SReynolds Posted August 7, 2012 Share Posted August 7, 2012 So I'm told by a knife manufacturer/seller of knife blades, that lead hardened carbon steel is "best" for a knife ?? I had never heard of that.......... Anyway, take high carbon blade and plunge it into boiling lead, then quickly quench in water. I was informed this is a very very old-school method that results in the best tempering. The edge lasts for a very very long time............ I know nothing about hardening as it don't work for me. You have to stand one one ear and only when the moon is waxing and then only on the second tuesday of month. Somebody once explaind to me how to harden spring steel and I was way lost and then when you ask another person same question, you get a totally different reply. "Water cools fastest" "Water cools slowest" "Quench after running colors" "Do NOT quench after running the colors" Thank the Lord for low carbon steel. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted August 7, 2012 Share Posted August 7, 2012 Lead baths were used, and still are used, for some shaving razors. I am sure there are many other blades, springs, and other hardened items that were manufactured with a lead bath. It is the heat for hardening since lead melts at 621F. It boils at 3182F which is much hotter than desired. Since the lead will wet and protect the blade, scale does not have a chance to form. There still needs to be a tempering step after the quench. Molten salt baths are commonly employed for the same process in modern industry. Phil Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted August 7, 2012 Share Posted August 7, 2012 Actually yoir question may help you a lot in knowing about how to harden high carbon steel and it may also go a ways in trusting the advice you receive. However For me to type a short answer here will not help you at all. Almost all of us that get abreviated answers lose them in our memory bank. It would be nice if I could send you to the heat treat stickies on this site and trust that it would be of value. Maybe it will someday. So try a couple of things for your answer. A high carbon steel I like for hunting knives is 1084. It has enough carbon to do wot a blades should and the heat treat is a process that almost anyone can do in a home shop. Ask google about lthe heat treat process for this steel. Likely will point yoiu to a few sites. Look at the hardening temperatures required. and make a note on each of a coupe of sites Then google the melting temp of lead. And the boiling temp of lead.Make a note of that and compare wot the steel needs with wot lead can do. If you still are curious about wot you have been told, on the steel heat treat sites. look at wot quenchant the company that made the steel suggests to quench in after reaching proper temps, And if you wish further info: A steel such as 1084 that has been hardened will be too hard and brittle for use as a blade. It must be heated to a different temp and that will make it softer to a degree that allows it to be a blade.. Check those temps out while yoiua re at it. And to help with some of that confusion. Some charts say for a RC scale of this much,,heat at this temp for this long...Wot that means is that more heat during tlempering cycle can make the steel softer than less heat. SAy one temp at a set time will produce a 58rc hardness. while a higher temp at a set temp may produce a 52rc scale hardness. A knife maker will select what he wishes the hardness to be. and then use those guidelines to ,make his steel as good as possible for its future use. You may even wish to look back at the temp of molten lead to see if it fits into this process. Hope this does not confuse you even more. Quote Link to comment Share on other sites More sharing options...
SReynolds Posted August 7, 2012 Author Share Posted August 7, 2012 I would have to buy some "known steel" and have the exact specifications in which to harden/temper, then I could say that I know what I'm doing......with THAT steel and THAT steel only. For anyone to guess how to do it properly, with an unknown steel is like saying I know how to play the piano. I know how to play a piano, but I can't really "play" a piano outside chop sticks. Know what I'm saying. Phil had described how to harden and temper a particular spring steel he had given me. It was several weeks ago and I can't recall what to do. Before I try that, I'd have to get the specifics again. To attempt to wing it is a waste of time in my book. It don't work and the steel splits apart right after quenching it. To forge it then have it break apart is a waste. I haven't gotten to the pint of buying any known carbon steel. Then I won't feel so badly about working with it as I'd have some idea as to what to do. Quote Link to comment Share on other sites More sharing options...
