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Jeff Amundson

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Posts posted by Jeff Amundson

  1. Trying a new supply of wrought iron. It's the most steel-like WI I have seen. It came from a chain with links made of 3/4" rod. I had to etch it to confirm it was WI. I couldn't get it to split in the first tests. 

     
    These are steeled with 1075. 

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    • Like 7
  2. I've been playing with bronze metal clay for the finger bows on scissors. I'm trying to find an easy way to shape and polish the inside of the bows. After several false starts, I finished this pair. I chose wrought iron because I couldn't resist combining 13th century blades with 20th century bows.

     

    As discussed before on this forum, most metal clay is used for jewelry, not structural pieces. I chose a version called sculptor's bronze with a shrinkage rate of 9-14%. I took several measurements before and after firing. The shrink rate wasn't consistent within the part. For example, the bows shrank more top to bottom than side to side. However, the shrink was consistent from one part to the next. The pair went into the oven nearly identical, and they came out that way.

     

    Metal clay is water soluble, so joining two pieces together was a bit like welding with water. I chamfered the ends of two pieces of clay like I would with a metal weld. I then thinned the clay so I could drip it into the joint with a toothpick. For the subsequent passes I would make the clay a little thicker each time.

     

    Because of the shaping and sanding I did in the greenware state, after firing I was able to polish the inner surfaces of the bows with rubber polishing bobs. That's enough success to motivate me to try again.

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    • Like 7
  3. Yes, congratulations. I'm glad you're thinking about doing it again. The advice I have is to taper the back end of the 1075. This shows the taper I grind in both width and thickness. This is 1075 welded to 1018.

     

    Without the taper, the 1075 acts like a shear and cuts into the softer 1018. After I set the weld, blending in the tapered end is my first priority. It can take multiple heats because it cools so quickly.

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    • Like 2
  4. 1 hour ago, Bob Ouellette said:

    Welcome to the left hand nightmare living in a right hand world :lol:

    I've discovered that many left-handers struggle to use left-hand scissors. They have learned how to twist their left hand to use right-hand scissors. When presented with left scissors, they hand it back to me saying it won't cut. It's happened to me multiple times. I have to show them the correct way. And manufacturers are making left-handled scissors that put left-hand bows on right-hand scissors.

    • Haha 2
  5. 1 hour ago, Gerald Boggs said:

    As any left-hander has learned the first time they try to use them :-(

    More than once I have given left-handed scissors to left-handed people who hand them back saying they don't work. Many left-handed people are conditioned to contorting their hands to make right-handed scissors work.

     

    To accommodate that population, manufacturers are making left-handled scissors, which have plastic handles fit for the left hand mounted on right-handed blades.

  6. Welcome to the world of scissors, AlexDB. As you discovered, the internet isn't very helpful, so I'm happy that we'll make the internet a little smarter with this thread.

     

    I read somewhere, probably something Grace wrote, that "we're not making blades, we're making springs". Obviously that refers to the flex required to keep the two edges in contact, but it also suggests hardness isn't maximized. I think Grace aims for hardness in the mid-50s. I think you should choose an alloy that you can successfully heat treat to medium hardness.

     

    Your second question is more complicated. I don't like to use the word 'tension' to describe the force the blades put on each other. The ghosts of the engineers I've worked with won't let me, so instead I'll talk about the force required to open and close the scissors. An engineer who helped design plastic finger bows for Fiskars told me that our hands are much weaker opening than closing. Ever since then I try to adjust my scissors so they open as easily as possible.

     

    If you open most scissors so the blades are at 90* to each other, you'll find the pivot screws are not holding the blades tight to each other and the blades can wobble a little. When you start to close the scissors, the anatomy of your hand forces the two blades together. Your thumb pushes away and your fingers pull in, which is just what the scissors need to force the blades together. That only works for the first inch or two of blade, so the blades are bent to keep some force on the blades all the way to the tip.

     

    When I assemble a pair, the blades are flat on the inside, no bend. I adjust the pivot screw to what feels right, then Iock it by peening the threaded end. I only need the threads to make fine adjustments. After that it becomes a rivet. I put a decorative head on my homemade screws so people aren't tempted to adjust them. Once the pivot screw is set, I start making test cuts using the thin plastic produce bags from the grocery store. I bend the blades only as much as needed to make full clean cuts in the bags with little effort. Sometimes that process leaves a pair that seems too loose, but it passes my test just fine. They get handed back to me frequently by people who say they're "too loose" without even trying them. They cut just fine. I think another factor at play is sharpness. Dull blades require more force to keep material from passing between the blades. It seems reasonable to think sharp blades require less force.

