Anyone know of a thread to link to?

Here's a few questions of my own.

Is power buffing, either with a regular large or Dremel type wheel appropriate? Contingent on avoiding engraving. If so, what compound is suitable? Red Rouge is recommended for soft metals, not steel. Green compound is recommended for steel. Blue compound is finer than Green, and is recommended for materials like plastic, would it work as a final buff on steel?

If power buffing is not recommended, what materials and grits are appropriate for the hand polishing process?

Regards
Ken

Ken:

JUST A SHORT OVERVIEW:

1. First you have to anneal the part/parts packed tightly in your crucible, preferably in an adjustable fixture with bone & charcoal. You must anneal the parts at the 'critical temperature' and then let the furnace "cool down" at it's own rate without opening the door, usually at least a 24-36 hour cool down period. A natural 'cooling period' is critical IMO.

2. The better the surface condition, the better the results.

3. A high carbon steel wire wheel at slow speeds works well and shines up the parts quite nicely. Many folks bead blast instead of the wire wheel.

4. Then polish to a "mirror finish" with any of the numerous compounds available at most hardware stores.

5. Then clean to a spotless condition, removing all fingerprints and any other impurities on the surface of the parts. Acetone works well as do several other powerful cleaners such as Berryman's Carb Cleaner.

6. Re-pack in your crucible/fixture with bone and charcoal 70/30 or 60/40 etc. and fire with your furnace set to hold the temperature for 2 hours.

7. Quench.........

****8. Read and prepare for CCH if you are a beginner. Use test junk parts if you are a beginner. There are NO short cuts, each step is critical for good work.

****There is a lot written about CCH and I suggest you read everything you can.

I INTENTIONALLY DID NOT MENTION SPECIFIC TEMPERATURES, AS THIS IS A HIGHLY DEBATABLE TOPIC AND PROPRIETARY WITH MOST PEOPLE WHO CCH. AFTER STUDYING PUBLISHED PAPERS AND BOOKS YOU WILL READ WHAT IS RECOMMENDED BY SUCCESSFUL CCH SMITHS. EVERYONE HAS THEIR OWN SET OF STANDARDS WHICH HAVE PROVEN SUCCESSFUL FOR THEM.

JUST ABOUT ALL OF THE THREADS ON THIS BOARD END UP "A BIG ARGUMENT" WITH LOT'S OF PEOPLE WHO "HAVE NEVER" DONE ANY CCH THROWING IN THEIR TWO CENTS WORTH.....THEREFORE IT IS COUNTER PRODUCTIVE TO PASTE ANY OF THOSE THREADS UNLESS YOU WANT TO BE CONFUSED.

Best Regards,

Thanks Doug.

I've probably read them all over the last two years. Sounds like it's all going to require experimentation.

Hand polishing is by far the preferred method! If you use a buffer and compound you will dish out pin holes and lettering and round off edges...all of which will stick out like the proverbial sore thumb. I start with 320 wet or dry paper then 400 then 600 and final finish with well worn 600. The better the polish the brighter the colors.

PS...I back the paper with either a hardwood block or a file and for the best results with the 600 I glue the paper to a flat hardwood piece using CA.

Thanks Sam.

Have you ever bead-blasted before sanding? I've used it to clean up locks that were rusty, using very fine beads.

First, please accept that I'm not trying to stir any problem up.

I see anneal mentioned regularly. I think the process can be important for specific reasons. I have noticed that annealing doesn't seem to improve routine metal prep or the crucible heat charcoal process to get the new case colors.

Even though I was hugely reluctant to post this comment, I figured, why not just ask. How does the annealing seem to benefit here, only if you had a thought or two?

Ken, I have not tried bead blasting and avoid items with rust problems...I am working from the approach of an engraver which leads me to Craig's comment. I have only done the prep with the intent to engrave the item and without toning down the case hardened surface engraving is very problematic to totally not doable. Like trying to cut glass with a graver. None of this is directed to modern metal firearms that are through hardened...those I either cut as is or turn down the job. Some of the stainless guns can be very very difficult or impossible to cut.

