Hardness of steel rod…

[Bob Tascione]

I completely agree with David!
We all appreciate and learn much from your questions Tom. Take a look at the views and interaction of many of your tooling threads and you’ll see they have become some of if not the most popular discussions up here. When you disappeared for a few days a couple of weeks ago I started to panic! That’s why I contacted you to make sure all was ok. That contact was spurred on by David and others too so you know we mean what we’ve said here. We all learn from each others questions. Makes us think and work out solutions. Ouch!! “Think” and “Work”… both painful words in one short sentence. Remember Maynard G. Crebs’ reaction on the Dobie Gillis show when the word ‘Work’ was mentioned? May want to answer ‘no’ if you don’t want to date yourselves. As for only understanding half of what we’re talking about don’t worry about it. On a really good day, after re-reading my posts, I’m lucky if I can understand half of what I’ve written so looks like our comprehension is about even. 😡
All questions and help is appreciated up here.

Thanks guys,
Bob

[tmac1956]

Bob/David:

OK… I’ve been reading the PDF’s provided by Bob and i have a question. Up to this point, I’ve only hardened steel as directed in the video using a saline solution. If I wanted to do an oil quenching, what type of oil would I use?

Thanks!
Tom

[Bob Tascione]

Now that’s a really good question!!

There will be a lot of space between the points I’ll mention here that can be filled with technical and complex explanation but I’ll leave that to someone that knows what they’re talking about.
There are commercial quenching oils available which work great but many trades people use different types of ‘home’ oils depending on the type of metal, complexity of the part and desired hardness. These oils range anywhere from say standard motor oils, different types of vegetable, linseed, mineral, fish, paraffin and fuel oils like kerosene etc. etc. Some of these oils will harden more than others. It depends on the specific heat of the oil. The higher the specific heat the harder the results. Oil quenching will produce a better balance between toughness, hardness, and warp-age than the brine used in the videos or plain water. Brine will produce the hardest surface with water following close behind. Both brine and water will leave a fairly clean surface. Oil will not harden as much as it doesn’t permit the metal to cool as quickly as the saline or pure water. The faster the cooling the harder the results. With rapid cooling comes the danger of cracking or shattering which is especially true with parts having sharp corners, shoulders and edges. Complex parts tend to warp much more with brine or pure water quenches than with oil. Also some metals are more suited to water quench and some to oil or air. David and I used to do our own heat treating in the tool rooms heat treating depts. These were highly controlled environments. We would always know the upper and lower critical points that a particular metals temperature needed to fall between. Under the lower critical point and no hardening took place after quench, a little above and results were unpredictable. We would normally take it right to the upper limit to allow for slight cooling during the transfer from oven to quench. The ovens pretty much did all the work. After setting them up you just waited ‘trance like’ until the parts reached the required temperature. There are times when it’s much more complicated than this as David mentioned in an earlier post. Some metals require vacuums and gases etc. but for normal heat treating of metals like 01, 52100 etc. it was pretty straight forward. I can’t cook a turkey without blowing it up so that should tell you something about how easy standard heat treating for manufacturing really is. Then there’s the way real people do it in ‘real’ life. That’s knife and sword makers, blacksmiths and home machinists and backyard inventors. That’s us. That’s more of an art form. Very enjoyable. We determine temps by testing and heating the metal and then watch the ‘heat rainbow’ change from one shade to another until we reach the color that will suit our needs then quickly quench and agitate the part in a witches brew of whatever we determine will produce the results we’re looking for. Maybe we dip it into a powder or paste of boric acid to keep scale from forming then wrap it up in iron binding wire to prevent warp-age. That’s the magic of it all. More of a dance than a trance.
So, what type of oil should you use? What do you have in the cupboard that you can sneak past the cook?

Bob
NOTE: CAUTION…any oil can ignite when a hot part hits it so keep an eye out. Also bigger parts make bigger flames!

