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Foam Sculpting

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Foam Sculpting
Posted by mreagant on Wednesday, September 1, 2021 6:21 PM

Has anyone used an electric serrated carving knife (two reciprocating blades) to carve foam?

I'm at a point in layout scenery construction that buying a hot foam cutter to use once or twice seems a waste.

Mike

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Posted by xdford on Wednesday, September 1, 2021 7:18 PM

Foam gives off formaldehyde when it is heated and an electric knife would generate a fair amount of localised heat.  Could I suggest using a bigger boxcutter type knife with the blade fully extended but inany event work in a very well ventilated area? I used a surfoam following a John Olsen article myself many years ago and created a snow storm but that was before I knew about the formaldehyde. 

Hope this helps,

Cheers from Australia

Trevor

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Posted by kasskaboose on Wednesday, September 1, 2021 7:29 PM

I use a drywall saw to cut large chunks of foam.  It works well, but it seems a pink or blue snowstorm is inevitable.  Sigh! Have that shopvac ready.

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Posted by hardcoalcase on Wednesday, September 1, 2021 8:26 PM

Maybe plaster hardshell isn't so messy afterall?

Jim

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Posted by mreagant on Wednesday, September 1, 2021 8:52 PM

The project I'm doing is small and could be done in 15 minutes +/-. Buying a hot foam cutter or dry wood saw doesn't seem practical. Hope we hear from someone who has actually tried the electric knife.

Mike

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Posted by Lastspikemike on Thursday, September 2, 2021 8:23 AM

Woodland Scenics makes a very sharp exacto style foam knife which is very effective for smaller cuts. We have also used a large blade box cutter style utility knife (snap off blades) which is similarly effective for longer spans of cutting by extending the blade out to its full length. The key is razor sharp blade. Another advantage to either type of knife is the thin blade.

Styrofoam  surprisingly abrasive on knife edges. I wouldn't use any type of kitchen knife on styrofoam because the blade will be ruined fairly quickly.

For rounding of cut surfaces I recommend the excellent Surform tools. They make a box plane size for smaller areas and a longer two handled bench plane size (though much narrower, more like a large bastard cut fake) for bigger jobs. There is also a bench file size made by more than one company (microplane) which we also use for grating hard cheese (I'm not allowed to use that particular one for woodwork but I'd buy one when I have a need for it).

I've used WS lower temperature hot wire cutter, rather like using a coping saw, with mixed success. It's very hard to cut lines but that may not be an issue for scenery. The wire style hot "knife" isn't very useful because the wire isn't rigid enough. Any type of hot wire will give off unpleasant fumes from regular styrofoam.

I haven't used one but an electric carving knife isn't going to cut it in my opinion. I've tried one for carving meat and they are completely useless for the designed task. 

Alyth Yard

Canada

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Posted by York1 on Thursday, September 2, 2021 8:35 AM

mreagant
The project I'm doing is small and could be done in 15 minutes +/-. Buying a hot foam cutter or dry wood saw doesn't seem practical. Hope we hear from someone who has actually tried the electric knife.

 

I didn't use the electric knife when I cut and shaped my foam, but I did use a kitchen serrated knife.  It worked very well and was fast.

I think the electric knife would work just as well.

I also used a Surform tool.  It worked the best for me.

York1 John       

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Posted by rrebell on Thursday, September 2, 2021 8:36 AM

The meat cutter dose not work well on foam, dosn't work that well on meat either. Buy a WS hot wire and look at it as an investment for future projects. Around $30 out the door for new.

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Posted by Lakeshore Sub on Thursday, September 2, 2021 8:47 AM

Like John, I use an old serated bread knife to cut foam.   Any fine corrections are done with a surform.   I too would believe that an electric knife would work fine.

 

Scott Sonntag

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Posted by Pruitt on Thursday, September 2, 2021 10:11 AM

I used one very briefly. If a saw generates a foam dust snowstorm, I can only describe what an electric carving knife generates as a full blown blizzard!

That aside, it worked well. But because of the mess, I went back to using an el-cheapo standard knife to do rough cuts.

And by the way, the electric knife doesn't generate anywhere near the heat required to make the foam start outgassing toxic fumes.

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Posted by mreagant on Thursday, September 2, 2021 11:12 AM

Thanks for the feedback. The project is on the near horizon so I take it all into account. I do have a surform plane so we'll see what happens.

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Posted by cats think well of me on Thursday, September 2, 2021 12:35 PM

I got a Woodland Scenics hot wire foam cutting tool and liked it a lot. ALWAYS get a spare wire pack, or two, it's worth it, as I snapped the wire a couple times trying to get it together. And snapped the wire when first trying it out. Definitely a tool to take your time with and let the cutter do the work. It took a bit of time to get the wire tightened properly but I like how it does not heat up the foam, or produce as much fumes, like another wire cutter tool I tried out, can't think of the name as I borrowed it from someone. I kept the room I worked in ventilated and only did so much work at once before taking a break. I'll work outside now that the days are getting a little cooler. 