Most of the engravers who have commented on annealing cch parts say temps in the 500 to 900 degree range are all that is necessary and coating with something like Brownell's pbc scale preventer works well.

You need to anneal in order to effectively polish the metal or do any engraving work. It softens the metal and makes it easier to work with.

It is best to avoid any sort of power buffing for reasons mentioned above. Careful hand work pays off big time in doing the job right when it comes to this stuff.

The main reasons for annealing other than what has already been mentioned are to avoid over carbonizing the metal which can create brittle portions especially on thin parts and to relieve stress to avoid warping upon re hardening. I stick with the method Doug has outlined above and it has been very good to me.
Steve

That's interesting, considering that it's usually pointed out that the parts need to be brought to above 1333F for annealing. The lower temp would "Draw the Temper", (semantics, I know, but is really a stress relief measure usually used after case hardening) but would not be true annealing. Annealing, as was mentioned by Doug, requires parts being packed in a crucible with charcoal, (I think wood charcoal only for this could be used, no need for an energizer like bone) the crucible then being brought to above 1333F and allowed to cool down inside the oven. If this is incorrect, someone please speak up.

Temperatures used for the coloring heat seem to be all over the place, but from several sources I've read it was stated that after the crucible was brought to above the critical heat (1333F) and held for a period, the temp could be reduced 200C before quenching. This would prevent warpage yet still result in excellent colors.

Doug's (PA24) work is spectacular.

Doug, will you please move that picture of the LC you colored from the Rust Bluing thread over here as an example?

Regards
Ken

If you quench much below the critical temp you will get colors but little to no surface hardness. Opinions vary and some very good craftsmen go this route. I like to have a hard outer skin for several reasons, to inhibit corrosion, to prevent wear on parts that pivot and to preserve engraving. One gentlemen I know gets great colors but little hardness and he feels that the much reduced chance of warping occurring at a lower temp and the softer surface that comes with it is far better than a damaged customer frame. He is a board member here and may comment on this thread. You can find several good threads on the ASSRA and Marlin forums as well. Interesting stuff and with the new digital controlled ovens quite a bit of guess work can be removed from the process. I would like to see some pictures of crucibles people are using as I'm unhappy with mine. I was given them by a friend but I think his design could be improved upon.

I only throw this out for consideration.

What Sam mentioned, particularly around 900*, is actually not tempering, but a process that might be called spheroidizing annealing. There are various good reasons to consider it, but two that come to my mind, the part never needs to reach critical temperature, and the exact make up of the hardened steel, that someone elects to soften, is unknown.

Because the hardened steel case is unknown, it is possible to convert that steel to a less than ideal form, distribution of the carbon, just by cooling it too slowly during annealing.

Steve, as an aside, I'm not so sure annealing can prevent over carburizing. On it's own, annealing shouldn't remove or add carbon to the steel case. I suspect if the steel skin is heated, particularly above critical, in a wood charcoal pack, presumably(?) to eliminate oxygen, there is a pretty fair chance that available carbon is driven towards the part under those conditions.

This is only discussion, and no heartburn with anyone's preferred methods. I appreciate the small look in other shops.

Marlin 1892 .32 that I did....Originally $1.00 extra for CCH frame from the factory in the 1890's, what a deal...!...Neat little gun...








A different L.C. that I did, the one above is a 12 gauge ejector, this one is a 16 gauge extractor....





Best Regards,

More food for thought.

First, thanks Doug.

Second, the dropping of the temperature before quenching is only after holding the piece above critical temperature. I've read many references about the processes that use lower temps to achieve color, but, true, it is said it results in colors but doesn't achieve true hardening. In my trials I'll experiment with the process, and since I'm associated with an industrial heat treating company with a lab, I'll be able to report if true hardening occurred. I'll also do a test at consistent low temp as well, (below critical) to see what hardness results from that process.

Is packing in charcoal for annealing really necessary? That's the real question.

I agree, the thread on the Marlin site is great, and is probably the most comprehensive thread about CC info on the Net.