[david pierce]

Tom, Bob,
I have a personal rule of no open flames inside my house. This especially includes welding or anything else that involves a tourch. I clear an open space on my driveway and have a large fire extinguisher on hand. When I was experimenting with NAPTHA as a cleaning solvent in my ultrasonic cleaner, I took it out to my driveway and used it there first. When I do it now (inside) I still put it in a sink just in case.
Oil can and does sometimes flame when a red hot piece of steel is dropped into it. I recommend a fairly heavy metal container that will not easily tip over plus a metal lid to cut off the oxygen supply if the oil should flame up. If your are holding the part with your pliers you don’t want to accidently knock the can over when you are swirling the part around in the oil. A cooking pot with a lid will work. You can use pretty much any oil however peanut oil does not smell as bad as nasty motor oil when it is used for this purpose. The tempering can be done in a toaster oven if you want a little more consistancy with your temperature control.
By the way. You said that your rod was S7. S7 is an air hardening steel. The material is designed to give its best performance when hardened this way. All you have to do is heat it to the proper temperature (1700-1750) degrees and then blow air on it. All of the expensive materials that went into making this steel give it this property. We used to heat air hardening tool steel in a small gas furnace after sealing it in stainless steel foil. When the proper temperature was reached the foil was removed and the part was cooled with a small pedestal desk fan.
david

[tmac1956]

@Bob Tascione wrote:

Now that’s a really good question!!

There will be a lot of space between the points I’ll mention here that can be filled with technical and complex explanation but I’ll leave that to someone that knows what they’re talking about.
There are commercial quenching oils available which work great but many trades people use different types of ‘home’ oils depending on the type of metal, complexity of the part and desired hardness. These oils range anywhere from say standard motor oils, different types of vegetable, linseed, mineral, fish, paraffin and fuel oils like kerosene etc. etc. Some of these oils will harden more than others. It depends on the specific heat of the oil. The higher the specific heat the harder the results. Oil quenching will produce a better balance between toughness, hardness, and warp-age than the brine used in the videos or plain water. Brine will produce the hardest surface with water following close behind. Both brine and water will leave a fairly clean surface. Oil will not harden as much as it doesn’t permit the metal to cool as quickly as the saline or pure water. The faster the cooling the harder the results. With rapid cooling comes the danger of cracking or shattering which is especially true with parts having sharp corners, shoulders and edges. Complex parts tend to warp much more with brine or pure water quenches than with oil. Also some metals are more suited to water quench and some to oil or air. David and I used to do our own heat treating in the tool rooms heat treating depts. These were highly controlled environments. We would always know the upper and lower critical points that a particular metals temperature needed to fall between. Under the lower critical point and no hardening took place after quench, a little above and results were unpredictable. We would normally take it right to the upper limit to allow for slight cooling during the transfer from oven to quench. The ovens pretty much did all the work. After setting them up you just waited ‘trance like’ until the parts reached the required temperature. There are times when it’s much more complicated than this as David mentioned in an earlier post. Some metals require vacuums and gases etc. but for normal heat treating of metals like 01, 52100 etc. it was pretty straight forward. I can’t cook a turkey without blowing it up so that should tell you something about how easy standard heat treating for manufacturing really is. Then there’s the way real people do it in ‘real’ life. That’s knife and sword makers, blacksmiths and home machinists and backyard inventors. That’s us. That’s more of an art form. Very enjoyable. We determine temps by testing and heating the metal and then watch the ‘heat rainbow’ change from one shade to another until we reach the color that will suit our needs then quickly quench and agitate the part in a witches brew of whatever we determine will produce the results we’re looking for. Maybe we dip it into a powder or paste of boric acid to keep scale from forming then wrap it up in iron binding wire to prevent warp-age. That’s the magic of it all. More of a dance than a trance.
So, what type of oil should you use? What do you have in the cupboard that you can sneak past the cook?

Bob
NOTE: CAUTION…any oil can ignite when a hot part hits it so keep an eye out. Also bigger parts make bigger flames!

