A hole

[bluedog225]

I bet one of you machinist types knows.

If there is a hole in a plate of metal, does heating make the hole smaller or larger?

Same question for cooling.

I can imagine it both ways.

I’m trying to drift pins out of a thing and they are galled, corroded, electrolized, or otherwise stuck.

It might or might not be my pressure cookers.

Thanks!

[Paul Pless]

the hole expands when the surrounding metal is heated evenly

[Peerie Maa]

I bet one of you machinist types knows.

If there is a hole in a plate of metal, does heating make the hole smaller or larger?

Same question for cooling.

I can imagine it both ways.

I’m trying to drift pins out of a thing and they are galled, corroded, electrolized, or otherwise stuck.

It might or might not be my pressure cookers.

Thanks!

Look up the coeficcients of expansion of the metal in the body/lid, and of the metal of the pins.

Try spot heating the pins with a soldering iron to expamd them. That may break up/crumble the corrosion producrta.

[CWSmith]

^ I'm guessing it changes shape, too.

[Peerie Maa]

^ I'm guessing it changes shape, too.

No reason why it would.

[bluedog225]

I would thing with something like a piston, it might compress the hole prior to the block getting hot. So I get the even heating. Thanks.

[Jim Mahan]

Try spot heating the pins with a soldering iron to expamd them. That may break up/crumble the corrosion producrta.

Or, if the configuration allows it, heat the whole up a bit, and then put an ice cube on the pin. Note that that's 'whole,' with an initial 'w.' Cuz you can't heat up a hole. You can only heat up the thing the hole is in.

[Too Little Time]

I bet one of you machinist types knows.

If there is a hole in a plate of metal, does heating make the hole smaller or larger?

Same question for cooling.

I can imagine it both ways.

I’m trying to drift pins out of a thing and they are galled, corroded, electrolized, or otherwise stuck.

It might or might not be my pressure cookers.

Thanks!

Ever see the experiment with a ball and 2 rings. All made of the same material. The inside of one ring shrinks when heated. The inside of the other expands when heated.

[Jim Bow]

I think there’s a procedure at Boeing where a large pin is frozen in a nitrogen cask and pressed into a hole within seconds. I don’t believe it’s ever removable.

[Paul Pless]

The inside of one ring shrinks when heated.

a metal ring? seems implausible and contrary to the laws of physics, the thermal expansion of rings is defined by the linear expansion of the material

[Too Little Time]

a metal ring? seems implausible and contrary to the laws of physics, the thermal expansion of rings is defined by the linear expansion of the material

That is the beauty of it. Make the ring think enough and it acts like a plate. As others have said there the hole shrinks.

[Paul Pless]

i would like to see the specific example that you are citing

[CWSmith]

^ I'm guessing it changes shape, too.

No reason why it would.

Not all holes are round and very few heating sources are uniform.

However, you made me rethink the problem and I think you are right for the idealized case.

[Keith Wilson]

The hole gets bigger when heated. Shrink-fitting is a standard technique for assembling things tightly. Machine for an interference fit, heat the outside bit, cool the inside, put 'em together and let everything come back to to room temperature. Depending on the shape of the part and how you heat it the hole can change shape a little, but in most cases it doesn't matter.

[Art Haberland]

much of what you want also depends on the metals you are playing with and their mass. You might be able to get away with heating everything up a nice warm glow and rapidly cooling the pins. They would shrink faster than the plate and should be easier to drive out that way.

[bluedog225]

I’ll try heating the alu without melting it. The pin is steel.

Hard to cool the pin independently.

Thanks all.

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[bluedog225]

I’ve beaten one out. But I’ma little worried about breaking the ears.

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[Keith Wilson]

FWIW, aluminum expands about 2-1/2 times as much as steel when heated the same amount.

[bluedog225]

Excellent. Thanks.

[P.I. Stazzer-Newt]

Back when I was a lad and dinosaurs ruled the earth - my very first science teacher had a nice demonstration with a ball and a ring - he didn't invent the demo and he wasn't the last guy to use it -



I've known SWMBO use the same principles to remove a stuck trumpet mouthpiece using a hot coffee and some ice cream.

[Jim Mahan]

And the murders began…

[StevenBauer]

Did anyone hear the talk on public radio last week around the question of how many holes a straw has? Seems some people think a straw has two holes and some think it has one. What do you guys think?

[Paul Pless]

a straw has one hole

[bluedog225]

Corn kernels don’t enter your body when you eat them.

[Peerie Maa]

I’ll try heating the alu without melting it. The pin is steel.

Hard to cool the pin independently.

Thanks all.

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A lump of dry ice should do it. The opposite of a soldering iron tip.

[Peerie Maa]

Back when I was a lad and dinosaurs ruled the earth - my very first science teacher had a nice demonstration with a ball and a ring - he didn't invent the demo and he wasn't the last guy to use it -



I've known SWMBO use the same principles to remove a stuck trumpet mouthpiece using a hot coffee and some ice cream.

Some apple of his mother's eye thought it smart to heat the ring, lower the ball in, and then pour cold water on the ring.

My class found out about that trick when the metal work tutor was asked to get them apart again.

[Keith Wilson]

I presume the steel doodad with threads is a loose fit on the pin, and the only tight fit is between the pin and the aluminum casting, right?

Ah, just heat it up with a propane torch and give the pin a lusty whack. I bet it will come out nicely. Make sure you're bashing on the un-knurled end, though.

[StevenBauer]

Did anyone hear the talk on public radio last week around the question of how many holes a straw has? Seems some people think a straw has two holes and some think it has one. What do you guys think?

a straw has one hole

Yet that’s not what most people think.

[bluedog225]

6672968[/URL]]I presume the steel doodad with threads is a loose fit on the pin, and the only tight fit is between the pin and the aluminum casting, right?

Ah, just heat it up with a propane torch and give the pin a lusty whack. I bet it will come out nicely. Make sure you're bashing on the un-knurled end, though.

yep and yep. It’s out baking in the sun right now. Will break out the propane a little later.

[Lew Barrett]

How can straws not have two holes? They have two ends!

Another benefit of heat....it melts Loctite.

[Peerie Maa]

Yet that’s not what most people think.

Only one. Topology says so.

[bluedog225]

Can’t find my propane or mapp. Everything is up a the place. Big downside of cleaning the place out.

Went ahead and put it on the gas stove. The first one tapped right out with no drama.

Thanks all!

edit-and they are all done. Piece of cake. You guys are experts at….this.

[David G]

Did anyone hear the talk on public radio last week around the question of how many holes a straw has? Seems some people think a straw has two holes and some think it has one. What do you guys think?

Depends on who you ask.

The engineer will say one.

But some highbrow mathematician (n-space geometer?) will come along and tell you it has infinity.

[Paul Pless]

You guys are experts at….this.

that makes us ahole specialists?

[Jim Mahan]

How many entrances does an elevator in a two story building have?