Welding on a Jack Hammer Bit

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Help me understand...Can I weld to a Jack Hammer Bit  ?I wish to insert a Jack Hammer Bit into a 1-1/2" schedule 80 carbon steel tube and ring weld it.I want to drive the tube in the ground about 6-7 foot for a core sample, then pull it back out.My thoughts are pre heat, post heat, and using 309, 316, 347 or even inconel ??Will it last.... or will it crack /Thanks.A puddle is a puddle ...
Reply:From what I understand jackhammer bits are often 1045, 8630, 1078, 9260 or 15B30 depending on the manufacturer. This makes them a medium to high carbon steel.1045 suggested welding is with low hydrogen electrodes like 7018, preheat and interpass temperature is usually 400 to 600 degrees F, slow cooled in something like vermiculite and stress relieved at 1050-1250 F. A note I've read is that 1045 should not be welded in the through-hardened, tempered and flame or induction hardened condition, so you may have to anneal the bit 1st.Info I've found on 8630 also recommends a LH rod like 7018 if welding to low carbon steel,  preheat and interpass temperature is also usually 400 to 600 degrees F, slow cooled and is usually heat treated afterwards.If I was going to do something like this I'd probably weld a solid into the pipe and drive it with a pin driver myself. Jackhammer bits are often reforged to sharpen them if broken, so it may be possible to take one, heat the end in a forge and upset the end to form a similar style driver.https://www.crowdersupply.com/pavingbreakertools2.htm.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:Make a head up to drive the rods that a hammer bit sockets in to. (cut one off if you have to)  That is how they generally make the compaction plates. Weld it and it will crack pretty quickly.Also while a jack hammer might knock in your tubes, it wont pull them out!
Reply:DWS, Thanks for the reply.I understand anneal, and I understand welding a solid to the tube and then using a driver. My intent was to use the ring on the bit (while still installed in the hammer) to retraced the tube from the ground. I guess I could drive the tube into the ground, then disconnect the hammer and retraced the bit by other mechanical means.Cheers..A puddle is a puddle ...
Reply:Originally Posted by jackdawgAlso while a jack hammer might knock in your tubes, it wont pull them out!
Reply:I hadn't really thought about pulling the pipe. I'm not sure if the hammer will work that way well from experience. Usually if I stick a bit, pulling up on the hammer while hammering never worked well for me. I'd always have to break out a 2nd bit and chip around the 1st bit to free it up. Of course I never tried hooking a hoist up to the bit to exert upward pressure while hammering.Typically to pull posts/ pipes like that we'd just wrap a chain around the post and pull them with the excavator. Welding a cross stop to keep the chain from sliding up the pipe would be my 1st thought.Years ago I had mixed results welding to hammer points. I made up a dirt shovel for our medium sized chipping gun using a really worn bit. It worked for a fairly good length of time before one of the guys tried to pry with it and the welds pulled out of the bit material. I will admit I really didn't know what I was doing way back when. It's only in the last few years that I really looked into welding/forging jackhammer bits as I was looking into using broken bits as anvil tooling..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:I weld hardened? demo bits fairly often. I tig weld them with no preheat and ER70S-2. If I was doing them in my shop I would preheat but the boss doesn't give me the time to do it. While I don't preheat with a torch, I heat them up quite a bit with the tig torch before I form the puddle. I might start the arc and let it sit for 5 or 10 seconds before forming the puddle and welding. These are 1"hex bit with a 4" plug welded to the end and used for compaction of soils/rock in a concrete testing lab. They break eventually but it's normally after many months of daily abuse. If I were doing your job I would preheat the shank to a few hundred degrees where the weld will be and do your best. Watch the heat line to make sure that you don't temper the end which will be inside of the jackhammer. If you try and mig weld them cold they will break immediately, haven't tried to stick weld them.
Reply:Originally Posted by Welder760Correct. I'll just pop the hammer off and pull the tube with a cable to the backhoe bucket.
Reply:What kind of hammer are we using for this project? Do you need to preserve the core sample that the pipe pulls out?What is the method to get the sample out of the tube?
Reply:Depending somewhat on soil type, I don't think you will get more than 6" of soil in the tube before the end plugs solid.
Reply:Originally Posted by bentDepending somewhat on soil type, I don't think you will get more than 6" of soil in the tube before the end plugs solid.
Reply:I was going to use a 90lbs Jack Hammer. Most likely an over kill as the soil is soft and with little rock. The top soil is muddy as its been raining for more than a week. As for removal of the core I had hoped to push it out from a slit at the top using a rod.I hadn't really though that it might plug up first ... interesting.Last edited by Welder760; 12-30-2015 at 09:44 PM.A puddle is a puddle ...
Reply:Dont matter how soft and muddy the top is. 6-7feet is a long way down. And its still iffy for a 90# hammer to sink it in without issues or binding.And yes, if it does get in there deep enough, it will be tough getting the tube cleared out.Lastly, assuming your going to need an 8' foot pipe to get 7 feet in, Your gonna have to get that 90 pounder 10 feet off ground level and operate it safely. Maybe you have this part planned out already but just some further thoughts on the subject.
Reply:BRAZE IT!  Silver braze, 50N or 56 is strongest but very expensive.  Bronze brazing is an inexpensive alternative and worth a try if you're allowed a second chance to go with silver afterwards.  Consider bronze brazing is around 45ksi tensile and low carbon steel is also similar.  Lh welding is obviously 70ksi and silver brazing comes in around 112ksi.  Silver brazing is done at a low enough temperature that cracking becomes much less of an issue.
Reply:Just to update this...I decided to have the bit pressed into a sleeve eliminating the weld.Thanks everyone for the info.A puddle is a puddle ...