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Joined: Dec 2001
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I have had quite a few guns CCH over the years. Most of them had no warpage or a very slight amount, knowing how to hard fit parts comes in very useful.

I recently had a breech block done. It had a striker disc in it which had very fine threads. It did not move much but the disc did not want to go back in. Lots of patience, a diamond file here and there and some lapping compound did the job. The lower legs on the block spread just enough to not go back in the action as well. Some very gentle work in my machinist vise fixed the issue.

For me a very important component of the process is ending up with a hard skin. If you quench at so low of a temp. to completely avoid warpage this hard skin is not present.

Always do wood work first, metal finish last. Any other way is a headache.


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Booking African hunts, firearms import services

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I have a few bags of both...I need to give it a go.


http://www.bertramandco.com/
Booking African hunts, firearms import services

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Travis

Simple answer is Yes.

Laws of physics dictates it.

We all know that steel expands when it’s heated, and contracts when it’s cool, and will do so at varying rates depending on the thickness of the steel, so a 1 inch thick block will cool slower than a 1/8 inch shim… only makes sense right? The greater the mass, the longer it will retain heat.

So, what happens if you have that 1 inch block, but you also have a bunch of places with only 1/8th or 1/16 inch thickness? Well we know that the thinner pieces will be completely cool, while the thicker pieces are still hot, they will expand and or cool at different rates…. It’s gotta happen….thus you have warpage. …the steel has to move, even if you have blocking. It will just move after you take the blocks out…

Back in the day, most companies had “hard fitters” who would tweak the parts back into shape. Many firearm companies stopped case hardening once better steels were developed; just for that reason too much warpage.

Think Winchester had 5-10% failure rate, so in 1903 Stopped CCH altogether.

Last edited by Mike Hunter; 05/05/20 11:02 AM.
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Hard fitting is a hard necessity I have had to learn. Some problems I have ran into is sometimes getting larger percentage of grey on receivers. What is causing this to happen as other times they come out near perfect.

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Grey= Air. The parts were exposed to air before hitting the quench tank.

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That's what I thought. My crucible I'm using is similar to brownells and I'm dumping with the lid still on top and coals all the way to the lid and packed. Is there something I'm missing when this happens as I'm flipping the crucible over to dump it?

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When wood/bone char is heated to over 1000 deg F, they start to off gas carbon dioxide and carbon monoxide, this gaseous carbon is what gets infused into the steel at elevated temperatures.

These gasses also displace the air/oxygen within the container; carbon monoxide being slightly lighter than air, and carbon dioxide being slightly heavier than air. So you’re kinda covered both ways (some pushing up/some pushing down).

What you need to do when quenching is to ensure that the parts remain in this carbon envelope all the way to the water. Drop distance between the container and quench water is another variable, in my set-up I allow no more than ˝ inch.

Early on in my development I actually thought about adding dry ice to the quench tank, it would serve two purposes, cool the water, and provide a layer of carbon dioxide gas to the surface of the water, displacing the O2. That was a long time ago, never did try it… I may have to just for fun

So bottom line is that air is getting to your parts; it’s up to you to determine how/why.

Now if someone would offer me 10K, I would build them an almost foolproof CCH set-up 

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The carbon from CO takes time and temperature to diffuse into the surface of low carbon steel. Just thinking that maybe, if someone wanted to play with displacing O2 for the quench, it might be quick and easy to flood the top of the quench tank with some welding gas?

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I appreciate the input! I am going to try and run one tonight and am going to try a few things different to decrease the chances of oxygen exposure.

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Awesome thread.

Hereford I can't wait to see how tonight's efforts turn out.

I do not have a set up yet but have been working on a crucible design that gets placed on a rack just barely over the surface of the water and the rack has a built in sliding anvil that only until the crucible is in place and settled does the anvil get a sideways whack making the bottom of the crucible come off releasing the contents. the contents are not poured, just a single vertical dump from a fully stabilized crucible.

Mike and others, does this idea have any merit in helping to mitigate the possibility of 02 intrusion as result of a sliding pour?

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