Seat Belt bolt sheared

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Zaphod
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Seat Belt bolt sheared

Post by Zaphod »

While getting my car cleared for new carpets I sheared the drivers side seat belt bolt on the inside of the car (the one that is fixed to the chassis) so far it has resisted my attempts to remove it. so far I have tried..

Welding a nut on the remaining sections.. however I cant get any good penetration on the remains of the bolt so it just shears off again :(
Tried 'Irwin' extractors, which just slip and chew the end up.
Tried drilling it out but only succeeded in blunting the drill bits..
Tried reverse drill bits but that does the same as above but in a different direction..

Any good methods for this, or if making the above method work before I die of old age?
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1957 MGA 1500
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel

Marten
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Re: Seat Belt bolt sheared

Post by Marten »

Zaphod wrote:
Sat Jul 09, 2022 22:51
While getting my car cleared for new carpets I sheared the drivers side seat belt bolt on the inside of the car (the one that is fixed to the chassis) so far it has resisted my attempts to remove it. so far I have tried..

Welding a nut on the remaining sections.. however I cant get any good penetration on the remains of the bolt so it just shears off again :(
Tried 'Irwin' extractors, which just slip and chew the end up.
Tried drilling it out but only succeeded in blunting the drill bits..
Tried reverse drill bits but that does the same as above but in a different direction..

Any good methods for this, or if making the above method work before I die of old age?
Some general rules:
be very carefull with any type of extractor, they often break leaving very hard bits of metal behind making further drilling impossible.

Instead of welding on a nut it is often easier to weld on a washer first (so you are welding to the bolt and not just filling the hole up) and weld a nut to that. If it pops off do it again, repeated heatcycles are good.

Drills can be regrinded, keep the revs down and apply sufficient pressure to keep it from skating instead of biting

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DavidOliver
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Re: Seat Belt bolt sheared

Post by DavidOliver »

Just a long shot. I recently bought some Bosch drills (made in China) which could not drill through butter.
I managed to get a set of high grade drills, probably German made, as compensation. A huge difference.

I have never managed success with extractor tools, probably for the same bad quality reason.

Dave the cog

John
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Re: Seat Belt bolt sheared

Post by John »

Agree with Dave, I've never had any luck with extractors. Heat, PlusGas penetrating fluid, and welding bits on all worth a try, if you do have to resort to driling then top quality drill bits and some light oil to keep the bit from overheating. I recently bought a countersink bit from TC Fixings, superb quality and made in Austria. Not cheap but got the job done and in a different league to DIY store tat.

Good luck

Cheers John

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Re: Seat Belt bolt sheared

Post by John »

Also drill pilot hole first with a bit half the size, then another slightly bigger before final size. Don't risk too small a pilot though, snapping the bit would be a possibility!

Zaphod
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Re: Seat Belt bolt sheared

Post by Zaphod »

Well I found my Bosch drill set.. and now have a 5mm hole all the way through it..
Would a 9.9mm drill but be an acceptable alternative to the 25/64th bit prior to tapping? (25/64 being 9.921mm)
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1957 MGA 1500
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel

Marten
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Re: Seat Belt bolt sheared

Post by Marten »

Zaphod wrote:
Sun Jul 10, 2022 15:32
Well I found my Bosch drill set.. and now have a 5mm hole all the way through it..
Would a 9.9mm drill but be an acceptable alternative to the 25/64th bit prior to tapping? (25/64 being 9.921mm)
You'll never manage to drill a 9.921 mm hole with a handdrill. drilling isn't that precise. But I'd sneak up on the final size, because chances are your pilot isn't exactly centered and you might cut through into the threads earlier.
And then most of the tension will be gone and you could try removing the remains with chisel or whatever

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Re: Seat Belt bolt sheared

Post by Pete Boole »

Marten wrote:
Sun Jul 10, 2022 16:19
Zaphod wrote:
Sun Jul 10, 2022 15:32
Well I found my Bosch drill set.. and now have a 5mm hole all the way through it..
Would a 9.9mm drill but be an acceptable alternative to the 25/64th bit prior to tapping? (25/64 being 9.921mm)
You'll never manage to drill a 9.921 mm hole with a hand drill. drilling isn't that precise. But I'd sneak up on the final size, because chances are your pilot isn't exactly centred and you might cut through into the threads earlier.
And then most of the tension will be gone and you could try removing the remains with chisel or whatever
Good advice. I'd go up 1mm at a time until you start seeing the remains of the threaded hole. Try to get someone to spray cutting fluid while drilling - I use a plant spray.

Pete

Zaphod
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Re: Seat Belt bolt sheared

Post by Zaphod »

I am rather hoping the remains will collapse before it gets to tapping..
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1957 MGA 1500
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel

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Alan_M
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Re: Seat Belt bolt sheared

Post by Alan_M »

If any help. This is the other side of the bolt.

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Zaphod
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Re: Seat Belt bolt sheared

Post by Zaphod »

It’s the other bolt, that holds the catch to the transmission tunnel!
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1957 MGA 1500
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel

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Re: Seat Belt bolt sheared

Post by AndyC »

Given what the bolt is for and just how bad it would be if you had to try and repair the captive nut, I'd suggest building a small drill jig to get central and parallel to the bolt line. Even if it's just a nut that screws on part of one thread, then with a bit of steel fitted in the other side of that, it should make it more likely to drill most/ all of the bolt out (except the thread) without damaging the captive nut.

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Re: Seat Belt bolt sheared

Post by DavidOliver »

As a start is the bolt rusted in or just tight?
Not a dealership suggestion, but as the bolt works in shear and does not rely on 100% thread integrity (tension) with a small hacksaw blade hand held in an 8mm pilot drilling you can now cut through the remaining bolt wall to release the existing load and a bit of a poke with a small chisel should free the remaining bolt.
If your pilot drilling is off centre just hacksaw cut through the thinnest part of the bolt wall.
If rusted in, once cut through the bolt wall and partly released, penetrating oil should release the rest of the contact.

Dave the cog.

Zaphod
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Re: Seat Belt bolt sheared

Post by Zaphod »

DavidOliver wrote:
Mon Jul 11, 2022 11:08
As a start is the bolt rusted in or just tight?
I think that the inner end must have rust on it, the part that broke was all clean shiny metal, it should have come undone, and now has no tension on it with the end missing. we shall see! I can't see a way of looking at the other end of it, as when I get it all out i would like to use a longer bolt and put a nut on the other side!
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1957 MGA 1500
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel

Pete Boole
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Re: Seat Belt bolt sheared

Post by Pete Boole »

The threaded tube that the bolt sits in goes the full width of the tunnel if I remember correctly - you cannot see the end of the bolt.

Pete

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