Hardening drill rod?
I need to make a short run 7/8" round punch. I figured I would get some oil or water hardening drill rod to make the male part of the punch. Maybe some oil or water hardening flat stock to make the female part of the punch. I also thought a good way to do the female side of the punch was to use a 7/8" drill bushing. Seems to me it would work if I surface grind it so the ID edges have no chamfer. From what I can gather oil hardening material is better. So my questions are:
What is the procedure for hardening this material?
What type of oil do I use?
From what I can gather a forge is better that a torch. Unfortunately I don't have a forge will a torch work OK? Again, this is a short run (30 pieces) punch for some stainless steel screen. Wire diameter of the screen is .016"
Last edited by TimH; 01-03-2012 at 12:10 PM.
Reason: more questions
For that size of run, and, if you don't have a programable oven, I would send the work out for Hardening and stress relieving.
My 2 pesos,
First warm up some peanut oil (100 degrees or so) set it buy your drill rod,then heat your drill rod to cherry red, when its hot enough it will wont be magnetic. Using tongs set the drill rod into the oil then let cool. When its cool temper it in a oven until its 350 degrees through out the part. I would use a broad tip on your torch so you dont melt the drill rod. Your die (the female part of the punch) Youll have to make out of larger drill rod or tool steel. Make sure you provide some clearance in the die or bad things happen. also you will need a stripper of some sort or your material will stick to the punch. Checkout Amazon or something for a book called punch and die fundamentals
I would avoid high carbon steel. It offers no advantages and a lot of question marks. I would also avoid hardening tool steel with a forge or a torch because you have no temperature control and the odds of decarburizing the part are quite high. To get rid of decarbed surfaces you will have to grind about .010 off all working surfaces of both the punch and die.
Cost wise I would use A2. Its often cheaper than O1 and is more stable than oil hardening steels. If you insist on hardening the steel yourself, use oil specifically for heat treating. Engine oil will not work plus you will have lots of smoke and possibilities of fire.
Locally, you could get thirty punch sets done professionally for about $30-$50. Then you know what you have.
Edit: Do you have a way of mounting the punch and die for alignment, as in a press or die set? To punch .016 SS screen, you will need nearly zero die clearance to keep from smearing the wire which means a very accurate die holder.
All this you may know, but I mention it because of your lack of knowledge on the heat treating side.
As TD says, punch and die clearance is quite fussy for that fine of wire. If you don't think you can get it right in your die set, leave the die soft for starters and shear it in.
As for heat treatment, I'd just do it. I could have the punch heat treated before you could even fill out the heat treat book. Set your torch about 3x carburizing and don't let the cutting edge out of the flame until you drop in the quench. About any oil will work for such a one-off project.
O1, A2, S7 would all work. I doubt you could ever tell the difference in 30 piece service.
Hardening and tempering this part should be a simple task. O-1 would be an excellent choice for a short run punch. I have many similar tools from O-1 using a Mapp Gas torch and Canola oil leftover from the kitchen! Virtually any oil will conduct the heat out of the part successfully. No need to heat the oil or use any magic potion. Motor oil is fine too, just stinky.
One nice thing to use on the part to prevent decarbing the surface is Brownell's Anti-Scale. It is easy to use and is very effective and intended for just this kind of application. Applying it to the part prior to hardening elliminates surface carbon loss and so makes post-hardening grinding unnecessary. I find this a big bonus as the part can be made on-size and then hardened.
Heat the part to a nice cherry red and then plunge it into the oil moving around in the oil vigorously as it cools. This ensures uniform cooling. Then put the part in boiling water to cause the antiscale to fall off or dissolve. Then draw to a deep yellow to temper it. This would apply to both the male and female parts. I am assuming the female part will not be a thin flat as this might warp in these circumstances. (There are ways around that too, but let's keep it simple) A round robust "donut" should be no problem. Use a piece of "tie-wire" to hold the donut as you plunge into the oil. Only the business end of the punch should need hardening.
Good luck and please let us know how you come out on this.
