Tempering Tantrums

[George91946]

Can the group please explain frizzen tempering? I've been building a lock from parts that were either left over from other projects, wore were milled out in my shop, or were purchased from suppliers. I bought a frizzen from TOTW. Their instructions were to drill the hole for the frizzen screw, and then temper the metal. Hole drilled ok, but today, I tried tempering using methods described in Ravenshear's book. Heated the metal to cherry red with oxyacetylene. Checked for lack of magnetic attraction (there was none), and then quenched in motor oil. Then immersed the frizzen face in motor oil and boiled it off using the torch.

No Spark when I checked it in the lock.

Redid the tempering complete with magnet check. Still no spark, but a file skipped over the metal surface.

So I then reheated the frizzen to cherry red, and dipped the flint face in Casenite. Reheated the frizzen to cherry red, and quenched in cold water.

Now sparks like mad every time the trigger gets pulled.

What did I do wrong on the oil quenching method? And will the case hardening eventually wear out? Can you get the steel too brittle and lose sparking ability by overtempering?

Thanks

Lisle George

 

[LRB]

Motor oil is a poor quench medium, and I think you may have over tempered. In dim light, bring it to a red-orange. Simple non-magnetic is not enough. Quench in warm canola oil. then temper at 375° in your kitchen range, using a separate oven thermometer. If the file skipped, but it gives no spark, it may have been too hard. If you took the piece away from the heat to check non-magnetic you got a false reading. Once steel goes non-magnetic, it has to cool way down before magnetic draw comes back. The use of a magnet in heat treat is only good to tell you to go higher in heat. Non-magnetic occurs at 1414°. To fully harden steel you need 50° to 75° more heat. A full shade of color higher. The Kasenit will wear away very soon. It only goes maybe .002/.003 deep, but by water quenching, you may have gotten the steel hard enough to solve your problem anyways. However, it may be very brittle now, and you might want to temper it at 375° for an hour. You also want temper the tail and arm of the frizzen to a blue color to keep it from breaking.

 

Wick's got good info. One thing that might be the reason you didn't get a spark after oil quenching is that it's possible you had a thin layer of decarbinized metal, nearly pure iron from the heat of bringing it up to critical temp. You get this anytime hot steel is exposed to oxygen. Normally this is a very thin layer, and will be taken off with just a little finish sanding. It's normally thin enough that you won't even notice it with the file test, but it might be enough to keep the flint from sparking. It's possible that if you kept striking with the flint it would have started to spark. I would think as soft as the decarb is it would stick to the underside of the flint and clog it as well and prevent a spark if you didn't clean it off.

Then again it might be that you didn't draw the temper enough and it was just too hard. Hard to tell without looking at it or being there during the heat treat.

Colors look different to everyone, but in low light critical temp looks more like a bright orange to me, not a red.

Also you can use motor oil, but it's less than ideal. I find for mystery steel vegetable oil works well. If I know the steel I taylor the quench speed for it. What ever oil you use it works better if it's heated, somewhere between 100 and 130 deg. F. works well with thiner oils like cooking oil, just be careful and have a way to cover the oil if it flares up.

 

[rootsy]

Just did a Q&T on a frizzen that was poorly sparking out of the box last night. Actually this is the second Q&T. The first I quenched in oil and it never achieved proper hardness. So I quenched in warm water, maybe 90F in temp and then tempered in my oven & 375. Think I could catch the carpet on fire with it now if I'm not careful.

This frizzen was 1095 BTW and knowing the material the frizzen is made of is of primary importance before even considering a treatment.

With the material known you can then consult proper references for heat treating that material to achieve a proper hardness... Quenching will make it very hard and very brittle. Tempering will reduce the hardness and increase toughness and this is why maintaining the proper tempering temperature is important.

My last step is to face the striking surface on the belt sander and temper the foot on the frizzen with a propane pencil torch.

 

[jerrywh]

Motor oil is a poor hardening substance as stated before. But it could have also been too hard to spark. You are incorrect in your terminology. You have hardening confused with tempering. They are not the same. After hardening , which is what you did, tempering is required. The frizzen should be brought up to between 350°F and 400°F depending on one preference in order to make it spark according to your wishes. A higher tempering temp will give you more sparks and longer lasting sparks of a redder color but will reduce the lifespan of the frizzen. You do not have an accurate measuring devise for temperature so you do not know exactly how hot you got the frizzen each time you quenched it. You just got more lucky the third time. Kasanite is good stuff for small parts like screws but it is short lived when it comes to frizzen hardening. I know this is blasphemy but I'm not a big fan of Kit Ravenshears book. Most of it works sometimes but might not be the best methods. However[ it is written] That's what counts to most people. If it's in a book or a video it's a fact to them regardless.

