SpaceTEC® Resource Blog for Aerospace Technicians

Archive for December, 2011

Torque Wrenches

AF Master Sgt Miller uses a torque wrench on flight hardware. Credit Mountz Inc.

A common tool that is used by the aerospace technician is the torque wrench.  The purpose of the wrench is to precisely place the required amount of torque or tightening of a nut on a bolt without under or over torquing the nut.  It is a misconception that people believe that “the tighter the better” applies to all nut/bolt arrangements.  That is not true.  Over-tightening a nut can crush the gaskets underneath, warp the bold threads, or cause the nut to be difficult to remove.  Under-tightening can result in the nut coming off at an inopportune time.  Using a torque wrench, you ensure that the nut is at the proper torque that is required avoiding damage or breakage.

There are four major types of torque wrenches an aerospace technician can use: Flexible beam, Rigid frame with a dial indicator, preset or “clicker” torque, or digital.

Flexible Beam Torque Wrench Credit Joseph Dille

Flexible Beam Torque Wrench in Use. Credit Joseph Dille

Flexible beam is used by grasping the center of the handle, turning the nut until the needle points to the torque desired.

Rigid Frame Torque Wrench. Credit Hydroponicsonline.com

Rigid Frame torque wrenches use a dial indicator to read the torque being applied.

Preset or “Clicker” Torque Wrench. Credit Joseph Dille

Preset or “Clicker” Torque Wrench in Use. Credit Joseph Dille

Preset or “Clicker” torque wrenches can be set to the desired torque and will “click” when the proper torque is reached.  The unit showed above can be set for either english standard or metric.

Digital Torque Wrench. Credit Protorquetools.com

Digital torque wrenches will show the torque being applied via a digital readout and some models will actually beep when you have achieved the torque desired.

When using a torque wrench, keep these things in mind:

  • Select the proper wrench for the measurement being called for.  If inch/lbs are called for, then you select a inch/lb wrench.  If  inch/grams are called for, then select a wrench that is measured in grams.
  • Check the calibration date on the wrench.  If it is outdated, return to logistics and get a wrench that is within the calibration date.
  • Always test the torque wrench on a torque measuring device to ensure that it is still calibrated and reading accurately.
  • Never jerk the wrench, but pull on it slowly keeping close eye on the torque being applied.
  • Always set the wrench back to it’s lowest torque setting after use to ensure that the spring does not compress and end up with “memory.”
  • Always handle torque wrenches with care.  Do not drop them or bang them around.  Return them to their foam case once finished.

Torque is determined by the formula:

Torque=force X distance

For example if a an engineering drawing requires a 120 lb inch pound torque for a specific nut and you have a 10 inch torque wrench, you would figure out the following:

120 inch/lb=force X 10 inches

or

120 inch/lb divided by 10 inches=force X 10 inches divided by 10 inches

or 120 inch/lb divided by 10 inches= force

12 lb=force

Therefore you need 12 lbs of force to achieve 120 inch/lbs using a 10 inch torque wrench.

This formula is very useful in determining the torque required.

Some technicians have been known to alter the length of their torque wrench by adding an extender.  If that is done, then the force required to achieve 120 inch/lb of torque is changed.  Let’s look at the same problem again and assume the aerospace technician has decided to add a 15 inch extender on his wrench.

120 inch/lb=force X (10 inches (wrench length) + 15 inches (extension length))

120 inch/lb=force X 25 inches

120 inch/lb divided by 25 inches=force X 25 inches divided by 25 inches

120 inch/lb divided by 25 inches=force

4.8 lbs=force

Note the difference in force required!  If you had not taken into account the added length of the wrench, you would have over torqued the nut possible resulting in damage to the aerospace hardware.

With good care and timely calibrations, your torque wrench should last and be an invaluable tool in your work.

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Monday, December 12th, 2011 Applied Mechanics Comments Off on Torque Wrenches

Safe Work Practices

 

Today we are going to wrap up our safety series.  We have covered the purpose of safety in the workplace, appropriate safety dress, and housekeeping.  Now we will cover safe work practices and fire prevention.

Safe work practices always involve knowing your surroundings.  You should always keep your “head on a swivel” so to speak.  Who is near you?  What are they doing?  Is there a potential for their work or your work interfering and causing a safety hazard?  Do you have some form of safety barrier up such as a rope or sign while doing a hazardous function to prevent other workers from inadvertently walking into your work area?  If working at a height, are you tied off with a harness and rope?  Do you have a catch basin or net below to catch falling objects?

When lifting a heavy object, are you using safe lifting practices?  Don’t be a “he-man” when lifting a heavy object.  Ask for help.  Always protect your back.  You only have one.  Safe lifting practices include:

  • Check your immediate area to ensure it’s clear of any obstacles that may cause tripping.
  • Assume a squatting position with the knees bent and the back straight.
  • Pull the object you are lifting in towards your body.  Don’t keep it extended out from you causing an imbalance.
  • Lift using your leg muscles and not your back.
  • If you must set the object back on the floor at another location, do the safe lifting practice in reverse keeping your back straight and using your legs.

Credit Gonzaga.edu

Another way to protect your back is to always try to do your work at a waist level or slightly higher bench.  Some parts that you’re working on can be placed on a bench and is more favorable to your back then bending over constantly doing the work.  If the part you’re working on is below your waist and you cannot lift it onto a bench, then consider kneeling or squatting while doing the work, taking frequent breaks to stretch your legs.

Though we might enjoy working with our co-workers, horseplay is just out of the question.  In an industrial setting, there is just too many opportunities for an accident.  People do get hurt during horseplay and is not appropriate for the workplace.  I once saw a young woman who was employed at a water park get injured during horseplay.  It was the last day of the season and a group of employees were horsing around chasing each other with squirt guns.  The girl slipped on the wet pavement and ended up getting reconstruction surgery on her face due to her injuries.  A bad ending to an otherwise celebratory day for the crew.

Also make note where the eye wash and shower stations are.  Do you know how to operate them?  If not, request an inservice on it.

Do you know where the fire extinguishers are at your workplace?  Do you know how to work one?   Are the extinguishers visible or hidden by clutter?  Are their inspection stickers up to date?

You should also know where the ELSA masks, exits, and marshaling areas are.  In the event of an emergency requiring evacuation, you should already have an idea where to go and how to get there.

Safety is an everyday practice for the aerospace technician.  Though it is the responsibility of your employer to provide safety equipment, training, etc., it is your responsibility to practice safe habits and to expect it of your co-workers.   Remember, the ultimate goal of each and every work day to return home to your loved ones unharmed after each shift.

Be safe.

 

 

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Sunday, December 11th, 2011 Aerospace Safety Comments Off on Safe Work Practices