ytuyuty Posted January 7, 2016 Share Posted January 7, 2016 Critiques, please Newbie here, in the process of making some basic tools to make knives, flint strikers, and other little things. I am using junkyard steel for now, like leaf and coil springs. I found myself in need of a hot cut. So I made this chisel from a jack hammer bit (that was about 1-1/8 inches thick). It was hard as hell, had to work it really hot and coax it with a 4-lb sledge until I got it thinned out a bit. Obviously didn't turn out as planned, taller and thinner than I intended, but here it is. For my use it should be adequate, though. I ground an appleseed edge. Normalized it for 30 minutes when it became non-magnetic, but then I had trouble running the forge at a low enough heat to soak it at that color. It kept getting hotter. What can do to fix this? If I turn down the gas any lower it sputters out. Quenched in oil until ambient and immediately tempered at 450 deg F for 2 hours. Plan for second temper at 500 deg for 2 hours. I made a knife, but that was a little forging and a lot of grinding. This is the second thing I've ever forged, but the only grinding was to form the edge. The amount of scale loss was astonishing, I will have to plan better for that next time. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted January 7, 2016 Share Posted January 7, 2016 Looks like a slitting chisel. I use my slitting chisels a whole lot more than a thick chisel. Now normalizing is heating to critical temp and cooling in still air; did you mean soaking? Most Jackhammer bits are around 1050 that doesn't require a long soak. Was that warm oil? Check the hardness before you do a higher temper. Multiple temper cycles at the same temp are usually done. I only go higher when I feel it's too hard/brittle at the temper temp I am using. Quote Link to comment Share on other sites More sharing options...
ytuyuty Posted January 7, 2016 Author Share Posted January 7, 2016 Normalizing - After forging was complete, I heated it for 30 minutes at non-magnetic and then let it air cool. 1050? I have been playing a lot with leaf springs and coil springs, and the jack hammer bit was a helluva lot harder than either of those steels. It barely budged under a 4-pound sledge, unlike the spring steel. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted January 8, 2016 Share Posted January 8, 2016 please look up grain growth. Were the other pieces you tried the same size? Quote Link to comment Share on other sites More sharing options...
ytuyuty Posted January 8, 2016 Author Share Posted January 8, 2016 13 hours ago, ThomasPowers said: please look up grain growth. Were the other pieces you tried the same size? The references that I have suggest that jack hammer bits are S7 steel, and soak times for normalizing and hardening at 30 minutes per inch. Since the tool is 1 inch thick, I used 30 minutes. The only other piece I made was a 1/4" leaf spring knife blade, and I know that's just a knife-shaped object. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted January 8, 2016 Share Posted January 8, 2016 What reference is it? I would really like to know as a fellow on this forum's career was repointing bits and out of more than a million he had done he said only a handful were anything fancier than 1050. Now a LOT of Junkyard steel lists list jack hammer bits as S7 because in the alloy listing in Machinerys Handbook is said that it would be a great alloy for jackhammer bits; which it would. Solid gold makes great frying pans, titanium would make great non-rusting, light, strong car bodies---you see any gold fry pans around? (Save for the one in that National Geographic article on gold decades ago...) Got a Ti bodied car? So I'd like to track down your source and see where they got their information and follow it back till we get to a primary source and research *that*! Info on the net is a bit dodgy to say the least; give me half an hour and I can put up a web page claiming that *you* are a love child of Margret Thatcher and Elvis Presley, and once people start quoting other people it can get odd fast... Quote Link to comment Share on other sites More sharing options...
Charlotte Posted January 8, 2016 Share Posted January 8, 2016 Just two suggestions for you: One: buy a piece of S7 steel and compare spark test and forging difficulty to the bits you have. The results will settle it in your own mind. S7 is air hardening so normalizing etc is not really an issue in hot cuts in my mind. Two: Since you seem inclined to follow traditional techniques you should take a look at Mark Aspery's book "The Skills of A Blacksmith: Vol I" The chapter on Bottom Tools should interest you. Quote Link to comment Share on other sites More sharing options...
ytuyuty Posted January 8, 2016 Author Share Posted January 8, 2016 I understand that junkyard steel is a big unknown. For the past month I've been hammering on A36, leaf springs, coil springs and this jack hammer bit. That jack hammer bit was the toughest stuff I'll tried, by far. I had to get it really hot and pound it with a 4-pound hammer to get it to move. Is that consistent with 1050? The leaf spring was also pretty hard, but nowhere near as hard as the jack hammer bit. The coil spring was softer still. I did buy some A36 and W1 to make things out of known steel, but right now I'm playing with junk. I guess I really should stick with known steels. Aspery's Vol I purchased. Thanks all. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted January 8, 2016 Share Posted January 8, 2016 OK I dug out Grant Sarvers post on jackhammer bit steels from back in 2009: "Having been a manufacturer of paving breaker bits, I can tell you that no one uses S-7 or any real tool steel ( at least not in 1", 1-1/8, 1-1/4). I've had just about every one spectrographed. B&L is a modified 1045, Vulcan used to use 1078 but now uses 15B30, Pioneer/DelSteel is 1078 or 9260 for their "alloy" bits. Apex (my old brand) are 8630. These things sell new (at full discount) for about what tool steel costs per pound. Everybody is looking for the cheapest thing that will do the job. People expect these bits to be really great stuff, perception trumps reality every time. BTW: "Paving breaker" bits are solid, "jackhammer" bits have a hole down the center." Quote Link to comment Share on other sites More sharing options...
Charles R. Stevens Posted January 8, 2016 Share Posted January 8, 2016 Unless your using high red hardness tool steels ( H13,S7 etc.) anything other than normalizing is a waste of time for a hot cut tool. Thin is good for hot cut tools. Quote Link to comment Share on other sites More sharing options...
House of D Posted January 9, 2016 Share Posted January 9, 2016 I agree with Charles. It's a hot cut. Unless it a specialty steel.... Forge it, normalize It and put it to work. The odds of you messing up any hardening and tempering you did are very good especially when cutting large stock. I use A-33 for my hot stuff for that reason. Forge it, quench it, use it... If you get it over red hot toss it in the slack tub and go again. D Quote Link to comment Share on other sites More sharing options...
ytuyuty Posted January 9, 2016 Author Share Posted January 9, 2016 Great info, thanks again Quote Link to comment Share on other sites More sharing options...
bigfootnampa Posted January 9, 2016 Share Posted January 9, 2016 IME jackhammer bits and star drills do NOT behave like 1050! I think that they generally have trace alloy elements that make them much more wear resistant than plain 1050. I do not doubt that few are as exotic (or expensive) as S7 or H13... but they do seem to perform better than plain old 1050 for me. They do seem harder to forge.. impact resistance? They also seem to hold sharp points and edges better... abrasion resistance? I believe that they are often specialized alloys that mimic properties of steels like S7 but cost much less. It is amazing what a difference tiny percentages of alloying elements can make! Anyway, for my uses, these are good sources of cheap material that performs effectively! BTW I have found that they are significantly more difficult to grind! I often use my ceramic belts when rough grinding these steels. Possibly attributable to more abrasion resistance? I have long suspected that they have some silica traces, but I cannot be sure of that. Quote Link to comment Share on other sites More sharing options...
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