kraythe Posted August 20, 2011 Share Posted August 20, 2011 Greetings. Attached is a spark test off some paving breaker bits I got used at the hardware store. I have an opinion on what the steel is but I would prefer not to bias the assessment. If anyone can help identify it, that would be great. All opinions are eagerly solicited. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted August 20, 2011 Share Posted August 20, 2011 I don't see the attachment. If you go through the archives you will see several discussions about the possibilities almost all of them trumped by one member who used to make the things as a business! Quote Link to comment Share on other sites More sharing options...
kraythe Posted August 20, 2011 Author Share Posted August 20, 2011 I don't see the attachment. If you go through the archives you will see several discussions about the possibilities almost all of them trumped by one member who used to make the things as a business! Yeah I couldnt upload the video. I ended up putting it on youtube. I have read a lot about spark testing .I am more interested in if my opinion is right or not. More of a cross check. Quote Link to comment Share on other sites More sharing options...
Old N Rusty Posted August 20, 2011 Share Posted August 20, 2011 If you have a known piece of H.C. tool steel, say a cold chisel from anywhere but the "any tool for $1.00" bin or "harb fret", MAYBE one from the place that sells "craftsman" brand tools Do a comparison test, spark the struck end, while your ears are still ringing go to a piece of ordinary mild steel, then hit the bit you want to test. It will be obvious there is a difference. What you want to see against a DARK background is sparks that travel a short distance then explode, some do travel farther. The mild steel sparks has some that explode, most travel. Cast iron sparks all explode in a very short distance. and wrought iron sparks has very few sparks that explode. It is the carbon init that makes the fireworks.......is this a TRICK question? Quote Link to comment Share on other sites More sharing options...
kraythe Posted August 20, 2011 Author Share Posted August 20, 2011 If you have a known piece of H.C. tool steel, say a cold chisel from anywhere but the "any tool for $1.00" bin or "harb fret", MAYBE one from the place that sells "craftsman" brand tools Do a comparison test, spark the struck end, while your ears are still ringing go to a piece of ordinary mild steel, then hit the bit you want to test. It will be obvious there is a difference. What you want to see against a DARK background is sparks that travel a short distance then explode, some do travel farther. The mild steel sparks has some that explode, most travel. Cast iron sparks all explode in a very short distance. and wrought iron sparks has very few sparks that explode. It is the carbon init that makes the fireworks.......is this a TRICK question? Uh no not really. Just wonder what poeple think it is. Did you look at the video? Quote Link to comment Share on other sites More sharing options...
Old N Rusty Posted August 20, 2011 Share Posted August 20, 2011 yup, I looked. Quote Link to comment Share on other sites More sharing options...
stevomiller Posted August 21, 2011 Share Posted August 21, 2011 I think that it is a pavement breaker ;~)' Do they have a manufacturer's mark on them? Quote Link to comment Share on other sites More sharing options...
MattBower Posted August 21, 2011 Share Posted August 21, 2011 I don't have a lot of confidence in my spark testing abilities, but breaker bits are overwhelmingly something in the range of 1040. That's according to Grant Sarver, who used to make the things and got all his major competitors' products analyzed. And it corresponds to the results I got when I had a piece of a bit analyzed. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted August 21, 2011 Share Posted August 21, 2011 The best answer is to build a library of samples from known stock so you can refer to these samples while spark testing. It is not expensive or difficult, but does require proper labeling of materials from known sources. Phil Quote Link to comment Share on other sites More sharing options...
Jason @ MacTalis Ironworks Posted August 24, 2011 Share Posted August 24, 2011 And, keep in mind, sparktesting is really only useful to get a ballpark idea of the carbon content, other minerals in the alloy can bugger spark tests all to heck. I use spark testing only to get an idea if something is high or low carbon, from there, I make a sample about 1/4 x 1 x 6 or so, cut it in half, and first quench in oil, checking for hardening with the file "skate test". If I don't get hardening, I try brine, then water. Once I have hardening, I put my sample in the vise and give it a good rap with the hammer to check it's brittleness, trying to break it. If it breaks, it requires tempering, if it doesn't, I find it is usually fine for most tool applications at full hard. If my sample broke, I then quench the second sample in the appropriate quenchant and run my temper up the piece and again play with it in the vise to see which temper point seems to be most suitable for my application. I know this method isn't new or anything, but just figured I'd put it out there again... Quote Link to comment Share on other sites More sharing options...
Francis Trez Cole Posted August 24, 2011 Share Posted August 24, 2011 What do you want to learn from the test? Jack hammer bits they are great for making tools. I like the idea of having a library of test pieces a metallurgist I know has about 8 different pieces from wrought iron to high tec tool steel and when some one has a question of what the scrap they have he pulls out the box and makes the person do the test. Good learning tool. Quote Link to comment Share on other sites More sharing options...
evfreek Posted August 24, 2011 Share Posted August 24, 2011 Could you show a similar test with known samples? Maybe your grinding wheel is making the sparks look funny. Also, your video does not show enough fine detail. Anyway, this is not the spark pattern from a simple 1040 type bit, which most are. Note that this is most, not all. I have several bits, and about 80-90% are the simple medium carbon steel. This is a high molybdenum alloy, with possibly some chromium (cannot tell with the fuzzy video). There is more moly than 4140, and I would guess an S series steel, even though most people think that pavement breaker bits are never made out of this kind of steel. Check my gallery photos. Quote Link to comment Share on other sites More sharing options...
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