     

    I can understand why the mild steel didn't work for your tests. It probably bends too easily.

     

    Here are a couple other factors to consider. Tin snips are about as long as your blades, but they have no bend in them. They're flat on the inside. Is it just their stiffness that makes that work? The blades in this post are not bent. They are angled relative to each other, so the tips cross, but the blades themselves are flat on the inside. This doesn't work in a pivoted scissors, because it would be too tight, bent in a straight line from pivot to tip.

    • Like 1
  7. On 12/25/2022 at 5:12 AM, Hoy's Forge said:

    Did I miss something

    Yes, you missed it. I start with 1018, then I weld 1075 to it. On the inside, it's flat first, then a hollow is ground, leaving only a tiny bit of flat left at the cutting edge. 
    3 hours ago, Dick Sexstone said:

    ruff dimensions ?

    These are all about 7 1/2" overall, 3 1/4" - 3 1/2" cutting edge. 
    3 hours ago, Dick Sexstone said:

    nice photo too

    Thanks, Dick. There are little blobs of clay propping up some of the blades to eliminate the glare. 

  8. This is a few years old (before scissors). The cherry wood is nicely aged. The knives are 1084. I wanted a small twist, so it's only 270 degrees. That means the blade and handle were forged flat in the same plane. The blade and handle are rectangular in cross-section. The transition from blade to handle is square, which is where the twist is. The handles have a nice flex.

     

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    The rack has 1/8" thick magnets that hold the knives in place. I drilled holes through 1/8" thick aircraft plywood to hold the magnets. Then I covered one side with cherry veneer.

     

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    A bonus - the magnets also hold everything on the side of the refrigerator.

     

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    • Like 4
  9. On 12/22/2022 at 11:04 AM, Alan Longmire said:

    diggin'

     

    On 12/22/2022 at 6:58 PM, Matt Walker said:

    Impressive

     

    16 hours ago, AJ Chalifoux said:

    Most impressive

     

    9 hours ago, Hoy's Forge said:

    awesome

     

    9 hours ago, kidterico said:

    WOW

    Thank you very much for all the compliments.

    9 hours ago, Hoy's Forge said:

    do they cut good ?

    Yes, they cut. I'm a toolmaker. My previous post explains how I test them. https://www.bladesmithsforum.com/index.php?/topic/42842-forging-scissors-photos-of-my-current-process/
    9 hours ago, Hoy's Forge said:

    is a bit of over bite needed in each blade to get that shearing action?

    Thanks for asking. This seems to be the mystique of scissors making. In my learning, I looked at the shearing action of many tools, including tin snips and foot operated shears. It's helpful if the shearing blades are sharp, but it's critical that nothing passes between them. For scissors, human anatomy forces the two blades together naturally. As your hand closes, the fingers pull and the thumb pushes. This is only effective for the first couple inches as a scissors closes, so a slight curvature (yaw, as opposed to pitch or roll) in the blades is necessary to maintain that force all the way to the tip of the blades.
  10. I went into production mode with these two designs. The process and tooling are the same for both, so I was able to focus on process refinements. I processed them in batches of 2, meaning 4 blades welded and forged, ready for heat treat before I'd start another batch. By having blades at various stages, the bottlenecks show up fast. It turns out the hot work is about 25% of the total time to make a pair. 

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    • Like 8
  11. I had to modify the sharpener so the angle I want is in the middle of its adjustment range.

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    Sharp blades with a screw. The blades are still flat.

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    The screw is really an adjustable rivet. Locking the final adjustment is still an adventure for me. Peening the end of the screw without changing the adjustment or damaging the screw head is a challenge.

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    It looks crude, but this is the only tool I need for adding a curve to the blades. I start at the tip and work my way back as necessary. The blades are mostly mild steel, so it doesn't take much force. 

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    After adding the curve, the points cross slightly. These blades are about half open.

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    When closed, the blades touch at the tips only. The thin white line is the gap between the blades. 

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    Cutting paper is easy, so I test using flimsy produce bags from the grocery store instead. I get a smooth cut all the way to the tip.

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    • Like 3
  12. Here's how I currently grind scissors. It's based on my understanding of how scissors are supposed to work and the tools available to me in my shop. 

     

    I do most of my grinding freehand on a 2x72 using both platen and contact wheels. I grind the inside faces flat on the platen. Then I add a hollow grind to those faces with an 8" contact wheel. I use the same wheel to grind the primary and secondary bevels on the outside face. After grinding, I sharpen the edge using diamond stones. The stones are pretty demanding when it comes to flat and straight.