Packing in charcoal for annealing provides an oxygen free environment to prevent scaling. There are other methods. It can be done in an inert gas oven and some people use a steel wrap especially made for this. I've tried the wrap and do not care for it. I have had things hardened in a gas furnace but never annealed. I always anneal and feel it is a very necessary part of the process.

OK, makes sense. Now, what about the post-coloring stress relief heat? I'm guessing that it also requires a charcoal pack to prevent scaling.

This I fully believe. Aside from some machining/engraving, I was just wondering, why.

You had an earlier crucible question, I thought I'd pass along comments on a short tv demo that Connecticut Shotgun did on their case coloring process. They used a round crucible that looked to be 5" inner diameter by about 6 to 7" deep. Pretty heavy gauge with formed raised rings around the outside so that a non clamping 'U' fork style holder wouldn't slide up or down on the crucible.

It had a slip fit, but fairly close looking fitting cover. They put a quick, medium tan colored, refractory cement coating around the seam of the cover. The base of the crucible had legs on it, at least a 1/2" maybe a bit more, probably so it would heat up more evenly.

Separately from the crucible, their process was, a claimed wood, cow and chicken bone, and leather charcoal. The camera man zoomed in on a 1332* kiln setting with the temp reading 1331* when the pack went in the oven. It stayed in a claimed 2 1/2 hrs. It seemed to take about 10 seconds before the part was quenched. When everything was inverted over the quench tank, the cover stayed on and took a couple light taps with a small hammer, standing by, to release the cover and everything else into the quench. They wired the receiver to a tab on the inside of the crucible, so it couldn't drop down into the container, but it dangled probably a couple of inches in the quench. There was no comment about the quench or how it was prepped.

It appeared to be a credible demonstration on a real A10 receiver, that they made it appear like the same receiver was shown on a finished gun. I've used a welded up pipe crucible with cobbled up similar to the above, but quite a bit smaller. I just thought there might be some interest in a technique that was shown, but maybe not widely known.

I also appreciate that you commented about the true hardness of safe, sound, real world gun receivers. And, the preference for hardened wear surfaces, but the reality that it may not always be so.

Maybe Ken, a little caution here. I have seen case colors start muddying and fading by about 350*. Your colors may stand up to higher heat, but in all likelihood at temps that're quite a bit below the ability to scale steel.

"What Sam mentioned, particularly around 900*, is actually not tempering, but a process that might be called spheroidizing annealing."

Craig, you are right there. Engravers are only interested in getting the metal drawn back to a level easily engraved. If too soft it will ding too easily making for a lot of minor cleanup/polishing during the project.

OK,

Is the concept of a third stress relief heat after the annealing and coloring heats valid? If so, at what temp and for what duration? I've read instances of the metal being fairly brittle after the coloring heat and prone to flaking.

It's interesting that CS puts their temp at just a degree or two less than the 1333F critical temperature. Considering the wide range of temps used from other sources, some significantly higher.

A key to using the stainless steel wrap when annealing is to put a little piece of fine steel wool in with the part. That way the steel wool will burn and use up any air left in the wrapped package thus preventing any scale.

What a good idea! Does this apply to crucible use in the other heats as well?

Not really since the packing in charcoal in a crucible (tapping while packing) is meant to fill all the voids in and around the metal parts contained. So no need to have to put anything in it to burn up the air if it is packed right.

The steel wool makes sense. I'll need to try that. The charcoal off gases CO and CO2 and provides the oxygen free environment. Make sure you have good ventilation and a CO monitor is cheap insurance as well. The last time I annealed something with the door closed in the shop the CO alarm went nuts.

interesting stuff on the Temp. as well. Most things I have read call for a quench around 1450 F, I enjoyed Craig's post on the CSM video(which I need to track down) and it seems both CSM and ken's info come in at 1333 or so. Where did you come across this number Ken ?

is this the crucible?

http://www.brownells.com/gunsmith-tools-...24780-3746.aspx

1333F is the carburizing, or "critical" temp for steel. From what I've read, it's above that temp that the carbon absorption and consequential hardening occurs upon quenching. That's also the temp that needs to be attained/exceeded for annealing. I could be wrong, I've also seen it listed at 900C, about 1650F. But, I think 1333F is for low carbon steel.

