Questions: Case hardening with Cherry Red Powder

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Looking for opinions from folks more experienced than I.

Is this stuff any good? http://usaknifemaker.com/heat-treat-ove ... r-1lb.html

Is a handheld propane torch going to put sufficient heat into a part to get it to cherry red?

I have some hammer notches that need a bit of tweaking. The geometry is simple, but I want to re-harden after filing..

Help? :confused:

EDIT: One more question - anyone familiar with good technique for bending a hammer spur? My plan is to go cherry red, get a jig set up with some nails in a two by four, bend with that, and then again use this cherry red powder stuff to reharden..

Re: Questions: Case hardening with Cherry Red Powder

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A hammer should be steel with a high enough carbon content to harden on its own without case hardening the surface.

You shouldn't have to re-harden after just a little file work on the notches.

For spur bending, I would make a plan that prevents heating the notch areas, rather than messing with re-hardening. A small oxy acetylene torch will give you more localized heating that would make such work easier. There are various clay-like products for protecting areas of a part while heating other areas of a part. I would likely do something like clamp some pieces of aluminum around the lower portion of the hammer while working on the spur, work quickly, and then quench the lower portion (aluminum still in place) while leaving the spur above the water to cool more slowly.

Re: Questions: Case hardening with Cherry Red Powder

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Fukshot wrote:A hammer should be steel with a high enough carbon content to harden on its own without case hardening the surface.

You shouldn't have to re-harden after just a little file work on the notches.

For spur bending, I would make a plan that prevents heating the notch areas, rather than messing with re-hardening. A small oxy acetylene torch will give you more localized heating that would make such work easier. There are various clay-like products for protecting areas of a part while heating other areas of a part. I would likely do something like clamp some pieces of aluminum around the lower portion of the hammer while working on the spur, work quickly, and then quench the lower portion (aluminum still in place) while leaving the spur above the water to cool more slowly.
What about MIM parts? I know that they can be filed and stoned without too much drama (assuming they were properly made in the first place) but I can't say that I've ever heard of anyone doing a full heat-and-bend on a MIM part... Given that the hardening is throughout the piece (vs case-only) it seems like there would be some additional changes that might occur in this instance that might not be a consideration with a traditionally cast or forged steel part.

Re: Questions: Case hardening with Cherry Red Powder

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swissdog wrote:
Fukshot wrote:A hammer should be steel with a high enough carbon content to harden on its own without case hardening the surface.

You shouldn't have to re-harden after just a little file work on the notches.

For spur bending, I would make a plan that prevents heating the notch areas, rather than messing with re-hardening. A small oxy acetylene torch will give you more localized heating that would make such work easier. There are various clay-like products for protecting areas of a part while heating other areas of a part. I would likely do something like clamp some pieces of aluminum around the lower portion of the hammer while working on the spur, work quickly, and then quench the lower portion (aluminum still in place) while leaving the spur above the water to cool more slowly.
What about MIM parts? I know that they can be filed and stoned without too much drama (assuming they were properly made in the first place) but I can't say that I've ever heard of anyone doing a full heat-and-bend on a MIM part... Given that the hardening is throughout the piece (vs case-only) it seems like there would be some additional changes that might occur in this instance that might not be a consideration with a traditionally cast or forged steel part.
I have no idea what the internal microstructure of MIM parts is. If it's a solid piece of steel, then it's a solid piece of steel. If somebody wants to buy a MIM hammer or trigger and send it to me, I'd be willing to spend a little time in the shop to give some definitive answers. I expect that MIM stuff is close-enough to solid that it acts like solid when heated.

The only time the hardening doesn't go all the way through a part this small is when the part is made from soft steel or iron and then surface hardened. The difference in material cost between fully hardenable steel and soft steel has been less than the cost of the more complex heat-treating procedure of surface hardening in parts this size for more than fifty years. Probably closer to 100 years.

Re: Questions: Case hardening with Cherry Red Powder

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Fukshot wrote: I have no idea what the internal microstructure of MIM parts is. If it's a solid piece of steel, then it's a solid piece of steel. If somebody wants to buy a MIM hammer or trigger and send it to me, I'd be willing to spend a little time in the shop to give some definitive answers. I expect that MIM stuff is close-enough to solid that it acts like solid when heated.