I also have a hot knife tool for cutting large sections I got from Harbor Freight that with some work proved quite helpful. I just ordered Woodland Scenic's knife and some spare blades, but haven't gotten it yet. Though found I like using a single edge razor blade on some cuts, so I imagine I'll like the WS styrofoam knife a lot more. 

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Posted by MisterBeasley on Thursday, September 2, 2021 12:36 PM

My hot wire cutter is at least ten years old.  I still use it occasionally.  I do more score-and-snap to cut large pieces, and plain knife cutting for the smaller stuff.

 Model railroading causes one to amass a lot of specialized tools, but you'll find you use them over and over.  A layout is never really finished, so you never stop needing your layout building tools.

It takes an iron man to play with a toy iron horse. 

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Posted by Lastspikemike on Thursday, September 2, 2021 1:49 PM

Power tools facilitate making mistakes far more efficiently than when using hand tools. I find very few power tools are required for model making or even a lot of the layout building. Drill and a saw.

Hand tools allow slower and less possibly damaging work to be done.

For foam carving one advantage of the Surform tool is a good deal of the shavings end up inside the tool, retained by static charge. A vacuum cleaner can take much of that directly out of the Surform. It also removes material fairly slowly allowing sculpting on the go so to speak.

Like much of WS products their hot wire and foam knife do exactly what they claim they do. The wire tends to break more easily if you force the wire rather than exploit the melting effect. It's tempting to cut like a cheese wire but it doesn't cut it melts it's way through the foam. Almost no resistance should be felt or you're rushing the cut.

The foam knife works best if you use a slicing motion rather than a pressing cut. The blade is literally razor sharp and works best to slice rather than simply cut. Mind you most knives cut far better as slicers than from pressure on the knife edge. Be aware the foam knife is hazardous in the same way as any sharp wood working tool would be.

Alyth Yard

Canada

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Posted by rrebell on Friday, September 3, 2021 8:26 AM

Also be aware that the Woodland Scenics hot wire foam cutter dose not get hot enough to be toxic unlike other brands, you will get a smell but it is non toxic only getting to arround 425degrees, the toxic number is 467degrees and is very toxic.

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Posted by The Milwaukee Road Warrior on Saturday, September 18, 2021 8:31 AM

kasskaboose

I use a drywall saw to cut large chunks of foam.  It works well, but it seems a pink or blue snowstorm is inevitable.  Sigh! Have that shopvac ready.

 

Yep, I do the same.  Works well but quite a bit of dust.  I just can't seem to pull the trigger on a hot wire cutter.  I also use a surform, which makes even smaller dust.  I've not ever tried a sanding block on foam, not sure how well that would work but I'm sure that would create the worst dust of all.  A jigsaw works good for cutting the basic edges of foam (not landscaping obviously).

Andy

--------------------------------------------------------------------------------------------

Milwaukee native modeling the Milwaukee Road in 1950's Milwaukee.

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Posted by Overmod on Monday, September 20, 2021 3:53 PM

The electric knife, which uses two reciprocating blades running in opposition, promises to be nearly as useful as a straight hot-wire cutter... but only if the blades have comparatively long 'wave' serrations.  Any kind of teeth or pointy serration will produce pretty dramatic shredding and likely crumb generation.

I had fun in high school with a (then ginormous) medical ultrasound device rigidly coupled to a cutting blade: this could use a straight razor-knife edge to produce a clean cut even in flexible foam with no shredding at all.  There are a couple of 30 to 40 kHz devices made now that offer foam cutting but the blades are small and the price still comparatively high ($400 or so).

I well remember a cautionary tale of horror regarding how effectively the Hamilton Beach electric knife could 'carve'.  Back in the days when New Year's was a great drunk holiday in the United States -- this would be '66  to '67, I think -- my father had been given one of those things as a Christmas present.  Along comes New Year's Eve and my mother had made up that contemporary staple of New Year cuisine, a bunch of Rock Cornish game hens.  Of course after 'a few cocktails' nothing would do but the electric knife to 'carve' these little birds, and that's exactly what my father proceeded to do... straight across on the bias.  That knife carved meat like butter... also bones, wood skewers, and anything else equally effortlessly.  The result on our plates was a kind of meat axial tomogram of a bird; I remember looking at the tiny but anatomically correct slivers of meat either side of a section of rib and a vertebra or something and thinking 'is this the way we're supposed to eat this"?

Interestingly I never remember the knife being taken out of its box again, not for Easter ham or filet roast, not for Thanksgiving... not ever.  There are some things Mankind was not really meant to know...

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Posted by SeeYou190 on Monday, September 20, 2021 6:27 PM

mreagant
Has anyone used an electric serrated carving knife (two reciprocating blades) to carve foam?

Send me an email.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by Bigjim7 on Tuesday, September 21, 2021 10:08 AM
A cheap dry wall knife or hole saw works great. I am not a big fan of foam but it does have its place.

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