Jump to content
  • Announcements

    • Alan Longmire

      IMPORTANT Registration rules   02/12/2017

      Use your real name or you will NOT get in.  No aliases or nicknames, no numerals in your name. Do not use the words knives, blades, swords, forge, smith (unless that is your name of course) etc. We are all bladesmiths and knifemakers here.  If you feel you need an exception or are having difficulty registering, send a personal email to the forum registrar here.  

John N

Supporting Member
  • Content count

  • Joined

  • Last visited

  • Days Won


John N last won the day on June 20 2016

John N had the most liked content!

Community Reputation

13 Good


About John N

  • Birthday 04/18/1975

Contact Methods

  • Website URL
  • ICQ

Profile Information

  • Gender
  • Location
    Manchester UK

Recent Profile Visitors

250 profile views
  1. Blade warping O1

    * ahhh, just thought of a semi suitable analogy, its like bending a candy bar, a bit..... maybe..
  2. Blade warping O1

    If your grind is not even it will pull one way or the other no matter what you do ! For thin knives (kitchen) I harden first, then grind the bevels in. Not that much of a chore with modern ceramic belts. Remember you get a min or so to straighten any warps immediately after the quench, before it goes 'snappy' - I wear a a pair of the red welders gauntlets when I quench a blade, when its quenched, but still hot (guess 100 deg C or so?) a quick wipe with a rag, and then gentle 'push with thumbs' to take out any warp. Its odd, the blade feels different to me when its quenched, but before the M has finished forming. If you gently bend it to a new shape it just holds it.
  3. The check valve on the lower control valve could be faulty / not seating properly. The valves run through cast iron tubes that are pressed into the frame, one of these might have grabbed onto the valve and rotated a bit in the frame. The 'ball' check valve ( the one visible when you remove the ram cover) might not be seating / missing / or gasket obstructing the air passage (cut out) that provides the pneumatic buffer to the ram. The sleeve that the compressor piston runs in might have moved a bit vertically, changing the compression. The air 'supplement' holes (behind the 2 small square covers on the compressor end) might be obstructed. Oil has probably got something to do with it, incorrect grade / quantity consistency of supply etc. It might be a combination of a couple of things Its incorrect to say they are simple machines, the more you get to know air hammers, the more you realise you dont know everything about them ! I've worked on forging machinery 25 years, and still learning a lot about it !
  4. You might find the performance of the hammer worse with new piston rings. It takes the rings a long while to 'bed' against the insides of the cylinder. You will witness this on the old rings / wipers with their 'wear' pattern, which is really just bedding. IIRC your hammer is only a couple of years old, occasionally used ? it should just be at the 'bedding in point' not replacing them point, that should be 15 years in the future !
  5. First Kitchen Knife

    Lovely clean welding on the chain ! its nearly a seax'y kitchen knife
  6. Back in the game

    good to see you back at it Alan, very satisfying looking couple of pieces of work - hope you and yours are keeping well.
  7. Its a spring loaded cast iron wiper, sort of the opposite of a piston ring, as it pulls in against the rod with pressure from the spring, rather than pushing out against a cylinder liner. I do not think the 'assembly screws' coming loose will affect the performance of the hammer. They are only in there to allow it to be assembled. When I have been in a bind before I have just used 1/2" of matchstick to hold it all in place when the piston is re-assembled, with the reasoning that when it works its way out, 1/2 a matchstick will not damage anything. Once the piston is in position, the wipers can not collapse inwards, hence it just being an assembly screw.
  8. What did TZ say ? if you move the handlever a bit is there a position that the tup stays at the top ? most likely to be mechanical wear to the faces that meet to arrest the valves in a certain position to keep the the 'top setting' position (or floating ram or what ever they call it in chinglish). If you can find a handlever position where it stays at the top you will need to adjust the faces by welding up or whatever. There are no gaskets in the hammer that would cause this. I dont know where that information has come from. Piston rings, maybe. The Teng Zhou hammers I have seen were constructed to such a terrible standard nothing would surprise me when you get into it a bit.
  9. The solid stainless machined burner flare on my welding forge has pretty well eroded to nothing due to how hot it gets ! The burner stays cold at the gas injection end though, I assume that is because of all the cold propane, and air that is whistling down it.
  10. Issues with First Damascus Welds

    I have found success improves greatly if, after you have done your initial welding passes you chuck it straight back into the forge, let it get back up to welding heat and let it have a good soak at temp for 5 mins or so. Gives all the layers a chance to get to know each other before you start putting more work into the billet.
  11. Forging vs. Stock Removal

    When I purchase big lumps of die steel, from the big boys, they specify the grain flow direction so you can machine it in the correct orientation. I don't know enough to discredit this - I think they know enough to back it up http://www.somersforge.com/assets/public/pdfs/Somers%20Forge%20Die%20Steels%20Handbook.pdf
  12. Questionable pattern weld

    Im with you on this one Stew, the grain looks like crap (might have been you when you heated it to break it ?) - When ive snapped 15n20 / 20C (similar to your claimed recipe) Its looked homogeneous. Those horizontal lines look like bad welds to me. Normalise it a few times and make a knife !
  13. It was probably induction hardened originally. The 1/8" that matters heated up real quick, and got cold real quick. If I was to have a guess at material I would say 1040 / 1045 ish for that kind of tool. I have flame hardened en8 die blocks for power hammers (which is basically the same process / material as induction hardening) and got 60Rc from the quench before tempering back a bit to make them usable. - I did not undertake this process myself, used a pro heat treat firm. Your process is not dropping the temp fast enough, or the steel is auto tempering from the core, if I were to have a guess at whats going on.
  14. Hunk o'steel

    Looks like crap, so good job its from a reputable source ! do you have decent power tools to reduce it ?
  15. Fix cracks in billet posible ?

    The cracks are probably not bad luck, but caused by forging too hot (overheating the steel during forging process). Spring steels can be a bit more fussy to forging temperature than simple carbon steels. Some steels 'cottage cheese' when you get them to hot which can be interesting ! If you overheated a few times, and then quenched without any normalisation cycles the grain the steel may have been moohasive when you did the oil quench, which would not have helped with it remaining homogeneous ! It would be interesting to break a bit of the billet and have a look. If the steels in a billet are very different you can also get problems with heat treatment when they have different contraction (or expansion!) rates on quench, and the billet will tear itself apart. Both Owen Bush and Mick Maxen (whose skills I am in awe of) told me in my very early days of pattern welding, when I was messing with 'unknown' steels, that known steel was very cheap in the overall scheme of things. They were 100% right. I still think I learnt a lot more about patternwelding from having to ponder what when wrong when welding the back of a filing cabinet to a landy leaf spring than I would have done if I just got a load of compatible 15n20 & 20c from the outset though !