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M6 or M8 bolt in M7 hole?
Posted: Sun Mar 03, 2024 11:16 am
by Belgian951
I have to fit a stud through a hole, but I believe the hole is bigger than M6, yet smaller than M8. This means a M7 stud would be my best bet, but I can't find this specific ball stud size it seems. Is it possible to fit a M6 bolt in the hole, even if it's bigger? My idea would be to use a washer on each side and a lock nut from behind.
Re: M6 or M8 bolt in M7 hole?
Posted: Sun Mar 03, 2024 11:29 am
by Tom
Belgian951 wrote: Sun Mar 03, 2024 11:16 am
I have to fit a stud through a hole, but I believe the hole is bigger than M6, yet smaller than M8. This means a M7 stud would be my best bet, but I can't find this specific ball stud size it seems. Is it possible to fit a M6 bolt in the hole, even if it's bigger? My idea would be to use a washer on each side and a lock nut from behind.
Hard to answer without knowing more. What are you bolting together? Random info in case helpful -- 1/4 inch and 5/16 inch are both between 6 and 8mm.... M7 fasteners are mighty rare...
Re: M6 or M8 bolt in M7 hole?
Posted: Sun Mar 03, 2024 1:06 pm
by Belgian951
I removed the ball mount for my hood strut, and I plan to use a ball stud to replace it without welding.
Re: M6 or M8 bolt in M7 hole?
Posted: Sun Mar 03, 2024 1:15 pm
by Tom
Belgian951 wrote: Sun Mar 03, 2024 1:06 pm
I removed the ball mount for my hood strut, and I plan to use a ball stud to replace it without welding.
Can you post a picture of what you're looking at there? I may have an idea
Re: M6 or M8 bolt in M7 hole?
Posted: Mon Mar 04, 2024 12:49 am
by 911-Purist
Belgian951 wrote: Sun Mar 03, 2024 1:06 pmI removed the ball mount for my hood strut, and I plan to use a ball stud to replace it without welding.
A bit lost as to why you removed it and now want to install a bolt-on ball stud. I take it your hydraulic hood strut will attach to it again.
And is this what you are looking for...
- Ball Mount
- B2430.jpg (28.49 KiB) Viewed 1330 times
Re: M6 or M8 bolt in M7 hole?
Posted: Mon Mar 04, 2024 2:58 am
by Belgian951
Re: M6 or M8 bolt in M7 hole?
Posted: Mon Mar 04, 2024 5:31 am
by icb
Watching this one with interest. I noticed my passenger side ball mount is loose as well a little while ago. Welding is definitely the best option but it would be a nightmare to weld there without making a huge mess, unless you were in the middle of a major restoration project. It seems like that bracket is in an extremely challenging spot for any kind of attachment method.
Re: M6 or M8 bolt in M7 hole?
Posted: Mon Mar 04, 2024 7:30 am
by Tom
Just spit-balling, but if you can get a nut behind it and the M6 stud has the right ball size, why not drill the hole a bit so the m6 ball stud fits squarely in the hole? I'd smother it in red loctite if you go that route...
I've had success in the past drilling brackets like that off the car with a spot-well bit. Then on the bench you can either replicate it with the right ball or replace the whole thing with one similarly removed from a junk car. Putting them back on via a plug weld is fairly easy if you have access (and a TIG welder might help there). They make spring-loaded spot weld drill bits that work like magic.
https://www.amazon.com/Blair-11096-Cutt ... r=8-6&th=1
If all that is out of the question and that M6 stud ball you have is otherwise the right size (?), you might be able to get away with a rivnut. A rivnut crimps in place and adds solid threads to sheet metal. Might be worth a try as you can always fall back to the welding or nut route if it fails.
https://www.mcmaster.com/products/rivnu ... ivet-nuts/
Re: M6 or M8 bolt in M7 hole?
Posted: Mon Mar 04, 2024 11:06 am
by Belgian951
Tom wrote: Mon Mar 04, 2024 7:30 am
Just spit-balling, but if you can get a nut behind it and the M6 stud has the right ball size, why not drill the hole a bit so the m6 ball stud fits squarely in the hole? I'd smother it in red loctite if you go that route...
I've had success in the past drilling brackets like that off the car with a spot-well bit. Then on the bench you can either replicate it with the right ball or replace the whole thing with one similarly removed from a junk car. Putting them back on via a plug weld is fairly easy if you have access (and a TIG welder might help there). They make spring-loaded spot weld drill bits that work like magic.
https://www.amazon.com/Blair-11096-Cutt ... r=8-6&th=1
If all that is out of the question and that M6 stud ball you have is otherwise the right size (?), you might be able to get away with a rivnut. A rivnut crimps in place and adds solid threads to sheet metal. Might be worth a try as you can always fall back to the welding or nut route if it fails.
https://www.mcmaster.com/products/rivnu ... ivet-nuts/
I don't think putting the stud half way through the hole would be stronger than actually putting the threads through and then nutting it.
Drilling out the spot welds would be my last resort, and would be combined with replacing the whole mount with OEM parts.
A rivnut is indeed an option, one that I will definitely try when the stud and lock nut fails. I wanted to try this first because a rivnut would be weaker, although probably way easier to install.
This is a picture of how I want to approach it (M6 ball stud or M8).
- ball stud.png (26.55 KiB) Viewed 1291 times
Re: M6 or M8 bolt in M7 hole?
Posted: Mon Mar 04, 2024 11:23 am
by Tom
Yes, that approach seems worth a try. I think I misunderstood your "crooked in the hole' comment above. I thought the hole was too small, which is why I suggested drilling it a little. If the hole is too big, then a couple of washers might hold everything in place. Hard to know how strong all of this will be but can't hurt to try. None of that will prevent you from popping off that little stanchion and welding on a replacement with ball from another car, which ultimately would be the best solution I'm sure.