# incredibly confused about hardening silver steel



## Anko (Mar 15, 2011)

Hi to all

Time has come and I need to make a custom tap for my boring head, in question is a M8x0,5

For this step I made a lot of reserach, in this forum and the net, but all I can get is a confusing 1000 metods to archieve the hardening process

some are extreme simple like "heat to cherry-red then quenching then temper", other come with a full cientific explanation and lots of temperatures ranges etc...

I only need to harder my custom tap (not made yet) at my home and I dont know how to proceed, this is all I have found and confused myself:

first heat up to "cherry-red", with a magnet check for the critical point (ok I understand it)

then quench the tap intro ??? 

1) water (ambient temperature or with ice cubes I dont know the diference): this as far as I know will give me the max hardening, but the steel will be too brittle.

2) oil: this will made it a little less brittle, but still brittle (cant tell more ???)

For like 30-60 seconds

Then the tempering:

First of, clean the black finish on the tool to see the steel color, then heat up to a emmmm straw color (white yellow I believe) or at any color depending the hardeness requiered (I seen a lots of color and degree list for tempering)

Then I dont know, some people let it slow cool in the air, some other quench it again I dont know in water or oil..

All I got is: 8mm Silver steel rod, a butane/propane torch, a magnet and burned motor oil

nothing to measure the temperature or a powerfull oven to let it temper for 2 hours (only a kitchen oven)

how I should proced? my thoughts:

Heat to the point that is not magnetic, then quench on oil then heat to yellow "straw" color then... ???

In my search in the forum see lots of you guys hardening stuff for your engines and tooling, seems like a so easy process, but finding a lot of ways to do it that Im just to confused to go on 

please some one can give me a straight answer on how to do?? I will appreciate it a lot

Saludos!


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## gbritnell (Mar 15, 2011)

First off it would help to know what kind of drill rod/silver steel you have. There are 3 basic types, air hardening, oil hardening and water hardening. The two most used types are oil and water.

 The process for heating is the same for both, heat the tool until it's no longer magnetic (carrot orange) and then immerse in the appropriate liquid. 

 The tool needs to be plunged straight in and swirled around. If you were to drop the tool in sideways one side would cool quicker than the other and the tool would warp very badly. 

 Some tools need to be tempered and some don't. I find that if the tool has sharp little projections, like a tap, it's best to temper it. The tempering process takes the brittleness out of the tool. The seat of the pants process is to polish a section of the tool and then slowly heat until it just starts to turn a light straw yellow. When it reaches that point immediately quench. 

 That should give you a satisfactory tool. 
gbritnell


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## Anko (Mar 15, 2011)

Thanks for the quick responce gbritnell!

I know that are 3 types, but mine I puscashed just for silver steel, so I dont know what of those type are, and I don't believe that the seller know either jaja has to be the more common I think

there is a way to tell the diference?? like the sparks that come out when grinding? (like a post here I read)



> and then slowly heat until it just starts to turn a light straw yellow. When it reaches that point immediately quench.



quench in the same appropriate liquid?? and about the appropriate liquid, should use that burned motor oil or water?? or ice water???

Thank again!

Saludos


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## Anko (Mar 15, 2011)

do you mean by appropriate liquid.. that the fact on use water or oil depends extrictly on what type or silver steel I got??

That mean that if I got, lets said, the water type and use oil to quench, the result will be a poor hardered tool???

how can tell what type of silver steel I got?

Saludos


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## jpeter (Mar 15, 2011)

I didn't read too many responses so this may be a repeat but here goes. Heat it cherry red. I like to do this while spinning it in a portable drill for uniform heating. Next, with your most athletic move, fast, quench it in oil and swurl it around in a figure 8 pattern until cool enough to touch for a moment, keep the drill turning for even cooling. If you don't swurl it it won't harden properly. If you quench it with a circular pattern it won't harden properly either. Try water for quench medium because its easier to get a gallon or so of it. Have it at room temperature. If the water feels warm it won't harden it, if its cold, like right out of the tap, it'll crack it. I find oil sometimes won't harden cheaper, lower carbon content, steel either. To temper it bake it like a cake in the oven for at least 1/2 hour at say 400 degrees. If I was tempering a tool like a punch I'd heat it up the shaft from the point with a torch and watch the colors turn at the tip but a tool like a tap needs a different approach cuz you need to put the heat right on the tip and only the skin would get to the desired color. The oven method allows the heat to get down into the steel. Tell the wife you're baking dinner. Grind it to shape and sharpen with a Dremal after you're done. There's lots of ways to do it but that's how I'd do it.


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## steamer (Mar 15, 2011)

Hi Anko,

With a tap, you want the cutting edges hard and sharp. You want the shank softer and tough.

You want it hard, but you don't want to burn the steel.

