I use a homemade thermal wire stripper for exactly this kind of thing. I wouldn't really share this, as crummy as it sounds, except for the fact it is awesome AND that it still works, perfectly, ten years later.
It's just a pair of "tweezers" made by gluing two strips of wood to a small block of wood at one end as a spacer, to form a pair of wooden tweezers. Then this is hotsnotted to the side of a single 18650 li ion battery. That's the basic mechanicals. You squeeze, and the jaws of the tweezers close. The ends are angled about 30 degrees from square.
Now for the magic. It's two bits of thin nichrome wire. The exact gauge is 27AWG / 0.0142" diameter. Alloy is KA1. It has to be really thin AND long enough, else the battery wouldn't be powerful enough, right? So to get this thin wire strong enough, structurally, I looped it through a bit of protoboard to give it a jaw shape AND to give it more length. So you see, you loop it through a 2 hole gap in the protoboard on the plain side. Then on the copper side, you loop it back one hole, then on the plain side you loop it forward 2 holes, again. So you get two loops of wire 2 holes wide, but they are overlapped by one hole. So you have two overlapping semicircles of wire that cross with a wee bit of height off the board, enough height to cut through a wire insulation. Then you solder two pins behind these jaws, extending out the copper side for terminal posts, and you wind the ends of the wire around these posts.
For the other jaw, you do the same thing, but you have to make sure that when the loops cross each other, they are going to lock with the other jaw, so ... the top left loop/half-jaw will slide in front of the top right loop/half-jaw. But the bottom left loop/half-jaw will slide behind the bottom right loop/half-jaw.
Then you glue these to the insides of the end of the wooden tweezers.
I use just a simple DIY contact switch, using a solder blob and a piece of thin, flexible copper clad. And there's also a slide switch in series (for a safety). There's also an LED in parallel, just for visual indicator so you know when power is being applied.
When you wire the two jaws, you have to make sure the polarity is such that the flow goes through each jaw, not jumping from one jaw to the other, of course. So
the top of each jaw must both be positive and the bottom of each jaw negative, or vice versa. And to reduce the wire clutter, I used a strip of veroboard glued to the outside of each tweezer half to carry the current.
So you put the wire in, you squeeze the tweezers together, then you shift your thumb to hit the contact switch. The LED comes on, one second later you can feel the tweezers melt through the insulation and close tighter, then you rock your thumb back to let off the power. Then you twist and remove the end of the insulation.
When you get too much insulation bits stuck in the jaws. You just give it a pulse for a second and remove the blob with tweezers. EZ peezy.
Fits the palm of your hand.
The guy I am today wonder where this dude went, because he was pretty smart.
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