How would you repair this???

[70herald]

I need to replace the door hinges since 1. some DPO welded them IN THE WRONG POSITION and 2. they are just worn out.

What I discovered is that in addition to welding the hinge to the body the @#$%^ jammed M8 screws into the 5/16 unf holes. Now the threaded bit on a Herald is a captive steel plate. It moves around for alignment but no real way to take it out.

I can think of two option. 1. rethread to 5/16 using Timeserts, which is probably the best, but since the plate is hidden in the A pillar not the easiest or 2. properly tap the holes for M8 bolts and be done with it.

So, how would anyone here do it?

 

[Guest]

Which is larger, an M8 or 5/16" bolt? I would think that if the M8 was jambed into the threads it may well have wallowed out the hole size and a next-larger bolt may well have to be used. Inserting a time-sert in will really be a trick. Tapping may be the only realistic option, with the captive plate held in place with one jambed bolt, do your business on the free one and go from there. The problem will be freeing up the weld, hoping he didn't penetrate the metal and weld the captive plate. Bummer.

 

[70herald]

M8 is a bit larger and a much coarser thread. The problem with going to the next size bolt is that then I will have to drill out the matching holes in the hinge.
Taping to M8 is of course the easiest since DPO has done most of the work, and it will just be a matter of cleaning up the threads properly. The down side is that if the hole was mucked up enough, it may not be quite strong enough, and doors are heavy.

On one side, the weld came off with the angle grinder. I cut through the hinge first to get it out of the way, and then used a course sanding disk to remove the weld line and remaining bits of the hinge. DPO's welding abilities were better than his mechanical skills. At least he didn't burn a hole in the sheet metal or weld to the captive plate!

 

[TR3driver]

Taping to M8 is of course the easiest since DPO has done most of the work, and it will just be a matter of cleaning up the threads properly.

But of course that will be exactly the problem, since the two threads are different pitches. Instead of nice smooth threads, you are going to wind up with a bunch of points where the peaks happen to match up, and a bunch of voids where the peaks match the valleys. The result will be very weak and prone to failure.

Personally, I would Heli-coil back to 5/16NF. Since the od is smaller than a Time-sert, you won't have to enlarge the hole in the sheet metal as much; and it won't hurt if the end of the insert hangs out in space beyond the nut plate. I've done similar repairs on my TR3A, and they've held for many years. Be sure to clean as thoroughly as possible and use a few drops of Loctite on the insert; should work fine.

 

[dklawson]

Are you SURE the DPO used M8x1.25 bolts? There ARE fine thread M8x1 bolts and those are VERY close to 5/16-24. Yes, they're still wrong but they will do much less damage to the plates. If you find that fine pitch metric bolts were used, try chasing the existing threads with the metric tap and use new M8 bolts. If the DPO used coarse metric bolts, I'd go the HeliCoil route that you and Ranall mentioned.

It sounds like you'll need to carefully cut away the weld, avoiding the bodywork, then grind away what you can to have a suitable surface.

 

[70herald]

Are you SURE the DPO used M8x1.25 bolts? There ARE fine thread M8x1 bolts and those are VERY close to 5/16-24. Yes, they're still wrong but they will do much less damage to the plates.

This car was previously owned by Pedro's evil brother. Obviously the course thread bolts were used. Same Kmart junk bolts that Tinster had been fighting with. Maybe it is about time for me to get a HeliCoil set.

 

[Jon80spit]

Mine had broken off screws. I bent back threaded plate retainers on my Spit and removed the captive plate. If you have the same set-up. make new plates.