Cutting holes in foam

[Allan Waterfall]

I need to cut some 100mm holes in some 30mm thick foam.The foam is basically the same as used in upholstery and is too soft to hold by any normal means.
Only thing I can think of at the moment is to turn up something like a cookie cutter and press and twist that through,but any other ideas would be appreciated.

Allan

[ahs437]

Some foams cut really nice with a heated wire. They are cheap and easy to build. If you google, I'm sure you will turn up a lot of simple stuff. I've seen them built them from both nichrome and regular iron wire and using everything from light-bulbs to variacs to adjust heat. Check out homemade aircraft groups... a lot of experimental designs utilize ridgid built-up foam that was profiled with a hot wire system. Soft foams... the tool of choice is a yard-sale electric knife.


Andy

[macona]

Electric Knives work well. A lot of upholsters use generic electric kitchen knives to sculpt foam.

[Patch]

How many?

What are they for?

What size foam sheet are you working with?

[Allan Waterfall]

Thanks for the suggestions.

Not sure if a hot wire would cut this type of foam rubber.

I think I'd struggle to get a decent 100mm hole through 30mm of foam rubber with a knife.The foam is to make donuts to use as tyres on a model speed bike.Normal rubber tyres balloon too much.

[Patch]

Do you own a lathe?

[Allan Waterfall]

Yes, and a mill.

Allan

[knedvecki]

Can you freeze the foam to give it some rigidity?

[Patch]

2 different methods I know of.

How many at one time do you need?

[Patch]

Strange, I see a double post.
Last poster was Allen, yet, at post #9 there are 2 more posts made by myself and not showing total post counts.

This is a test to see what is happening.