Tempering steel

[Clencher]

Help, please guys. I need to temper/harden the blade on one of my land irons, copper nails are turning the edge which isn’t the object at all!

Granfer showed me how to do this back in the 1950s but the memory has dimmed. I have a vague recollection of heating, letting it cool to cherry red and then cold plunging, but there’s probably more to it than that. I'm not sure what the type of steel is in the blade so it may not take hardening/tempering but I have to give it a try. Many thanks.

(BTW I did a search on ‘temper’ and got a lot of weird stuff back, not what I’d intended at all.)

[AstoriaDave]

http://en.wikipedia.org/wiki/Tempering

[P.I. Stazzer-Newt]

Not sure what a "Land Iron" is, or how you use it, but it sounds as though you want a harder edge on a piece of steel.

You could heat the edge to a dull red and quench - I've seen old engine oil used as the bath.

But.

The risk is "embrittlement", where the edge (indeed the whole thing) can become hard but shatter-prone - real nasty in anything you plan to hit with a hammer.

"Tempering" is usually reserved for the heat and slow cool cycle which follows the hardening
The steel is then tempered by heating between the ranges of 150°C-260°C (300°F-500°F) and 370°C-650°C (700°F-1200°F). Tempering in the range of 260°C-370°C (500°F-700°F) is sometimes avoided to reduce temper brittling.

The whole process can be a bit "hit and miss" - I remember my father trying to make a new spring for an antique hammer shotgun - took seven or eight attempts to get just the right degree of "spring" without breaking.

[norseman]

Assuming the iron is spring steel or tool steel;

Hardening -Heat until non-magnetic or bright red, quench in lukewarm oil(vegetable oil or motor oil) or water while moving the iron back and forth to ensure cooling effect .
Annealing- Using a propane torch, a coal fire or similar - slowly heat until straw/bronze colour and quench again. Darker colour means softer edge but less brittle. This can be done twice to make sure.

You will need to stone or sand away some of the scale to see the coulour change (oxide layer) when tempering. A belt sander is my favourite. Any machining should be done before hardening.

[SamSam]

Help, please guys. I need to temper/harden the blade on one of my land irons, copper nails are turning the edge which isn’t the object at all!


I don't think you will get a temper that will cut copper nails without turning the edge, if that's what you want.

Here's a color chart of temperatures. It's a British site so it must be centigrade. Use Google Images to search for steel tempering.
http://www.westyorkssteel.com/images/tmpcha3.gif

[Ron Carter]

Noresman is spot on in his directions. You surely should be able to achieve an edge that will cut copper nails. That is assuning there is enough carbon in the steel to properly harden. If it is very low carbon you won't get a good result regardless of technique.

[Battenkiller]

Following Norseman's method, use a magnet to test the steel. When it no longer attracts then quench the steel immediately in the oil and swish continuously. You will know it is tool steel at this point if a file won't cut it.

Tempering is best done in an oven set at 375F for a hard temper. Leave it in for an hour. No need to quench for this step if done in an oven.

Test the blade. If it is still too soft, go through the whole process again but oven treat at a lower temp, maybe 325F. This will make a more brittle blade but the edge will be harder.

[pipefitter]

Another alternative would be to have it's cutting edge hard faced with a different harder alloy if cutting metal is what the tool is to be used for. The proper alloy will reduce the amount of times the tool has to be sharpened/heated which also will distemper the steel unless you are really careful.

[Clencher]

Thank you guys, that's just what I was looking for - the stuff I found on the web was too much metallurgy not enough 'hands on'. What I'd forgotten was the tempering after the hardening.

I've no doubt you have a different name for a land iron from me. It's simply one of those cold chisels with a flattened, cranked blade for cutting nails between planks when you want to take a plank out. Use with care or you'll do some damage. Don't ask me how I know this. Pic below shows the two I have, the one on the left needs hardening & tempering, the one on the right will do 20 nails or more before it needs a sharp-up.

http://pic40.picturetrail.com/VOL370/9115650/16752884/308720863.jpg

Thanks again.

[Battenkiller]

Clencher, it seems to me that you have a pretty shallow angle ground on your bevels. That could be part of the problem. You might think of grinding a secondary bevel that is a lot steeper. That's part of the reason a cold chisel can work on steel without getting dull. It's a combination of hardness and geometry. With an angle that is too shallow you will either turn the edge if the tool is tempered on the soft side or you will chip it if it is tempered on the hard side.

Also, now that I see the tool I can offer another suggestion. Just heat the front (working) half of the blade to a hardening temp. If you heat the whole thing and then quench the tool will be too brittle and will crack at the bend when you strike it, even if you temper it. Or you can re-heat the handle and the bent portion until blue colored and the quench immediately. This will put a spring temper in the back end of the tool while leaving the cutting edge hard.

