Just a note: For those without access to sophisticated heat-treat resources, it is likely better to avoid the temptation to use a High Alloy Steel for small parts inasmuch as some of those require more sophisticated quenching medium than is available to most of us. Sub-zero quenches like Liquid Nitrogen...don't have much of that laying around.
Material for firing pin
- Thread starter johnm1
- Start date
.Bill DeShivs
New member
I make a lot of springs and have for years. I use 1095 almost exclusively and I quench in canola oil. I have never had a customer return a broken spring.
Real quenching oils are expensive and not available in small quantities. Canola doesn't flare up or smoke too much, and you can buy it by the quart.
JamesK- your springs broke because they were not tempered properly, not because of the oil. You left them too hard.
Real quenching oils are expensive and not available in small quantities. Canola doesn't flare up or smoke too much, and you can buy it by the quart.
JamesK- your springs broke because they were not tempered properly, not because of the oil. You left them too hard.
This subject becomes more interesting the more I read about it. I have gathered about all of the information from the internet that I care to (this forum excepted). Does anyone have a suggestion for a book I would be likely to get at the local library. I do live in Mesa, AZ near Phoenix so I probably have some decent resourses available to me.
Now for a dumb question. Can a piece of hardened steel be machined and still retain its hardness? I figure the heat generated in the machining process would work against the hardning. But if I don't ask I'll not know for sure.
Now for a dumb question. Can a piece of hardened steel be machined and still retain its hardness? I figure the heat generated in the machining process would work against the hardning. But if I don't ask I'll not know for sure.
I've made several firing pins from O-1. Works fine. Tempering temperatures and some other properties are here. Quench for O-1 is 1450-1500°F, and they recommend you heat the oil to 125°-150°F to avoid distortion and cracking. After the quench, you want to draw a firing pin back at 800°-900°F. That's a little tough in the toaster oven, but that Rockwell C scale hardness of around 45 to 50 is where you want to be to absorb impact without deforming, yet not be brittle.
I bought a gallon can of Brownells Tough Quench awhile back. Pricey but, if a gallon lasts as long as it lasts me, that's of no consequence. I'm not doing large parts. Special reamers are about as long as I get.
The fellow who builds muzzle loaders out here uses 20 weight non-detergent motor oil for his spring tempering, and rather than a second heat and quench, he pulls the hot steel out of the first quench and sets fire to the oil on it. Let's the flame draw it back.
For the firing pin, a couple of things: There is a phenomenon called 500° embrittlement in steel, wherein the strength actually declines between around 500° and 700°. You generally want to skip over that temperature range. I find cylindrical shapes that are long will warp easily in the quench, so I get a wire hook on them and spin them with a variable speed drill while I quench them. It seems to average the error out and they stay pretty straight. Maybe it just keeps the bubble from favoring any particular spot?
I bought a gallon can of Brownells Tough Quench awhile back. Pricey but, if a gallon lasts as long as it lasts me, that's of no consequence. I'm not doing large parts. Special reamers are about as long as I get.
The fellow who builds muzzle loaders out here uses 20 weight non-detergent motor oil for his spring tempering, and rather than a second heat and quench, he pulls the hot steel out of the first quench and sets fire to the oil on it. Let's the flame draw it back.
For the firing pin, a couple of things: There is a phenomenon called 500° embrittlement in steel, wherein the strength actually declines between around 500° and 700°. You generally want to skip over that temperature range. I find cylindrical shapes that are long will warp easily in the quench, so I get a wire hook on them and spin them with a variable speed drill while I quench them. It seems to average the error out and they stay pretty straight. Maybe it just keeps the bubble from favoring any particular spot?
www.mcmaster.com also sells quenching oil. A motor oil also will work .
Yes you can machine a hardened steel part but you will need carbide tooling or have to grind. It's very easy to overheat small parts when grinding !! as many knife makers have found when the overheat the tips especially.
There should be a basic ht or metallurgy book at you local library or college library.
You can always ask me here.
Yes you can machine a hardened steel part but you will need carbide tooling or have to grind. It's very easy to overheat small parts when grinding !! as many knife makers have found when the overheat the tips especially.
There should be a basic ht or metallurgy book at you local library or college library.
You can always ask me here.
Mete,
I've got a metallurgy question for you: Since it comes up frequently in case annealing questions, do you know where to find exposure time v. temperature for stress relieving 70:30 brass? I have attached the chart I have for 1 hour exposure, and I know empirically and from reading that 5-10 seconds at 650°F to 700°F will do it. Does it simply speed up exponentially with temperature? I'd be interested to learn what the function looks like.
For the OP: check on British hobby books for heat treating. They seem to have got into hand-building and machining more than we do. I have at least one nice small one (can't lay hands on at the moment) with good color plates of temperature and oxide color from different draws on carbon steel. If I find where I hid it, I'll post a reference. The guys at the Practical Machinist forum may well have a good one to recommend.
Thanks.
