I'd like to have some 'ball park' figures for the torque which typical
wood screws can handle. Can anyone give me some typical figures or
point me at a web site that has them? I would emphasise that I'm
after the torque figure, i.e. the amount of twist needed to break
them. I realise this doesn't directly relate to the strength of the
screw holding things together which would simply be given by the
tensile stregth of the screw.

I'd prefer the figures for metric screws (i.e. diameters in mm) and in
Nm but I'm quite happy to convert if necessary. The actual screws I'm
using are ScrewFix TurboGold and the stainless steel versions of the
same. I would guess however that most good quality screws are going
to be similar, I'm not after accurate figures, just an idea of what
is likely to break them.

--
Chris Green

wrote:
I'd like to have some 'ball park' figures for the torque which typical
wood screws can handle. Can anyone give me some typical figures or
point me at a web site that has them? I would emphasise that I'm
after the torque figure, i.e. the amount of twist needed to break
them. I realise this doesn't directly relate to the strength of the
screw holding things together which would simply be given by the
tensile stregth of the screw.

Actually, it pretty much is tensile strength.
Steel (of any sort) pretty much has a constant stiffness.
If you stretch it a given amount, it'll stretch a certain distance.

If you think about what's happening in the screw, if you draw lines along
the shank of the screw, when you turn it, it gets twisted into a spiral.
As each line is now longer, that means that it's under tension on the
outside, and the inside is under compression.
At some point the force just gets too high, and the screw either tears,
snaps or bends.

IMO, this figure is utterly irrelevant in most cases, it's hard to
get most types of screwdriver bit to exert enough force on the screw
to get it to fail this way.
And if you could, it's not relevant as by the time you've reached that
number, in nearly all cases the screw has gone too deep.

IMO, this figure is utterly irrelevant in most cases, it's hard to
get most types of screwdriver bit to exert enough force on the screw
to get it to fail this way.
And if you could, it's not relevant as by the time you've reached that
number, in nearly all cases the screw has gone too deep.

I managed to shear off the head of a dry-wall screw last week with a normal
screwdriver! (just wouldnt go in that fraction more I wanted, ended up using
a nail in that spot )

a wrote:
IMO, this figure is utterly irrelevant in most cases, it's hard to
get most types of screwdriver bit to exert enough force on the screw
to get it to fail this way.
And if you could, it's not relevant as by the time you've reached that
number, in nearly all cases the screw has gone too deep.

I managed to shear off the head of a dry-wall screw last week with a normal
screwdriver! (just wouldnt go in that fraction more I wanted, ended up using
a nail in that spot )

Well, you can get screws made of alloys with the tensile strength of
extra-mature cheddar...

In article ,
Ian Stirling wrote:
IMO, this figure is utterly irrelevant in most cases, it's hard to
get most types of screwdriver bit to exert enough force on the screw
to get it to fail this way.
And if you could, it's not relevant as by the time you've reached that
number, in nearly all cases the screw has gone too deep.

Yup. I often use my mains drill for screwdriving and it's got much more
torque than most cordless ones and no clutch.
A screw breaking is a rare event - they usually 'cam out' first with
Pozidriv

--
*Never put off until tomorrow what you can avoid altogether *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:

Yup. I often use my mains drill for screwdriving and it's got much more
torque than most cordless ones and no clutch.
A screw breaking is a rare event - they usually 'cam out' first with
Pozidriv

I've broken quite a few Torx screws (SpaX) with my 18V combi, including
some very large ones (150mm size 8).

--
Grunff

I've broken quite a few Torx screws (SpaX) with my 18V combi, including
some very large ones (150mm size 8).

Ooer - a competition...