Bob:

I have a former student and now buddy (yea I know that’s rare) who makes swords, knives, and armor doing the blacksmith thingy, so I think I’ll pick his brain about how he heats he metals. I do know that he has a home built furnace that is fired by propane. Anyway – every time I talk to him I get the feeling that what he does is more alchemy than science. He just made a batch of mead (he has bees as well) so I think I’ll drink some of that. It’ll all make sense then.

This is really helpful!
Later,
Tom

[Bob Tascione]

Wow Tom if at all possible pick his brain! Those blacksmiths know all the oldtime tricks. Can’t think of any other trade that gets you that close and intimate to the steel they’re working with. Also pass any info along to us please!!
In fact…since this is a members only forum you might ask if he has an interest in Clocks and/or Watches. If so I would be happy to give him a free membership to the Ultra course just so we can drag him up here to ask a few ‘occasional’ questions. Purely selfish motivation on my part I might add.
Just had a talk with David this morning about Japanese sword and wood chisel making. Hadn’t heard about the chisels before. Interesting heat treating techniques. You friend probably knows a lot about the process.
If he doesn’t have much interest in horology maybe you can coax him a little by letting him know that it was the Blacksmith that made our first clocks! They were the first Clockmakers.

Bob

[tmac1956]

Bob:

I will pass along the invitation and get back to you.

Thanks!
Tom

[tmac1956]

Guys:

I threaded the 3/16″dia. S7 steel rod and it seemed to work OK. However, when I look at the threads they appear to be a little “chewed up”. I turned the die about two turns and then backed it up so as to clear the material out before repeating the process. The thread die is HSS. They accept the nut just fine, but it bothers me that the threads look this way. Is it the steel, or is it me?

Thoughts?

P.s. I guess you can tell this is the first time I’ve ever done this.

Thanks!
Tom

[david pierce]

Tom,
It is possible that a different tapping fluid will produce a nicer looking thread. We used a tapping fluid of last resort called MOLLY DEE. It was some really nasty smelling stuff but it worked well.
david

[tmac1956]

david:

I used Tap Magic, but I don’t have a particular affinity for it. I’ll certainly give your recommendation a try.

Thanks!
Tom

[david pierce]

Tom,
If you used the TAP MAGIC that contains TRICHLOROETHANE (the thin watery stuff), it will not work well with hand tapping. It works great under power where enough frictional heat is generated to cause the liquid to fume off, but with hand tapping it is just a watery liquid. It is essentially dry cleaning fluid. If you put this stuff in a container and heat it, the fumes will disolve the grease off of a shop rag. We used it for years and the entire shop smelled like burned cinnamon every single day all day long. For health reasons we switched to other less toxic chemicals.
david

[tmac1956]

david:

Thanks! I have some of your stuff ordered.

Later,
Tom

[tmac1956]

David, et. al.

I want to machine some custom punches and I’m looking at using some drill rod. I’ll be hardeninig them myself. Would A2 tool steel drill rod be appropriate? I have some 2L14 steel rod on hand but I think it might be too softn even after trying to harden it.

Your thoughts?

Thanks!
Tom

[david pierce]

Tom,
I have not heard of 2L14 before. I have heard of 12L14 and 12L14 with tellurirm. Both of these are called screw machine stock; also known as leaded stock. You can bury a cutter into the steel, run the RPMs up and and produce a finish that looks like it was polished. The tinsile strength is relatively low @68,000 psi. The carbon content is extremely low .09% and it contains .15%-.35% lead. There is no steel that I know of that machined as well as this stuff but it was extremely difficult if not impossible to weld. Steels designed to be hardened contain a carbon content of .3% up to 1.02%. The higher end carbon content steels are used for low tinsile strength high hardness applications such as ball bearings.
A2 would be a much better choice for a punch and die.
david

[david pierce]

Bob,
The video of the clock makers, for which you provided a link, showed a clockmaker cutting a hand made dovetail. The chisel he was using was a Japanese chisel. Unlike the English and American chisels which are designed to be driven with a wooden mallet, the Japanese chisels are designed to be driven with a steel hammer.
david

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