frizzen tempering temperature/color -- what am I missing?

[bgf]

I keep seeing 375dF for frizzen tempering temperature, but at the same time, I see to look for pale yellow, very pale yellow, straw, etc.  From the charts, I can't see any way to get pale yellow at 375dF -- they all say 420+ for that range of colors.  I got inspired by the frizzen hardening thread and decided after much procrasination to re-temper my Durs Egg frizzen, which seemed a little too hard and was sparking adequately but not spectacularly.  I got the Frizzen off, polished it a bit, then stuck it in a can full of sand at 425dF (verified by oven thermometer -- the oven was steady but the temps were off a bit) for an hour.  I got exactly the pale yellow/very pale yellow I was expecting from the charts and the temperature I tried my best to maintain.  I put the frizzen back in, got a bunch more sparks and just a little deeper scratch (they were very light before), so as far as I'm concerned, the operation was successful, but as usual, I am not happy not understanding what is going on.  Please advise why the temperature usually stated (375) is so far from the color(s) usually stated.  I could live with the assertion that color doesn't matter, only temperature, or vice versa, but I can't figure out why I keep seeing what appear to be two distinct temperature ranges equated.

[Bob Roller]

Temper colors are tied directly to what is being tempered.I think Barbie was talking about 1095. Bill Cox at L&R told me they are using my favorite which is 52-100 and your frizzen might be one of the later ones.
I got call today from a German gun maker that wants me to make up a group of flint pistol locks using the L&R small Manton with my own mechanism and maybe I will go for it. I old him about the 52-100 and that it is ball bearing material.He told me that there are no flintlock target pistols made in Europe now and the ones that were made are either wearing out or worn out. I recall a fine Manton copy made by an Italian maker and sold by Hege in Germany as their own work.

Bob Roller

[T*O*F]

I got call today from a German gun maker that wants me to make up a group of flint pistol locks using the L&R small Manton with my own mechanism and maybe I will go for it.

Bob.
Will you do any lefty Mantons?  I'm still waiting for a matched pair by you.  I've had all the parts for the rest of the gun for years for a Bedford double rifle in the style of Peter White.

Dave Kanger

[Bob Roller]

Dave,
Maybe this Fall on some left hand locks.
Bob Roller

[bgf]

Mr. Roller,
Thanks for the response.  I didn't mean to single out the Chamber's advice (and didn't really pay that much attention to the specifics in that post), as I have been trying to sort this out for some time, which is one of the reasons I had put off the retreating.  I just happened to feel like rolling the dice on 425dF after what research I had done, being willing to reharden and retreat again if necessary.   I can only assume that some slight color change must occur on some steels much earlier than 420dF?  I had seen several posts where 400dF setting on oven was required, and sometimes higher.  Knowing that ovens run a little hot, I thought 425 was probably a reasonable risk, given also the temper color charts.

Thanks for the information on the L&R material. I actually like my Durs Egg (a little over a year old), and it suffers from my ineptitude -- smaller, faster, and made better by you would be something else!  I can only imagine how fast a small Manton would be after you got you hands on it. 

[LRB]

  Temper color charts often differ some, as well as different peoples perception of color. That is why it is best to go by a good thermometer. Light, and it's source can also cause variation. The colors are from oxidation, and any oils from fingers or other contamination can cause variations. Putting your part in sand was a good way to go to keep the temp more even, but contaminates in the sand, or even what was cooked in the oven the night before can also affect the colors.

[curly]

Bgf, Bob just finished a left hand Durrs Egg for me, and I can't tell you how happy I am with this lock. What he does with a main spring and all the internals is just amazing. Very very fast.

Curly

[Dphariss]

Time may be a factor. A friend is moving so he has two places right now. Put a frizzen in the oven, forgot left it about 24 hours. Came out blue using 375.
I get faint pale gold/yellow at 375, checked with 2 oven thermometers.

Dan

[bgf]

LRB & Dan,
I was also thinking also that the sand may be somewhat reducing oxygen and reducing temperature maximum for that duration, whereas a part in the open oven may have more oxygen and likely see higher heat even than a thermometer can respond to during the cycle.  I have taken parts open on a clay tile to blue in the same oven  with it at 550 (w/o checking thermometer much), so I strongly suspect may see at least a little more heat than indicated by setting or thermometer that way.  I even wondered if the 375 setting often recommended wasn't fudged for safety factoring in the unmoderated temp swing seen in most ovens.  Regarding the last thing baked, either a trigger or some fish sticks (high in carbon if my wife burnt them!) !  I appreciate your feedback.

Curly,
That doesn't surprise me.  My dream lock is a Roller Large Manton/Manton-Ashmore/Late English, whatever you want to call it -- I think that would be the best combination of style and functionality a mortal could hope for, but of course I know my tastes are a little later than most!

[Bob Roller]

Tests in years past show that frizzens as soft as 44Rc will fire just fine.It all depends on the carbon content. A frizzen in the over 60Rc area is getting near the hardness of a high speed lathe bit or pre war German Boker knife blade and may not fire well at all.The sparks generated by a flint against steel are miniscule fragments of steel that are momentarily on fire and hot enough to ignite black powder and if those fragments are not available due to a super hard frizzen no ignition is to had.
The 44Rc is supposedly the hardness of a properly tempered mainspring made from 1075.This may also apply to 1095 but I never use it so I don't know. I got the info on the 1075 from a metallurgist here in a machine shop that tested one of my mainsprings some years ago.

Bob Roller