I`ve sheared 12mm bolts before now - not the monkey metal kind :-}

--
Please add "[newsgroup]" in the subject of any personal replies via email
--- My new email address has "ngspamtrap" & @btinternet.com in it ;-) ---

On Friday, 29 October 2004 16:47:50 UTC+1, Dave Plowman (News) wrote:
In article ,

Yup. I often use my mains drill for screwdriving and it's got much more
torque than most cordless ones and no clutch.
A screw breaking is a rare event - they usually 'cam out' first with
Pozidriv

When I used to do that I snapped a fair few. They were mostly 32mm screwfix black plasterboard screws with Philips no2 heads.


NT

On 06/01/16 17:34, wrote:
On Friday, 29 October 2004 16:47:50 UTC+1, Dave Plowman (News) wrote:
In article ,

Yup. I often use my mains drill for screwdriving and it's got much more
torque than most cordless ones and no clutch.
A screw breaking is a rare event - they usually 'cam out' first with
Pozidriv

When I used to do that I snapped a fair few. They were mostly 32mm screwfix black plasterboard screws with Philips no2 heads.


NT

I've lost count of how many I've snapped.
Mainlyt te smaller shafts - is it No 4?

But I've snapped car studs of a lot bigger diameter than that


--
Bureaucracy defends the status quo long past the time the quo has lost
its status.

Laurence Peter

In article ,
The Natural Philosopher wrote:
On 06/01/16 17:34, wrote:
On Friday, 29 October 2004 16:47:50 UTC+1, Dave Plowman (News) wrote:
In article ,

Yup. I often use my mains drill for screwdriving and it's got much more
torque than most cordless ones and no clutch.
A screw breaking is a rare event - they usually 'cam out' first with
Pozidriv

When I used to do that I snapped a fair few. They were mostly 32mm screwfix black plasterboard screws with Philips no2 heads.


NT

I've lost count of how many I've snapped.
Mainlyt te smaller shafts - is it No 4?

But I've snapped car studs of a lot bigger diameter than that

Back in the early 70s, I snapped a 5" no 14 - only using a handbrace. The
screws cost 14/- each, too. Shows how much I was upset - I can still
remember it.

--
Please note new email address:

On Wed, 06 Jan 2016 17:34:10 -0000, wrote:

On Friday, 29 October 2004 16:47:50 UTC+1, Dave Plowman (News) wrote:
In article ,

Yup. I often use my mains drill for screwdriving and it's got much more
torque than most cordless ones and no clutch.
A screw breaking is a rare event - they usually 'cam out' first with
Pozidriv

When I used to do that I snapped a fair few. They were mostly 32mm screwfix black plasterboard screws with Philips no2 heads.

All drills I've ever seen have an "accelerator pedal". Does your 2.5 litre car always go 150mph without control? You don't pull the lever all the way in when screwing!

--
In the UK, 90% of things are prohibited. The other 10% are compulsory.

On 06/01/2016 18:02, Mr Macaw wrote:
On Wed, 06 Jan 2016 17:34:10 -0000, wrote:

On Friday, 29 October 2004 16:47:50 UTC+1, Dave Plowman (News) wrote:
In article ,

Yup. I often use my mains drill for screwdriving and it's got much more
torque than most cordless ones and no clutch.
A screw breaking is a rare event - they usually 'cam out' first with
Pozidriv

When I used to do that I snapped a fair few. They were mostly 32mm
screwfix black plasterboard screws with Philips no2 heads.

All drills I've ever seen have an "accelerator pedal". Does your 2.5
litre car always go 150mph without control? You don't pull the lever
all the way in when screwing!

Is that what she said last night? ;-)

--
Bod

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

On Wednesday, 6 January 2016 18:02:30 UTC, Mr Macaw wrote:
On Wed, 06 Jan 2016 17:34:10 -0000, tabbypurr wrote:
On Friday, 29 October 2004 16:47:50 UTC+1, Dave Plowman (News) wrote:
In article ,

Yup. I often use my mains drill for screwdriving and it's got much more
torque than most cordless ones and no clutch.
A screw breaking is a rare event - they usually 'cam out' first with
Pozidriv

When I used to do that I snapped a fair few. They were mostly 32mm screwfix black plasterboard screws with Philips no2 heads.

