Need help with finishes on C96

[ithacaartist]

Originally Posted by John Sabato

Alvin keep your eye on Harbor Freight sales. They often offer digital calipers that are plenty close enough in accuracy for reloading work.

http://www.harborfreight.com/6-in-di...ngs-68304.html

John, this is the same calipers that I bought from Harbor Freight a couple of years ago. There is an offset of the claws that do inside measurement, when the O.D. jaws are zero. But I compensate by locking the travel down on an I.D. and measuring the claws' spacing with a micrometer. Mine also gradually began to lose its consistency, as in when drawing the jaws apart, an extra 1/4" or so adds itself to the displayed dimension. I am inexperienced with the electronic calipers and suspect a weakening battery?

[alvin]

I tried 7.62mm Tokarev Snap Caps, they could not even stands well on the clip -- shaking the clip, a few snap caps will fall off from the clip. The fitting is very poor. By visual, I cannot tell snap caps dimensional difference either.

I bet Serbian made PPU 7.63mm were modified from their 7.62mm Tokarev. Historically, Yugoslav had tons of Tokarevs, not many Mausers. It would make sense for them to create 7.63 Mauser from 7.62 Tokarev for US C&R market.

[alvin]

For nitre blue, what's the temperature used, and how long you soaked the parts into the melted salt? How do you control the temperature at a constant?

Curious, because I saw many restored guns have darker nitre blue finish than original guns. I guess the color tone being temperature and time related... but not sure.

[Olle]

Originally Posted by alvin

For nitre blue, what's the temperature used, and how long you soaked the parts into the melted salt? How do you control the temperature at a constant?

Curious, because I saw many restored guns have darker nitre blue finish than original guns. I guess the color tone being temperature and time related... but not sure.

I used a torch for some of them, but sent off the difficult ones to Paladinpainter. The color does depend on the temperature and can be adjusted as necessary. I don't believe the time matters, as long as the temperature is correct. Of course, the time will matter if the temperature is too high, simply because of the heat sink effect. This would also give you different colors on the same part, depending on how quickly thinner and thicker sections got up to temperature.

You need to keep in mind that it's a very fragile finish, and the best way to get an idea of the original color is to take a part off the gun and inspect areas that haven't been exposed to wear. I believe the colors on this one are actually close to original, just darker because there's no age on it.

[Olle]

Originally Posted by alvin

I guess the color tone being temperature and time related... but not sure.

Found a web site that explains this quite well: http://tincanbandit.blogspot.com/201...at-bluing.html . One of the pictures shows the colors you get at different temperatures, and here you can see that nitre bluing and strawing is the same type of process, just different temperatures.

[alvin]

I bought a worn C96 extractor which lost its finish. Planned to use it on a range gun.

Also bought a bucket of nitre blue salt and a temperature meter. If my spouse allows me to borrow her cooking stove, I will have some fun in Christmas. She told me that she will think about that and let me know.

Surely, I will experiment on scrap steel first.

But there is a strength problem -- does this 570F - 670F temperature anneal the steel?

[DonVoigt]

Originally Posted by alvin

I bought a worn C96 extractor which lost its finish. Planned to use it on a range gun.

Also bought a bucket of nitre blue salt and a temperature meter. If my spouse allows me to borrow her cooking stove, I will have some fun in Christmas. She told me that she will think about that and let me know.

Surely, I will experiment on scrap steel first.

But there is a strength problem -- does this 570F - 670F temperature anneal the steel?

Alvin,
can you explain exactly what you bought as "nitre" blue salt and how it is to be used?

I have a lot of experience with hot salt bluing and it is not something you will want to do in the kitchen.

Yes, anytime you heat metal it "anneals" it, but the temperature you will reach in hot salt bluing will not significantly affect the "strength".

Annealing will remove any stresses built up from machining, forging and forming steel. Your part has already likely experienced those temperatures.

[Olle]

The color you see on the on original parts is not meant as a finish, it's actually a byproduct of the tempering process they used at the factory. The good thing about it is that the color is a great temperature indicator, so if you heat it to the factory color you won't exceed the temperature the factory used to temper it. You can do any part like that without hurting it, and some say you might even prolong the life of parts that have become "work hardened" by years of use. However, if you heat it too much, you have to reharden and temper again.

Annealing is a totally different animal. This is done to soften the steel before you work on it, and you have to heat it to a much higher temperature (glowing hot). The only color you get is steel grey.

[alvin]

Originally Posted by DonVoigt

Alvin,
can you explain exactly what you bought as "nitre" blue salt and how it is to be used?

I have never done things like this before. From youtube.com video, midwayusa showed how -- the nitre blue salt is a pink color solid stuff, he put the salt into a pan and "cook" it. The salt melted. Then, he dipped small parts into the melted salt, the metal color changed, then he took it out. That's it.

He did not explain the theory. Here is my guess -- that salt melts around 600F. So it's just temperature control media. This is obviously more controllable than using a torch to create fire blue on small parts -- using torch, you have no control on temperature, using this type of salt, it's much easier to control, and the metal is heated much more uniformly. Unlike regular bluing process, I don't think there is a chemical reaction between the nitre salt and metal. Just a guess.

Here is the video:

https://www.youtube.com/watch?v=-vF3zKiUIkY

[Olle]

Originally Posted by alvin

I have never done things like this before. From youtube.com video, midwayusa showed how -- the nitre blue salt is a pink color solid stuff, he put the salt into a pan and "cook" it. The salt melted. Then, he dipped small parts into the melted salt, the metal color changed, then he took it out. That's it.

