Cutting Celotex insulating foam
 

Hi All

I'm insulating the roof of my garage conversion with Celotex, between and
below the rafters but I'm having a bit of a job cutting the Celotex
accurately.

The manufacturers recommend a trimming knife or a fine tooth saw, does
anyone have any experience of cutting this stuff.

I'm using 50mm thick between the rafters so in order to cut it with a craft
knife I'm using one of the snap off blade types with a blade fully extended,
this reaches nearly right through the Celotex but because the blade is
quite thin it is incline to wander from the straight line in the depth of
the material. I tried a sharp kitchen knife which is better but because the
blade is thicker the Celotex grips it making it difficult to pull through.

I'd rather not use a saw because of the toxic dust.

Is there a technique to cutting this stuff that I need to learn?

Any advice gratefully received

Thanks
Roger

"Roger" wrote in message
...
Hi All

I'm insulating the roof of my garage conversion with Celotex, between and
below the rafters but I'm having a bit of a job cutting the Celotex
accurately.

The manufacturers recommend a trimming knife or a fine tooth saw, does
anyone have any experience of cutting this stuff.

I'm using 50mm thick between the rafters so in order to cut it with a
craft
knife I'm using one of the snap off blade types with a blade fully
extended,
this reaches nearly right through the Celotex but because the blade is
quite thin it is incline to wander from the straight line in the depth of
the material. I tried a sharp kitchen knife which is better but because
the
blade is thicker the Celotex grips it making it difficult to pull
through.

I'd rather not use a saw because of the toxic dust.

Is there a technique to cutting this stuff that I need to learn?

Any advice gratefully received

Thanks
Roger



A serrated steak knife is usually a good cutter for this stuff. The steak
knife doesn't create to much dust, but it's always wise to wear some kind of
protection against breathing any kind of dust particles, especially in
confined spaces. It's also a good idea to have a vacuum cleaner running in
the background, even an upright lying on its back, to catch anything that
escapes from around the cut.

On Tue, 16 Nov 2004 19:26:46 -0000, "Roger"
strung together this:

Is there a technique to cutting this stuff that I need to learn?

Yes, buy a woodsaw. Works fine here.
--

SJW
A.C.S. Ltd

"Roger" wrote in message
...
Hi All

I'm insulating the roof of my garage conversion with Celotex, between and
below the rafters but I'm having a bit of a job cutting the Celotex
accurately.

The manufacturers recommend a trimming knife or a fine tooth saw, does
anyone have any experience of cutting this stuff.

I'm using 50mm thick between the rafters so in order to cut it with a
craft knife I'm using one of the snap off blade types with a blade fully
extended, this reaches nearly right through the Celotex but because the
blade is quite thin it is incline to wander from the straight line in the
depth of the material. I tried a sharp kitchen knife which is better but
because the blade is thicker the Celotex grips it making it difficult to
pull through.

I'd rather not use a saw because of the toxic dust.

Is there a technique to cutting this stuff that I need to learn?

Any advice gratefully received

An old serrated bread knife works well, as long as the blade isn't too
bendy.

Rick

BigWallop wrote:

"Roger" wrote in message
...
Hi All

I'm insulating the roof of my garage conversion with Celotex, between and
below the rafters but I'm having a bit of a job cutting the Celotex
accurately.
Snip
A serrated steak knife is usually a good cutter for this stuff. The steak
knife doesn't create to much dust, but it's always wise to wear some kind of
protection against breathing any kind of dust particles, especially in
confined spaces. It's also a good idea to have a vacuum cleaner running in
the background, even an upright lying on its back, to catch anything that
escapes from around the cut.

An occasional smear of margarine or wax on the blade makes for easier cutting
and less dust.

On Tue, 16 Nov 2004 19:26:46 -0000, Roger wrote:

The manufacturers recommend a trimming knife or a fine tooth saw,
does anyone have any experience of cutting this stuff.

25mm bonded to 9mm plasterboard snaps very easyly. Not tried it on
50mm unbonded but I suspect a good deepish cut from a craft knife then
putting the cut above a batten and pushing down would have the desired
effect. A bit like cutting glass.

I'd rather not use a saw because of the toxic dust.

Is it toxic or just an irritant? Can't be worse than the dust that
comes off fibre glass. As has alreday been said a vacum running will
stop dust levels getting too high, very good at keeping dust levels to
light mist instead of thick fog when sanding filler/plaster down...