     

    I don't grind much before the heat treat. I do grind the blade ends even, the inside faces flat, and I start the primary bevel. I leave the profile grinding for later, because the hollow grind gets difficult if the tips are pointed. 

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    I use an electric oven to normalize, austenize, and temper the 1075. I quench in Parks 50. I get very little warpage. 

     

    After heat treat, all grinding is done to 320 grit, which seems to be fine enough for the rust blue finish I use. I start on the platen to get the inside faces flat. I also grind the cutting edge straight. More on why the edge needs to be straight later.

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    Switching to the 8" wheel, I grind the primary bevel on the outside face. This bevel is mostly for weight reduction and cosmetics. I aim for a thickness under 1/16" at the edge.

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    The hollow on the inside provides clearance for the cutting edges. The hollow extends from the tip to the pivot hole. What remains of the flat face is referred to as the ride line - where the blades contact each other running the length of the cutting edge and wrapping around the pivot hole. 

     

    This hollow grind is why my scissors have straight edges. My blades have straight edges because I don't know how to grind a curved hollow with the tools in my shop.

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    This is the tooling I designed to help me improve the secondary bevel grind. I borrowed the idea of the guide rod from the sharpening system I use. It is set to grind 35* off 90. Said another way, it's a 55* included angle on the blade.

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    Finally the profile is done. The next steps are to sharpen the edge, make the screw, blue everything, and do the final assembly. 

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    • Like 5
  13. Here's the rest of the hot work on these scissors. At this point the shanks and bows can take many different shapes. I've been designing shapes that are usable as-forged, because I don't like the grinding and polishing that's required on the inside surfaces of the bows. This design uses a very long taper, mostly round, that gets wrapped around a mandrel to form the bows, like this post.

     

     

    I use drawing dies on a power hammer as much as I can, but these small pieces go wonky easily, so I spend plenty of time on the anvil. When I'm rounding everything, I have to remind myself it's what I do instead of grinding. 

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    Pivot holes are next. I use a laser to help align the blades to the centerline. I drill one side, then transfer punch to drill the second. One hole is tapped, one is reamed. You can see that the blades are different lengths. That's because I forge them to thickness, not length. I align the shoulders of the shanks, not the ends of the blades, before I drill. 

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    The shanks are formed. Everything needs a tool. 

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    This is the fixture for shaping the bows. The oval mandrel is adjustable left and right. The mandrel is replaceable with a different shape or size. For this design the center of the mandrel is offset 3/4" from the centerline. I use an o/a torch to do the wrap.

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    The laser helps me keep track of the centerline in space.

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    This pair has asymmetric bows. The thumb bow is moved 1/4" closer to the pivot to better match the anatomy of the hand. These are ready for a pickle before grinding.

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    • Like 3
  14. You want complete? I thought I  could let people imagine their own bows. Actually, it was lunch time. I can finish the hot work to be true to the post's title. I've got about 1 1/2 hours into this, with many more to go.  The grinding, finishing, and assembly work don't belong in this thread. Thanks for the compliment. 

    • Like 1
    • Thanks 1
  15. First I fuller vertically to divide the blade from the shank. The tooling is mounted in a treadle hammer. The steel is 1018 CRS, 516" X 5/8". 

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    Next I weld the cutting edge - 1075, 5/32" x 5/16". It took me a while to get used to putting the cutting edge on top like this. It looks wrong if you're thinking knives. 

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    The weld is blended in and forged back to the original dimensions. This is a combination of hand forging and power hammer.

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    The shank is drawn out square.

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    The horizontal fuller is the tricky one. It provides a thickness target for subsequent forging and grinding. It also provides some clearance in the pivot area. I have to eyeball its location relative to the first fuller. This is on the treadle hammer again. I have to take it slowly, because the little humps sticking out the sides of the bar get real big if I don't correct it often. 

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    Next I draw the blades out to uniform thickness. This is done on the flat dies of a power hammer, taking little bites at a time so the blade grows in length but not much in width. There's plenty of hand forging to keep the cutting edge straight. As I approach the final thickness, I focus on flat and straight. It makes for easier grinding. 

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    The last forging will be to draw out the shanks and bows.

    • Like 3
  16. I made this in bronze because it lives in Hawaii. I forged it using silicon bronze, C655, which is 97% copper and 3% silicon. It crumbled if forged too hot. I would heat it medium red (best in a dark room), set it on the anvil for a few seconds, and then it would forge beautifully. It forges cold, too, until it work hardens. Heat and repeat.bronze print.jpg

    • Like 1
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