Thanks for all the input. I think for the female part I'm going to try and use a hardened drill bushing. I can grind the chamfer off it so it will have a nice cutting edge. I plan on taking a round piece of stock, ream a 7/8" hole through it to guide the male half of the punch. I will then cut a slot through this part to allow me to put the screen in between the guiding half and the half that will hold drill bushing. I will press the drill bushing into the bottom half of this block. Hopefully this will work. I'll keep y'all posted how it goes.
What do you mean by "Then draw to a deep yellow to temper it."?
I have just made a few gun parts that should be hardened. I usually send them out, but I have been looking for a simple way to do small (1 or 2 piece) jobs at the shop. What you describe sounds simple enough, but you lost me at the "draw to a deep yellow" part. Could you please explain this procedure in just alittle more detail?
01 is the better choice. W1 is too easily warped,changes size some,and can crack in the quench more easily. Also,doesn't have the alloys of 01. If you don't overheat,you won't have a decarb problem.Use the magnet as a test.
I use A2 for our punches,but it takes an accurate furnace,and stainless steel foil wrap,or it will definitely decarb. A2 warps and changes size less than any of the water or oil hardening steels,and has better wearing properties. I have an electric furnace with controls,though,and the stainless foil is expensive to buy unless you'll be using the whole roll.
Harden as described. Then,sand off the black skin,and slowly heat the part. It will turn a gold color(yellow),then a light brown,then darker brown,then purple,then blue,then dead gray. You will want the punch to be light brown. I think yellow might be too brittle. It depends upon the shape of your punch.
If there are any holes drilled in your punch,STOMP them tightly with fine steel wool and a flat nosed punch and hammer. Drilled holes can crack, Remember to use the steel wool. This is an important tip. The inside of the hole will still harden,but the hole won't crack. Clay used to be used,but the insides of the holes would not harden with clay in them.
Once the part has been hardened, you shine it up with a little emery and heat it slowly. The color change of the steel indicates the temperature. It's a pretty reliable old school method for gauging the tempering temperature. For smaller parts it works great; for something like a 7/8" punch I would take some measures so that it takes a good 20 minutes to reach the yellow (straw) color.
Originally Posted by critter221
For gun parts that need to be hardened straw is going to be too hard (in general), you would want a purple to deep blue (in general).
By the way,a toaster oven is good for tempering steel. Especially if you have an accurate high temperature thermometer with a long rod on the back(probe) that you can insert into it. Don't rely on the built in thermometer.
The magnet trick should see you through the hardening process,but in reality,there is only about a 25º "window" for hardening and tempering that gives you the optimum temperature to get the best performance from your steel. A good thermometer is a good investment. Brownell's gunsmithing supplies sells them,though someone suggested a cheaper source some time ago.
You should quench your part until you can barely hold it in your hand,and immediately place the part in a PRE HEATED toaster oven. This is austempering,and will enhance the life of your punch.
To get the best results a small oven would be desirable. You can make due with torches but you must measure the temperature carefully. One strategy for keeping the temperature even is to put the drill rod in a steel or brass casing. Drill a bore for the rod in one end and smaller bore in the other end for the thermocouple.
If you are new at this I would strongly suggest using a thermocouple. You can get a cheap k-type thermocouple probe for $12 and a digital readout for $40 from meter-depot.com.
Remember the rod has to be HELD at the critical temperature, the bigger the rod, the longer the hold time. With a torch it is difficult to be keeping a consistent temperature for 10 minutes or however long it requires. Sizable dies and punches can require significant soak times. For a 7/8" rod I would expect a soak time of something like 20-30 minutes.
Making simple punches is easy, but there are some nuances so definitely get good reference works on the subject or consult an experienced hand so you do not make an obvious mistake.
I do not think there is a truck big enough to legally haul all the O1 that is heat treated in the United states each year by being quenched into used motor oil ;-). Maybe not the BEST way, but if you do it that way it seems to get hard enough to ruin any file I ever applied to it afterwards ;-).
Originally Posted by TDegenhart
If you can find a pal who casts bullets he may let you use his lead pot to temper.
