The blacksmithing content here is that you have to take stuff apart to get the steel stock for forging! There is even "heating and beating" going on, but the object is to NOT deform the work.
Anyway, I just put up a webpage on the subject at:
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Did you try going to blacksmithsjournal.com, clicking on the "Top 50 Blacksmithing sites" icon at the left side of the opening page, and then clicking on "French Creek Valley Forge"?
Pete Stanaitis
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Chilla wrote:
Yep, didn't work. I'll wait to see what the company comes up with, otherwise I'll have to use some "special" software.
Regards Charles
spaco wrote:
Lets look at heat physics.
Heat a rod and it get skinny and long. Heat a nut or washer - and the hole gets larger.
Now consider a stuck pin in a rod. The rod has a hole - so it is like a washer. Hole gets larger. The pin gets longer and skinny. It might push out.
Some rings are small - needed to be heated to fit over a rod...clamps tight.
Mart> Yep, didn't work. I'll wait to see what the company comes up with,
I don't think that will work, unless the metal of the pin is completely different composition from the rod. If you were able to heat the surrounding material to a greater temperature fast enough (quicker than the surrounded material) then sure, it would expand and release the caught pin. If they're close in composition though and you go to heating them, they'll heat up at roughly the same rate and expand at roughly the same rate, if I remember my highschool science class correctly, putting you in the same position you're in.
Of course I don't suppose that it would hurt to experiment with it. Usually when I have something stuck, I either grab a can of Rust-eze or WD-40.
Taladan
The rod does not get skinny. It grows in all directions.
Pete Stanaitis
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Mart> Lets look at heat physics.
Heating the outer piece does work, but there are a couple of caveats: This works best when the parts are stuck because of corrosion (rust, etc.). Then they are no longer in intimate contact; the oxides at the interface act as an insulator. So, you have a chance to heat the outer part faster than the inner part. But, you need to be able to heat the outer part fast enough or even at reduced heat transfer rates, the inner part can heat up. However, in your favor, as you heat the parts, the differential heat causes the oxides to crush and/or dissociate, which helps to free the parts. As far as heat goes: I'd use a Mapp gas torch as a minimum. The hardware store type propane torches just don't get the heat there fast enough. I usually use my oxyacetylene torch, with a #1 tip. That way, I can direct the flame quite accurately and the high temp heats the part in a few seconds.
Pete Stanaitis
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two things that i have learned, oxy- acetylene torch heat turns rust to dust. when trying to free up threaded hardware go back and forth both directions to start with rather than just one direction. that will help prevent a gulling effect on the threads. have fun, mark
I think the process is thermal expansion linear is greater than volumetric. When a rod gets longer the volume comes from something. The diameter decreases before volume takes over.
Mart> The rod does not get skinny. It grows in all directions.
Not sure where you took your physics, but I've never heard of anything like that either.
It will expand in all directions equally. The hole will get larger, but the pin will expand just as much at the same time.
Like the others have said, your only hope is if you can heat the rod faster than the pin in order for expansion to free it - unless the rod and pin are made of materials with different coefficients of thermal expansion _and_ the rod expands more than the pin in response to heat.
I guess if you had a rod (or pipe) through a hole, and could heat up the rod from while keeping the surrounding materiel colder, you might force the rod to expand lengthwise because it couldn't expand outward, and then when it cooled, would end up skinner.
I suspect often when heat works to break a suck piece it has less to do with the simple expansion making room and more to do with how the heat is effecting the chemistry and structure of the bond that's holding the pieces together.
It has been more than 40 years since I took a Physics class - but still remember the ring and the ball experiment.
The ring inner diameter is smaller than the diameter of the ball. When both are heated together, they are on handles, the ring slips off. When cold - won't go back on.
Railroad track expands such that they have slip joints here and there. The old fashioned click clack is the expansion joints and the wheels. They weld the rails now - easier than hammering on the wheels but have to have the release joint.
The mystery isn't easy to solve since the pin and rod are made of different metals. Expansion is different for alloys and pure materials.
Mart> "Mart>> Lets look at heat physics.
I think it's been too many years since you saw the experiment...
Nice - but they only worked on volumetric expansion of the ball. The ring stayed static.
They missed the other half of the experiment. Likely due to complexity of double duty learn> "Mart>> It has been more than 40 years since I took a Physics class - but
Well, the experiment as you suggest it can't be done in a simple class room setting with a Bunsen burner. There is no way to know the temperature of the ring and ball are really the same. How do you know the ring isn't actually hotter than the ball at the time it slips off? You can't. If you attempt to heat them up together, the ring, which is probably thiner than the ball, is more likely to heat up faster.
To really prove your point using the ring and ball, you would have to perform the test inside a heat controlled oven where you allow the two to soak in the heat for an extended period before performing the test (which would also need to be done inside the oven without opening it with remote manipulators of some type. It's not the type of test they would have every shown you in a class room in my view.
Were you suggesting the ring and ball were made of different materials (brass and iron for example) and as such had different coefficients of thermal expansion? If that's so, then sure, it's possible the effect you talk about could happen. But all the links I saw on the internet for the experiment used brass for both the ring and the ball.
Nothing I've yet found or know of makes be believe the shape of the object will change it's thermal expansion as you suggest. Certainly the shape can effect how the heat moves through the piece which effects how it expands when the heat is not constant through the material. And any solid piece with a heat differential could undergo distortions past the yield points creating a permanent warp of some type. But nothing I've found suggests the things you seem to be suggesting.
If I'm wrong, and there is something more complex happening with heat expansion, I'd really like to know about it seeing it's something I have to deal with (or make use of) as a blacksmith and steel fabricator.
I'd agree with your assessment of the situation. Pattern makers and metal casters would be real surprised if metal didn't expand equally in all directions. I have had several items cast in metals over the years, particulary cast iron, tool steel and aluminum. I've machined bronze and brass castings, as well. For instance, the general rule for cast iron is that the pattern needs to be 1/8" per foot larger than the finished part needs to be. It's 3/16" per foot for steel (because it has to be heated several hundreds of degrees hotter to melt it). And, they don't tell you that it's any different in one direction.
You can look in Machinery's Handbook. I think the expansion rate for steel is about 0.0000063 inches per °F and for aluminum, 0.0000120 inches per °F. They don't talk about which direction.
Pete Stanaitis
--------------------- Curt Welch wrote:
I want to say the ball uses volume expansion and the ring is liner expans= ion.
It is to late to look up anything but I seem to recall that for a given delta temp, linear expansion expands more than volume.
Volume is all directions and linear is in the edges. Ring larger and wid= er making for thin metal in an extreme case.
A blacksmith should know as he heats a rod to extend it puts on a head and cools for a tight fit as the rod gets shorter and thus thicker.
This is an old dead horse by now. Try your case and give us feedback did you get it one one way or another.
I bet the ball pops out when the rod with it within is headed.
Mart> I'd agree with your assessment of the situation. Pattern makers and=20
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