The only time the hardening doesn't go all the way through a part this small is when the part is made from soft steel or iron and then surface hardened. The difference in material cost between fully hardenable steel and soft steel has been less than the cost of the more complex heat-treating procedure of surface hardening in parts this size for more than fifty years. Probably closer to 100 years.
The use of binding agents before the MIM parts are sintered almost certainly yields a very different structure than the crystallization of a blob of molten metal cooling... This is why I'd be concerned with heating such a part up to the point of it becoming malleable, as it seems like some kind of different crystallization (and thus a difference in physical properties) would occur.

As for the modernity of heat treating processes? Firearms manufacturers aren't always known for the modernity of their processes. I know that it's not hard to blow right past the hardening on certain revolver parts and that this is absolutely an issue on even modern pre-MIM S&W's and that failures in this regard can be pretty nasty.

Re: Questions: Case hardening with Cherry Red Powder

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Many thanks! (The hammers in question are Uberti manufacture, for what it's worth..)

I've heard people rumble in apocalyptic tones about filing the notches on a hammer without re-hardening, but I'm honestly not too worried, I didn't take off THAT much material...

That heat paste seems like pretty neat stuff.
For spur bending, I would make a plan that prevents heating the notch areas, rather than messing with re-hardening. A small oxy acetylene torch will give you more localized heating that would make such work easier. There are various clay-like products for protecting areas of a part while heating other areas of a part. I would likely do something like clamp some pieces of aluminum around the lower portion of the hammer while working on the spur, work quickly, and then quench the lower portion (aluminum still in place) while leaving the spur above the water to cool more slowly.
This sounds like a good plan. If I work up the nerves, I'll try it this way.
Last edited by Fiddler on Mon Jun 30, 2014 4:29 pm, edited 1 time in total.

Re: Questions: Case hardening with Cherry Red Powder

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swissdog wrote:
Fukshot wrote: I have no idea what the internal microstructure of MIM parts is. If it's a solid piece of steel, then it's a solid piece of steel. If somebody wants to buy a MIM hammer or trigger and send it to me, I'd be willing to spend a little time in the shop to give some definitive answers. I expect that MIM stuff is close-enough to solid that it acts like solid when heated.

The only time the hardening doesn't go all the way through a part this small is when the part is made from soft steel or iron and then surface hardened. The difference in material cost between fully hardenable steel and soft steel has been less than the cost of the more complex heat-treating procedure of surface hardening in parts this size for more than fifty years. Probably closer to 100 years.
The use of binding agents before the MIM parts are sintered almost certainly yields a very different structure than the crystallization of a blob of molten metal cooling... This is why I'd be concerned with heating such a part up to the point of it becoming malleable, as it seems like some kind of different crystallization (and thus a difference in physical properties) would occur.

As for the modernity of heat treating processes? Firearms manufacturers aren't always known for the modernity of their processes. I know that it's not hard to blow right past the hardening on certain revolver parts and that this is absolutely an issue on even modern pre-MIM S&W's and that failures in this regard can be pretty nasty.
If re-hardening is needed it should only need a normal heat treat, rather than a case.

Re: Questions: Case hardening with Cherry Red Powder

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Hardened parts are brittle, and must be drawn back to give them toughness, even case hardened parts. Case hardening does have an advantage of leaving a hard wear resistant outer skin about .03" deep, and a soft tough resilient core. Parts made from hardenable steels tend to be hard all the way through and while having high tensile/compressive strength have crap impact strength unless drawn down below about Rockwell C 50. Typically, this means a draw temperature above 500°F.

A flame hardening setup would be good if you use as Fukshot noted a good hot torch, oxyacetylene being the best. Heat the area fast, follow whatever instructions the case material suggests but try to make the rest of the part as cool as possible. It will probably take a little time to soak the part at temperature to get the case into the steel, then quench. Polish the area up, and this time using something like a propane torch heat the part in the hardened area until it changes color (which is why you polish it to make the color easier to see) according to the chart attached. You probably want dark purple.
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I carry due to toxic masculinity.......just other people's.
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