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Posted: 9/28/2015 10:29:02 AM EDT
Link Posted: 9/28/2015 11:29:59 AM EDT
[#1]
All of the material around the hole contracts as it gets colder, so the hole gets smaller, too.  The best way to get out a stuck pin is to heat the metal around the hole without applying heat to the pin.  
A lot of pressed bearings are installed using this same principle by heating up the bearing race before pressing or hammering in the bearing.  
Eventually, the heat from the metal will migrate into the pin, causing it to expand as well; but there is a time-lag that allows for the best chance of removal.  

This principle works great for barrel installs in a tight fitting barrel extension.  Just put the barrel in the freezer for an hour.
Link Posted: 9/28/2015 12:16:16 PM EDT
[#2]
If the material around a hole contracts, doesn't the hole get bigger?
Link Posted: 9/28/2015 1:16:48 PM EDT
[#3]
Link Posted: 9/28/2015 1:27:10 PM EDT
[#4]
Link Posted: 9/28/2015 1:38:50 PM EDT
[#5]
The hole gets smaller for a decrease in temperature.  Let me find a good source that explains this.


ETA: Here's a scanned excerpt from one of my textbooks.




Note that the text discusses the case for when an object is heated in that the hole expands.  Since you're asking what happens when it is cooled, the opposite happens, and the hole contracts.

Think of the implications of using heat to form an interference fit between two parts.  When you initially heat a part with a hole in it, the hole expands, and you can more easily fit a shaft (for example) within the hole.  As the part cools, the hole contracts.

A good example of this (since we're at ar15.com ) could be if you need to take a heat gun to a gas block to get it off.  If heating the gas block made the hole for the barrel smaller, then using heat would be the wrong answer.
Link Posted: 9/28/2015 3:19:11 PM EDT
[#6]
Link Posted: 9/28/2015 3:28:13 PM EDT
[#7]
No worries there.  The class where our Chinese Thermodynamics professor tried to explain it to a bunch of students didn't go very well.
Link Posted: 9/28/2015 9:23:30 PM EDT
[#8]
Link Posted: 9/28/2015 11:15:35 PM EDT
[#9]
A hole in a uniform ,material moves exactly the same as a rod the same size as the hole.
Hot larger diameter and circumference, cold smaller.
Link Posted: 9/29/2015 4:27:57 AM EDT
[#10]
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And this is why I'm a lawyer, and not an engineer.  I get it now, thanks.
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I was going to mention the coefficient of expansion as CPT Morgan did:  you could play with the different alphas to possibly get the desired results.

For example, the alpha for Aluminum is significantly greater than that of steel.
Link Posted: 10/3/2015 12:10:01 PM EDT
[#11]
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Quoted:


I was going to mention the coefficient of expansion as CPT Morgan did:  you could play with the different alphas to possibly get the desired results.

For example, the alpha for Aluminum is significantly greater than that of steel.
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Quoted:
Quoted:
And this is why I'm a lawyer, and not an engineer.  I get it now, thanks.


I was going to mention the coefficient of expansion as CPT Morgan did:  you could play with the different alphas to possibly get the desired results.

For example, the alpha for Aluminum is significantly greater than that of steel.


Often referred to as imply 'TEMPCO' for TEMPerture COefficient

It is actually unit-less except the 1/temperature portion.
Things like micro-inches per inch per degree are not uncommon.
(microinch/(inch* F))

5 microinches per inch per F means a 1 inch dimension changes by 1 micro-inch for each degree F
Link Posted: 11/3/2015 10:54:18 PM EDT
[#12]
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Quoted:
And this is why I'm a lawyer, and not an engineer.  I get it now, thanks.
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I'm both.  Patent law is a lot of fun.
Link Posted: 11/3/2015 11:08:20 PM EDT
[#13]
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Quoted:


I was going to mention the coefficient of expansion as CPT Morgan did:  you could play with the different alphas to possibly get the desired results.

For example, the alpha for Aluminum is significantly greater than that of steel.
View Quote View All Quotes
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Discussion ForumsJump to Quoted PostQuote History
Quoted:
Quoted:
And this is why I'm a lawyer, and not an engineer.  I get it now, thanks.


I was going to mention the coefficient of expansion as CPT Morgan did:  you could play with the different alphas to possibly get the desired results.

For example, the alpha for Aluminum is significantly greater than that of steel.


This convenient fact is how I managed to finally remove the world's most frozen-up 10-22 barrel.  Used a heat gun to heat up the interface, and I knew that the aluminum receiver would expand to a much greater degree than the barrel.  Popped right apart after that.
Link Posted: 11/5/2015 4:22:59 PM EDT
[#14]
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Quoted:


This convenient fact is how I managed to finally remove the world's most frozen-up 10-22 barrel.  Used a heat gun to heat up the interface, and I knew that the aluminum receiver would expand to a much greater degree than the barrel.  Popped right apart after that.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Quoted:
Quoted:
And this is why I'm a lawyer, and not an engineer.  I get it now, thanks.


I was going to mention the coefficient of expansion as CPT Morgan did:  you could play with the different alphas to possibly get the desired results.

For example, the alpha for Aluminum is significantly greater than that of steel.


This convenient fact is how I managed to finally remove the world's most frozen-up 10-22 barrel.  Used a heat gun to heat up the interface, and I knew that the aluminum receiver would expand to a much greater degree than the barrel.  Popped right apart after that.



Just remember for most common materials a hole moves like a cylinder of the same material.
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