 

[Ron1953]

General rule of thumb regarding quenching. The more severe the quench (faster), the harder the final result.

I won't mention the most severe quenching medium because someone would try it and poison themselves. After that comes a saturate solution of sal ammoniac in water, then water, then oils of various weights, then air blast, then still air. (Not a complete list, just a good range.) Thick heavy oil transmits heat slowly compared to water for example so common carbon steel quenched in water will be harder than the same metal quenched in oil. The oil doesn't boil away from the hot metal like water so not much convective cooling. Water really carries away heat fast.

Industrial supply houses sell crayons called Tempilstiks that melt at specific temperatures, you mark the metal with it and when it melts it is at a set temperature. Great for tempering when you know the alloy in question and need to get to a specific temperature for tempering or drawing back the hardness. Don't want a frizzen that is hard as glass.

 

[George91946]

Thanks everyone. As soon as I'm done cooking my tamales tonight, I'll throw that sucker in the oven for an hour.

Lisle George

 

[LRB]

General rule of thumb regarding quenching. The more severe the quench (faster), the harder the final result.

I won't mention the most severe quenching medium because someone would try it and poison themselves. After that comes a saturate solution of sal ammoniac in water, then water, then oils of various weights, then air blast, then still air. (Not a complete list, just a good range.) Thick heavy oil transmits heat slowly compared to water for example so common carbon steel quenched in water will be harder than the same metal quenched in oil. The oil doesn't boil away from the hot metal like water so not much convective cooling. Water really carries away heat fast.

Industrial supply houses sell crayons called Tempilstiks that melt at specific temperatures, you mark the metal with it and when it melts it is at a set temperature. Great for tempering when you know the alloy in question and need to get to a specific temperature for tempering or drawing back the hardness. Don't want a frizzen that is hard as glass.

When quenching in water, one has to be prepared for the steel to crack. It is an ever present risk.

 

[ebiggs1]

At the shop where I work, we purchase “Quenching Oil” in five gallon barrels. I don't know exactly what it is made from but it looks a lot like ATF with out the odor.

 

[jerrywh]

The faster the quench the more likely the part is to crack. It is not necessary to have a radical quench like salt water or ice water. Most of the time I just use automatic transmission oil. or water with a film or transmission oil on top to break the shock. It always works.
Some of the springs produced nowadays are made of 6150 steel. 6150 does not get real hard like 1095 or 01 does when quenched because it has al low carbon content. This has to be ignored and the regular tempering process should be carried out regardless. The spring will turn out just fine if done properly

 

[LRB]

There are a number of different quench oils for different steels, but I can assure you they are not deodorized ATF. The different oils are formulated for different cooling speeds. One type does not fit all. Of these, Parks #50 is the fastest. If you quenched 01 in Parks #50, it would likely cause the steel to break. 01 likes a medium cooling oil like Parks AAA, and if you quenched 1095 in AAA, it would not get even close to being full hard. ATF will not bring 1095 to full hard either, but it will do for frizzens. Just barely, but will do OK.

 

[jerrywh]

There are about a hundred flintlock springs around that I hardened in transmission fluid. For about 400 years nobody ever heard of modern quenching oil. In the 55 years That I have been working on mostly flintlocks I have only had two articles crack when quenching. The cause of both of them was overheating before quenching. Just for the record A lot of them were quenched in plain water. In the 18th and 19th centuries it was recommended that springs be quenched in mineral or animal oil. [ bacon grease]
I been using the same gallon of trany fluid for the last 15 years. I not only harden springs in it and fizzens but milling cutters, taps and dies and countersinks and such also.

 

[Tumblernotch]

I've always used Bud Siler's method for hardening and tempering and it works great. Heat the frizzen to an orange either in the forge or with the torch and quench in motor oil then polish the frizzen face. Take a steel lid or other shallow steel container and put 1/2 inch of clean sand in it. Lay the frizzen on the sand so that the polished face can be seen. Place on a kitchen stove burner (or other heat source that will get hot enough). Heat until the color runs to a light straw. Set aside to air cool.

The last frizzen I did was on an L&R lock and the first time around I didn't get it hard enough to temper. Turns out I had to get it hotter (bright orange). Then I tempered and it throws sparks like I'd jammed a piece of tool steel against a grinder. Seems the steel of an L&R lock needs a little more heat than a Siler.