One last thing. I'm sure you know but I'll say it anyway. If you are grinding the edge to sharpen it and it shows color at all you have taken the hard temper out of it. You don't have to "blue" a cold chisel to destroy the hard temper, even turning it light tan colored will turn it into a wood cutting only chisel. Test with a file. If you can easily file the edge it is too soft for metal.

[norseman]

That is an interesting tool you've got. Hmmm maybe next winter ;). Lots of sound advise above.

now that I see the tool I can offer another suggestion. Just heat the front (working) half of the blade to a hardening temp. If you can easily file the edge it is too soft for metal.

This is spot on IMO. The whole process could be accomplished without heating the handle at all, heat from the handle forward during hardening and annealing or whatchacallit. To be safe,gring a flat say 1mm at the edge before hardening. Just run lightly across a grinding wheel. Otherwise the carbon may burn, especially if high-carbon steel. . This is similar to knife forging.

http://farm3.static.flickr.com/2175/2336093436_e20eac1efa.jpg

[Stiletto]

I remember my boss many years ago once showing me how to 'carburise' or add carbon to steel he was hardening by heating to a bright cherry red with an acetylene torch and then turning off the oxygen. The resultant sooty flame added a layer of carbon to the steel. The carbon added to the surface acts in the same way that the tyres thrown on top of a hot oil drum add temper to the steel when it is to be used for calypso music.

[Ron Carter]

Carburizing is good for surface hardening for wear etc. Typically only a few mil deep. On a cutting tool it would be sharpened through rather quickly.

Norseman, Good looking knife. What kind of steel?

[paladin]

Here's something that may help.....I have a copy of the Bowie Knife presently at the Smithsonian, made from Swedish Tool Steel tempered this way, you can shave with it, and for a fact it was wedged between the door and frame of a Huey above the latch mechanism, and an army dude whacked the back of the knife with an M-14 and sheared the latch and didn't scratch the knife....
www.threeplanes.net/toolsteel.html

[Clencher]

Thanks again guys - I knew I'd get sound practical advice here. Next time I'm at the boat I'll have a go at hardening and tempering just the last inch or so of the blade, and grind a steeper angle. This last is a very good point Battenkiller as the angle on grandfathers original is much steeper and the blade is a bit thicker too.

Here's a couple more pics of grandfather's original land iron doing the business the other week:

http://pic40.picturetrail.com/VOL370/9115650/16752884/308787787.jpg

http://pic40.picturetrail.com/VOL370/9115650/16752884/308787790.jpg

[pipefitter]

How about being that the iron is thick enough, using one of these with a standard 18tpi hacksaw blade? The Irons would surely last much longer and save a bunch of grinding. You can actually fish a longer blade through the gap created by the iron and control it from touching plank or frame with a paint stick to steer the blade on it's free end. Standard hacksaw blades are a universal fit for all air saws and it would buzz through those fasteners like butter, whether copper, bronze or iron. This isn't much more than a third of a blade but can use them longer of course.

http://i99.photobucket.com/albums/l309/tigmaster/PB190037.jpg

[Clencher]

That's a good idea Pipefitter. I don't have air but even manually, a hacksaw blade in a padsaw handle does work exactly as you describe. I've used one in this way on galvanised and bronze fastenings which a land iron is no good for. An air saw would sure speed it up.

Mind, in skilled, confident hands (not mine!) a land iron will get a plank out of a copper fastened boat in double quick time. I once watched grandfather take a plank out of a 12' 6" boat in about ten minutes with one; bang, bang, bang, bang, bang. What took longest was drawing the nails in the hood ends and transom where the land iron couldn't be used.

[SamSam]

I remember my boss many years ago once showing me how to 'carburise' or add carbon to steel he was hardening by heating to a bright cherry red with an acetylene torch and then turning off the oxygen. The resultant sooty flame added a layer of carbon to the steel. The carbon added to the surface acts in the same way that the tyres thrown on top of a hot oil drum add temper to the steel when it is to be used for calypso music.

I remember reading about Medieval swordmakers having a young boy handy to take a whiz on red hot swords, to impart some sort of benefit through (maybe) uriac acid.

[norseman]

Norseman, Good looking knife. What kind of steel?

Thank you Ron. It's Sheffield steel, about .8 -.9% carbon laminated with mild steel.
http://farm4.static.flickr.com/3132/2337931602_9a3b8154da.jpg

Here is an adze made as pipefitter says above by welding tool steel to an old hammer. This is one example of where you could heat the blade only. With some experience hardening and annealing can be done in one heat.
http://farm4.static.flickr.com/3040/2337091961_02111d81fc.jpg

[pipefitter]

That's a good idea Pipefitter. I don't have air but even manually, a hacksaw blade in a padsaw handle does work exactly as you describe. I've used one in this way on galvanised and bronze fastenings which a land iron is no good for. An air saw would sure speed it up.

