Technical Damaged leaf-spring mounting bolt

[stjob001]

Many thanks to those who gave me advice regarding the removal of the shorn suspension-arm yoke bolt. I have removed it successfully and have replaced it with a high-tensile bolt through the wheel well.

Unfortunately my car keeps on giving. I have a problem with one of the bolts holding the leaf-spring and mountings. Basically, the top part of the thread on one of the bolts is completely gone and when trying to mount the leaf-spring I cannot get the nut in far enough to reach the undamaged thread.

Can the bolt be re-threaded to a smaller thread OR can the bolt be replaced in some way similar to how I replaced the suspension-arm bolt?

Regards...Brian

 

[the hobbler]

Sadly, the leaf-spring mount bolts are a 'different kettle of fish'--they are coming out of a sealed, boxed section. There are 2 ways around the problem---if there is still enough thread on the lower section of the stud, use a spacer between the aluminium mount and the nut (thick washer, or even a slightly oversize nut) between the nut and the aluminium mount to cover the damaged section of thread. OR, you have to cut out the area around the damaged stud (you have to cut out the section around both studs) and have a section of plate inserted inside the box section.The repair section has to be 'lipped' so that you have a good overlap area inside the boxed section and yet the outer part of the repair section is flush with the outer part of the boxed section--and then have it welded in place If you go this way with the repair, make sure the heads of the bolts (that will be used as mounting studs) are FULLY welded in place.

 

[the hobbler]

Suddenly thought of a 3rd way to carry out the repair. You buy the complete cross member (with the spring-mount studs in it), cut out the complete section aroung BOTH pairs of studs from the new cross member and have this welded into the original cross-member (having firstly cut out the matching section in the old cross-member that is on the car). Again,doubly check the welding of the studs.

 

[F123C]

My reading of the OP's problem is that it's the beginning of the thread that is damaged preventing the nut from going onto the stud.

If this is the case, it might be possible to 'repair' the damaged thread enough to allow the nut to start. There's a few different ways of attempting this, depending on what tools/equipment you have available.

The easiest way to do this at home with limited facilities, would probably be to cut a nut in half across the diameter to make a split die nut. Clamp the 2 halves around the stud on the good part of the thread, then wind downwards to try to clean up the damaged thread. The harder the nut material, the better this will work - try to get a Grade 12 nut, but even a Grade 8 (same? as the standard Fiat 80 nut that is used on the spring mounting) should work.

There are also 'Split Die Nuts' available (the type that comes in 2 halves, not the usual ones that have one split) for use in professional workshops (not really worth the expense for a one-off job at home).

You might be able to utilize what is called a 'Thread File'. This is a bar with 8 different pitches of thread teeth running lengthwise - select the part of the thread file that matches the damaged thread and gently file to restore the thread as best as possible - not easy to do in a confined space + you won't be able to access all the thread.

If you are sure that you have enough good thread to securely fit a nut to hold on the suspension spring, you could possibly cut off the damaged section and file a chamfer on the end to allow the nut to be started on its thread easily. But I suspect you might not actually have enough thread for this to work well - the extra thread length helps when fitting the suspension spring.

Al.