Forging Scissors - Question(s) about steel choice and proper tension

[AlexDB]

Hello. I've began my journey into scissor making, and have hit a potential snag and was wondering if anyone had any advice. I know it's not the most common practice, but maybe someone will know something. I've been a blacksmith for a while but never much a knife guy, so my expertise in steel choice is probably lacking a bit. There does seem to be higher amount of scissor-related posts here than other places I've checked, so maybe someone can help. Sorry for all the text in advance, trying to be thorough. Tl'dr at bottom.

 

Anyways, I finished a first pair made from 1095 and had a break when trying to get the bend into the blade (a final process for scissor making needed to get a good cut). I was bending by placing a blade in a notch of wood and manually pressuring it. It would flex, but never changed from straight (until it broke). I tried tapping the other piece lightly with a hammer and ultimately had the same results. I should mention the grain of the steel looked good (and was tempered to a straw color).

 

I know 1095 is classified as a spring steel, but was wondering if there would be a better alternative. A local steel mill does supply a lot of things, but for some alloys (like 5160), there's a 20' minimum purchase so I don't want to buy anything that would be a bad choice. I have some old coil springs but have never had the best results with heat treating them. I see a lot of scissor makers do tend to do a welded bit (especially in Japan), but the forge I built doesn't really get hot enough for secure welds, so I feel like that is not really an option right now, and am hence trying to find the best option for full spring steel body.

 

Wondering if anyone has any thoughts. I would assume 5160, but I thought I'd ask. I should also note I don't have a heat treating kiln (yet), and so would need something that isn't overally complicated to get a harden/temper.

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My other question is (probably) related, but a bit more nuanced, being related to getting tension right. With this pair (before it broke), and a mild steel pair I made to practice getting the bend, I often found that it would either be very tight, but cut, or feel like proper tension but not really cut at all. I assume the lack of proper bend makes a difference, and maybe that's all it is, but I feel like I'm missing something else. I've just been using a normal screw + nut + washers for this. One piece is drilled and tapped (8-32), and the other is drilled 2 degrees off and not tapped.

 

Just even when bending (and unbending) the mild steel pair maybe 30 times, I never really found a spot that felt right. The design I'm working with is really small, and probably has about a 2" cutting surface, so I imagine the bend would need to be super minimal anyways. I've seen people talk about peening one end of the screw, but I never really understood that unless you want the blades to be inseparable. I know this process is very hard, so maybe it'll just take practice. Too bad it takes so much work to get to this point though.

 

And before anyone directs me to any of these sources, I've done a ton of research, and just haven't found answers to these questions that were helpful to me...

-Watched every scissor related video on youtube

-Read every post here by Jeff Amundson (multiple times)

-Read Grace Horne's book

 

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TL;DR:

Best spring steel alloy choice to make scissors out of? Fully, no welded bit.

Any advice for getting tension right?

[Jerrod Miller]

This forum allows tagging people, so maybe now @Jeff Amundson will get pinged, see this thread, and offer some insight.  

 

Also, have you tried introducing the bend during temper/at temper temps?  Do your double temper, then shim the clamped blade while hot and hold it at temp while shimmed.  You could also grind/file/sand the bend into the piece.  

[AlexDB]

On 3/8/2023 at 5:53 PM, Jerrod Miller said:

This forum allows tagging people, so maybe now @Jeff Amundson will get pinged, see this thread, and offer some insight.  

 

Also, have you tried introducing the bend during temper/at temper temps?  Do your double temper, then shim the clamped blade while hot and hold it at temp while shimmed.  You could also grind/file/sand the bend into the piece.  

 

that's an interesting thought, no idea how feasible it is just on the grounds the bends are so finicky and needing to match, but perhaps it could work. will add to my rather short idea list. thanks!

[Jeff Amundson]

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.

[AlexDB]

Wow thanks! Very useful info. Even just knowing to treat to 50s is a big help, I'll do a bit of research before deciding on what steel to get knowing that. And like you said this info isn't really very prevalent online, and I sort of feel like a lot of the people who have scissor related content online are usually people doing a one and done. Which is fine, but not always the most helpful if you're really trying to understand the nuance of the craft.

 

All the info on the needed force and assembly seems very helpful, hopefully I'll be able to put it into practice well when I source the steel and give it another go. I do think you are right about the mild steel being too soft (and hence too bendy), and in turn I guess my other pair being too hard. Although I'm wondering if it might almost be easier to get the cutting ability right if I make slightly longer blades. I guess that is all things I need to experiment with and see what works for me. I know this is going to be a process regardless, and I am okay with that.

 

Thanks again!

[Gerald Boggs]

On 3/10/2023 at 1:45 PM, Jeff Amundson said:

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.

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

[Jeff Amundson]

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.

[Gerald Boggs]

4 hours ago, Jeff Amundson said:

Many left-handed people are conditioned to contorting their hands to make right-handed scissors work.

Interesting, I've used left handed scissors with no trouble, but since that means I would have to carry a pair around, I found it easier to  teach myself to use scissors with my right hand.