How do you cut sheeps-wool loft insulation?

[Dave Rove]

How do you cut sheeps-wool loft insulation?

100mm Thermafleece loft insulation to be precise. Large scissors are stopped dead. A Stanley Knife just scrapes small lumps from the surface. Even a single-edge razor blade from a windscreen scraper just glides over it. It can be torn, but very untidily.

Finally, I put down two boards with a couple of millimetres gap between them, laid the insulation across them, placed two matching boards across the top, stood on the upper boards to compress the insulation, trying not to wobble and needing several attempts to get the alignment right, then cut between the gap with a large sharp straight-edge carving knife. That worked.

So now I'm intending to build a cutting jig so that I can do the above without falling through the roof. But am I missing something? Should it really be that difficult?

(I had previously asked this group about putting extra insulation under a section of flat-roof but was dissuaded by warnings about moisture so I'll think about that another day. However, sheeps-wool insulation was mentioned, and that seemed an excellent choice for replacing the dirty old itchy 1" mineral-wool insulation in the main part of my loft.)

[Andrew Mawson]

When tidying up our ewes before lambing they have to be 'dagged' which is trimming the (usually shit encrusted) wool from their rear ends. For this we use 'dagging shears' . Dagging shears need sharpening VERY often as you get through the flock, so good luck getting through 100 mm thick compresed stuff.

Sheep shearing uses a shearing head very similar to the one used by your barber - though the good ones are self sharpening. However there you are cutting at approximately 90 degrees to the wool staple and it is being held firmly at the other end by the animal !

Andrew

[stuart noble]

I'd try a handsaw

[Tim Lamb]

In message , Dave Rove writes

Cut it with a sharp blade while it is still rolled up? Only done this once myself and that was rock wool. I actually used a bow saw with the teeth ground off the blade to leave a reasonably straight sharp edge. You need the ubiquitous angle grinder:-)

[Dave Liquorice]

I think that is the only way compress between boards. If you have a couple of clamps and thickish boards it might be easier to clamp the wool between the boards and use them as a guide for the knife, a scolloped edge might be better than straight.

[Bill Wright]

An electric kitchen knife of the type that has two opposing deeply serrated blades.

Bill

[PeterC]

When I was cutting the glass insulation for my loft I found that an old Kitchen Devil, with the scollops worn down to undulations, well sharpened was easy to use. I cut the rolls before unwrapping them - don't need to be dead accurate of course. With only a 10" blade, the main skill is in avoiding the dreaded spiral!

[Dave Rove]

Thanks for the comments. I decided to go with making a cutting jig:

A powered kitchen knife would have worked I'm sure, but I might have bought the wrong type and blown it up.

[Brian_Gaff]

Well there are people here who would answer Angle grinder even if the question was about brain surgery!

Brian

[Martin Bonner]

A board of wood underneath, a board on top, cut along the edge of the boards with a carving knife.

In other words, your original scheme, but only one board top and bottom.

[Bill Wright]

Forget the carving knife. Use an angle grinder with a thin blade. Or a stil saw.

Bill