I'm sharing some of the hot wire foam cutting gear I made thus far. Not in a step by step fashion but more as inspirational fashion to give you all some additional food for thought on  how you might want to make your own tools.

The basic principles if you are not familiar with them is you take a power supply source, be it A/C or D/C, though generally most are D/C. Connect it to a Nichrome or other suitable wire. The wire heats up - you cut foam or plastic with it. Or make toast... as it is the same principle that happens in your toaster. Or oven for that matter.

The basic construction design of all hot wire foam cutting tools are pretty much all the same. Including the ones I've made thus far and there are scores of step by step instructions on the web on how to make them out of a variety of materials from PVC to wood, from handheld cutters like the one shown to bows, router tables, and shape sleds to using batteries or variacs or computer power supplies as the power source. They all do the same thing - heat up a wire to cut foam in one fashion or another.

You can choose to go supper cheap or super expensive, you can get by with scrape materials or new materials for your version(s) of hot wire cutter(s). Personally I wanted something that was of a good quality, durable and didn't cost a fortune. I wanted certain features like using a universal plug to connect all my tools to the power source. And be somewhat esthetically pleasing not just tossed it together. And I wanted to make it myself.

So in building your tools, make a list of the features you like of all the diy tools you see on the web. That would be my first suggestion to you. And leave room for more features you can add on as you build it or that you discovered you would like to have after building your first tool that you can add to your next tool. For instance the handheld cutter in the first image was my first tool, first build. I wish I had added in an on/off switch to the handle with an LED indicator light. This is something I may still do, but will definitely do to my next tool build of the same likeness.

Enough said on all that... lets take a look at my tools and there construction so you can get some ideas for yours.

First thing you'll need is a power supply...

I decided to go with a 12v DC system. I wanted it fairly small with more than one outlet as well as have the ability to power all my tools be it a small handheld or a bow or a medium size router table cutter. So it needed to be variable output. I wanted circuit and system protection. And this is what I came up with...

The box is a hobby box from Radio Shack, the switches, fuse holder, led indicators, banana plugs and dial knob all came from Radio Shack.

As you can see it is a 12v DC with up to a 5 amp max load.

6 foot AC cord on the back.
Main Power switch lower center with led indicator.
Push on/off dial variable dimming for the Slave power switch.
Power indicator led upper center glows brighter the more power output you apply.
Output plugs accept either banana plugs or plain wire.
Two additional low profile banana plug receptacles on the side.

Inside here is the wiring...

You like the little transformer I used? The dimmer switch in the upper left is almost twice as big as the transformer.

Here's a better angle on the transformer...

The metal you see around it, is simply a clip that it slides into that holds it in place. So if I ever needed to replace it, I just slide it out unhook it and put the new one in. Actually it would be a little more involved than that as the wires are soldered.

And that is my power supply.

Next you need the cables to connect your tools to the power supply.

You can choose what ever type connectors you want. As stated above, to the power supply I went with banana plugs or bare wire. The decision as to what kind of wire to use was made pretty much by what 2 strand wire I had on hand that was also color coded and was at least 14 gauge stranded wire. Lamp or speaker wire is what I had, and is perfect for the type foam cutting I'll be doing and heavy enough for all my planed tool builds.

At the tool end I went with something a little smaller all in one connector and commonly found on ac/dc adapters. With a reason behind it. I wanted to be able to power at  least some of the tools, like a handheld cutter, not only by my power supply but by a few of my ac/dc adapters if I choose to do so. A little planning ahead and now more than one tool can be operated at the same time and by a variety of power sources including my home build one. As far as the connecter itself, I do believe I went with an "N" series connector and  used the standard positive pole center.


This is the business end of the hot or foam cutting hobby. And there are may type tools to be made depending on what type of material and cutting you need or plan on doing.

And probably you'll start as I did with the handheld cutter. It's the most basic of the cutting tools and easiest to make to get you started.

