Snaping bolts and screws

[Yoko]

I was messing with an old outboard at the weekend and while taking the lower part off (where the propeller goes) I easily snapped 4 of the 6 bolts!

Not really a huge problem as it’s a piece of old shit and will never run again any way.

But how do you avoid this happening? The nut snapped pretty easily and when I put force on the spanner it moved which made me think its starting to undo then it just went very lose and low and behold had snapped.

Would be a right bastard should this happen on a motorbike engine or something!
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Sheep Shagger

[stinkwheel]

I think if they snapped that easily, they were going to do it no matter what you did.

Have a look at the broken ends and see how much actual solid metal is left, I suspect not a lot.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Vincent]

It's quite often the case with sheared bolts that the bolt is a different metal to what ever it's screwed into as this alone can cause corrosion. So if your unscrewing a steel bolt from an alloy casing, beware.

[ZRX61]

[Diggs]

...or squirt in WD40 the night before, give it a wack with a hammer & chisel then try turning it ever-so-slightly the wrong way before the main attempt. It does sound like it was shagged already though...
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Now - Speed Triple, old ratty GS550, GSXR750M
Gone (in order of ownership) - Raleigh Runabout, AP50, KH125, GP125, KH250, CBX550, Z400, CB750FII, 250LC, GS550, ZXR750H1, Guzzi Targa, GSX750F, KH250 x2, Bimota SB6R and counting...

[adamj]

Theres quite a few tricks that can be done to help you stop shearing bolts, the ones I've used are:

Soaking it in penetrating oil, or wd40 if you don't have any, and leaving it over night - as previously mentioned.

Tighten the bolt up a small amount then undo a little, keep repeating to loosen it up, might take a while but eventually it will free up.

Hit the bolt across its length, usually using a copper bar - not exactly sure why this works but in my expirences it has lol.

To prevent it happening each time you leave bolts in for a while, put some oil on the end of the thread before you go to screw them back in.

If its two different metals like previously mentioned you're in for a hard time I'm afraid as if they're left together for a long time it's possible for them to bond together making them very difficult to undo

[stinkwheel]

You missed roasting the hell out of them with a blowlamp (until the metal is hot enough to vapourise a drop of oil on contact).

You can also get freeze and release spray which does a similar thing, the rapid expansion/contraction of the metals in response to extremes of temperature breaks any adhesion that has formed between them.

This works particularly well with dissimilar metals which expand and contract at different rates.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[adamj]