Used motor oil CAN put a THICK,BLACK CRUST on the objects you quench in it, from the carbon in it. I used used motor oil years ago to get just that result. The crust is quite thick,and hard as blazes. Perhaps if you could filter out all the crud and carbon in it,it might be o.k.. Gas station swindlers used to re sell used motor oil as new. They'd keep a barrel of it out back,and filter it through panty hose wrapped around the nozzle.
Never buy oil from a gas station that has opened cans of motor oil stacked up. It is not new oil. A station around here got caught doing that and was closed down back in the 70's. My father in law worked for Esso in the 60's,and told me about that trick.
Buy yourself some vegetable oil or peanut oil from the grocery store. Your quench needs to be large enough to not appreciably heat the quench.
We used a 5 gallon quench of automatic transmission fluid at work for years.
I only ever do small o1 parts as well as a fair bit of w1 (silver steel over here) Old car oil works fine for me (prefer that to water on some of the more complex W1 parts, your just trading some hardness which is not much of a issue if your going to a softer temper).
Regarding the build up of black carbon on the finished part. Oil that's seen only some 3K in a motor bike is much better than a oil that's seen a hard 20K in a diesel. The later is great though for oil blackening :-) Regardless of oil though, you don't want to be plungeing hot metal into a vat of any oil in your nylon shell suit in the middle of the nylon living room carpet with the doors - windows closed. Need good ventilation and some were if the oil does catch you can just smother it to extinguish.
As to flames, generally i don't get much unless im doing a lot. Recently blackening B sized QCTP holders i had made in a medium sized saucepan of used car oil. First 3 were pretty non eventful. 4th burned for about 30 seconds or so. I did not attempt the other 4 till things had cooled off. 5th would have bassed on my prior experience resulted in a very long possibly continues oil fire. Nothing exciting though so long as you only try and smother it with a steel plate or similar. Adding water is a bad bad idea! A great time to demonstrate to others though how to coolly and carmly deal with a oil fire.
On the water note, always break in a new tub of used oil carefully, if it has much water in it or in the tub your using it will boil off spitting very hot oil every were. Hence keep it dry, keep it in a sealed container once cool between uses and treat it as a tool, not the scrap substance it was in its former life.
Would you detail your blackening the steel with old motor oil?
Originally Posted by adama
In my case,the first time I used old motor oil to blacken something was in 1959. My chemistry teacher had a Smith and Wesson revolver that was missing the rear sight. He brought it to school,and asked me to make a sight for him. I carried it over to my shop class room,and made the sight. I got some blackened,old motor oil,heated up the sight to red hot and dumped it in. It put a good coat of black on the sight.
Try walking around with a gun on campus these days!! Of course,I didn't show it to anyone,but the shop class knew what I was doing. They were all retired Navy men going to college on the G.I. bill. I was the only student fresh out of high school. This was in the industrial arts program,which was in its first year at the college.
Have you tried just using a shim punch. For that small run it may save you a lot of trouble.
On the other hand this IS a good opportunity to learn a little about heat treating.
Originally Posted by gbent
Not much too it, clean the item back to bare metal. starting with plain CRS steels fine, just no scale or rust. Heat in my case by propane roofing like torch through the oxide colours till it turns dark grey again, circa 550C if i remember right. Does not want to be red, or fire risks and scaling go way up. But if its nearly dark out side barely glowing dull dull red is just ok. then lower rapidly into old oil. Leave to cool or nearly cool and fish out. Let the oil drain off and give it a wipe down. Will be a nice black colour all over. I like to then give it a final wipe down with some way oil. The resulting finnish so long as kept ever so slightly oily will practically never rust in a indoor environment. Unless the surface is totally dried out - degreased.
Consider the blackened layer akin to covering it in a thin but hard layer of sponge, keep the sponge oily and it protects the surface bellow. being a sponge like material on a microscopic scale, it means that oils not totally wiped off by handling. Its far tougher - more wear resistant than paint too.
I looked for a 7/8" shim punch. They are pretty expensive
Originally Posted by CMT John
As a follow up to this thread. I decided to buy a 7/8" drill bushing. I surface ground the bottom to give it a nice cutting edge. I bought oil hardening drill rod. I figured I would just try using the drill rod as is. I housed the two parts in alum so the male part would have a guide. It worked perfectly for the short run I had to do.