He did not explain the theory. Here is my guess -- that salt melts around 600F. So it's just temperature control media. This is obviously more controllable than using a torch to create fire blue on small parts -- using torch, you have no control on temperature, using this type of salt, it's much easier to control, and the metal is heated much more uniformly. Unlike regular bluing process, I don't think there is a chemical reaction between the nitre salt and metal. Just a guess.

Here is the video:

https://www.youtube.com/watch?v=-vF3zKiUIkY

That's correct. The nitre salt is just a media that allows you to apply the heat in a controlled manner, otherwise it's the same process and the same finish as you'd get with a torch or in the oven.

One reason why I don't use nitre salt (and bluing salt) is that I don't like the idea of working with salt heated to high temperatures. I figure it can make for some interesting steam explosions if there's rinse water left on the parts. Still, many videos show the guy dipping in the nitre bath, dipping in a cup of water, then back to the salt again etc. I might be overly cautious, but I figure the torch and the oven are much safer.

I do extractors on a thin piece of shim stock, I heat with a torch from underneath and when I have the right color I drop it in quenching oil to cool off. The color doesn't appear immediately and it can continue to develop after you quit torching the part, but the quenching will stop the process right at the moment it's submerged and keep it at the right color.

[DonVoigt]

Originally Posted by alvin

I have never done things like this before. From youtube.com video, midwayusa showed how -- the nitre blue salt is a pink color solid stuff, he put the salt into a pan and "cook" it. The salt melted. Then, he dipped small parts into the melted salt, the metal color changed, then he took it out. That's it.

He did not explain the theory. Here is my guess -- that salt melts around 600F. So it's just temperature control media. This is obviously more controllable than using a torch to create fire blue on small parts -- using torch, you have no control on temperature, using this type of salt, it's much easier to control, and the metal is heated much more uniformly. Unlike regular bluing process, I don't think there is a chemical reaction between the nitre salt and metal. Just a guess.

Here is the video:

https://www.youtube.com/watch?v=-vF3zKiUIkY

Alvin
What you describe is Not typical hot salt bluing. Which is a chemical reaction, not just heat. Salts consist of sodium hydroxide and sodium nitrate, and each contains some crystalized water.

Tempreature is controlled by adding back water as it boils off, or the temprature will increase as time goes by.

It is a hazardous and corrosive mixture, rubber gloves, rubber apron, face mask, etc are recommended as the salts will splash.

You will corrode your stove and vent if you do it much!

Salt bluing is best left to an expert with the proper set up and know how.

It is not a do it in the kitchen operation.

Metal preparation is the most important step, followed by degreasing before putting into the salt.

Poor prep = poor results.

What is shown in the video is the same as what the others are describing using the oven or hot sand in the oven, he is using a salt bath to
control the temperature to 600 degrees+/- to achieve the pretty blue. It is heat treating as Ollie has described.

[alanint]

Alvin,

The best thing to do is come up with a reason for your wife to leave the house for 6-8 hours and have everything cleaned up and aired out by the time she returns.

This will usually insure a second opportunity to blue.

[alvin]

No. Not salt blue.

Above video is nitre blue (a.k.a fire blue), which is applied on extractor, trigger, etc.. small parts finish.

[ithacaartist]

Here's the deal on the toaster oven and the sand. The oven is capable of reaching the temperature needed to make a piece of steel turn dark blue/black--in the 500's somewhere. Straw is 300-something IIRC. The toaster oven heats by direct radiation (that's what toasting is all about.), and maintains temperature within a range, via its adjustable thermostat. The element comes on and shines heat inside the box, and shuts off when the thermostat detects its limit. When it is heated, a part which has thick and thin areas (safety lever, takedown bolt) will have overheated thin portions if the thick portions are heated enough to achieve the right color, if the heat in the oven is above the prescribed temp for the target color. The box of sand at stable temp ensures the entire part reaches the exact temp--and no more! This ensures even color. The setting numbers on the oven's dial are used only to be a relative reference, and need not be strictly accurate.

[Olle]

I have actually tried a toaster oven, "baking" the parts in sand. The problem I had was that this particular oven couldn't reach the temperature needed to even get a straw color. Had the parts in there for an hour or two on full blast, but all I got was a very pale yellow. I used a $25 Walmart cheapo that I actually bought for this very purpose, but ended up getting mad and trowing it away. So does it take a higher quality toaster oven, or did I just get a dud?

[ithacaartist]

You may have had the bad luck to get a bad unit. The mark I made on the dial for where "Straw" happens in the oven is a lower temperature than the notch for heating a TV dinner, or re-heating a plate of food. For blue/black, I didn't use the sand, but set it on the highest setting and let it run for half an hour or so. Pics below of straw and blue, thanks to Black and Decker's $35 t.o.

[ithacaartist]

1 more

[DonVoigt]

No reason not to use the "real oven" in the kitchen.

Strawing makes no odor, it only takes about 400-420 degrees.

Getting to 600 for the bright blue.may/ would be a little tough, would need a heat treating oven for that-or a torch. The blue has a much smaller temperature band to achieve the blue color, which is why the salts work well if controlled to exactly 600 degrees.

One could do the same thing with any media that was inert to the metal at 600 degrees.

[alvin]

A great candidate for reblue:

http://www.simpsonltd.com/product_in...ducts_id=44753

It's a great project base gun. Only the blue was damaged. Reblue work can be done at home, no metal work needed.

I did not check Simpson everyday. Missed it. Someone got it.

[Olle]

Originally Posted by alvin

A great candidate for reblue:

http://www.simpsonltd.com/product_in...ducts_id=44753

It's a great project base gun. Only the blue was damaged. Reblue work can be done at home, no metal work needed.

I did not check Simpson everyday. Missed it. Someone got it.

A friend of mine called me yesterday and asked me if I could reblue it. Then he called again and said that he missed it by one minute.