All drills I've ever seen have an "accelerator pedal". Does your 2.5 litre car always go 150mph without control? You don't pull the lever all the way in when screwing!

We don't need reminding of your cluelessness

Ian Stirling wrote:
wrote:
I'd like to have some 'ball park' figures for the torque which typical
wood screws can handle. Can anyone give me some typical figures or
point me at a web site that has them? I would emphasise that I'm
after the torque figure, i.e. the amount of twist needed to break
them. I realise this doesn't directly relate to the strength of the
screw holding things together which would simply be given by the
tensile stregth of the screw.

Actually, it pretty much is tensile strength.
Steel (of any sort) pretty much has a constant stiffness.
If you stretch it a given amount, it'll stretch a certain distance.

If you think about what's happening in the screw, if you draw lines along
the shank of the screw, when you turn it, it gets twisted into a spiral.
As each line is now longer, that means that it's under tension on the
outside, and the inside is under compression.
At some point the force just gets too high, and the screw either tears,
snaps or bends.

IMO, this figure is utterly irrelevant in most cases, it's hard to
get most types of screwdriver bit to exert enough force on the screw
to get it to fail this way.
And if you could, it's not relevant as by the time you've reached that
number, in nearly all cases the screw has gone too deep.

Yes I *did* realise there would be a fairly direct relation to tensile
strength but that doesn't directly help me work out the 'torque
strength'.

Anyway it is quite easy to break Pozidriv screws in my experience and
I also use some hex head coach screws where you can apply effectively
unlimited torque.

--
Chris Green

wrote in message ...
I'd like to have some 'ball park' figures for the torque which typical
wood screws can handle. Can anyone give me some typical figures or
point me at a web site that has them? I would emphasise that I'm
after the torque figure, i.e. the amount of twist needed to break
them. I realise this doesn't directly relate to the strength of the
screw holding things together which would simply be given by the
tensile stregth of the screw.

I'd prefer the figures for metric screws (i.e. diameters in mm) and in
Nm but I'm quite happy to convert if necessary. The actual screws I'm
using are ScrewFix TurboGold and the stainless steel versions of the
same. I would guess however that most good quality screws are going
to be similar, I'm not after accurate figures, just an idea of what
is likely to break them.

--
Chris Green
Get a torque wrench and "break" a few. You will soon get what you want
easier than asking such a rediculous question,

Jim wrote:

[snip]

Get a torque wrench and "break" a few. You will soon get what you want
easier than asking such a rediculous question,

Is there such a thing as a ridculous question? I thought it was only
ridiculous answers?

Jim (remove $ ) wrote:

wood screws can handle. Can anyone give me some typical figures or
point me at a web site that has them? I would emphasise that I'm
after the torque figure, i.e. the amount of twist needed to break
them. I realise this doesn't directly relate to the strength of the
screw holding things together which would simply be given by the
tensile stregth of the screw.

I'd prefer the figures for metric screws (i.e. diameters in mm) and in
Nm but I'm quite happy to convert if necessary. The actual screws I'm
using are ScrewFix TurboGold and the stainless steel versions of the
same. I would guess however that most good quality screws are going
to be similar, I'm not after accurate figures, just an idea of what
is likely to break them.

Get a torque wrench and "break" a few. You will soon get what you want
easier than asking such a rediculous question,

Well I may need to do that ultimately, I do have a torque wrench and
it would be easy enough to try it with one of the hex head coach
screws. However I would have thought that at least some of the better
screw manufacturers would publish such figures.

--
Chris Green

However I would have thought that at least some of the better
screw manufacturers would publish such figures.


Well, for "high tensile" bolts you can usually work out the values from the
numbers stamped on the heads. But then, you might want to know the strength of
the bolts if (say) you were using six of them to hold a 2 inch flange on a 100
psi system. But you are not usually doing stress analysis on wooden structures
held together with screws. Why were you asking? Find a friendly metallurgy lab
and you might get them to measure the hardness for a particular type of screw,
then there are formulae. Usually what you want in carpentry is a joint that is
as strong in shear as the wood. You don't need much area of the weakest steel
to get enough normal force across the joint; friction and/or glue do the rest.

