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  • Marking Knife

    Hello,
    Just wanted to share my first successful cutting knife. I had resisted buying a marking knife, simply out of a personal pet peeve. I keep on buying things and/or tools even simple one that I can make myself. Every time, I say to myself, I will make it next time.
    Anyhow, I had tried making it before out of various metals etc and almost all were failures because of the metal being too soft. I finally managed to make one out of a reciprocating saw. It took me some time, which was good sign(hard metal) but I finally managed to make one that leave a fine line both on metal & wood. The Tip hasn't gone bad even after making a line on stainless steel
    Nothing much to look at, but absolutely fantastic for me


    Click image for larger version

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  • #2

    Re: Marking Knife

    Nicely done!

    What brand of blade was it? Do you find it flexes or stays rigid during use?

    They're hit and miss, but the plates used for circular/table/mitre/etc saws are often quite hard and can make useful little knives for scraping/marking/etc. When I have a dull one, I usually hit the plate with a drill to guestimate how hard it is. This was my most successful attempt, and gets a lot of use as a glue scraper:

    Click image for larger version

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    • #3

      Re: Marking Knife

      I tired 10" saw blade first, actually spent a lot of time shaping it, making a handle etc, except when it came time to use it, it was very soft...the tip would bend easily. What I had been doing to test the metal was using my spring loaded punch. Depending on the mark it would leave I was comparing the surface hardness of the metal. It barely made a dent on this blade. It is a milwaukee blade 1/16" thick, 9" long blade. Very stiff, when I try to bend it, if feels like it will snap rather than bend.

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      • #4

        Re: Marking Knife

        Ice skate blade steel is super hard, easy to find, and makes great marking knife blades.

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        • #5

          Re: Marking Knife

          Originally posted by stealthy View Post
          I tired 10" saw blade first, actually spent a lot of time shaping it, making a handle etc, except when it came time to use it, it was very soft...the tip would bend easily.
          I've come across some that seem to only be hard on the outside, some that were soft all over, and some that were hard all the way through. I've additionally tried heat treating the resulting knife blank (torch to non-magnetic and dunk in water) as well as tempering (baking in oven until straw coloured) with mixed results. Typically, by the time I've figured out how to make the steel from a given blade usefully hard, I've run out of blade... and the next blade will surely be different...

          I'll have to keep an eye out for discarded Milwaukee reciprocating saw blades...

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          • #6

            Re: Marking Knife

            Ah,
            Showed the photo to my buddy who is Tool & Die grinder by profession. He gave me a plate of A2 steel 10" x 10" 3/32 thick. Any ideas on the best use of it. I am thinking of making the replacement blades of two old hand planes that I have. The back of the existing blades are pitted and I think this would make a good blade.

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            • #7

              Re: Marking Knife

              Originally posted by stealthy View Post
              Ah,
              Showed the photo to my buddy who is Tool & Die grinder by profession. He gave me a plate of A2 steel 10" x 10" 3/32 thick. Any ideas on the best use of it. I am thinking of making the replacement blades of two old hand planes that I have. The back of the existing blades are pitted and I think this would make a good blade.
              I think A2 would make nice planer knives, a lot of wood cutters are made from A2, including many drill bits.

              What about an over-sized scraper a la Jimmy Diresta?
              I'm sure you could make a decent kitchen knife?

              Perhaps:
              2pcs 2x10 blanks for small (5" blade) knives (cut a shape, glue/pin scales on the sides)
              2pcs 3x6 for planer knives (you might have a bit of leftover out of this 6x6 section for another marking knife, depending how wide your planers are)
              1pcs 4x6 for a large hand scraper (could make the handle side a fun shape / something meaningful / etc)

              Once cut and ground, heat slowly to 1450F, then up to 1750F, hold for 30-45 minutes (3/32 is pretty thin, 30 mins will likely get you there), allow to air cool.
              I have nothing in my notes about how fast "slowly" is, or how much faster you can heat once you get to 1450. I've admittedly never worked with A2 (or any other air-cooled steel), but 1450F is just over the Curie temperature, I'd guess that the further heating and holding is related to creating conditions favourable to optimal grain formation while cooling, but I can't remember for sure. All I have regarding tempering is a temperature of 400F - no mention of cycles, soak time, or what hardness 400F should produce...

              A2 is widely available, you shouldn't have too much difficulty finding information about heat treat. You should be able to get small parts hot enough with a MAPP torch and you'd have no issue with an oxy-fuel torch. Keep a strong magnet stuck to the end of something metal to use as a probe. When the magnet stops sticking, you're just below 1450F. A chart like this can be useful to estimate other temperatures:

              Click image for larger version  Name:	Steel.Colours.and.Temperatures.jpg Views:	0 Size:	32.2 KB ID:	1325175

              G'luck! I'm looking forward to seeing what you come up with!

              Edit: You should probably ask your buddy what state the steel was in when he gave it to you. Was it annealed (soft) or hardened? If it's already hard, as long as you keep it below the tempering temperature while you form it, it should keep all its properties, which would allow you to skip the heat treating steps (that can be difficult without a forge / oxy-fuel torch / etc). That said, as long as you have a way of achieving the heat treating temperatures, the parts will be *much* easier to work if the steel is in its annealed state (if the steel is pre-hardened, you'll be reduced to only using abrasive cutters).
              Last edited by ThePracticalPeasant; 04-05-2021, 06:08 PM.

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              • #8

                Re: Marking Knife

                So I talked to my buddy because I intend to make a new blade for a vintage Stanley #7 jointer plane that I have. Going to his shop this weekend to cut the plate and trace the slot.
                He will this cut the slot on his Endmill. After that I will initially sharpen the blade, and bring it back to him for heat treatment. He has a small furnace/oven that he uses for heat treating. So basically, yeah he is going to do all the work...well for few beers.

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                • #9

                  Re: Marking Knife

                  Originally posted by stealthy View Post
                  So I talked to my buddy because I intend to make a new blade for a vintage Stanley #7 jointer plane that I have. Going to his shop this weekend to cut the plate and trace the slot.
                  He will this cut the slot on his Endmill. After that I will initially sharpen the blade, and bring it back to him for heat treatment. He has a small furnace/oven that he uses for heat treating. So basically, yeah he is going to do all the work...well for few beers.
                  Beautiful! A heat treat oven is *way* easier (and way more precise) than trying to do it with a torch. Since it sounds like your buddy knows exactly what he's doing, you should be able to get a fairly high end blade out of this endeavour!

                  Edit: I still suggest you take some of the scraps and make a knife or other useful item yourself, just for the experience.

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                  • #10

                    Re: Marking Knife

                    A2 makes great plane irons. Most of my Veritas plane irons are A2; it takes a decent edge and it is more durable than O1 but a bit tougher to hone.

                    Good luck with the project.

                    Ken

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