--
Cheers
Dave. pam is missing e-mail

On Tue, 16 Nov 2004 19:26:46 -0000, "Roger"
wrote:

Hi All

I'm insulating the roof of my garage conversion with Celotex, between and
below the rafters but I'm having a bit of a job cutting the Celotex
accurately.

The manufacturers recommend a trimming knife or a fine tooth saw, does
anyone have any experience of cutting this stuff.

I'm using 50mm thick between the rafters so in order to cut it with a craft
knife I'm using one of the snap off blade types with a blade fully extended,
this reaches nearly right through the Celotex but because the blade is
quite thin it is incline to wander from the straight line in the depth of
the material. I tried a sharp kitchen knife which is better but because the
blade is thicker the Celotex grips it making it difficult to pull through.

I'd rather not use a saw because of the toxic dust.

Is there a technique to cutting this stuff that I need to learn?

Any advice gratefully received

Thanks
Roger


I used a cheap old portable table saw bought from somebody locally and
then thrown away. It was used outside and together with a shop
vacuum to keep the dust down, but I used a mask as well.
This is a fast and accurate way.

Alternatively a cheap circular saw with dust hose hook up would work.

For smaller pieces and trrimming shapes, I used an old serrated bread
knife with a sawing action.


If you can find a secondhand table saw for about £30 then the time
saved will make it worthwhile. I have the teeshirt.







--

..andy

To email, substitute .nospam with .gl

Roger wrote:

I'm insulating the roof of my garage conversion with Celotex, between and
below the rafters but I'm having a bit of a job cutting the Celotex
accurately.

I did most of mine with a jigsaw (agressive blade, pendulum action on
full). Quite easy to do one handed as well. A knife can be useful for
final trimming at times. The dust created is not that bad (don't think
it is actully toxic anyway - although it will irritate if you get it in
your eyes).

The foil backed stuff will knacker blades given time, but a pack of five
jigsaw blades is cheap enough....


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Roger wrote:

Hi All

I'm insulating the roof of my garage conversion with Celotex, between and
below the rafters but I'm having a bit of a job cutting the Celotex
accurately.

The manufacturers recommend a trimming knife or a fine tooth saw, does
anyone have any experience of cutting this stuff.

I'm using 50mm thick between the rafters so in order to cut it with a craft
knife I'm using one of the snap off blade types with a blade fully extended,
this reaches nearly right through the Celotex but because the blade is
quite thin it is incline to wander from the straight line in the depth of
the material. I tried a sharp kitchen knife which is better but because the
blade is thicker the Celotex grips it making it difficult to pull through.

I'd rather not use a saw because of the toxic dust.


Actually I used many things, frm a woodsaw, to a bread knife.

The dust is highhly iritating, but not toxic I think. Wear a mask.

Is there a technique to cutting this stuff that I need to learn?


Fine toothed saw or ultra sharp kitchen knife.

Any advice gratefully received

Thanks
Roger

On Tue, 16 Nov 2004 21:15:38 +0000 (GMT), "Dave Liquorice"
wrote:

On Tue, 16 Nov 2004 19:26:46 -0000, Roger wrote:

The manufacturers recommend a trimming knife or a fine tooth saw,
does anyone have any experience of cutting this stuff.

25mm bonded to 9mm plasterboard snaps very easyly. Not tried it on
50mm unbonded but I suspect a good deepish cut from a craft knife then
putting the cut above a batten and pushing down would have the desired
effect. A bit like cutting glass.

Sadly not quite... The thicker boards have glass fibre threads in them
for strength. You can snap to an extent but unless you cut almost
through then no. The threads will pull out lumps and make a mess of
the edges.


I'd rather not use a saw because of the toxic dust.

Is it toxic or just an irritant? Can't be worse than the dust that
comes off fibre glass. As has alreday been said a vacum running will
stop dust levels getting too high, very good at keeping dust levels to
light mist instead of thick fog when sanding filler/plaster down...


--

..andy

To email, substitute .nospam with .gl

In message , Roger
writes
Hi All

I'm insulating the roof of my garage conversion with Celotex, between and
below the rafters but I'm having a bit of a job cutting the Celotex
accurately.

The manufacturers recommend a trimming knife or a fine tooth saw, does
anyone have any experience of cutting this stuff.

