resurface chipper bits???

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The owner of a large construction company called me today. He does a lot of wood chipping and runs through bits. The bits are 2.5" square and bolt onto the chipper drum. When new, the top edges are coated with  weld with carbide chipps embedded. once this edge wears off, the bit wears rapidly. My question is; what rod, stick or tig, if any, would be approiated for building up these worn down bits?ThanksWesMiller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:Apparently the teeth are off a tub grinder, not a chipper. Attached ImagesLast edited by wagin; 04-14-2010 at 11:09 PM.Reason: picturesMiller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:You can get some electrode products from Stoody with carbides, but looking at the pics, the large chunks look like stuff Kennametal offers for brazing.Matt
Reply:Wagin, did you mean to say it's a Stump grinder? If so, it has to have higher impact resistance than if it just cut wood because of the stones in the ground. Stoody and other companies make a good selection of materials, and generally they can give the best advice about their products; I'd recommend calling them with a detailed question.
Reply:If it's a mobile tub grinder they often feed huge piles of slash that have been push up with dozers and such. A lot of dirt and rocks going into the mix. Huge dust clouds .."The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:Thanks for all the info. guys.It is a Mobile tub grinder and in the second conversation the owner talked about pushed up piles having dirt and rock.I researched the job and decided on building up the severely worn areas with MIG weld. Then using Hard alloy 118/ 1/8"D stick rod to hard surface the hammers. The rod properties are: 20 Rc hardness when applied and work hardens to 55Rc while having a high impact rating. Here's pics of the finished, resurfaced hammers.ThanksWes Attached ImagesMiller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:Stoody or McKay both make electrodes that will deposit chrome carbides in an austenitic steel matrix.  I've also seen applications where the carbide held in a metal binder and an oxy-acetylene torch or TIG torch is used to braze/weld the composite to the base metal.  Wal lColmonoy (http://www.wallcolmonoy.com/Products...lications.html) makes some good products for this kind of application, but they are very expensive because they are high in cobalt.  Hardalloy  118 should be a good hardfacing choice too, if the bits are high manganese steel.  120 or 155 would be better if the bits are low alloy steel.  I'm curious, did the customer give you a new bit to examine?  I ask because I was surprised at the amount of buildup on the bits you show in the after photos.  I don't know what they look like when they're new.  So I was wondering if you had anything to go by for judgeing how much buildup and hardfacing to do...Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:The company I work for also has grinders. The teeth for out machine are something like 8$ ea. So building them back up would not be very cost effective. I would like to know how the teeth you rebuilt last compared to the original ones. I weld on the hammers using 7100 wire for build up and stoody 31 or 35 for hard face. The hard face likes to chip off in time though.thermal arc mst400, va4000 feeder, lincoln 175 min, victor torches, miller s32p feeder, air arc k4000 for work.
Reply:From research, some manufactures use T1 steel to cast the hammers and the apply a hard surface weld with carbide tungsten flakes.Yes I had access to new hammers and took measurements. The hammers I resurfaced look very similar to the new, minus all the bead definitions.I'm delivering the re worked hammers tomorrow. They are to be put into service to see how they hold up.Oh yeh..a new hammer costs $18.00.Miller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:Thanks for the followup posting.  I guessed that you had some guidance for how much buildup and hardfacing to apply.  Wow, at $18 a piece I'm surprised they're cost effective to restore and hardface.  Unless your customer is hoping that the repaired parts will last longer than the new ones...then it makes sense.How many hammers are used by the machine?Thanks for the original posting. Originally Posted by waginFrom research, some manufactures use T1 steel to cast the hammers and the apply a hard surface weld with carbide tungsten flakes.Yes I had access to new hammers and took measurements. The hammers I resurfaced look very similar to the new, minus all the bead definitions.I'm delivering the re worked hammers tomorrow. They are to be put into service to see how they hold up.Oh yeh..a new hammer costs $18.00.
Reply:Great repair. I always wonder what hard face to use on certain jobs.Please let us know how they hold up.
Reply:Originally Posted by A_DAB_will_doThanks for the followup posting.  I guessed that you had some guidance for how much buildup and hardfacing to apply.  Wow, at $18 a piece I'm surprised they're cost effective to restore and hardface.  Unless your customer is hoping that the repaired parts will last longer than the new ones...then it makes sense.How many hammers are used by the machine?Thanks for the original posting.
Reply:Good Luck Wagin,It looks like you could carve out a small re-manufacturing market for yourself here. I would also pay attention to the seat area and watch for deformation of the tool bottom from welding/brazing.There is a page of tool tips here (one similar to your post attached below);http://www.the-trader.com/html/carbide_patterns.htmlHere is a Kennametal PDF brocure for Tuf-Kote (carbide solids in matrix). I couldn't find one showing the larger chunks found on well drilling tools and railroad balast tamping tools that looks more like the sample grinder tool picture, but they make the stuff. There are premium asian imports also out there.http://www.kennametal.com/images/rep...tebrochure.pdfPhone calls are cheap when considering exotic materials, the makers don't want you to fail.RE;Then using Hard alloy 118/ 1/8"D stick rod to hard surface the hammers. The rod properties are: 20 Rc hardness when applied and work hardens to 55Rc while having a high impact rating.
Reply:Thanks for laying out the scope of the job.  That's a lot higher volume of work than I was imagining, and all of a sudden I see that you can make a tidy profit on this work.  6/hour @ $10 ea is good money.  36 hammers per week, is a solid day's work at a good rate.  I can see them stacked up on a work bench, and welding them out in an assembly line process.  One piece of advice that just occurred to me.  You may want to pay some attention to interpass temps on these if you're trying to crank them out.  There's probably an ideal number of hammers to queue up, so that by the time you finish a pass on the last one in a set, the first is just cooled enough to lay a good pass on.  If you can, you might get even better results by pre-heating them in an oven to a couple hundred °F.  Call your hardfacing filler metal supplier and have a thorough talk with their tech support guys.  They can give you the best pre-heat, interpass temp recommendations to get the ideal results. Originally Posted by waginI'm told when a grinder is in service a 40+ hour week, the hammers last a week. The before pics of the hammers show the wear resulting from a week in service, aprox.Switching to a FCAW hardfacing filler metal should up your productivity even more.  If you're doing 36 of these a week, I'm sure the volume of filler metal will more than justify the switch to a wire process....Food for thought.The number of hammers in a set vary by machine manufacture. This client has one that requires 12 hammers and a second that requires 24.This client has several hundred worn hammers that could potentially be re-surfaced, and stated contacts with owners of similar business.If the re-worked hammers prove longevity equal to or better than new. I plan to charge between  $9 and $10 per hammer, determined by quantity.I've established the process and once refined, I can re-work 4 to 6 hammers per hour.
Reply:A_DAB,Matt,Everyone,Thank you for taking interest in my project. The advice given by you Pro's is a great asset. I'm working to build a repeat client base and continuous revenue streams. The input y'all give helps greatly.WesleyMetal-Made.comMiller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180