Take some iron wire, like the auto repair people use, and wrap the tap up in wire. NOT the zinc plated stuff!  Now dip the tap in liquid hand soap. Neatness does not count, just cover it with plenty of wire and dip in soap.

The wire and soap will help exclude air from the tap and help keep it from oxidation during heating.

The other thing the wire does is give you something to hang onto while you do it! ;D

Silver solder flux works here too, I am told, though I have'nt tried that.

Heat it up to "Cherry Red" and keep it there for a couple of minutes.

Quech in your "appropriate liquid" vertical while moving it around.

Remove the wire, and clean the tap.

Once you harden the tap, check it with a file. Should be harder than woodpecker lips! ;D

Now clean and polish the cutting edges really well. MIRROR SMOOTH take your time, this part is important!

With the tap pointing up, and looking at the CUTTING EDGES with a magnifying glass, heat the SHANK at the bottom with the torch with a gentle flame....JUST THE VERY BOTTOM WHERE YOU TURN THE TAP WITH A WRENCH!

As the tap gets hotter, you will watch the color move up the tap toward the cutting edges.

When the CUTTING EDGES turn a pale straw yellow, quench immediately in you "appropriate liquid". This will stop the tempering process, leave the shank softer and tougher, and just temper the cutting edges.

The cutting edges at the front of the tap doe most of the work, and need to be hard, so don't over do it.

This is how the clockmakers make they're tools, and it works well for me....just go easy with the torch, it won't take much to do this

If you go too far, you have to go back to the beginnig and harden it again....and most steels don't like doing this too many times. practice on a piece of steel first, just to get the feel for it.

Practice,practice, practice.... The best way to learn is to do, get a piece of tool steel and harden it, you'll find out. THEN make your tap...

Dave


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## GailInNM (Mar 15, 2011)

Anko,
Traditionally Silver steel referred to water hardening steel or drill rod which was basically a high carbon steel and roughly the same as US grade of W1. If just asking for silver steel this if probably what you got. Of the three grades of water, oil and air hardening, water hardening is the least expensive.

The difference in quenching media determines how fast the steel is cooled, with water cooling the fastest and air cooling the slowest. 

One way to tell them apart in the home shop is to cut two small pieces. Put a groove in in or drill a hole in them so you can suspend them with a non coated steel or iron wire while heating it. Heat and quench as the others have outlined. One one of them quench in oil and the other quench in water. You don't need to temper for this test. Test for hardness with a file. The file will not cut a fully hardened part. If you can't cut either of them, then you have oil hardening. If you can tell any difference in hardness between the two samples with the file test, then you have water hardening. 

From the above you would think that you could just water harden either of them and get it over with, but water hardening of oil hardening steel leads to poor toughness, distortion and other nasty things. It does get the steel hard however. 

Gail in NM


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## narrowgauger (Mar 15, 2011)

Hi Hanko,

lots of excellent responses so far. However 2 questions have not been posed, namely:

- what are you going to tap; aluminium, brass, steel or some exotic material
- how many holes are you going to tap; one, two or many.

if the answer is few holes and in a relatively soft material I would suggest that you are creating a problem by hardening in the first place. we often need a special tap to thread a few holes in brass on a model and simply produce the tap from silver steel rod and use it as it comes. Never fails and the likelihood of a broken tap is miniscule.

that's my take on the matter.

have fun
Bernard


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## TroyO (Mar 15, 2011)

I once had some interest in knife making and while I'm certainly no expert, I made a few that are still working. 

Yep, the best way to find your method is just to play with it some. The basics are simple... heat it up till it glows red and stops being atrracted to a magnet then dunk it in something to harden it. If you don't know what you got, try from slow cooling to fast.... air is slow, oil faster and water the fastest. After each try smack it with a hammer. When it breaks instead of smooshing, it's hard. Use the slowest method that gets it there. I find swishing/swirling to help keep it even, but maybe it just keeps me from getting bored.

That gets it "glass hard" where it will shatter rather than give.

Then, back off from full hardness by tempering. Again, any way you can apply heat will work. Throw it in a ~ 425 degree fahrenheit oven and you will be close. I used to use an old yardsale deep fryer filled with motor oil.

Some will swear on quenching in the urine of a virgin unicorn gathered at midnight on the summer solstice.... when really midnight of the winter solstice is obviously the correct time to drain your unicorn. :

In short.... there is a lot of "voodoo" involved hardening/tempering but you can get decent results in as simple and crude a method as you feel like doing. Don't get too tied up in it... play with it some and you will find your own Voodoo that works for you too! (Who do? You do!)

http://www.anvilfire.com/FAQ-articl...s.htm&titleName=Temper Colors : anvilfire.com


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## steamer (Mar 15, 2011)

Great Reference TroyO, Was looking for something like that.... ;D

Dave


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## Anko (Mar 16, 2011)

Thanks a lot for the responses!