Again here is my first build...

Its features are:

It's very durable and stout.
As you can see, it can hang when in use or not in use.
It has a slide tensioner for the wire to keep the wire taunt.
It has a cutting width of almost 6 inches and a depth of 2.5 inches.
It can be powered by a common 12 AC adapter. (power output dependent of course)
The wire is easy to change and it accepts more than one type wire.
It's wired with 18 gauge wire. Over kill some may say but, that's the way I wanted it.
The wire won't slip off if accidentally pulled through the material too quickly.
It's not too heavy and fits comfortably in hand.
It didn't cost a fortune to make or take too long to do so.
It looks good to boot.

So how was it made?
It's made from two 4 inch paint rollers.

The process goes something like this:

  1. Cut the top part of the shaft off right below the bend. (The part that actually holds the paint roller. Or bend it straight if you want a deeper depth to your cutter.)
  2. Pull the handles off the shafts.
  3. File a small groove way and drill a small hole in the top tip of the metal shaft for the hot wire. (5/4 hole)
  4. File a tab and drill a small hole in the tab to solder the wires to on the other bottom end of the shafts. (5/64 hole)
  5. Solder the negative and positive wires to the metal shafts. (you'll need to use a propane torch for this)
  6. Sand the handles on one side equally. ( I used a 7" belt sander belt cut to make one 14" strip placed on the floor - 50 grit then 80 grit)
  7. Glue the handles together. ( My handles were polypropylene - Heat treated first then I used Loctite Plastic glue a 2 step glue)
  8. Drill holes in the handles for binding post. (1.5 inch binding post - 1/2 forstner or spade bit for the head)
  9. Drill a hole inside the mated handles to feed one of the wires through to the other side of the handle. (Drill above where the hole plugs end. Only if using a combined connector type otherwise the hole is not needed.)
  10. Feed the wires through each side of the new handle and put the shafts back on. (press to start - hammer and wood block to finish. Don't go too far - keep them equal)
  11. Put the binding posts in. (I used Loctite on the threads)
  12. Dry fit two 3/4 inch hole plugs and sand where they meet so they meet flush.
  13. Drill and install the connector to one of the hole plugs. (Use Loctite on the threads)
  14. Solder the wires to the connector.
  15. Install and glue the hole plugs/connector in place.
  16. Install the hot wire.
  17. Cut and/or file a groove in the spreader bar and install. (3/8 in diameter nylon spacer for 1/4 in shafts worked nicely for mine)
  18. Connect it all together with your power supply and do a final test.
  19. Go cut some foam into something useful.
  20. Pat yourself on the back - you did good!
  21. Post on the web what you built... (optional)

Here are some pics of the process or end results of the work.

4 inch Paint Rollers
Check handles to make sure they will mate properly!

First shaft head cut off
Notice the use of tape for cut lines!

Handles removed
Mark each so you know which shaft goes to which handle!
Shaft tab filed- drilled and positive lead wire soldered on.
Mini Butane torch soldering gun nor a soldering iron will work for this.
Small Propane torch made short work of the soldering!

Handles hand sanded and ready for the next step.
Dry fitting the binding posts

Handles Glued
Wires run - Shafts in - Connector Soldered on

Ends installed and testing continuity

Spreader Bar installed

Nichrome wire installed
Ready for testing.

Here are all the above components working in tandem taking a slice from a nice chunk of Styrofoam.

That's it for now, I hope I gave you some ideas you can use to make your foam cutting tools.

Here's is a little inspiration to get you to want to make them if you're into RC aircraft at all.

Not new, but still pretty dang cool and on my build list...
The JA 37 Viggen a build by Dave over at Flite Test. In this video as well as the link I provided, which is to the build log, you'll see yet another simple foam cutting tool you can build if you like as well as get plans to the JA 37 Viggen.

Till next time,
Keep creating, Keep those props turning and of course
Keep rendering!

- chase -

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