Heat treating bolts for dies

Hi guys,
I have been making crude dies for my 22lr loading exploits. Making them from 5/8 18 grade 8 bolts. I put these in sleeves that have 5/8 18 threads on the inside and regular 7/8 14 threads on the outside. The sleeves are made from old dies that are bored out and tapped. I am at the point where I want to start hardening my dies. Planning to just wing it by heating to color and guessing how long to quench... haven't determined the specs yet. Any suggestions would be appreciated (unless they are suggestions to not do it, then I won't appreciate those).

I haven't actually tried to heat treat grade 8 bolt material but I do have a future project that may benefit from this information. The little bit of research I have done tells me it needs to be oil quenched rather than water or air. I would think a good polish and heating on a drill press should get you close. At least the material is cheap enough to experiment on. I'd think a simple file scratch test will tell you what you need to know. Let us know how it works out!

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You may be happier with case hardening the bolts rather than a true hardening. Another consideration is to use allen cap head bolts as these are pre hardened and pretty tough to begin with. These will allow you to make the die and not worry about warpping or oxidation issues.

Hardening you want to heat it to dull red and hold it there for a set time then quench. As above not knowing the grade of steel I would also recommend an oil quench. Make sure your quench covers the part by several inches as it will boil off and it the part goes thru the surface you will have a fire. Once quenched it should be fully hard and may be to hard. Polish the part up and draw it back some. heat to a light straw blue color and let slowly cool This should take it back from the 60-65 Rockwell to around 50-55 maybe a little softer. A propane torch works good for this.

I would suggest using oil or air hardening tool steel instead of a bolt for your actual die. You could use something like leaded cold roll for your die body and make the actual die out of tool steel and either screw it in or use a retaining nut system to attach it to the die body. I prefer to use an air hardening tool steel for my dies because of less warpage in the heat treating process and I find it a little easier to heat treat than oil hardening.

Grade 8 bolts are made from 4140 Cro-Moly steel and already hardened to Rc 39 and 180,000 psi. That's why they are called Grade 8. Grade 5 bolts are hardened to 150,000 psi.

They will be fine just like they are for anything you want to do to them. If you try to re heat treat them you just destroy what's already there. And then they have to be annealed in order to start over.

Randy

double posted.

Randy's reply is probably right most of the time, but unless you get certs with them you can not be sure. Grade 8 does not specify alloy, just hardness and tensile strength. Bolts made from alloys other than 4140 are possible.

Also, counterfit Grade 8's are a possibility.

I have worked with grade 8 bolts to make dies with. First I soften them up as they are difficult to work with. Many are not hardened evenly at all . Heat red and let cool slowly . Do whatever you are going to do with them. I then heat to orange hot and quench. If it needs to be tough like in a swage die. Then a couple hours in a oven at 400F will make it less brittle. Pretty crude but works well enough. Traffer I am having good success in priming my percussion caps.I'm using your method of floating the cap dots off the paper with a knife. Best idea I have used to prime these.
n.h.schmidt

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Originally Posted by n.h.schmidt

I have worked with grade 8 bolts to make dies with. First I soften them up as they are difficult to work with. Many are not hardened evenly at all . Heat red and let cool slowly . Do whatever you are going to do with them. I then heat to orange hot and quench. If it needs to be tough like in a swage die. Then a couple hours in a oven at 400F will make it less brittle. Pretty crude but works well enough. Traffer I am having good success in priming my percussion caps.I'm using your method of floating the cap dots off the paper with a knife. Best idea I have used to prime these.
n.h.schmidt

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Thanks for the great reply and the encouragement that I have helped you with the caps. I don't know if you have been following Marshall's posts on primer in the "can you make primer compound", but the latest stuff he has been doing is really good. I think some of his newer formula's are as good or BETTER, than commercial primer.
Your reply about how to anneal and re-harden dies is exactly what I had hoped someone would help me with. Very practical and perhaps most of all, it is doable without costly equipment or years of practice. I have often encountered (nearly every bolt) the "hitting hard spots in the steel of hardened bolts" I used to think that the bits had become dull, but it is just an extremely hard spot in the bolt. I usually encounter it very near the head of the bolt. If you want to get some very good and inexpensive 7/8 14 bolts for dies, pm me.

