On 07/11/2011 21:35, Fred wrote:
On Sun, 06 Nov 2011 21:25:10 +0000 (GMT), "Dave Liquorice"
wrote:

with the tool you know it has been set
correctly not partially set or over done.

How does the tool "know" the bolt has been pulled as far as it can?

You feel the resistance step up dramatically...

After all, you can get these in different lengths, so surely it would
have to pull longer bolts further to fully set them?

Yes.

I can see that if it was under done, the "petals" would not have
opened fully, so would distribute the weight over a smaller area. What
is the problem of over doing it? Is it that it starts to draw the
fixing into the plasterboard, enlarging the hole?

Probably - although that would be hard to do with a setting tool.

To use the tool, do you pull the "trigger" once or do you have to pump
it a couple of times?

Several times - more than two usually - its a bit like one of those
single handed clamps if you ever used one. The action is quite "geared
down".

As for load bearing, they spread it over quite and area behind the
board and most loads are sheer. Must admit I'd be wary about fixing a
wash basin with them but that's more down to the plasterboard
deforming over time rather than a failure of the fixing.

I am surprised you can fit radiators with them, I hadn't realised
plasterboard was so strong. I had visions of the fitting being pulled
through the plasterboard and the plasterboard, rather than the fixing,
breaking.

Plaster board is actually very strong with loads in shear. Its far less
good with loads under tension. Needless to say, rads are close to the
wall, and present most of their load in shear.

(usually when fixing to a stud wall, you can arrange for at least one
rad bracket to align with a stud. Then you only need a PB fixing on one
side).



--
Cheers,

John.

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