Another tricky screw removal

[130]

Really?

You don't get that if the hole has enough around it the alloy expands in all directions and can push in ? It's not like heating a thin ring where the expansion in the kind dimension (circumference) increases diameter more than the thickening of the small dimension pushes in

 

[rtbcomp]

You heat pistons to fit the gudgeon pin. The hole in the piston gets bigger.

 

[130]

More often you heat the rods to expand the eye, or they go full floating

 

[RonA]

I'd make a drill bushing that was a snug fit over that ally boss and put a drill down through it.

Interesting video on Youtube using exactly the technique you describe. The only variation is the guy uses a left hand fluted twist drill which works naturally to rotate the damaged end out of the hole.
If racediagnostic is worried about swarf going down the intake, perhaps a “dam” of grease around the hole would trap the bits of swarf that escape.
Interesting car, is it a Maserati by any chance?
RonA

 

[rtbcomp]

More often you heat the rods to expand the eye, or they go full floating

That doesn't help the pin fit into the piston though. They regain their grip when the piston cools down. There are several different pin/piston/eye arrangements, but the point is heating a lump of aluminium with a hole in it makes the hole bigger.

 

[Seadog]

You don't get that if the hole has enough around it the alloy expands in all directions and can push in ?

No I don't. It's contrary to every textbook written on the subject of expansion in materials.

 

[130]

No I don't. It's contrary to every textbook written on the subject of expansion in materials.

it's as I said in the part you omitted from the quote.

 

[Pete.]

Holes don't expand inwards. When parts grow every dimension grows.

 

[Gareth J]

In this situation, I don't believe it really matters what gets bigger or smaller.

This is illustrated by the "weld-blob" technique. You put huge amounts of heat into the bolt - likely red hot, while the surrounding alloy and the giant heatsink it is stays pretty cool. So in theory, the bolt will expand masses and grip the hole further, which it does. But the big chunk of alloy next door and whatever penetrating fluid you use soon cools it down.

The helpful thing is that they've expanded by different amounts both due to what's been heated and what it's made of. That differential helps break the corrosion and loosen things off.

 

[Brad93]

it's as I said in the part you omitted from the quote.

Sorry mate but you are wrong you need to go look up thermodynamics.

For the hole to expand inwards it would need to compress the free edge, which means compressing the atoms - increasing density!

As we know, heat makes the spaces between atoms increase not decrease, and therefore expand.

https://physics.stackexchange.com/q...make-the-inner-radius-shrink-to-free-up-space

 

[slim_boy_fat]

I'll bet @RaceDiagnostics didn't anticipate all this when he started the thread....

 

[PhillipM]

Sorry mate but you are wrong you need to go look up thermodynamics.

For the hole to expand inwards it would need to compress the free edge, which means compressing the atoms - increasing density!

As we know, heat makes the spaces between atoms increase not decrease, and therefore expand.

https://physics.stackexchange.com/q...make-the-inner-radius-shrink-to-free-up-space

Which is why thin sheet warps and buckles if you heat it unevenly and won't shrink inwards unless you belt it with a big 'ammer.

 

[RaceDiagnostics]

Intuitively, I would think that if you heated the entire aly housing the hole would get bigger, but if you only heat the hole area it would get smaller as the hot expanding aly would be constricted by the cold aly around it.

However I have never tested this theory and have no idea what would really happen.

Anyway, still not got into the garage today yet.

 

[PhillipM]

It'll just bow/warp upwards to the free surfaces.

 

[RaceDiagnostics]

You can imaging that happening with sheet metal but what about thick castings?

 

[Seadog]

See post No. 30

 

[Wallace]

I hope the screw underneath that one is not seized as well when you get in there, I would also be careful with heat around that metering block.

 

[Sean]

You can imaging that happening with sheet metal but what about thick castings?

like an engine block?
no internal combustion engine( or external come to that) would get past the warmup if it were to follow your theory.

 

[RaceDiagnostics]

I ground down the screwdriver bit.

Sprayed on some freezer spray.

Hammered the impact screw driver.

It broke free on the first hit.

Thanks again for all the suggestions.

 

[Cobbler]

Good result, well done