Simple project, Making a tile chisel

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I am making a chisel to remove ceramic floor tile with my demolition hammer. I took a 4" brick mason's chisel and a chisel shaft that fits my demolition hammer and tapered them both. what would be the best process to use? I have mig (240V machine)(solid core .35) and I have stick (240V AC/DC). For the stick machine I have 6011, 7014, 7018 & some Messer 80T+. This is the second time I am doing this. The first time I didn't taper it enough and I used the mig. It held out for about 6 hours of constant hammering then broke. I know I burned in good, and it didn't break at the center of the weld. It actually broke at the edge of the weld and broke some of the original shaft, leaving a small piece of one shaft still welded to the other half.The first 2 pics show the failure of the first attempt, next is the pieces prepped for the second attempt. It might help if I understood why it failed, it almost looks like the weld held but the shaft was weakened and broke.Maybe I should fish plate it this time? Or sleeve the welded area with a pipe nipple?Last edited by bigb; 10-14-2011 at 11:16 PM.Miller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:next time shape the ends like a chisel point.  That way you can run a bead across the thickness then turn it over and grind out the root and weld other side.  After that alternate sides.  It is much easier than grinding a point.  The reason the joint broke is that you are welding tool steel.  I suggest that after you have welded the joint grind the weld a bit then heat it with a torch until it is blue.  Set it aside and let it cool in still air.  Hopefully it will temper the hardened area next to the weld and the connection will last a bit longer.  The reheat will also encourage the hydrogen to migrate out of the joint if you did not use low hydrogen rod such as E 7018.  Six hours of use is pretty good for just welding it but as you can see you have a brittle fracture.
Reply:SLEAVE IT ! way to brittle  to weld like that
Reply:They do make wide chisels to fit various hammers, especially the SDS plus ones. The older spline type ones are getting harder and harder to find around here.I never had much luck with this sort of thing either. I had about the same results you did when we tried to make a digging bit with an old chisel..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:First I agree that it lasting 6 hours on the first fix was pretty darn good...I also agree with the concept of using a sleeve ... But some other options might include making the top taper fit into a hole on the bottom end... so the force would be from the original metal to original metal...with the weld keeping it lined up.. hopefully..But it is pretty clear that some kind of heat treating is needed... not knowing the exact steel used makes that tricky.... but a good blacksmithing book might come in handy... like " The Complete Modern Blacksmith" by Alexander G. Weygers...  He gives several methods of hardening high carbon steel for use as tools... including for stone working tools.... The section ( page128) is interesting when describing the three main liquids for quenching steel... water, brine and oil...  He says that the outside will be the same hardness for all three... but that the slower inside cooling of the oil quench produces a more ductile inside... " the softer core makes the tool tough " is from that section of the book....   But as with most projects like this... one would need to heat the entire tool and then temper it according to function needed... So it would be heated, quenched and the sometimes selectively rewarmed to take out the brittleness... on these types of tools he shows using a heated sand box with the handle partially submerged  to introduce the heat starting at the handle and allowing the color of the working end to be monitored through its polished surface changing colors... so you can have a tough handle and shaft and still have a hardened tool cutting edge...Weldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.
Reply:Most likely an "S" type tool steel, if the chisel is expensive might be S-7 bigb. The 7014, 7018 and messer are all about the same because you need to temper the weld area at a pretty high heat.The area around the weld needs tempered above 1100F to live very long and should be hot for more than 15 minutes, 1/2 hour is better, don't worry if it gets to a dull red if you temper with a torch. Cooling in still air is OK.Good luckMatt
Reply:after you get the tile chiseled off,you may want to buy a needle scaler attacment for your air hammer  from hf to clean up the remaining thinset.miller thunderbolt 250vlincoln square wave tig 175 prolincoln idealarc mig sp250everlast tig 210EXTeverlast power plasma 50chicago electric (hf) 130 tig/90 arcchicago electric 90 amp flux wire3 sets oxy/acet
Reply:Thanks guys, I will try grinding it ito a flat chisel shape as suggested then sleeving it and heat treating it. DSW, they do make what I want but I am just having too much fun and learning here to go buy one!Miller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:Mig was just wrong, no time to fuse before filler metal blobbed up the joint, that is why we use run on/off tabs.I would torch weld it. Tig would be another option with preheat and maybe postheat, but flame will anneal the metal as you weld it. Then apply a nice slow cool to avoid hardening the H.A.Z. The edge of the weld is the brittle zone, it always is. By bringing up the whole area to temperature slowly, the grain structure has the best chance to relax. Sleeve or no sleeve, OFW or second choice GTAW and pre/post heat. Keep a small wire brush to clean between passes, a wire wheel would air quench it far too rapidly.  .That is my final answer Regis! City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:bigb, years ago I made a pipe pounding cap to fit over pipe that I was pounding into the ground to use as fence posts.  The cap took the pounding and the top of the pipe was only slightly deformed due to this cap which was made in two pieces, a size larger than the pipe used as the posts and a .250 top which I welded to it.  The welds around this pipe cap would break from the constant pounding of the sledge hammering.  After several repairs of my previous welds I finally used a rod which contained a high nickel content.  I think salmon colored, maybe manufactured by Eutectic. Don't have the number now but it didn't come apart after I used that rod and never rusted.  Used it for many years.  My point is maybe useing a rod with a high nickel content would work. BobLast edited by rhunt; 10-16-2011 at 07:24 AM.