Mind, in skilled, confident hands (not mine!) a land iron will get a plank out of a copper fastened boat in double quick time. I once watched grandfather take a plank out of a 12' 6" boat in about ten minutes with one; bang, bang, bang, bang, bang. What took longest was drawing the nails in the hood ends and transom where the land iron couldn't be used.

I am sure that someone used to using that iron would be quite efficient with it. I was just thinking about the fastener possibly being swept over, making the extraction of the severed fastener harder to remove from the frame being that the end is probably somewhat bent over before it is cut.

[pipefitter]

Thank you Ron. It's Sheffield steel, about .8 -.9% carbon laminated with mild steel.
http://farm4.static.flickr.com/3132/2337931602_9a3b8154da.jpg

Here is an adze made as pipefitter says above by welding tool steel to an old hammer. This is one example of where you could heat the blade only. With some experience hardening and annealing can be done in one heat.
http://farm4.static.flickr.com/3040/2337091961_02111d81fc.jpg

I wish I had more time to do that sort of metal work. I have always found metal forming and treatment fascinating. Great stuff there, norseman.

[Battenkiller]

Here is an adze made as pipefitter says above by welding tool steel to an old hammer. This is one example of where you could heat the blade only. With some experience hardening and annealing can be done in one heat.

Nice work, Norseman.

I meant to compliment you on that very handsome knife and now I see the beautiful adze you made. Forge welding in a coal fire is a skill beyond my level. I wish there was someone with your abilities locally. It'd be picking his brain for sure.

Do you do swords as well? Pattern welding? Love to see some pics if you do.

[Clencher]

Norseman - That knife is a work of art and the adze - wow! I have 4 or 5 old adze heads crying out for new blades - I wish I had your skills.

Pipefitter: "I am sure that someone used to using that iron would be quite efficient with it. I was just thinking about the fastener possibly being swept over, making the extraction of the severed fastener harder to remove from the frame being that the end is probably somewhat bent over before it is cut."

Quite right, this can happen (don't ask me how I know). The knack is to hit the land iron with just enough force to cut the nail cleanly. Under hit it and you'll just bend the nail in the hole and it's out with a hacksaw blade. Over hit it and you might drive the land iron far enough to break a frame or plank.

I've got some more pics of the whole process of driving a land iron. If there's interest I'll post 'em.

[donald branscom]

There are three kinds of steel for hardening.
Air hardened,oil hardened,and water hardened.
You have to know what you have.
Go to machinery's handbook for temperatures and times.

[norseman]

Thanks all! My work is more shipwrighting than blacksmithing but your comments are much appreciated. I took a course one winter and learned knifemaking from a real master. However about 50% of my blades are thrown away due to lap-welding errors. So I'm still experimenting with different steels and techniques. Initially the idea was to learn how to make mast hardware and as usual things got a little out of hand ;).

http://farm3.static.flickr.com/2041/2338438658_0bffbf06c8.jpg

http://farm3.static.flickr.com/2034/2337603435_a060250999.jpg

[pipefitter]

Really nice work, noresman.

Clencher, do you work on a lot of copper fastened boats? Post as many pics as you want. I would be curious, even if to see the boats themselves.

[Clencher]

Norseman - that really is impressive work - and I'm worrying about hardening the end of a blade? I should be ashamed. Shipwright and blacksmith, Norseman, that's my two granfers rolled into one.

Paladin, thank you for that link, excellent reference. I couldn't get it to work earlier but it just flew through and I've er made copy notes.

[ssor]

The tools in the picture appear to be plumbers caulking irons for lead filled joints on cast iron soil pipe. The method for heat treating such as those is to heat three inches of the working end to a bright red or cherry red. ( the color depends on the ambient light level) Then quench the last inch only in oil or water(try oil first) bring it out of the water and polish the end quickly with emery cloth on a stick and watch the heat color run towards the tip when the color is about the color of straw but before it goes to purple quench the entire tool. Check it with a file to see if you got it right. By using this method you have a very hard working end and a more malleable handle and striking end. When you apply a tool to a grinding wheel the pattern of sparks helps to define the carbon content of the steel. If the streams of sparks have many stars in them there is a high carbon content. If the color of the stream is very yellow you probably have a low alloy steel and if the color is more of a dull red and the spark stream is short with many stars you probably have an alloy steel that can be hardened and tempered.
edit to add:
Do a web search for spark testing tool steel. There is too much there to choose one site.

[PeterSibley]

http://farm4.static.flickr.com/3040/2337091961_02111d81fc.jpg

That ,Norseman , is a very good looking tool !:)

[Curtis George]

Hello
I took a coarse in black smithing a few years ago.

http://www.armourarchive.org/essays/essay__heat_treating.shtml

this web site is for armor. but the heat treating and color charts are very good.