I've got a metallurgy question for you: Since it comes up frequently in case annealing questions, do you know where to find exposure time v. temperature for stress relieving 70:30 brass? I have attached the chart I have for 1 hour exposure, and I know empirically and from reading that 5-10 seconds at 650°F to 700°F will do it. Does it simply speed up exponentially with temperature? I'd be interested to learn what the function looks like.
For the OP: check on British hobby books for heat treating. They seem to have got into hand-building and machining more than we do. I have at least one nice small one (can't lay hands on at the moment) with good color plates of temperature and oxide color from different draws on carbon steel. If I find where I hid it, I'll post a reference. The guys at the Practical Machinist forum may well have a good one to recommend.
Thanks.
Attachments
It is difficult to machine hardened parts even with carbide, and ceramic tool bits. Very high speed and a lot of pressure would need to be applied to enable a "cut"...I observed a machinist turn a hardened taper on a lathe at such high speed, that the chips were coming off the piece in a red, molten state. But the part was not just hardened high-carbon steel, it was some kind of high alloy steel that remained hard despite the resultant heat.
For high carbon steel precision grinding is usually the finishing method, using coolants.
Brass - annealing starts at about 450 F as noted. Also note the grainsize line ! You don't want large grains .I don't have the info you ask for , I'd have to search.
I assume you are asking about annealing cartridge cases ? With all the methods I've seen I refer you to an old Norma booklet [they ought to know something about it !] .Their method is to put the empty cases in a tray with water somewhat below the neck .Heat the cases one by one with a propane torch to red then immediately tip the case into the water . That will satisfacterly anneal the case quickly and without danger to annealing the body of the case.
I assume you are asking about annealing cartridge cases ? With all the methods I've seen I refer you to an old Norma booklet [they ought to know something about it !] .Their method is to put the empty cases in a tray with water somewhat below the neck .Heat the cases one by one with a propane torch to red then immediately tip the case into the water . That will satisfacterly anneal the case quickly and without danger to annealing the body of the case.
Current thinking on the subject of annealing cases is that red heat is too high and will result in the case necks becoming too soft resulting in poor/inconsistent bullet tension, possible prolapse of the case neck.
Instead of red-heat, temperature indicating substances are used to indicate correct temperature...which is below the red-heat range.
http://thefiringline.com/forums/showthread.php?t=421161&highlight=annealing+temperature
Instead of red-heat, temperature indicating substances are used to indicate correct temperature...which is below the red-heat range.
http://thefiringline.com/forums/showthread.php?t=421161&highlight=annealing+temperature
That comes to the heart of the matter. I've read the July 1996 article in Precision Shooting that pointed out red heat will grow grain and reduce tensile strength to the point case necks can split in as few as 3 reloads, whereas a properly stress-relieved neck can sometimes last 20 load cycles.
That chart I have came with an annealing fixture that consisted of 10 metal pins welded to a base plate. You heat the whole thing to 700°F and set the cases over the pins about 2 seconds apart, so you wind up exposing each case to a pin's heat for about 20 seconds. It tends to heat the necks to 650 or so over the first 10 or 15 seconds, and it stays in the range of 650 to 700 for the remaining 5 to 10 seconds. So, I know you can anneal without giving the grains enough time to grow over that time frame. The hot cases are then dropped in water which stops grain growth immediately.
Similarly, the usual methods of applying flame all seem to heat over several seconds, so that vague time frame would appear to be good for these temperatures and for using the Tempilaq indicator, as Ken Howell describes in that link. It's a time frame in which the thermal conductivity of brass (pretty high at about 125 W/mK) won't get enough heat to the head to approach the bottom of the stress relief temperature range.
What I am curious about are faster heating devices like the induction heater mentioned earlier. It gets to red heat, but it's barely a half second flash in the videos in the thread on the topic from several months ago. So the question I have is will red heat really be OK if it's brief enough, or will that also cause rapid grain growth?
That chart I have came with an annealing fixture that consisted of 10 metal pins welded to a base plate. You heat the whole thing to 700°F and set the cases over the pins about 2 seconds apart, so you wind up exposing each case to a pin's heat for about 20 seconds. It tends to heat the necks to 650 or so over the first 10 or 15 seconds, and it stays in the range of 650 to 700 for the remaining 5 to 10 seconds. So, I know you can anneal without giving the grains enough time to grow over that time frame. The hot cases are then dropped in water which stops grain growth immediately.
Similarly, the usual methods of applying flame all seem to heat over several seconds, so that vague time frame would appear to be good for these temperatures and for using the Tempilaq indicator, as Ken Howell describes in that link. It's a time frame in which the thermal conductivity of brass (pretty high at about 125 W/mK) won't get enough heat to the head to approach the bottom of the stress relief temperature range.
What I am curious about are faster heating devices like the induction heater mentioned earlier. It gets to red heat, but it's barely a half second flash in the videos in the thread on the topic from several months ago. So the question I have is will red heat really be OK if it's brief enough, or will that also cause rapid grain growth?
I guess I should have been more careful to explain time . It takes time to grow grains ! You should hold the flame on the case until it turns red then "immediately "tip it into the water .You don't hold it for 5 or 10 seconds !! It really isn't necessary to invent Rube Goldberg machines to anneal cases ,