The crucible in the piece was a commercial made one that looked cast, no welding, just a cover and everything else. Time is money, but I believe the Brownells crucible can be cobbled up pretty quick and easy, at least a fellow might be paying themselves a hundred bucks an hour to come up with something close.

Mine looks about the same. Instead of rings for the tongs, I just cut four v's off some angle iron with a chop saw and welded them on the sides, then the tong jaws go in between. For the cover, I decided to use a threaded pipe cap, and a grinder to clear out the threads for a slip fit. The only thing I'd do different that may not be a bad idea is some way to get the base off the kiln floor a little bit.

I've used stainless heat treat foil a bunch of times for other things. A little scrap of paper will consume any oxygen in there. A good consideration is to double wrap and burnish it down tight, but don't be surprised if some sharp corner pokes a hole in it.

I believe what happens somewhere around 133-something degrees is that steel looses magnetism. I believe that's the bare minimum change required for the steel to harden. Interesting thing, on the way up in temp, the point it becomes non magnetic is very precise, but on cooling back down, I know for myself that steel will stay non magnetic till quite a bit cooler and it will regain magnetism over a broad temp range.

I believe that is part of what's going on when there is an intentional delay between pulling the crucible from the oven and quenching. Maybe the 'art' part of it is the insulation of the crucible and charcoal on the slight cooling of the part, and the unevenness of the cooling of the part, just before it hits the quench.

I have case hardened steel for hammer or trigger sears or emergency homemade taps and dies using the old formula Kasenit, or even using plain table sugar to supply the surface carbon. But I have never done bone charcoal pack color case hardening, though I'd like to try it one day. The 1333 degree F temperature is the critical temperature for annealing steel. Hardening steel takes a higher temperature and involves a quench in air, oil, brine, or water, depending upon the steel alloy. Drawing the hardness is done at much lower temps. I have read of a wide range of temperatures that will work for carburizing or case hardening the surface of steel with time as an additional factor... lower temperatures naturally taking more time. Doug PA24 addressed this aspect earlier, and I do not know what effect time and temperature has on colors. Obviously, Doug has found a very nice combination of time, temperature, materials, and methods. I would assume that annealing steel in a pack of carbon rich charcoal or the like would not only prevent scale, but also add carbon to the surface of the steel, but would not result in colors or surface hardening without the quench.

The stainless steel foil does make a very good one-time use crucible, but as craigd notes, it is easy to puncture on a sharp edge. Speaking of sharp edges, the foil itself will cut you like a razor, so caution is required. Paper, sawdust, or the like placed inside with your parts will do a better job than steel wool of consuming any oxygen inside which would form scale because it will use up any free oxygen at a lower temperature. I've done just as well preventing scale when annealing parts or spring steel by using a capped section of pipe as a crucible with a very small vent hole drilled in one cap, and some wood or paper inside to consume the oxygen. A small plug of fire clay is used to seal the vent hole after the correct annealing temperature is reached. The large annealing furnaces at the steel mill where I did my electrical apprenticeship used inert gasses such as nitrogen and, believe it or not, hydrogen to purge out the oxygen and prevent scale. Our Salem furnaces used nothing more than dry sand to seal around the base of the furnace to keep oxygen from entering. We had a plant where we did catalytic cracking of liquid ammonia into nitrogen and hydrogen for the annealing departments.

Also, from what I've read, keeping the medium in close contact with the part is essential for good color coverage. The way the parts hit the quench is also important. The Marlin Forum thread shows extensive use of racks in some of the posts, with very nice results. On another site, I read where some students at a Gunsmithing school were wrapping parts with wire with good results as well. I'm going to be experimenting with those aspects, as well as with specific shielding to see what happens. One thing is certain, the Midway video that shows the parts and medium dropping loosely into the quench doesn't result in good color coverage.

I think the 1450* quench is to harden the simple steel, minimal alloying, of the thin case. And, that temp is likely about right to form that hard skin that folks don't like to machine or engrave.

