Not a good trick or tip

[GNRail]

Well I was considering earlier today to post a tip for cutting rigid styrofoam. I have been building up a few levels on one of my Ntrak modules to have a set of tracks at mountain division. To cut the curves I wanted in the 1" foam boards I thought I would use the electric carving knife. It actually worked very well when cutting only the thickness of the foam. Like most home kitchen tools they are not rated for continous cutting so I took my time allowing the motor to cool down during the long cuts. Things worked well until I got a little over ambitious with the knife and tried to use it to carve the foam like a christmas ham.

BAD choice.

The blades jammed and the nice plastic gear inside stripped. No more knife. Luckly it was an electric knife we picked up at garage sale and its only duty was to cut low density foam (seat cushions) but it is still a lesson in being careful when you try to use a tool for something it was not designed for.

Garry


PS Can I interest anyone in a manually operated electric carving Knife ? Cheap

 

[Ralph]

Garry,
Sometimes its good to hear what NOT to do. We'll benefit from your experience. Much appreciated! Oh, and thanks anyway but you can keep the knife!
Ralph

 

[RailRon]

Hey Garry, your advice came JUST IN TIME!

I plan to begin some landscaping in the following days, and to cut the foam boards I already 'borrowed' our electric knife from the kitchen drawer. So I'll put it silently back before wifey even notices its disappearance...

So thanks a lot for your anti-tip!

Ron

PS: Since you saved my knife, unfortunately I have no use for yours.

 

[MasonJar]

The anti-anti-tip...

It is really not hard to rig up a hotwire cutter which will go through the foam like, well, a hot wire...

All you need is the nichrome wire from the LHS and and old transformer (actually you can use whatever transformer you have), plus some bits that you probably have lying around. If you don't have anything lying around, ask cpr_paul "How did that happen?" .

Connect the nichrome wire across a frame of some sort. Run telephone wire or similar from the cutter to your variable out on the transformer. More speed = more heat = easier cutting. Just be sure to ventilate your workspace.

Now you have a hot wire cutter for about $3 - the cost of the wire - instead of $65 for the Woodland $cenic$ version.

If I can do it, you can too, 'cuz I am a complete electrical know-nuthin'!

Andrew

 

[GNRail]

Well Andrew

I came in to some nichrome wire (a friend had a roll in his work bench from the previous owner) and gave it a try. Just using a couple of aligator clips and a variable dc supply we were able to cut foam very nicely. Thanks for the tip.

For the technically interested the wire was 9.6 ohms per foot and we used about 18" which worked out to under 1 amp at 12v.

I still have to fashion a frame of some sort and a better way to connect (melted some of the plastic on the gator clip) to the wire. I think I would also include a fuse in the circuit because even 12v can be dangerous at 1 amp

Thanks again

Garry

 

[60103]

The first hot wire device I saw was made with 2 strips of board mounted on a pivot like scissors. Power wire along the length, something to mount the nichrome at the one end, terminals for the power supply at the other. Did some nice work with it. By squeezing the cool end, got some interesting curves (I was going to say arcs).
Is one amp a bit hot for the work?

 

[GNRail]

I'm not sure if that much is too hot. We tried one cut saw that it would work and then shut things down. A lower setting should work. How fast do these actually cut? I have never seen a comercial model work. We were able to zip through the test piece pretty quickly.

Gsrry

 

[MasonJar]

I ran mine off an old bachmann (train set) transformer at about 75% - hot enough to cut a foot in about 3-4 seconds. Hotter is better, it seems, since there is less strain on the wire.

I attached my nichrome to staples imbedded in a wood frame. I then wrapped the wire supplying power around the ends of the nichrome. Seemed ok - about 1/2 inch of bare phone wire - no melted plastic...

If you can make your frame so it keeps tension on the wire, that is good, since as it heats up, it tends to stretch and that can ruin the cut.

I am not sure how you would get a curve - David, can you explain your device a bit more...?

Andrew

 

[60103]

not my device, a friend's, and this was over 20 years ago.
It was really an X shape with the wire over two adjacent corners. If you squeeze the other two ends together, the wire goes from straight to curved. The actual curve is adjusted to look right. It could bend in assorted wrong directions. It looks as if you make an "artistic" decision.
Last year my friend had graduated to the Woodland Scenics version.