John B Posted August 7, 2012 Share Posted August 7, 2012 So I'm told by a knife manufacturer/seller of knife blades, that lead hardened carbon steel is "best" for a knife ?? I had never heard of that.......... Anyway, take high carbon blade and plunge it into boiling lead, then quickly quench in water. I was informed this is a very very old-school method that results in the best tempering. " As a bit of a fossil working in the industry for over 50 years, I think something here is incorrect, Hardened steels were tempered using lead and tin alloys in a molten state in a bath or tank and sometimes boiling linseed oil was also used as a tempering medium. After the hardening quench tools/blades were then placed in these baths or tanks. It was a precise way to control the heat as various alloys became molten at specific temperatures.. For example if tempering razors, a mix of 7 parts lead to 4 parts tin would be used, and this bacame molten at 420 degrees F that is in the pale yellow range, For axes or pocket knifes the ratio would be 19 lead to 4 tin and this became molten at 509 degrees F equivalent to Brown yellow For swords or watch springs 48 lead to 4 tin, equivalent to 550 degrees F or Purple Interestingly, now for an 8 degree rise, used for large springs or daggers, 50 parts lead to 2 parts tin gives a clear blue Boiling linseed oil is used for some hand saws and springs and is 600 degrees F For your softer items molten lead starts at 600 degrees F By allowing the items to soak in the tank for an appropriate length of time, the tempering was even throughout the workpieces So to sum up Hardening is done by quenching in the appropriate medium, and a lead/tin bath is used to temper the steel Salts also have their own particular melting point and can be used in the heat treating hardening process. Quote Link to comment Share on other sites More sharing options...
SReynolds Posted August 7, 2012 Author Share Posted August 7, 2012 That makes sense, but I read that when this razor maker performs the task, the razor is hand forged, thrust into molten lead and then quenched in water. Thus making it harder.The method of soaking was mentioned, but that makes perfect sense to perform the tasik that way as it would be no guess-work involved. Soak the durn thing at 525°F at thirty minutes sure as heck beats polishing and slowly heating to a particular color and hope the colors don't run out/off the spectrum prior to the next step of air cooling or quenching in something to stop the colors etc.etc. That however won't work for a chisel or horse shoe pritchel though would it ??? The entire thing would be soft, even the cutting edge. You'd have to heat that from the struck end to soften and run colors to the cutting end, eh??? Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted August 7, 2012 Share Posted August 7, 2012 What the lead quench is doing is dropping the temp down to a lower one with less shock than going straight to the water alone. Quote Link to comment Share on other sites More sharing options...
mat Posted August 7, 2012 Share Posted August 7, 2012 this is a neat old vid heat treating using lead. http://www.britishpathe.com/video/the-sword Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted August 7, 2012 Share Posted August 7, 2012 Big gun that really depends on the temp of the lead,,He mentioned boiling lead...over 3000f,,too hot for any of the steels I use, if it is left in there long enought to reach that temp. Molten lead is on the high end of the temps I use for tempering steels I use,,,and again that depends on the length of time in the lead. My whole point of the post was simply that he was told things that make no sense with the information given. The suggestions that I gave to research a bit clearly showed that. John B posted valid data to define wot could be done with lead alloys. To speak of heat treating we need lots of blanks filled in to define needs and then select a process. When that is done and we stick to just a few steels this is something most anyone can do at home with minimum smithing equipment. Those blanks are easy with information on this site and a wee bit of help from google. Quote Link to comment Share on other sites More sharing options...
Dogsoldat Posted August 8, 2012 Share Posted August 8, 2012 That is a most interesting video. Wife didn't like the idea of me building a drop hammer similiar to that, especially her powering it :) Quote Link to comment Share on other sites More sharing options...
pkrankow Posted August 8, 2012 Share Posted August 8, 2012 Thank you John B That was enlightening. The video is interesting as well Mat. Phil Quote Link to comment Share on other sites More sharing options...
ianinsa Posted August 8, 2012 Share Posted August 8, 2012 I wonder how little "Old Tom" was paid neat video . Thanks for posting Quote Link to comment Share on other sites More sharing options...
thingmaker3 Posted August 8, 2012 Share Posted August 8, 2012 Just a quick note, since no one has mentioned it yet: Molten lead and especially boiling lead produce unhealthy fumes. Use adequate ventalation and a respirator specifically designed for said fumes. If you plan to try HT with lead, you can check the NIOSH website for more information. Quote Link to comment Share on other sites More sharing options...
forgemaster Posted September 5, 2012 Share Posted September 5, 2012 Steel strapping used to strap pallets for transport etc is normmally heated for HT in a lead bath so as it doesnt scale up. Thats the limit of all I know about it. Can find out more if needed,(theres a stapping plant in town that one of my ex apprentices worked at) Phil Quote Link to comment Share on other sites More sharing options...
mat Posted September 23, 2012 Share Posted September 23, 2012 more use of lead in this vid Straight Razors Quote Link to comment Share on other sites More sharing options...
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