Hi YouTube, my name’s Geoff and I’m the VegOilGuy.
I’m making an electric foundry which I’ll be sharing with you soon and I needed to make
some resistance coil heating elements.
So I came up with this really simple Jig.
In a moment I’ll be showing you how to make this and a little later I’ll be covering
the relevant Maths if you need help in making all the necessary calculations.
Starting with the resistance wire, many folks go with Ni-Chrome but I opted for Kanthal
wire which has a good performance reputation.
Kanthal coils are quite pricey but the wire itself is surprisingly cheap.
Measure off the amount you need and add this to a separate spool.
This can then sit at your feet.
There’s no fancy spool holders needed.
Next you’ll need a metal bar that matches the internal diameter of your required coil.
This one is 8mm in diameter and roughly a meter or 3 feet long.
You’ll need to drill a small hole at one end.
A couple of scraps of wood are required to form the body of the jig.
Size and shape isn’t critical.
These get screwed together – but no glue is used.
A nice straight hole is drilled through both blocks and this hole matches exactly the diameter
of the bar.
It’s a snug fit so a little oil might help keep things moving.
The blocks of wood are then unscrewed and the centre hole is enlarged in one piece only.
This hole needs to be big enough to give a little clearance to the finished coil.
In my case I’ve enlarged it to 12mm, giving an extra 2 mil all around.
Now’s a good time to decide where the top of the jig is going to be and mark this for
convenience.
Using an ordinary hacksaw blade, a small, shallow grove is carefully sawn into the front
piece.
This should be just large enough to accommodate the wire.
Don’t go too deep or too wide.
Everything is then screwed back together and you can see I’ve also attached a simple
base that can be clamped or screwed down for stability.
And believe it or not, that’s it.
It’s that simple.
The wire is fed into the small groove and the only tricky bit is pulling the wire through.
Long-nosed pliers work best.
The metal bar is then inserted and the wire is hooked through the hole in the bar.
On the other end of the bar, a drill is attached and this turns nice and slowly.
As it turns, the wire grows taught, gets looped around the bar and a perfect coil is formed.
The wire coil then slowly pulls the bar through the jig and eventually you either run out
of wire or bar.
The coil can then be slipped off the bar and it’s completed.
Just remember to stretch it before use.
This a very simple jig produces excellent results.
The maths associated with the coil can be a little more daunting.
There’s three formulas common to electronics and physics which may be of use to you but
before this certain information is needed.
The first is Voltage and this is either the mains voltage in your area or the voltage
you’re going to be applying to the coils.
In the UK, for instance, mains voltage is around 230 volts, though this can vary slightly
between regions and is certainly worth measuring for true accuracy.
The next requirement is Current and generally speaking the higher the current input, the
more powerful your heating coils will be.
But you must be sensible and careful.
In the UK for instance, the average mains outlet is restricted to 13 Amps.
Now personally I would NOT max out a device at 13 Amps.
I prefer to reduce current down a few amps and as 10 is a nice round number, that’s
what I’d personally go for.
Your situation and circumstances may be different but please be careful with current – this
is the dangerous aspect of electronics.
The next requirement is the resistance of the wire you’re using.
If you’ve obtained appropriate resistance wire, this information should be made available
to you by the manufacturer, usually measured in Ohms per unit length.
The final requirement is the inner diameter of the coil.
This is just the size of the bar you use is the coil making jig.
From this we can work out the length of wire we need, the likely power output, the resistance
of the coil and the number of turns necessary to make it.
For maths lovers, here you can see an example of the calculations and doubtless from this
you can see what’s necessary.
If you fancy an easier time of it, have a look at my website here.
There’s you’ll find an online calculator.
Select whether you prefer metric or imperial measurements and then simply type in the relevant
data.
This will work things out nice and easily for you.
So there you go, a simple coil making jig and a free online calculator.
We can call that a finished video I think.
I hope you enjoyed it and found it helpful.
I’ll be bringing you my electric foundry video soon, but in the meantime please look
out for my other videos on my YouTube channel.
Please subscribe if you haven’t already and feel free to send me your comments and
questions.
So that’s it for now guys, thanks for watching.