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steel selection for scissors


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My method of making a scissors blade is to forge weld a tool steel cutting edge to a 1018 body. I've tried a few different tool steel alloys, but I'd like some expert opinions to help me optimize my choice.

 

This photo shows how the tool steel sits on the 1018 for welding. The forged blade (that I pulled from my scrap pile) shows how the blade is drawn out. I forge to thickness, not length. The blade starts 5/16 thick, and I forge it to 5/32, which about doubles its length. I've used 01, 1084, and 5160.

20220202_105812_2.jpg

 

I have two main criteria I'm trying to consider in alloy selection. The first is the alloy's tendency to air harden. I work in thin sections that don't hold heat long, so I want to avoid an alloy that's prone to air hardening. The second criteria is demonstrated in this photo. The mild steel moves easier, so it squeezes out the end. That creates a shear along the weld line.

 

20220202_105826_2.jpg

 

I know if I work only at high heat, both these issues are minimized with any alloy. I'm trying to optimize, so I want to know if there are differences, especially with the air hardening. Anybody have opinions on alloys in this application?

 

I have an Evenheat oven and a couple different quenchants, so the heat treat requirements aren't a factor in my choice. Thanks for your comments.

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Have you asked Grace how she does it?  

 

I am no expert, and you know more about scissors than I do, but I do have theories about laminated blades done in the "historical" fashion. That is, to make it work best, use the alloys closest to what the old guys were using.  If I had to use 1018 for the low carbon, I'd want low-Mn 1075 for the high carbon. Or 1060, 1050, etc., a low-hardenability water-quench steel at any rate. Keep it simple.  I would have thought the old steeled scissors would have been more like the Japanese single-laminate blades, a thin HC sheet laid flat-ways on a thicker wrought iron back, rather than the full-length butt-weld you're doing.  But, you have been studying this and I haven't.  I assume you've seen etched cross-sections of old ones that show it was done the way you're doing it?

 

One thing I can tell you, based on the wrought iron and steel seaxes I've done: If you don't want the wrought to run out from under the steel, don't use equal length bars to start with.  Forge the wrought to a one-sided point and weld the steel to the long side. When you forge it to thickness, the iron will spread to fill the space available.  If there's no iron (other than at the very end pointy tip of the weld) on the billet to spread, it won't flow past the end.  A version of that technique is how you get the patterned bars to follow the curve of the edge bar in saxes.  Since you want to keep a straight edge on the steel, adjust the angle of the point on the iron until it does what you want.  Start with a 45-degree, and if that doesn't give you as much low-C as you want at the point, make a more obtuse angle.  Might be you'd like an 80 degree to get a flatter point?  

 

At any rate, you want very low hardenability in the edge steel.  You want it to take a hard surface, yes, but it also has to be not-hard just below the surface so it can flex with the low carbon backing material without shearing the weld. I think that's why your O-1 didn't work as well as one might think, even accounting for the air hardening.  Use low Mn, medium carbon steel so it absolutely will not air harden in thin section, even on a cold anvil.  Steel, in other words, that acts like the steel they had when they were using that technique.  If it makes a good hamon in a water quench, it should do what you want in this application. Not that you should water quench it, of course! 

 

 

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Thanks Alan. I don't think Grace forges. As far as historical practice, I've seen scissors produced both ways. I learned the butt weld because my first scissors were little one-piece spring shears, and they are made that way. I bought one an Amazon and reverse engineered it. When I started to make pivoted scissors, I decided to see if I could scale up the technique. It seemed to work, and I've since seen some historical examples.

 

I've seen videos of scissors produced with the flatwise laminate you described. I haven't been tempted to try it, because I don't know what I'd gain by it, except maybe some warpage issues I don't have now. 

 

I'm not worried about having the ends uneven after forging. They get ground off anyway. I'm just want to reduce the shearing effect on the weld. I think I have to do that with heat, not alloy selection.

 

1 hour ago, Alan Longmire said:

At any rate, you want very low hardenability in the edge steel. 

Thanks. That's what I was wondering - if alloy selection would make my forging technique a little less critical.

 

And thanks for providing a forum for this discussion.

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  • 6 months later...
On 2/2/2022 at 4:45 PM, Jeff Amundson said:

, and I've since seen some historical examples.

At the time I wrote that, 'some' meant 'a few'. I hadn't yet read a wonderful little book titled "Knives and Scabbards" by Cowgill, de Neergaard and Griffiths. It's a detailed study of medieval knives, shears and scissors found in garbage dumps near London. It turns out my butt weld technique would be right at home in the 13th century. Most of the blades analyzed were wrought iron with a steeled edge. 

 

I took Alan's advice and have been using 1075 on the edge. The picture shows blades of 1018/1075 after they were drawn to half the original thickness. The two alloys moved about the same amount. 

 

I'm also more careful to work at high heats. I used to do some straightening at lower heats, but I can see how that created shear along the weld. I now take a heat to straighten as well as to forge. 

20220802_151831~2.jpg

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