to hold, just thoughts.

 

[ajlelectronics]

What's the reason for not simply returning it as faulty?

Because they will (reasonably) claim user error. They really should be supplied with new nuts etc if they are not compatible with the original fittings. As it was a stiff nut and took some removal, it didn't feel unusual to have it stiff going down too.

 

[bricol]

I wouldn't be too comfortable with reducing a suspension component mounting stud to M6 - that's got to hand onto the full droop load. If the original was M8, one would assume there was a reason for it not to be M6 in the first place.

 

[GRW]

Where I work, drilling out & replacing snapped bolts & studs us a regular occurrence (not me doing it btw).
If the thread cannot be saved, then it's drilled out with the specific drill size, then tapped to accept a genuine Recoil (the original Helicoil) insert which is screwed-in to restore the original thread size.

However.... they will not ever do such a repair to any braking, suspension or steering component, end of. There are of course plenty of people who do such repairs - but given the consequences of any failure it's not something the boss is prepared to undertake for customers.

 

[Agroshield]

Seeing the picture of it, that would fit into a lathe with a big enough bore. What is its maximum diameter with the spring removed?

Then you could turn it down, weld it up, turn back to 8mm and re-thread.

Even on a smaller lathe, with some care, you could mount it on the cross slide (two semi-circular wooden blocks) and do the same procedure.