My annealing technique is to wrap it up in aluminum foil and put it in the center of a pile of barbecue charcoal. Light the charcoal and let it burn out and cool overnight without disturbing it. The steel softens nicely.
For hardening I never could get the color temperature right because it is so dependent on your experience, eyes, surface finish, and ambient light. I use the curie point method where you heat the steel until it loses its magnetism and then hold it at that temperature a couple minutes before quenching.

grade 8 bolt makes good dies, that is what im using right now to swage my bullets with.. first i anneal them at 1,300*F-1,400*F for 15 minutes in my kiln and let them cool down slowly so they are soft enough to machine with no hard spots. i then machine the dies like i would using regular bar in the lathe.. i then prepolish the dies so there is less work after the heat treating. i then heat treat them at 1,500*F for 20 minutes and quench them in water till they are cool enough to touch.. i then polish the inside of the die to a near mirror finish. the grade 8 bolts i got will water quench harder than a file.. be aware though that most grade 8 bolt material when heat treated the bore of the die will grow almost 0.002in so you must make the hole smaller than you plan on to allow for it.. i usually ream it with my reamer to 0.306, heat treat it, then polish the bore with fine clover brand lapping compound and it ends up being about right.. if your unsure of what your metal will do then just take a small section of the bolt, drill it, then heat treat it like you would the die and it will give you an idea of what the metal will do..


but Idz. you want to be in a dark room when you heat treat by color as any light will throw you off.. you bring it up to red with no shadows seen and then quench it like you want to..

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Originally Posted by Mauser 98K

grade 8 bolt makes good dies, that is what im using right now to swage my bullets with.. first i anneal them at 1,300*F-1,400*F for 15 minutes in my kiln and let them cool down slowly so they are soft enough to machine with no hard spots. i then machine the dies like i would using regular bar in the lathe.. i then prepolish the dies so there is less work after the heat treating. i then heat treat them at 1,500*F for 20 minutes and quench them in water till they are cool enough to touch.. i then polish the inside of the die to a near mirror finish. the grade 8 bolts i got will water quench harder than a file.. be aware though that most grade 8 bolt material when heat treated the bore of the die will grow almost 0.002in so you must make the hole smaller than you plan on to allow for it.. i usually ream it with my reamer to 0.306, heat treat it, then polish the bore with fine clover brand lapping compound and it ends up being about right.. if your unsure of what your metal will do then just take a small section of the bolt, drill it, then heat treat it like you would the die and it will give you an idea of what the metal will do..


but Idz. you want to be in a dark room when you heat treat by color as any light will throw you off.. you bring it up to red with no shadows seen and then quench it like you want to..

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Thank you, that is very helpful. Is just barely red in a dark room 1500 degrees? What color would 1300 to 1400 be? I did some heat treating many years ago so I have gained somewhat of an eye for it but now I don't have an oxy-acetylene torch. So I am going to have to make an improvised forge. Too much stuff to make. Wish I had money to just buy stuff. lol

I do a lot of my heating of bolts in my fireplace. If burning oak or other hardwood you can get to red hot easily. You can also make a rocket stove( Google search) .Burns wood with intensity. One of the charcoal burner cans for getting charcoal going before spreading out on the grill. They get really hot. A little fan blowing into the vent holes really gets things going.
You can harden these bolts to glass hard. They sometimes need to be tempered down to not crack if under a lot of stress.
n.h.schmidt

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Originally Posted by n.h.schmidt

I do a lot of my heating of bolts in my fireplace. If burning oak or other hardwood you can get to red hot easily. You can also make a rocket stove( Google search) .Burns wood with intensity. One of the charcoal burner cans for getting charcoal going before spreading out on the grill. They get really hot. A little fan blowing into the vent holes really gets things going.
You can harden these bolts to glass hard. They sometimes need to be tempered down to not crack if under a lot of stress.
n.h.schmidt

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Thanks, Yes I knew there were several different ways to generate the heat but haven't decided on which way to go yet. When I was a kid we would just use a compressor blowing air into a coffee can full of charcoal. Now with those leaf blowers you can practically make an iron melting furnace.