The modern alloy likely in the CSM receiver may have the ability to through harden. So, they may be picking temps that don't change the properties of the steel too much in order to get the finish that they want on the surface.

Since Ken brought it up, shielding and blocking techniques for parts headed for case coloring are tough to come by. What's also tough to come by is 'finishing', or what the 'freer's' did to actions/guns on final assembly after the parts came back from the case hardener. How was significant warpage, hideous gaposis,etc, dealt with accurately and without marring the finish. But, that's entirely something else, probably a career or three.

what about tempering? is that not the next step in the process, after the quench?

Lots of great info.

Doug, nice work as always.

I’ll throw my two cents in, about all it’s worth...

From my point of view, annealing is a necessity, not only does it make the steel softer, but also burns off a lot of garbage on the steel; rust etc. Makes it so much easier to clean up.
Carbon in steel is cumulative, every time a part is case hardened, you are adding carbon, annealing helps diffuse the carbon into the steel.

There is a reason that many, if not most folks practicing CCH today are not doing true case hardening. True case hardening temps are high, I have original recipes from a couple of manufacturers, temps that they were using are in excess of 1600 deg F. That’s ok if you are a manufacturer, you can afford a certain percent waste… but for the modern guy, working on someone’s pride and joy, or a one of one gun, you cannot afford to make mistakes, and you cannot afford to crack a frame. You’ve got one shot to do it right. So most will safe side it.

In my mind, tempering after quench is an absolute must. It relieves strains in the metal, and, allows the metal to be tweaked slightly. Remember, when cases hardening you are changing the temperature of the steel by more than 1000 deg F. The steel is going to move, and more than likely, you will have to move it back. Tempering will allow you to do this with less likelihood of cracking. I generally temper around 400 deg F, with little to no change in coloration.

I know some folks will say that blocking will prevent this; it helps, but it does not prevent movement. I use blocks in certain areas, on more than once occasion I have watched the parts move after the blocks were removed. Now I always temper with blocks in place.


Mike

Thanks much Mike, I appreciate the comments.

That annealing with temps high enough for carbon migration would make me wonder if wood charcoal pack annealing wouldn't drive more carbon towards the piece. It might be hugely disappointing if there were signs that carbon migrated out of the part. Thanks for the thoughts, worth keeping in mind.

Great contribution Mike, thanks.

Any chance of a picture of an action with blocks in place? Are you recommending recoloring at lower temperatures, say around the 1333F temp that CS uses?

Regards,
Ken

One must remember that blocks and fixtures only do so much. Since the braces are at the same temp as the part being colored, they are able to move among with the part.

No, I’m not telling you that 1331 deg F is where you should case, there are a lot of variables.

Quench water temp; big difference in results and drawbacks between 45 deg F and 90 deg F.

How big is your quench tank; does it have enough volume to quickly absorb the heat?

How far does the part drop after hitting the quench water; 14 inches vs. 3 feet can make a difference.

Is the water moving or stagnant? If moving, how, air or water pump?

What is the oxygen content of the water?

What is the hardness of the water? Softer water cools quicker.
Any additives?

Additives such as brine can actually cause the parts to cool quicker.

90% of this you learn via trial and error.

It’s kinda like someone who has never driven before asking if 70 MPH is the optimum driving speed. Highway or back road, night or day, rain, snow etc… you get the idea.

On blocks, take a look at the parts to be case hardened, you can pretty much figure out where they are likely to warp: generally thin areas. So side plates come to mind, also the tang areas where you have long thin pieces just hanging out there.

B. Dudley is absolutely correct, the blocks can warp. I make mine out of 304 stainless, make them as large /thick as possible. I had a block that I put between the rails on lever actions, the block was 3 inches long and about a half inch thick. After a couple of runs, it warped approximately .05

mike

Thanks Mike.

Yeah, I've read about all of those variables. Besides the one's that have been mentioned in the previous posts. I'll just plan on extensive test runs and develop my own specific process.

One account I read was of Parker employees being encouraged to urinate in the quench water. I'm not sure yet if I'll be manipulating that one.

Regards
Ken