Making a hot wire

[Tyrtill]

I made a long cut foam board cutter currently it 4' but I will be trying 8' tomorrow (hopefully not to much resistance)




Using picture hanging wire (or probably .030 welding wire) I made a 5 ft length attached to a board with a screw. On the other end was a bolt that was set below a platform for the foam board. Just put the wire on the line and turn on the juice and you get a nice straight cut.

[ghcoe]

Good Job!

[GPW]

A Pivot wire system like that , can also cut out tapered shapes with a template on the other end … Check this guy out …. https://hackaday.com/2015/05/14/move-ov ... you-wings/ Any ideas ???

[Tyrtill]

8 FT was a real slow cut ~ 1 minute for an 8 foot cut but it looks just as nice as the other cut.

I did see someone using a template and it made me think of useing shelf brackets or L Brackets to make perfectly straight and square cuts every time but my "by hand" method seems to be giving me reasonable results.

[featherliteCT1]

Thanks for posting the video ... your method appears to work great!

[GPW]

T’ , for shorter cuts with our bow we use the gravity method laying the wire across the foam , bow underneath , then turn on the electricity and the hot wire just falls through the foam , producing exact cuts every time , and if we want an angled cut we just tilt the foam …

[Hamilton Felix]

This is all interesting. Sounds like it does not take a lot of heat to cut foam.

I have a Harbor Freight "hot knife," but it's rather thick, something I bought to work with synthetic rope.

I was thinking that with the right wire, I should be able to make something to work off of my old Weller D650 soldering gun. I see many others have done so. That is 200 or 300 watts, depending on trigger position. Might be overkill. I wish I knew what happened to my old 100/140 watt Weller 8200 N. I inherited an old Craftsman gun that I think is 120 watt, but it doesn't appear to be designed to replace its tips. Might sacrifice that one to science...

Too bad Weller doesn't offer foam tips. They do make plastic working tips. Oh well, we'll make our own.

[GPW]

Ham, getting the heat right is important!!! …. Too little heat doesn’t cut , too hot makes big Wallowing cuts … It’s most practical to make a Bow type hot wire and use some type of adjustable DC power supply ( like an old train transformer) . We still use an old Variac , but that puts low AC on the bow ( dangerous) …
Over the years we’ve cut literally hundreds of Foam wings for model planes …. Once you do a few , you can get great results , and with smaller cutting wires and a pair of templates , you can cut most any shape you want ...the sky is the limit ...

Ps. our Favorite Hot wire is still Stainless steel Fishing leader material ( solid) … Cuts great , lasts a long time , and it’s cheap and available … Remember you don’t want the wire glowing HOT , just hot enough to melt the foam …

Ps , Don’t do like I did using an AC plug at the wire end ( fits my Variac) , as someone might accidentally plug it in the wall … Big alligator clips work great instead … With a wire , polarity doesn’t seem to matter ...

[Tyrtill]

With mine for an 8' cut I'm using around 200 watts (8 to 10 amps at 24v). In the case of the wire I'm using 6-10 Amps cuts pretty well but over that it cuts about 1/8" and if you let it stay put too long it can cut almost 1/2".

[Hamilton Felix]

LOL! Someone would only plug that directly into 120VAC once!

I can see how some kind of variable power supply is the way to go. If your cutter is relatively low wattage, there might even be some dimmers that would work. My soldering gun gives you 300 watts, 200 watts, or nothing. Not great options.

I’ll have to poke around in my shop. Maybe there’s a forgotten old variac at work...

I like that bow saw design above. I might even have an old bow saw around here.

[GPW]

And just sayin’, my Variac is fused for 5 amps , and we’ve only blown the fuse once in about 30 years … I only turn it up slowly till it begins to cut , that's all ...

[twisted lines]

Anyone try a variac / soldering gun combo,
Thought’s ?

[twisted lines]

A few are using mig wire;
Neat trick I learned, long scrap’s put one end in a vice the other in a drill and pull tight, spin the wire!

This thread has some casual warnings, so if you are challenged this may be catastrophic
You must take your finger off the trigger before it goes pop.

The goal is to have a firm straight piece of twisted wire
I had it break the wire the first time but it was straight, I have done pieces 25 to 30’ long then cut to length for filler wire, guessing around 6 twist per inch, it works very well to get ride of the curl

[twisted lines]

And just sayin’, my Variac is fused for 5 amps , and we’ve only blown the fuse once in about 30 years … I only turn it up slowly till it begins to cut , that's all ...

I have pondered how and made my first at home, more with time or need
First Variac plugged a soldering gun in nothing after bending a wire, blown fuse weard with no spare.
Second one blew the fuse after these test and finishing what I needed one more +&-
First (Top wire) Left test cut too deep, .043 SS Filler wire;
Second .035 SS Fishing leader, I did what I wanted with the but I think the larger wire let me push harder went faster.

[twisted lines]

Cutting some corner pieces for some electrical addition's (Needed)
Using this old saw for the outside, and after trying a inside cut; Not so good.
Idea of using this spring set up with Insulators and a pattern, It was a easy way to get several done and test the do I really want one, itch.
Using .035 welding wire That was twisted with a drill, but it breaks when tightening a loop.