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Thread: Grinding away

  1. #1
    Senior Member milkbaby's Avatar
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    Question Grinding away

    So, I made my first knife by stock removal of 1084 and propane torch heat treat. Not sure I got the heat treat right, but the edge seemed hard. I tried to thin the blade post-heat treat on a silicon carbide stone and dished the stone horribly, LOL, I had to retemper at a higher oven temp. I learned that I need better way to heat treat instead of heating by torch with the blade inside the hole of a concrete block, so I have some soft insulating firebricks on order to make a miniforge.

    Anyhow, I realized that in my inpatience, I didn't grind the blade thin enough. It started out as 1/8 inch stock and it seemed like I was grinding forever. I thinned it out down by the edge considerably post-HT, but it's still a bit too thick to cut large carrots well. It cuts zucchini nicely tho, I got the edge sharp enough that it's sticking in my board if I'm not careful.

    I still have more than three feet of this steel left to make more knives and I'm wondering if I'll ever get the hang of grinding it down with the belt sander (1x30). It felt like I was making it convex at the top and bottom with the fattest part not at the spine. I think part of that was I was too aggressive grinding at the start and saw that I had a few bad low spots, so I went conservative later on and didn't grind enough.

    Since I'm wanting to make some kitchen knives which need to be fairly thin for good performance, any tips for grinding the starting stock down thin enough? Is it just a matter of being patient? My lowest grit belts are 50 grit zirconia. I was originally planning to start with thinner stock, but the price and rep for 1084 from NJ Steel Baron/Aldo was too good to pass up.

  2. #2

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    Cool!!! Gogogo have a good time!!

    Just some perspective; I have a 3 hp 2x72. I grind my knives almost completely post HT to be able to correct warps that way. I spend maybe 3-5 hours just coarse grinding a 240. I think I go through 3 ceramic 60 grit belts for one knife. With my grinder close to full speed. It's challenging to say it gently, to make a decent chef knife. Post HT you need ceramics, and they need to be fresh.

    If I was doing it like you, I would grind it as thin as I dare before HT, hope to be able to straighten in tempering heat, but be willing to step down from my desired hardness. Rather 61 hrc than a bent blade to scrap.

    I would probably begin chugging away pre ht freehand with a angle grinder with flap discs.
    Email preferred to pm; Robin@dalmanknives.com
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  3. #3

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    Also pre ht: draw file! Get a bigass bastard file. That will help you even the grind out. You'll also get some nice swole ****
    Email preferred to pm; Robin@dalmanknives.com
    I answer new inquirys once per week.

  4. #4
    Senior Member jessf's Avatar
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    Pics of your knife would help people understand what youve done so far.

  5. #5
    Matus's Avatar
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    I can not really comment on HT as that is something I outsource to experts, but you can get a lot of work done with 1x30" I have one too. You can get grit 60 and 120 Norton blaze (orange) belts from TruGrit and they are fantastic. I have a bunch of Sait 7S belts I got from UK. They are great too, but since you are in US it would make little sense to buy from overseas if you do not have to.

    I also grind as much as possible prior to HT. I have ground one D2 blade stupid thin (thinner than I wated) prior to HT and it had very little bend when it came back - it was fixable by hand.

    To grind monosteel blades after HT on a stone will take you forever. I did that with one HRC 62 O1 blade (just 160mm) and I needed about 6 hours on Atoma 140 to thin down. Get those Norton belts for your 1x30" and give it a go. Do not push too hard - you will either stall the belt (easy to do with 1/3 hp) or just push too hard on that flimsy 'platen' and it will give under the pressure and you will not have a well defined place where you remove metal.

    Staying with a simple carbon steels is a good idea - those are easier to grind/sand than tool steels. The experience with grinding a 240 mm D2 blade with a file learned me a lot

    I personally find that learning how to remove scratches with the belt grinder as well as possible is not easy - I am not quite there yet. I guess it would be easier on a proper 2x72" where you have a lot more space and a solid, flat platen. Hand sanding a monosteel blade from 180 grit up to say 800 is a LOT of work.

    If you check out my signature - I have posted some experience of mine on my blog.

    Have fun

  6. #6
    Senior Member milkbaby's Avatar
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    Thanks to Robin, Jess, and Matus for the info and inspiration; I always get inspired by your work, forum and instagram posts, and blog! If it wasn't for people like y'all, I would never have started trying knifemaking. It's a lot of fun to learn and try this out!

    As suggested by Jess, here are a few pictures. The ones without scale are pre-HT grind, the ones with scale are post-HT grind. Right now I just left it at 120 grit because I'm not confident the heat treat was all that decent. I sharpened to test because I didn't want to waste the wood scales if the blade was total crap. To be honest, due to the limitations of my tooling an apartment porch setup, I'll probably keep the knives I'll be making towards the rustic less finished side for now. Also, I figure this very first knife is mostly a learning experiment, and I definitely learned a LOT!










    The one thing I've learned looking at the knives in my collection is that cutting performance through hard food (like tall carrots) seems really dependent on the thinness behind the edge. All the best cutters I have are very thin behind the edge even when the middle of the blade is thick.

    Robin, thanks for the info about how long it takes to grind your kitchen knives. I wasn't sure how long it really took, and the first time I did the grind, I was surprised how long it took to get even semi-close to a knife-like shape. I'm out of shape right now, so your tip about using a bastard file might pump my arms back up to what they used to be, LOL!

  7. #7
    Matus's Avatar
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    That knife looks great. The grind does look relatively 'robust'. It may be a good idea to make it thinner higher up the bkade prior to HT as that will save you a lot of work after without risking too much. It is a good approach to try the knife before proceeding with finishing. Yes, hand sanding the blade is way to work on your arms

    One thing draw-filing (in particular when using the edge of the file) is effective, but will also leave deep scratches (grooves would be the better word) - keep in mind that to remove them will mean removing some more steel, so switch to finer file and then to coarse sanding paper before you reach your final thickness.

  8. #8
    Senior Member jessf's Avatar
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    Sweet knife. I use more of an axe grind towards the heel then flatten that out towards the tip. Gives me a greater range of cutting options. For me, i find that if i want to section out large carrots i tend to use the heel area which helps split the dense pieces like an axe through logs. When i want a fine dice i use the tip so that area is much thinner behind the edge as well as having distal taper. For this reason a choil shot tells only 1/3 the whole storey of what the blade and grind are doing.

  9. #9
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    Looking good. I'm refinishing a beat up Sabatier and after more than an hour of thinning i didn't see much result yesterday. Pits are still pits. Edge still dull as can be. Looking at this nice piece of works in the making makes me want to get back in there tomorrow.

  10. #10

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    Hey Milk- there have been several postings regarding Aaron Goughs flat grinding jig- your situation is a perfect example of where it excels... you can thin and bevel accurately and most importantly slowly (creep up on it).

    Im no expert at HT but you say you have several feet of the 1084 left over- HT 2 pieces the same at the same time (to control variables as much as possible) and then sacrifice one to check grain and structure and toughness.

    The design looks sweet- what kind of scales are you planning? Like RL says- GO and Have Fun!

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