# Insulation knife



## Bud9051 (Nov 11, 2015)

For mineral wool I use a serrated bread knife. For fiberglass my utility knife does fine, but you need to compress the insulation. 

They do make utility knives with break-off blades where you can extend them beyond the snap point. I picked up one from the blue box. I like the blade, but hate the knife. Eventually I will get mad enough at it to find a replacement.

If you are doing a large job, set up a cutting table where the length is pre-marked and you have a rafter square and a 9' piece of metal edge to compress and guide your cut. For the 9' metal edge I used a heavy duty hat channel.

Bud


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## joecaption (Nov 30, 2011)

Even just using a piece of 2 X 4 to compress it will work.
A utility knifes all I've ever used.


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## ryansdiydad (Aug 16, 2015)

A knife with snap off blades is ideal because u can extend the blade longer than a utility knife which can help with thicker insulation... As others said you also need to compress the batt. I use my aluminum carpenters square for cross cuts and a ripped 2x4 for the long ones.. I just found having something thinner to help compress the batt was easier to work with.. Easier to run the blade along it and get a good cut in the batt.. But thats just me..

Also if it's Kraft faced cut it with the paper side down..


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## oh'mike (Sep 18, 2009)

Bud9051 said:


> For mineral wool I use a serrated bread knife. For fiberglass my utility knife does fine, but you need to compress the insulation.
> 
> 
> 
> Bud



Yep----A serrated bread knife is fast and good.


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## Millertyme (Apr 20, 2010)

My biggest problem was the utility seemed a little short for the job. I've always used them in the past but those longer knives seem more efficient. Thanks for the responses


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## Piedmont (Nov 1, 2007)

Hmm... I purchased a fiberglass cutter from Home Depot but can't seem to find them online to show you a picture. I wouldn't think they'd have stopped making/selling them. 

It's a guard that goes onto a utility knife (which it came with) that wraps around it like a finger guard of a sword the blade pokes through it. Because of the guard, you just push it down and easily cut fiberglass without any additional tools and it glides and cuts it with such ease I love it. 

I guess I better keep onto mine, it's a funny lime-yellow color so easy to find. *EDIT* I found an image of it, this is it! It's called a "Stanley Insulation Knife". There's a person selling them on ebay, $4.50 with $4.29 shipping so less than $9 and even includes the utility knife.


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## raymondburke (9 mo ago)

Millertyme said:


> Looking for a good knife. Why do the pros use this link? My utility knife doesn't seem like the right tool. Any brands to recommend? For batt insulation.


What is the best style or size or length of knife for cutting Armaflex tubing?


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## chandler48 (Jun 5, 2017)

@raymondburke welcome to the forums. This is a 7 year old thread about cutting insulation. It would be best to start your own thread and ask questions. It will garner much better information.


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