I will make the test to see what type of silver steel I got! I will do the file test first and then the hammer fun!

For the kitchen oven temper, Im too young to get married yet, actually still living with my parents, but sure my mom will love "motor oiled tap in the kitchen oven" recipie jaja , but mine only reach 250°C at maximum and without something to check the temperature to tell if the 250° are true (these 250°C will be 482°F, it may work, but not sure if the oven will reach the 250°C true)



> With the tap pointing up, and looking at the CUTTING EDGES with a magnifying glass, heat the SHANK at the bottom with the torch with a gentle flame....JUST THE VERY BOTTOM WHERE YOU TURN THE TAP WITH A WRENCH!
> 
> As the tap gets hotter, you will watch the color move up the tap toward the cutting edges.
> 
> ...



Hi Steamer, again your post is a great help!, but I got some questions: if I heat the shank to do the temper, the heat will goin up heating the tap, then when reach the yellow straw color go to quench, but that mean that the shank of the tap will be at more temperature that the upper teeths, quenching all the tap maybe will make the more heated shank to get brittler??

And the last line, my english is betraying me, I know that the front teeths made all the work, but dont over do it, do you mean not to try temper again?

Narrowgauger:

jaja your right! its for only one hole in some scrap brass I found in my scap yard, and here I consulted my uncle that are a mechanic and he tell me the same thing! you are pure making problems!, all of you two are right, but this is not to make just a tap hole, is for learning how to harder the silver steel thing, Im still a beginer in machining and for future proyects and engines Im just sure that I will need to make special cutting tools and stuff that require hardness, so even this special tap maybe not requiere hardening, is a good opportunity to learn how to!

anyway thaks for the response! sure the hardening stuff are tedious, for future light cutters I will not harder the silver steel and use like you said

And yeah, there is a lot of ways to do, thats was I get confused! that "voodoo" thing is very tricky, now I get a general idea of this subject!

Great responses here! thanks for all! just came to mind maybe will be a good idea to create a special section in the forum (like there were said unit converter, downloads etc..) like a place where we can put all this info like articles how to hardening, how to calculate gears, tramming the tailstock and stuff, that kind of matters that are frequently of interest, just thinking :

until tomorrow!!

Saludos


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## steamer (Mar 16, 2011)

Hi Anko,

If you heat from the shank first, the shank will not be as hard as the front cutting edges. This is exactly what you want in a tap.

From the first quench from "cherry red" the steel is very hard. It is so hard that it can not be used as a tool without breaking. It is too brittle.

When you "draw the temper" , you are taking a piece of steel that is hard as glass from the first quench, and make it just a little softer so that it is not so brittle. It is tougher now.

You have to do it this way because that is how the steel behaves. There is no way to harden it to its final condition in one step.  First you must harden it, then you must temper it. It must be these two steps.

I hope that helps.



Dave


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## Mainer (Mar 16, 2011)

If you quench in water, you'll get better results if you boil the water first to drive the air out of it, then let it cool to room temperature before using it as a quench.

I don't know if it's available where you are, but "Keep Bryte Anti-Scale Compound" works very well to protect the metal against oxidation and scaling when you heat it up. The soft soap trick mentioned in a previous post also works. 

For tempering, I use the kitchen oven. Bake at 400F (About 200C) for 30 minutes or until done.

Brass can be very difficult to tap unless the tap is very sharp.


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## Antman (Mar 17, 2011)

I'm a bit late on this thread but thanks all for a most informative bunch of replies. I bought a meter of 12mm silver steel last month and have just started playing with it.

 Ant


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## Anko (Mar 17, 2011)

I do the test on the silver steel!

I heated up to the point there are not magnetic, hold the temperature for like 20 seconds then with all the speed that I can perform I turn off the torch, grab the piece and quench it

the piece in water: cant done anything with the file, then I use the hammer, several strikes was need to take a part off (only a part, the piece not exploted or anything like that)

The piece in oil: the same thing but when quenching I use the 8 figure for like 40 secs, the piece was hard but the file did remove some material, then with the hammer the punches slightly deform te piece, but no craks

(the burned motor oil I got was very dense)

so this mean that I have the water type..

Tomorrow I will do it to the custom tap! any recomendations about the water? like temperature?

Saludos


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## arnoldb (Mar 18, 2011)

Good going Anko.

Don't worry about the water temperature; just ordinary cool tap water will do fine.

And as you have now discovered, it's really easy to do - there really is not a lot of funny stuff involved.

Regards, Arnold


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## steamer (Mar 18, 2011)

Wrap the tool in Wire Anko and dip it in soft hand soap.

Hold the part by the wire basket. You can get it in the oil real fast that way.

Saludos! ;D

Dave


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## steamer (Mar 25, 2011)

Hey Anko! 


So what happened with your tap?

Dave


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