Introduction: How to Make a Pair of Scissors
Scissors. That's just a pair of knives screwed together right? Nope. Like most things in life, on closer examination they are more complicated than I had initially thought.
I needed a pair of scissors in my shed. So I thought I'd make some. Sure, I could have taken a pair from the house but where's the fun in that?
I carefully examined all the scissors in our house (why we have quite so many pairs remains a bit of a mystery). I took several pairs apart. There are 2 key features that are not readily apparent when you look at scissors, but are critical to their success:
1. The insides of the scissors are not flat. They are slightly curved towards each other lengthwise.
2. One of the screw holes is not parallel. It leans very slightly so that when you tighten the screw it pulls the tip of the scissors closer.
Hmm fiendishly subtle. Subtly fiendish. But can we achieve this at home? Yes we can. Here's how...
Step 1: Materials
Suitable high carbon steel suitable for knives (1095 etc). You could use old leaf springs or circular saw blades.
It's easier if you get it in a suitable thickness (mine was 3mm) rather than hammer and grind it. But if you want to hammer and grind your steel I'm not going to stop you.
Bolt with a flat head. I went for M4.
Step 2: Tools
Angle grinder. (1)
Tap and die. (2)
Files or sander.
Oil in metal container to quench.
Heat source that can get to around 500c (930f) to heat treat blades. I used a self cleaning oven but you can fiddle about with a blowtorch as in my folding knife instructable here. (5)
Workaround alternatives if you don't have the above equipment.
2. You could just use a nut and bolt instead.
3. If you don't have a protractor you could just look up the angles you want online and print them on a piece of paper. I've done this before I eventually stumped up £3 for a protractor.
4. You could do this whole project with a propane, or better still mapp, blowtorch and some fireproof bricks. Or a coffee can forge like I used for part of this.
5. If you can't get to 500c, you could just temper them in your oven to around 200c (400f) The scissors will still work, but not quite so well as the blades will not be so springy.
Step 3: Design
Look at lots of scissors and figure out how you want yours to look. I didn't have enough steel to attempt some like my wife's fabulous mahoosive Victorian material shears. Shame!
I took an old crappy pair apart and used these as basic templates. The template is for the blades, and a rough idea of the handle length.
Step 4: Making the Cut
If your steel is hardened it is worth annealing it here to soften it up. Heat it up in your forge until it is red and no longer magnetic. Quickly put it in a buck of perlite or similar to let it slowly cool.
Unfortunately my pieces of steel were not long enough, so I drew around the blade parts, then had to allow enough to bend out and form the handles. If your steel is long enough life will be slightly easier.
Cut your steel to shape. Angle grinders or hacksaws are good.
It is useful here to mark the top scissor and bottom scissor on their outward face (I did T and B with a sharpie). This will help you keep track.
Step 5: Bend
Using a forge or blowtorch shape the finger holes. For mine I hammered the steel to a taper then bent them around a piece of pipe.
I used my little homemade forge for this as it was handy to keep the blade parts out of the heat to keep them flat.
My handles are rough and not too pretty as this is my first pair and I am more interested in the working end at the moment. The next pair will look prettier...
Step 6: Bend Again. But Subtler.
The blades on scissors are very subtly bent towards each other toward the tip. This enables a proper cut for the whole length. Scissors will still work without this, but not so well. If you are going to the trouble of making scissors you want them to be good.
I achieved this by gently heating and tapping them over the curve of my vice and kept checking against the flat surface of my anvil.
Step 7: You Know the Drill...
When you have the 2 parts cut roughly into shape mark the centres and drill them.
As mentioned in my intro, one hole is drilled at a very slight angle (I went for 2 degrees and it has worked well) leaning away from the tip. Make sure you drill the outside face. Use a sharpie and mark this one 'tap'.
You can shim a block of wood at that angle.
I drilled smaller than I will eventually drill so that I can test them as I go. I drilled 3mm then used the drill bit as a pivot.
Step 8: Bend. Again.
With the pivot in place, clamp the scissor blades together in a vice in their correct final closed position.
Using a blowtorch heat the handles and adjust them so that the finger holes meet each other. Take them out of the vice and check and repeat until they function correctly.
Step 9: Bump N' Grind
With the drill bit pivot in place, mark each blade with how far you want the cutting edge to come up. Mark the front and sides so that you can see the mark clearly while grinding.
Clamp the scissors together in their correct position and sand the top of the tips to shape.
Scissor cutting edges come in various angles and the internet is full of suggestions. Too many suggestions. I measured the angle on my example pair and they were 25 degrees. Good enough for me.
I cut a block of wood to 25 degrees then screwed it to the tool rest on my belt sander. I didn't actually attach the blades to it, but it was a very handy guide to keep checking against as I was sanding.
When you've sanded enough away to meet the flat sides, stop. Have a coffee and a scratch. Now very lightly sand the flat sides with sandpaper just to remove the burr.
With the pivot in place check the action. While squeezing them together they should work slightly, like the worst pair of scissors you've ever used.
Step 10: Tap and Die. But Don't Die. That's a Tap and Die Joke. You're Welcome.
Drill a suitable hole for the tap in the blade marked 'tap'. I used a M4 bolt so used a 3.3mm drill bit.
Tap a thread.
Drill a suitable hole for (4mm in my case) in the blade with the 90 degree hole. This side does not get a thread tapped.
Step 11: Heat Treat. Heat. Quench.
Wrap the blades together with wire, putting a thin metal shim between them in the centre to maintain the subtle inward bend.
Heat the blades until they are no longer magnetic (the Curie point) then quench them in oil (any sort will do).
Check that they are have kept their shape and haven't bent in the heat.
Your scissors are now hard but brittle and not bendy enough.
Step 12: Temper Temper...
Tempering reduce a steels hardness/brittleness. In the case of scissors you need to temper them to become springs (so that the subtle bends can pull together). This requires a heat of around 500c. Not easy. Not unless you have a self cleaning oven (we do) and you can do it while your partner was at work (I did).
It's best if you can do this for 1 - 2 hours, but any tempering to approx the right temp would be good.
Step 13: Clean Up.
Lightly sand all the crap off. Polish them to whatever level of finish you want. Sharpen the blades.
You should now be the proud owner of a pair of working scissors.
Step 14: Finishing Up
OPTIONAL STEP (although I suppose all steps are optional; I'm not going to come round and insist)
Once you're happy with the screw tension you can if you wish peen the end of the bolt to lock them in that state forever. This does mean that you won't be able to adjust them, but it also means they shouldn't really need adjustment unless they get a ton of use. I have not peened mine yet, but I probably will once I'm fully happy with the action. Here's how to do it.
Cut some small grooves in the hole where the bolt exits. I used a dremel, but a chisel would do the job.
Make sure you have enough bolt protruding. The blacksmith rule of thumb for rivets is 1.5 x the diameter of the hole. So 6mm in my case. Adjust the bolt until the action is right. Mark the bolt and scissors on both sides so that you'll know if it slips. Support the scissors with the head of the bolt resting on something strong (anvil, head of a hammer etc). Hit the protruding bolt repeatedly preferably with the ball end of a hammer until it mushrooms over. Some of this new head will fill the grooves you cut and prevent the colt from moving.
Using a blowtorch BRIEFLY to soften the bolt will help if you're struggling, but be really careful not to heat up up the scissor blades as you will ruin the temper.
Step 15: Cut!
Thanks for reading!
My scissors may not look that beautiful, but they cut like a broken heart. If you do make some, please let me know how it goes.
Oh and if you feel like giving me a vote for the metalwork contest, thanks indeed!
Runner Up in the