I'm told that mineral oil is better, but I have a can of 10W40 handy and that's what I use on all my parts. I know some oldtimers used to use molten lead for the tempering phase, but this works well enough for me. A friend of mine likes to hold the torch flame on the foot of the frizzen and allow the colors to run up the face and he is pleased with that method. I may try it on one of my Chambers locks that I'm putting together. I've done it with other parts before.

 

The trouble with what was done 400 years ago was they were often 1 part rite and 2 parts wrong. Metallurgy has come a long long way. Also the steel used then was primarily iron and carbon, even standard 1095 or 1084 has different trace elements than what they had. And a lot of them were "close enough", close enough that it worked well. And there were a lot of knives, and springs, that were sub par to what we have now.

For a frizzen or even a spring, as long as it gets hard and you temper it back you'll probably never notice an issue.

Where it really comes to light is in extreme endurance testing, primarily with cutting edges.

I use commercial quench oils, not because I can't use something else, but because it keeps me from having to re invent the wheel and gives me consistency from batch to batch and saves me time. It takes one variable out of the equation. If you've got a lot of one type of oil you can play with the oil temp to speed up or slow down the quench, normally the hotter the oil the faster the quench, to a point. I've played with different oils, and while I don't use them anymore I did learn a lot from experimenting and had fun.

The idea of tempering the face by heating the tail of the frizzen is a good one, it gets the tail softer than the face. Just be careful not to over shoot your temps. Straw sounds about rite, just make sure there's no oil on the polished face, it can change the tempering colors.

 

[jerrywh]

I can except what you say when it comes to modern high tech steels. Carbon spring steel is not all that high tech.
I know for sure that they never had a 60% failure rate in the 18th century. They probably had close to 100% success when it came to tempering springs. In Europe it was all done by guilded professionals. Most gunsmiths in this country used the lead bath from my observations. In working on old guns I have found the paticles of lead on the springs I removed and replaced.
Spring steel was in very short supply in this country in colonial times. I also have seen springs that were tempered by the burn off method in American made muzzle loaders. I know both methods work but the lead bath is the most consistant of the two. I use a electric futnace now. Blade smiths are a differnt breed of alien.
PS-- How about the clock makers and the instument makers of the 18th century. How many people now can make jewelers saw blade by hand??? HUH? And the tools to make it with?
TRY THIS ---http://www.antique-watch.com/des/w5182.html

 

[jerrywh]

Look up 18th century chronometers and tell me they never knew how to temper back then.

 

[LRB]

Jerry, their chronometers weren't that good until Huntsman re-discovered cast steel that produced a higher quality controlled steel that allowed much more uniformity in steel for springs. I think 1740's?

 

[J.D.]

There is a lot of good information in this thread, the only thing I can add is quenching in about a gallon of warmed canola oil or peanut oil, but canola is less expensive. I seem to get better results from quenching in Canola, as opposed to ATF, but ATF can work too.

For home tempering in the kitchen oven, use the average temp of a minimum of two oven thermometers to determine the correct temp. The more the better, as thermocouples in kitchen ovens can be off as much as 100 degrees and some cheap oven thermometers aren't much better.

IMHO, soaking the frizzen with Kasnite prior to quenching will add some carbon to the surface, or at least reduce the loss of surface carbon, making for a hotter, somewhat longer lasting frizzen. Use the oil quench to prevent stress cracks from forming.

I do hope your frizzen hasn't developed stress fractures from the water quench. It may last for years, or it may break the next time you use it. Who knows? Let's hope for the former.

IMHO, every good heat treater has developed a system, over time, that works for them. Some get good results using one type of quench and one method for tempering. Others seem to get better results from other quench materials and other methods of tempering.

The end result is what counts, and there are obviously several ways to get there.

God bless

 

[J.D.]

almost forget, pure lead melts around 615 degrees F, which is too hot to temper frizzens, but works well for tempering springs, depending on the alloy of the part.

 

[Tumblernotch]

That's what I like about using parts from Siler, Chambers and L&R. All of the parts I've used are very close in their characteristics and I can use the same tried and true methods and pretty much get the same results. One of my frizzens has been on a heavily used rifle for over 20 years and though worn pretty thin still sparks like it always did. The only reason I'll probably replace it soon is that the pivot area has worn enough that it's not as tight as it should be and rather than build it up I've got a bag full of new frizzens to replace it with. It will be the first part I've replaced on that old Bud Siler kit lock.

However, I've found it can be a bit dicey when making parts from old scrap steel with unknown characteristics. That's another story altogether. Not having any metallurgy background I have to rely on oldtime tricks of the trade that I've read or had shown to me, not to mention a lot of trial and error. But that's what makes it interesting and satisfying (though oftentimes frustrating). If it was easy everybody would be doing it. :grin: