weldnfab

what is best way to cut holes in styrofoam?

26 posts in this topic

well, I am pondering cutting holes for 2.75 inch net pots in a floating styrofoam mat... is there a neater/cleaner looking way to accomplish this?

Robertbab likes this

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Hi weldnfab,

One method I seen used is to heat a thin-walled steel pipe of the appropriate diameter and push that through the Styrofoam. Try a hole saw on scrap of the material and see how that works. If the styrofoam is dense enough, the hole saw method should work OK.

Some plastics suppliers can cut Styrofoam to order - complete with holes - but I don't know the specifics.

Gary

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I used the hole-saw method with the drill. Worked fine for me. Can be a bit messy but worked out OK. I have since changed my rafts over to Corflute that sits an inch above the water. Results are good so far.

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As Helo says the bet way to cut it is with a hot wire. The main reason is you get a sharp sealed cut and avoid all the mess and chipout with other methods. You can make a hot knife by stretching filiment (wire) in a basic wood frame and attach a battery by wire to each end completing the circuit. The filiment gets hot quickly and cuts like butter, you will be amazed how easily. I have seen instructions on the instructables web site that look equaly as easy. Good luck.

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Hi

I buy square pots and cut square holes with retractable trimming knife in 50 mm high density styrofoam sheets.

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good ideas all... thanks. considering the hot wire method.... any specific type of wire work best?.. or just thin copper? also found a soup can that is close.... maybe a backup plan.

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I have always used stainless steel safety wire. But any wire would work. The thinner the wire the less it will take to get it hot and to cut, but if you go to thin it will break easy when hot. I have always used either .20" or .30" wire.

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Usually I use a aircraft battery, but what ever size will get the wire you choose hot. A 6 volt lantern battery should be plenty, but a car battery will do it for sure.

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NiChrome or an olg guitar string are good choices for the wire also as they will no giv off fumes when heated.

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appreciate the input wacker... thought I had heard about a nichrome wire before but wasnt sure it applied here.

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I just cut 2 inch holes with a hole saw but was disappointed the the fit is quite loose. Is that common? Almost wonder if a 1 7/8's hole saw would have been better?

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Hi Cecil,

I remembered seeing this post showing how the folks at BYAP did it.

I'm also aware of some growers who do not use the small cup filled with media......one option is a slender "collar" arrangement (about 1" in diam) into which the seedlings are placed. In another option that I've seen used, the seedlings are just placed into the holes....with the leaves holding the seedling in place.

Gary

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I just use a hole saw. I run the drill at it's fastest setting and push very lightly on the foam. It gives a good clean cut this way.

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I just use a hole saw. I run the drill at it's fastest setting and push very lightly on the foam. It gives a good clean cut this way.

That's what I did. Just disappointed that the net pots are so loosely fitted. I had one fall through.

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I too used a hole saw, and with a 1 3/4" bit, the 2"pots are very snug and I have to force them in.

Cecil likes this

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I've used a 1 7/8" hole saw for the 2" net pots, and they have fit really nicely. I also use little 1" net pots for a bunch of tomato starts that I transfer to the "dirt garden" later and also give to friends and family for their gardens. These are a bit more of a challenge since there's much less room for error. I've used a metric measured hole saw for those because it had a nice fit, but can't remember the size.

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I've used a 1 7/8" hole saw for the 2" net pots, and they have fit really nicely. I also use little 1" net pots for a bunch of tomato starts that I transfer to the "dirt garden" later and also give to friends and family for their gardens. These are a bit more of a challenge since there's much less room for error. I've used a metric measured hole saw for those because it had a nice fit, but can't remember the size.

1 7/8's inch hole saw will be what it will be in the future. In the mean time I've added a couple of tiny zip ties to the pots on each side and it keeps them in their holes.

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I too used a hole saw, and with a 1 3/4" bit, the 2"pots are very snug and I have to force them in.

Thanks!

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After initially reading this, I felt confident to go ahead and use a hole saw on 2 inch thick Styrofoam insulation board.   Using a 1.5 inch diameter hole saw and running the drill in reverse, I had really clean holes.  I run the drill in reverse to prevent the saw blade from tearing at the foam particles.  Due to the low density, the blade goes through smoothly and cleanly.   In my opinion, much easier than hooking up a hot wire and trying to make a perfect circle.  Thanks to all so I could consider my options and make an informed choice.  Just FYI, I am growing Sugar Beets.  I will be using an aeroponic system on a timer to keep the root system moist.  I can not use net pots due to the beet being a root crop and growing to 3-5 lbs.   I started the plants in starter plugs. The diameter of the hole is such that the starter plugs will have a compressed fit and hold the plant in place. 

Edited by tmyers (see edit history)

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Hi,

 

If I recall correctly, BYAP used a thin-walled steel pipe of the correct diameter.  They'd heat the pipe and push it through the styrofoam.

 

I hadn't heard about the the idea of running a hole saw i reverse......that sounds good, too.

 

 

Gary

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Do not use a tungsten tip hole saw as they will cut oversize. You can also run the drill in reverse and see how that goes. Cheers

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