RichardS noone@invalid wrote:
wrote in message ...
John wrote:
wrote:
snip
BUT WHY????? If it is so you don't break any during 'installation' turn
your
torque ring down so the screw is proud and then increase it till it's
flush!
Nobody on here seems to know the answer to a question that seems
irrelevant!!
Well it's really to find out how much torque is needed to screw them
in successfully and how much will break them. I'm looking for a new
cordless driver and want to know what sort of torque figure is useful
and how much is simply too much. The cordless driver specifications
give their maximum torquer but nowhere can I find any figures for how
much torque is actually needed to screw screws in.
I see where you're coming from, but I'm not entirely sure that it has any
relevance other than purely academic or theoretical. It's an interesting
question, though, and I'm surprised that ability to withstand up to X amount
of torque isn't somewhere within screw specifications. Perhaps your best
bet is to hunt down and contact the manufacturers of the particular screws
that you're using - I don't really see that you can work out shear strength
for a particular size of screw in general because they're all going to be
made from slightly different materials and to slightly different
specifications, which could have a disproportionately large effect on the
shear strength.
I wouldn't have thought that different types of steel would have huge
effects. I'm not interested in exact figure. I just want to know if
(for example) a 5mm screw will shear at 10nM or a 100nM. OK,
different steel screws might well have a shear torque ranging from 15
to 50nM but even that sort of range gives me an idea.
All the manufacturers of Industrial-rated tools seem to give two figures for
maximum torque - one for "soft" joints and one for "hard" joints - anyone
have a clue what the difference is here, and whether there is actually a
standardised test for measuring these?
I think 'soft' and 'hard' is just the torque in the high gear and the
low gear of their two speed gearboxes isn't it? Why on earth they're
called 'soft' and 'hard' I don't know.
As for buying a drill/driver, I think that the thing is to go for as high a
torque as you can find for a particular voltage & price point - it will
indicate better cells and motor. 20 or so step torque control is pretty
much essential. Then just play about until you get the ideal maximum torque
setting for a particular screw in whatever it's going into. Even if you
expect to be driving only no.8 screws in normal use, you can always use the
torque control to reduce the torque, but you can't turn up a less powerful
drill if you have the need to drive in occasional long no.12s for instance.
As I've just reported in my original thread asking about cordless
drivers I've bought a Metabo SBT12 which produces a maximum torque of
53Nm. I've just used it for the first time and I'm impressed. It
screwed the 8mm x 100mm Turbogold screws into fence posts (the
application I specifically wanted it for) effortlessly - excellent!
Incidentally, you ought not to get close to shearing a screw in an ideal
situation - received wisdom in the woodworking community appears to be that
maximum holding strength from a screw is achieved when a pilot hole of the
_correct size_ is drilled first. It's pretty much essential when using
brass screws, but an often skipped step with stronger screws that can be
driven directly into the material with a modern driver.
I don't drill pilot holes purely to save time, I'm not aiming for
beauty when screwing fences together. I use screws rather than nails
simply because it eases taking them apart if it's ever necessary and
because it's stronger, nails pull out (especially if half a ton of
horse leans on the other side).
--
Chris Green