Basically the heat treating (no matter how you do it.) makes carbon steel hard, and Annealing make the harden steel tough.

You need to use both methods to have a good hard, workable tool.

thats my two cents worth of it.
I hope it helps.
C.A.G.

[Mike DeHart]

Don't try to heat the tool with a typical propane blowtorch for hardening. There just isn't enough heat to do the job right. Also, a blowtorch flame has an excess of oxygen in the flame which will cause the carbon in the steel to migrate out. Carbon in the steel is what makes it harenable. Use an oxy-acetylene torch with the flame adjusted a little fuel rich. Or use a coal forge and forced air. Either will have an excess of available carbon that will preserve the hardening properties of the steel. Heat the steel to "cherry red" at the working end. Best to do this in dull light. Bright orange is not cherry red and will "burn" the steel, making it brittle. Cherry red is just a little brighter than the color of fresh blood. Pinch your finger in the tongs if you need a reference. Quench in oil by plunging the tool straight in vertically about 2 inches and move it up and down a little so you don't get a sharp transition from soft to hard zones. When all the red color is gone, drop the whole tool in until it cools. The steel should be dead hard at the blade, such that a file will skate off of it. It is too hard to use at this point and must be "tempered" or "drawn back" or it will shatter like glass when you strike it. DAMHIKT!

Polish the bevel face bright with fine sandpaper. Slowly heat the handle end. You can use the propane burner for this. Watch the polished surface for the tempering colors to start showing. For a chisel you want a "straw" color at the edge. Straw is a light gold-ish color. Heat slowly so you get the colors forming slowly and evenly. If you heat too fast and shoot past straw and get into purple or blue, you wrecked it and have to start over. If you heat too fast with a too hot flame, the surface of the tip will show straw, but the core of the tip will be hotter and softer. You are looking for a constant temperature through the whole cross section. When the straw color is at the edge, drop the whole tool in a bucket of water. If you need a reference for the tempering colors, polish a steel rod with sandpaper, heat one end, watch the colors run down the rod, and quench it. The colors will stay put and you can study them closely.

[Clencher]

Thanks again guys – I now have a library on hardening and tempering thanks to you. This Forum is amazing.
Mike D – that’s an excellent description and another good link from Curtis G.

Ssor - that's a good tp about the sparks. You could be right about the origin of of the iron I need to harden, I picked that up in a boat jumble for £1. The other one though I know was custom made as a land iron by a blacksmith for my grandfather.

Pipefitter, apologies I missed your question last night - yes over the years I’ve done quite a bit with copper fastened boats, but I am no pro – strictly amateur. I’ll go off and put some more pics in picturetrail and post anon so you can see what I'm trying to do.

[Clencher]

Really nice work, noresman.

Clencher, do you work on a lot of copper fastened boats? Post as many pics as you want. I would be curious, even if to see the boats themselves.

Pipefitter - here you go, this is what I'm up to, taking out garboards for replacement (I hope!)

http://pic40.picturetrail.com/VOL370/9115650/16752884/308960810.jpg

Land iron and big hammer ready.


http://pic40.picturetrail.com/VOL370/9115650/16752884/308960815.jpg

Land iron 'started' - I've just tapped it in gently between rib/frame/timber and the hog until I can feel it up against the nail. (Grandfather didn't mess about like this, he'd just put the iron in place and bang.)

http://pic40.picturetrail.com/VOL370/9115650/16752884/308960814.jpg

Land iron driven. The nail is cut through and you can see the rove has popped and the paint cracked. You can now just prise the rove and cut piece of nail out. Notice in this part of the boat I've attacked the other copper roves with an angle grinder to remove the peining so the roves will pop off and nails can be driven. This was because I wouldn't want to use the land iron to drive between the land garboard to hog for fear of damaging the keel and I know that no. 1 plank has some shakes near its edge and didn't want to do further damage.

http://pic40.picturetrail.com/VOL370/9115650/16752884/308960812.jpg

Cut nail through rib and ground roves popped off. Now what remains is to punch the nails through so they can be drawn from the outside.

http://pic40.picturetrail.com/VOL370/9115650/16752884/308960816.jpg

Object achieved, both garboards out. Whether I'll have the skill to put new ones in is another matter. I've been taking lots of pics as I go along and should I succeed, will post the whole process.

[norseman]

I have 4 or 5 old adze heads crying out for new blades

Nice boat Clencher and interesting topic.
A blacksmith should be able to rehab those adzes with solid tool steel welded on.
It's still a lot of work but a lot easier than making new ones from scratch.
Basically you cut and grind an x joint, weld with basic covered electrodes and forge the blade. Maybe Pipefitter will step in here and explain the welding process in more detail ;).