Best Wire for Hot Wire Foam Cutter - RC Groups
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Jun 04, 2005, 10:33 PM
novice flyer

Best Wire for Hot Wire Foam Cutter

I have built a hot wire bow and used an old guitar string as the hot wire with a 12V battery, but it burnt up as I was cutting a wing every time I tried it. Does anyone know of a good hot wire and where to get it at a good price? Thanks
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Jun 04, 2005, 10:44 PM
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ExtremeSkyes's Avatar
You need to get "resistance wire"...I think some people use nichrome (??). I think I've read that Nichrome is probably not the best. Not sure what type of wire it is, but one I use just had "resistance wire" and cost about $5.

Jun 04, 2005, 11:24 PM
Gravity sucks.
mrittinger's Avatar
I use a high E guitar string (Ernie Ball Super Slinky .008), havent burned one out in 3 years.
SIG sells Nichrome foam cutting wire if you want that.
I do not use a 12 volt battery, I use a rheostat transformer. Some old train transformers work great, if they put out enough amps.
Jun 05, 2005, 05:45 AM
Registered User
Nichrome wire is the only thing to use.
Available from Sig. May also be available from RCM
Bob G
Jun 05, 2005, 07:36 AM
Lori, hey, you're home early
CarreraGTSCS's Avatar
I use stainless steel fishing leader wire. Get it at a sporting goods or tackle shop. I have been using it for years. For the longest time I never tried cutting foam because I didn't have nichrome. Cheap too. Comes in 25 or 50 foot lengths if I remember correctly. I bought two pack and never opened the second it lasts so long. I don't remember the diameter. Pretty thin though.
Jun 05, 2005, 09:10 AM
Registered User
jimsp's Avatar
I've tried both the Sig and RCM foam cutting wire and I prefer the RCM wire. It's heavier than the Sig wire. You can order it online for $3.95 (5' piece). There is no charge for shipping.
Jun 05, 2005, 10:04 AM
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flypaper 2's Avatar
I use .020 piano wire. Shouldn't need enough heat to break the guitar string. only takes around 3-350 degrees F to melt the foam. I use a variac at 8 to 10 amps. Been cutting foam wings since the late 60s. The cutting bow that I use most is a piece of plastic 1/2 in. hot water pipe bent around into a bow with the wire as the bowstring. I have about four different bows from 4 1/2 ft. to 6 in. long. The reason I like the water pipe bow is, it weighs very little.
Jun 05, 2005, 01:09 PM
Registered User
Which_way_is_up's Avatar
Originally Posted by andyg
I have built a hot wire bow and used an old guitar string as the hot wire with a 12V battery, but it burnt up as I was cutting a wing every time I tried it. Does anyone know of a good hot wire and where to get it at a good price? Thanks
The reason you're burning out your wire is that you can't adjust the voltage you need for a given length of wire regardless of what the wire is made of. People get away with using fixed voltage power sources like batteries and battery chargers only because they were lucky enough to build a bow that was long enough and used heavy enough wire that it didn't burn out the first time they used it and so just continued to use that combination. You can use lots of different wire sizes, thicknesses and alloys for a cutting bow but you've got to have a variable voltage source to be more then just lucky at cutting foam. So you can actually control the wire temperature and be able to repeat that time after time after time.

Your most important question should be to everyone is "what kind of power source do you use with your cutting bow?" Then "what kind of wire do you use?"
Jun 05, 2005, 01:24 PM
I use a cheap car battery charger plugged into a light dimmer switch,with the stainless steel fishing line leader. Works great. If all you have is a car battery try using light bulbs in series with the wire to act as a resistor. The fishing wire is stronger than the nichrome and allows greater tension for less "sag" or bowing of the wire.
Jun 05, 2005, 02:06 PM
Registered User
"Which Way" is right. You need to be able to vary your power to the bow. I have a FeatherCut system that has been used for five years and at last count had done a little over 400 wings. When the wire broke I bought the following:

Inconel Lockwire, .025 diameter, 600 grade, one pound 532 ft. Buying it by the pound is expensive,$43 but if you can split the cost between several folks you will have a lifetime supply. There are different diameters available. I use mine on 28", 48", and 60" bows without problems.

Click on this web link:

The distributor is MSC Direct. They are also an excellent source for glass rods and assorted tools and building materials. They are in most major cities and you can get the product same day.

Good luck
Jun 05, 2005, 03:26 PM
Registered User
rccrasher1967's Avatar
how about MIG (welding) wire ? I am a weldor and have lots of .035 mig wire from work.I am thinking of using it with a 12 volt transformer and a light dimmer . The transformer is made for cb's and stuff and what about 1" pvc for a bow?
Jun 05, 2005, 04:33 PM
dougmontgomery's Avatar
I have used both .035 and .023 welding wire. The .035 created too much drag when pulling it over your templates, if you adjust your heat up it get brittle and breaks. It is a pain trying to get your wire out of the foam at this point. I have had great luck with the .023 wire and i was given a 40 # roll. I have replaced it on my 48" bow wire 1x after about my 10th wing because i was forcing it through due to the wrong voltage setting. The 24" bow has a piece of nichrome wire from sig and it is a lot easier to cut with. I believe it is around .015? Hope this helps. The welding wire will work fine until you get accustomed to cutting. Doug
Jun 05, 2005, 10:37 PM
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SpiritQuest's Avatar
Stainless steel safety wire, AIRCRAFT GRADE .18 thous. or 20 or 22 what ever you need is available at any Aircraft FBO or parts shop at any airport. Used often for safety wiring many different things on fullsize A/C. The great thing is it costs about $20 bucks for a lifetime supply! You can put quite a bit of tension on it too. Get beautiful flawless cuts in foam when you figure out the right temp. Anothr way to vary your temp is an old train transformer. They are really cheap. Many on eBay. i got one for $12 bucks! For less than $30 bucks you'll be happy!
Jun 05, 2005, 10:56 PM
Registered User
Yep the stainless locking wire is awesome 020 seems about perfect. Tried guitar strings and nichrome... ended up here. I'm sure the stainless leader is great as well. Another nice way to vary temp is by using an old speed control if you have an extra kickin' around.

Jun 05, 2005, 11:05 PM
Battery Junkie
wrenwright's Avatar
I've got an old Lionel train transformer that must be 50 years old, but it works very well. I like ss safety wire and .020" ss fishing leader.

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