OldScrawn wrote:
However I would have thought that at least some of the better
screw manufacturers would publish such figures.


Well, for "high tensile" bolts you can usually work out the values from the
numbers stamped on the heads. But then, you might want to know the strength of
the bolts if (say) you were using six of them to hold a 2 inch flange on a 100
psi system. But you are not usually doing stress analysis on wooden structures
held together with screws. Why were you asking? Find a friendly metallurgy lab
and you might get them to measure the hardness for a particular type of screw,
then there are formulae. Usually what you want in carpentry is a joint that is
as strong in shear as the wood. You don't need much area of the weakest steel
to get enough normal force across the joint; friction and/or glue do the rest.

As I was trying to explain in my original question I'm not in the
slightest bit interested (well, not for this question anyway) what the
*tensile* strength of screws is. So it's not about how well they hold
things together.

What I'm after is how easy it is to break them, especially with a
power screwdriver.

--
Chris Green

wrote:
What I'm after is how easy it is to break them, especially with a
power screwdriver.
http://www.grkfasteners.com/selection_guide.htm

Any good?

Regards
Capitol

wrote:
OldScrawn wrote:
However I would have thought that at least some of the better
screw manufacturers would publish such figures.


Well, for "high tensile" bolts you can usually work out the values
from the numbers stamped on the heads. But then, you might want to
know the strength of the bolts if (say) you were using six of them
to hold a 2 inch flange on a 100 psi system. But you are not usually
doing stress analysis on wooden structures held together with
screws. Why were you asking? Find a friendly metallurgy lab and you
might get them to measure the hardness for a particular type of
screw, then there are formulae. Usually what you want in carpentry
is a joint that is as strong in shear as the wood. You don't need
much area of the weakest steel to get enough normal force across the
joint; friction and/or glue do the rest.

As I was trying to explain in my original question I'm not in the
slightest bit interested (well, not for this question anyway) what the
*tensile* strength of screws is. So it's not about how well they hold
things together.

What I'm after is how easy it is to break them, especially with a
power screwdriver.

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!!

John

wrote in :

I'd like to have some 'ball park' figures for the torque which typical
wood screws can handle. Can anyone give me some typical figures or
point me at a web site that has them? I would emphasise that I'm
after the torque figure, i.e. the amount of twist needed to break
them.

Ask the buggers who fitted my double glazing

mike

On Fri, 29 Oct 2004 11:25:07 +0000, usene wrote:

I'd like to have some 'ball park' figures for the torque which typical
wood screws can handle. Can anyone give me some typical figures or
point me at a web site that has them? I would emphasise that I'm
after the torque figure, i.e. the amount of twist needed to break
them. I realise this doesn't directly relate to the strength of the
screw holding things together which would simply be given by the
tensile stregth of the screw.

I'd prefer the figures for metric screws (i.e. diameters in mm) and in
Nm but I'm quite happy to convert if necessary. The actual screws I'm
using are ScrewFix TurboGold and the stainless steel versions of the
same. I would guess however that most good quality screws are going
to be similar, I'm not after accurate figures, just an idea of what
is likely to break them.

In my experience it is much more easy to over cook 4mm screws by
forgetting to reduce the torque setting then it is to break them.
In fact the only way in my experience is not drill a masonry hole
deep enough and then to get a really good screw/hole/plug combination.

I would reckon that you would never break a 4mm screw on the high speed
setting (you'd stall the motor first). A typical pro quality 12v cordless
is rated at about 20Nm. The high speed would typically be around 6Nm.

So I guess the ball park to break a 4mm gold screw is the better part of
20 Nm. I would reckon that it is nigh on impossible to get that tightness
into softwood only hardwood or a blind masonry hole.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

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