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 Torque is the tendency of a force to cause or change rotational motion of a body.

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Presentation on theme: " Torque is the tendency of a force to cause or change rotational motion of a body."— Presentation transcript:

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3  Torque is the tendency of a force to cause or change rotational motion of a body.

4  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.

5  2 main factors determine the torque specs used.  1 st 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.

6  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.

7  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

8  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.

9 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.

10 THE TECH WRENCH

11  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.

12 THE DIAL WRENCH

13  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

14 ADJUSTABLE CLICKING WRENCH

15  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.

16 PRESET TORQUE WRENCH

17  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.

18 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.

19  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.

20  We then tried the same screws at a higher degree of angle setting to see the effect it would have.

21  We found on average it took to Nm to break friction. Well this doesn’t seem to be enough to break a 4mm hex bit.

22  Next we decided to try a different type of adaptor.  Maybe the material selection has an affect on the value?

23  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 to Nm to break friction

24  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 to Nm to break friction.  Now I think were on onto something!!!

25 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 Nm  Then we tried an Insert Bit commonly found in any hardware store.

26  The cheap Insert Bit shattered sending a small shard flying at Nm  Then we tried a German made product Hazet and it sheared off at  Lastly we tried a Proto and it finally failed by stripping and twisting at Nm.

27  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.

28  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.

29  THANK YOU!!!!!!  ANY QUESTIONS?????


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