TALKING TORQUE IN O&P
 Torque is the tendency of a force to cause or
change rotational motion of a body.
 It is to set a standard so a screw or bolt is not
under tightened which will result in failure
from loosening, or over tightening which can
result in breaking or stripping of the screw.
 The values determined are set in place to
keep a constant force on an object to keep
from moving.
 2 main factors determine the torque specs
used.
 1st is the size of screw and thread pitch
 Common size is an M5 x.8 which is M (Metric
sizing 5 ( diameter of the screw) and .8 which
is the space in between threads.
 Next is the type of material used to make up
the screw.
 A rule of thumb is the higher the grade of
screw the higher the torque spec and
therefore a greater force can be applied.
 Please note that different plating types used
affect the torque values.
 An example of these forces is a clamp screw is
used to keep the pylon adaptor in place and
resist rotational forces.
 An M5 x .8 bolt with a rating of 12 Nm
does not allow the same forces applied as an
M6 x 1 can achieve of 15 Nm
 Another example are the 4 grub screws which
we use to set our alignment and hold the
Pyramid in place.
 The rule of thumb still applies for material
grade, pitch and plating.
Common Torque Wrenches
 What are some of the common Torque
Wrenches used and how do they effect the
outcome of achieving the specifications set
out by the Mfg.
THE TECH WRENCH
 These wrenches can range from 2 Nm to 25
Nm with a very low rate of accuracy!!!
 NOT available in preset
 Although they only need servicing a few
weeks a year with careful maintenance they
can last 30+ years.
 Benefit is a firm handshake and a strong arm.
THE DIAL WRENCH
 This wrench is commonly found in hardware
stores and depending on the make may have
a +/- 4 – 5% accuracy rate.
 These usually have a larger incremental value
in the lines and going over 1 or 2 lines make a
huge difference.
 Not recommended for applications where
accuracy is very important
ADJUSTABLE CLICKING WRENCH
 These wrenches come in wide range of
settings from 4 – 20 Nm and up to 500 Nm.
 Important that all wrenches have some sort
of validation or testing.
 Higher degree of accuracy as they let the user
know when they have hit the required setting
by an audible clicking sound.
PRESET TORQUE WRENCH
 These wrenches are basically fool proof as
they are already set at a designated setting.
 Coupled with an audible clicking sound make
these the ideal types of wrenches.
 These types are also usually certified and
tested to meet or exceed international
standards for Torque.
Why do our bits keep breaking?
 We tried to find out some of the factors why
these occur on a sometimes regular basis.
 Our findings are first based on the force
required to loosen screws torqued to spec at
15 Nm on a Titanium Adaptor.
 We determined that breakage occurred more
often on loosening that tightening.
 We first examined 4 different types of grub
screws all torqued to spec with 242 loctite at
a neutral angle setting.
 We found that there was very little variance in
the amount of torque required to loosen
these screws.
 We then tried the same screws at a higher
degree of angle setting to see the effect it
would have.
 We found on average it took 7.908938032 to
8.473862177 Nm to break friction.
Well this doesn’t seem to be enough to break a
4mm hex bit.
 Next we decided to try a different type of
adaptor.
 Maybe the material selection has an affect on
the value?
 So we tried an Aluminum Adaptor set at
approx the same angle with the grub screws
provided which were probably a mild steel.
No Loctite was used.
 WOW!!!!
 We found on average that it took
11.298482902 to 12.993255338 Nm to break
friction
 Well we’ve gone this far let’s try SS using the
same specs as we did for the Aluminum.
 We found that it took on average
10.733558757 to 14.123103628 Nm to break
friction.
 Now I think were on onto something!!!
What does it take to break a
4mm 3/8” drive hex bit???
 We tested 4 different makes of hex bits to see
at what value did they fail.
 First we tried a Signet 4mm Bit and it failed
by shearing off clean at 27.11635897 Nm
 Then we tried an Insert Bit commonly found
in any hardware store.
 The cheap Insert Bit shattered sending a
small shard flying at 25.98651068 Nm
 Then we tried a German made product Hazet
and it sheared off at 27.11635897
 Lastly we tried a Proto and it finally failed by
stripping and twisting at 33.89544871 Nm.
 From this we can conclude that there are
some other outside factors that contribute to
these bits failing since the values for breaking
friction are to low.
 Some of these are but have not yet been
tested are:
 Amount and type of loctite used.
 Foreign bodies getting into the threads like
sand and dirt.
 Lastly and possible the most plausible is rust
or seizing of the threads due to fluids.
 THANK YOU!!!!!!
 ANY QUESTIONS?????