Looking for recommendations for a cutting knife for Celotex

[peak experience]

Hi all, 

I'm using Celotex foam for my scenery. It's a dense foam used in loft insulation. I'm making rocks/cliff faces i.e, a gorge/landslip. I'm guessing it's a common material to use and I wondered what tools/techniques others had used to sculpt it. A Stanley knife blade is too short for some of the deep cuts I'd be wanting to make. I'm looking for a tool that'll leave flat, smooth surfaces so I'm guessing a serrated edge wouldn't be an option. I'd be grateful for any hints/tips etc anyone could provide. 


 

[crompton 33]

The only tools i used when cutting Celotex foam board . Was a 12'in haksaw blade and a Stanley knife .  Then used used Polyfilla  mixed with water and PVA to cover the foam in places. Then cover with Grass and bushes .  Look's like this when done. IMGP0436 by ALF WESTLEY, on Flickr

[Oldddudders]

 A hot-wire tool, sold for sculpting foam, is helpful. The one I bought also had a piercing pointy thing, which is great for getting a nice hole through which to pass wires. A piercing saw will have the depth of cut, while a Stanley Shaper file (are they still sold?) can smooth things. I’m afraid whatever the method, this is messy stuff, producing lots of lightweight dusty particles. Not recommended for use in the lounge, or other parts of shared accommodation! 

[TheQ]

I've used a hacksaw blade in one of those single ended handles like this..

https://www.amazon.co.uk/Atoplee-Adjustable-Handle-Handheld-Hacksaw/dp/B0746C6JBQ/ref=sr_1_1_sspa?ie=UTF8&qid=1551958759&sr=8-1-spons&keywords=hacksaw+handle&psc=1.

 

if it's a small enough chunk of Celotex, then a hot wire is easier.

 

Hot wire.. need good ventilated area.

Sawing, wear a dust mask...

 

For chopping smaller bits for scenery, a steak knife, I'm going to cover it with pollyfilla /pva mix anyway..

[Campaman]

A bread knife could be as good option, not as rough as a piecing saw

[Goochie]

I've recently been cutting sheets of Celotex insulation for the deck of my layout. The knife I used was an old Sabatier style cook's knife, re-sharpened for the job in hand. Cutting along the length of a sheet, knife at a low angle, using a steel straight edge as a guide, it cut through easily with minimal dust and kept a smooth edge . With a thick sheet you may need two or more cuts to go right through, but any waste generated tends to be in sliver form. Provided you don't use the knife too vertically, it shouldn't snag causing a lump of insulation to come out. Keeping the blade sharp also helps. The Stanley shapers (Surforms), mentioned above, are still available and will remove material quite quickly. A good coat of neat pva will help to seal the foam edges, ready for plaster bandage, polyfilla or other detailing medium.

 

Andy

[peak experience]

9 hours ago, Goochie said:

I've recently been cutting sheets of Celotex insulation for the deck of my layout. The knife I used was an old Sabatier style cook's knife, re-sharpened for the job in hand. Cutting along the length of a sheet, knife at a low angle, using a steel straight edge as a guide, it cut through easily with minimal dust and kept a smooth edge . With a thick sheet you may need two or more cuts to go right through, but any waste generated tends to be in sliver form. Provided you don't use the knife too vertically, it shouldn't snag causing a lump of insulation to come out. Keeping the blade sharp also helps. The Stanley shapers (Surforms), mentioned above, are still available and will remove material quite quickly. A good coat of neat pva will help to seal the foam edges, ready for plaster bandage, polyfilla or other detailing medium.

 

Andy

Thanks Andy. I'm hoping not to have to cover it. I want to sculpt it and then just paint it. I feel, from working on a small piece with a Stanley blade, that that's going to give the best result. I may spray it was something like Plasticote just to give it a bit more strength and robustness against knocks.  

[peak experience]

Thanks for all your replies. A hot wire cutter sounds interesting. I'll look into that. 

[Bill_J]

Some plumbers/builders merchants, sell a toothless saw specifically designed for cutting insulation and foam pipe lagging. Gives a clean cut with no mess.

 

 

[rab]

On 07/03/2019 at 11:43, TheQ said:

 

For chopping smaller bits for scenery, a steak knife, I'm going to cover it with pollyfilla /pva mix anyway.

 

Cover what, the scenery or the steak knife .

[TheQ]

Me, the steak knife, the floor, and anything else I can make a mess of. Maybe some will make it to the scenery...