I welded a magnet to a piece of steel rod about 30 inches long to test for proper heat. when magnet won't stick I know its right temp. Works for knife making.

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Originally Posted by flint45

I welded a magnet to a piece of steel rod about 30 inches long to test for proper heat. when magnet won't stick I know its right temp. Works for knife making.

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Another great idea. Thanks

Being an electrician I always have a magnetic torpedo level. This is what I use when heat treating knives, dies, reamers etc. You need 1500 deg or thereabouts. It will go non magnetic at about 1450. Once there I keep it in the fire for another minute or so and quench. Worked for me lots of times.

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Originally Posted by Wolfer

Being an electrician I always have a magnetic torpedo level. This is what I use when heat treating knives, dies, reamers etc. You need 1500 deg or thereabouts. It will go non magnetic at about 1450. Once there I keep it in the fire for another minute or so and quench. Worked for me lots of times.

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Thank you folks for the great responses. I have learned a lot here about heat treating. And by all means if you have any more suggestions I would love to hear them. I like the fact that there are fairly simple solutions to these tasks. I also use
O-1 and various other hardened drill rod for making tip punches hollow punches etc. Would hardening them be much the same process?

just so you know I am a custom knife maker. supporting my family solely by making and selling forged hand made knives. I have been doing this for 20 years.

there is some good advise here and some only mediocre.

A good anneal is going to make things much easier for you. heating to red holding a short time and cooling as slow as possible. The best way to accomplish this is with an electric kiln with a digital control. It can also be done by heating to red/orange and burying it in a can of lime until cold. another way if you have said digitally controlled kiln/oven is a sub-critical anneal, here you bring the part in question to 950- 1325 degrees and hold it for a time. the lower temps require longer hold times. I like to use 1250 for two hours. this will make your bolt machine like it is butter and set the molecular structure up for hardening. When hardening there are several products on the market that can be used to protect a polished part so that labor intensive clean up post hardening can be avoided, there will still need to be some done however. hardening can again be accomplished in several ways and the best way is again with a digitally controlled kiln. this is the most accurate and takes the least amount of skill and knowledge. heat to 1500-1550 hold 3-5 minutes and quench in fast oil or water/brine. this should make the part in question as hard as glass and a new file should just skate across without any kind of bite into the metal. heating in any other manner is color dependent and will not be as reliable without a good bit of practice and skill. in a dark room steel just begins to turn red at about 900 degrees 1500-1550 is actually more orange than red. that is all I can say that will really help. But there are a couple of things you can do to help. first is the magnet test mentioned already. carbon steel becomes nonmagnetic at 1325~1390 actual temp is dependent on carbon content. higher carbon steel has a lower nonmagnetic / curie point than lower carbon steel. another way used in conjunction with the magnet trick, is to bring the steel up to nonmagnetic then continue to heat until it is turning orange. you may notice that it will be bright red to orange then slightly darken then continue on to orange heat you may not. when hot remove flame and watch the piece. you should nice that it starts to darken then a brighter spot should form and spread of the part and then darken again. this is the point where the metal becomes magnetic again. you absolutely have to be above this temp for the part to harden. after hardening the part should be tempered to avoid shattering under stress. to temper heat in an oven to 325 to 350. this will leave the hardened part fully hard with little reduction in hardness. it will probably be better for your purpose to heat to 450-500. this should leave the part in the mid 50's Rockwell hardness. tempering should be done at a minimum of two times for one hour each time cooling to room temp between tempering cycles.

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Originally Posted by Traffer

Hi guys,
I have been making crude dies for my 22lr loading exploits. Making them from 5/8 18 grade 8 bolts. I put these in sleeves that have 5/8 18 threads on the inside and regular 7/8 14 threads on the outside. The sleeves are made from old dies that are bored out and tapped. I am at the point where I want to start hardening my dies. Planning to just wing it by heating to color and guessing how long to quench... haven't determined the specs yet. Any suggestions would be appreciated (unless they are suggestions to not do it, then I won't appreciate those).

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Check around for any blacksmiths or knife makers. Usually if they do not have heat treat oven they can steer you to someone who does. Saves a lot of problems and a great source of real hands on information.