I'm using 50mm thick between the rafters so in order to cut it with a craft
knife I'm using one of the snap off blade types with a blade fully extended,
this reaches nearly right through the Celotex but because the blade is
quite thin it is incline to wander from the straight line in the depth of
the material. I tried a sharp kitchen knife which is better but because the
blade is thicker the Celotex grips it making it difficult to pull through.

I'd rather not use a saw because of the toxic dust.

Is there a technique to cutting this stuff that I need to learn?

We use a jigsaw fitted with an old blade that has had the teeth ground
off to form a knife edge.
I think you can actually buy them too.
--
mark

On Tue, 16 Nov 2004 23:18:30 +0000, Andy Hall wrote:

Sadly not quite... The thicker boards have glass fibre threads in
them for strength. You can snap to an extent but unless you cut
almost through then no. The threads will pull out lumps and make a
mess of the edges.

My new thing for today, won't get caught now. B-)

Can you not open the cut over the batten and slice the threads or are
they random through the body rather than descrete layers of open weave
matting?

--
Cheers
Dave. pam is missing e-mail

On Wed, 17 Nov 2004 14:15:17 +0000 (GMT), "Dave Liquorice"
wrote:

On Tue, 16 Nov 2004 23:18:30 +0000, Andy Hall wrote:

Sadly not quite... The thicker boards have glass fibre threads in
them for strength. You can snap to an extent but unless you cut
almost through then no. The threads will pull out lumps and make a
mess of the edges.

My new thing for today, won't get caught now. B-)

Can you not open the cut over the batten and slice the threads or are
they random through the body rather than descrete layers of open weave
matting?



They seem to be pretty random fibres. Not very thick, but enough to
mean that snapping doesn't work all that well if you're looking for a
clean edge.



--

..andy

To email, substitute .nospam with .gl

Andy Hall wrote:

They seem to be pretty random fibres. Not very thick, but enough to
mean that snapping doesn't work all that well if you're looking for a
clean edge.

Must admit to not finding any threads in the PIR foam I used (made by
Ecotherm)... must be something that varies with manufacturer. Having
said that, snapping would still not work that well due the material not
breaking cleanly anyway.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

I've just had delivered 9 x 8x4 sheets of the Celotex delivered but
its 90mm thick, sounds like I'm doing to have fun with it ! Definitely
a saw and mask job I think.

Peter

mark wrote in message ...
In message , Roger

We use a jigsaw fitted with an old blade that has had the teeth ground
off to form a knife edge.
I think you can actually buy them too.

How about those electric carving knifes?!?

Thanks for some great advice everyone, very useful as usual.
What a great newsgroup this is.

Rgds
Roger
"adder" wrote in message
om...
mark wrote in message
...
In message , Roger

We use a jigsaw fitted with an old blade that has had the teeth ground
off to form a knife edge.
I think you can actually buy them too.

How about those electric carving knifes?!?

On Tue, 16 Nov 2004 19:26:46 -0000, "Roger"
wrote:

Hi All

I'm insulating the roof of my garage conversion with Celotex, between and
below the rafters but I'm having a bit of a job cutting the Celotex
accurately.

The manufacturers recommend a trimming knife or a fine tooth saw, does
anyone have any experience of cutting this stuff.

I'm using 50mm thick between the rafters so in order to cut it with a craft
knife I'm using one of the snap off blade types with a blade fully extended,
this reaches nearly right through the Celotex but because the blade is
quite thin it is incline to wander from the straight line in the depth of
the material. I tried a sharp kitchen knife which is better but because the
blade is thicker the Celotex grips it making it difficult to pull through.

I'd rather not use a saw because of the toxic dust.

Is there a technique to cutting this stuff that I need to learn?

Any advice gratefully received

Thanks
Roger


I cut it roughly, put one side in against the rafter so the other is
too big, and then using a bread knife, cut it using the other rafter
as a guide. Wack it home with a quick slap.

Rick

"Peter Cherry" wrote in message
om...
I've just had delivered 9 x 8x4 sheets of the Celotex delivered but
its 90mm thick, sounds like I'm doing to have fun with it ! Definitely
a saw and mask job I think.

Buy a new woodsaw. Biggest problem with thick sheets (I use 120mm a lot) is
keeping the cut parallel. Sometimes have to revert to a bit of scrapeing
away afterwards.