Torque Wrench Question, User error?

[aprikh1]

I know this is probably going to be a rather simple question with a rudimentary answer, but I figure I will go ahead and ask anyway. For my birthday I got the Gearwrench 3/8 digital torque wrench, which is specked to 100 foot/ pounds. As a test of the wrench I decided to torque down my lug nuts. The Acura specifies that the lug nuts on my RL should be torqued to 95 pounds.

So with that in mind I set off to test my new torque wrench. When I torqued the lug nuts to 95 foot pounds it did not feel as if the lug nuts were securely attached. When for testing purposes I proceeded to use the torque wrench to remove the lug nuts I just torqued down, and noticed that the pressure indicator was all over the board with values ranging between 50 and 70 foot pounds.

What am I missing here? Can I use the torque wrench to test the torque values by removing a lug nut with the torque wrench?

Yes, I did read the manual. Three times in fact. Also, I did not use the torque wrench as a breaker bar to originally remove the lug nuts.

Thanks!
http://www.garagejournal.com/forum/images/smilies/twitch.gif

 

[D9H 90V]

When for testing purposes I proceeded to use the torque wrench to remove the lug nuts I just torqued down, I did not use the torque wrench as a breaker bar to originally remove the lug nuts.
]

You say you did use the tourque wrench to remove the lug nuts then you say you didnt??

Tourque wrenches dont usually work backwards, they work best when you are tightening the fastener, to check your tourque wrench you would need another that you know for a fact is dead on

 

[aprikh1]

I used an impact wrench to remove the lug nuts before I initially torqued them down. Only after I used the torque wrench to set them to 95 foot pounds, did I try to remove the lugs using the torque wrench.

Sorry for the confusion.

 

[kms]

I have also been told that torque wrenches have something of a sweet spot in the middle of their given range, and that using a 1-100lb wrench for a 95lb task is not ideal. The wrench is less accurate at the limits and it also stresses the mechanism (others who know more than I please correct me here if I'm off).

Also, as mentioned, when loosening you have to overcome static friction, hence you should always need more torque to loosen than tighten.

 

[lynam]

im still confused.. sorry.

Im pretty sure loosening torque is more so then tightening torque.

 

[williaty]

The electronic torque wrenches are not as particular as to where in their measurement range they are due to the differences in how they're constructed. That's why you'll often see an electronic wrench with a bigger range than the "equivalent" clicker-type.

However, as noted above, in general, the torque to loosen a fastener will require considerably more torque than was required to set the fastener. I would recommend a quick check of your wrench. 95ft-lbs is 1140in-lbs. Measure the distance from the center of the 3/8" square drive to the middle of the handle. Divide 1140 by whatever your measurement is. This is the amount of force that should be required to make the wrench indicate. So say the distance you measured between drive and handle was 20". Divide 1140 by 20 to get 57lbs. Clamp a bolt in the vise. Fasten the wrench to the bolt using the correct socket. Get a digital "fish scale" from someplace cheap like Harbor Freight. If you hook the fish scale onto the center of the handle and pull on the fish scale, the wrench should indicate 95ft-lbs of torque when the fish scale reads 57lbs.

Complicated, yes, but it sounds like something you need to do.

 

[Wakefield]

95 ft-lb. should feel pretty tight,certainly much much tighter than anything most people can do with a screwdriver type handle.
Before I knew better,I used to take my old Craftsman click style torque wrench,which is reversible,set it to its max 150 ft-lb. and use it to take off lugs. If it clicked I knew enough to stop pulling.
It might have been before I had that thing-still have it-that I used to use a round head Craftsman ratchet to take the wheel lugs off of the 1967 Olds I had. Didn't know any better. Once when the lugs had been tightened carelessly at State inspection with an air gun I managed to snap off a stud with that thing. Because it is only about a foot long you had to pull or push very hard on that thing.

 

[Treeman]

NO, YOU SHOULD NOT USE YOUR TORQUE WRENCH TO LOOSEN FASTENERS.

The breakaway torque will always be higher than the tightening torque. In your case, since you were at the upper end of your scale, you certainly exceeded the capacity of your wrench and may have damaged it.

While the "sweet spot" is in the middle of the wrench range, you can certainly use it up to it's full scale and it should be within the calibration specs. Maybe just not as accurate by a % or two (moot point).

Here are tips from the CDI (Snap on) FAQ site:

# All mechanical torque wrenches are calibrated from 20% to 100% of full scale, therefore, they should never be used below or above those limits

# To determine which torque wrench capacity is best suited for an application, many factors must be considered. However, as a recommendation, use a torque wrench in the middle 50% of the overall capacity of the tool. This will result in longer tool life, ease of use for the operator and increased accuracy from "clicker" type torque wrenches

# Always grasp handle firmly in the center of the grip

# Approach final torque slowly and evenly

# Stop pulling wrench immediately when target torque is reached

# Never use a torque wrench to break fasteners loose

# Should be cleaned and stored properly

# Should always be stored at it’s lowest torque setting

# Wrenches should be re-calibrated if dropped. Should never be used in excess of it’s capacity

# Torque wrenches should be "exercised" a minimum of three times at 100% of full scale before use

# The wrench selected should be calibrated in the same torque units that are specified

# Use of a "cheater bar" will result in an inaccurate reading and can possibly damage the wrench

# Torque wrenches will last longer if reasonable care is taken. Always unwind handle to the lowest setting after each use. Do not attempt to lubricate the internal torque mechanism. Clean torque wrench by wiping, do not immerse. The wrench should be sent to a qualified calibration lab once every year or every 5000 cycles for re-calibration

 

[kms]

I would recommend a quick check of your wrench. 95ft-lbs is 1140in-lbs. Measure the distance from the center of the 3/8" square drive to the middle of the handle. Divide 1140 by whatever your measurement is. This is the amount of force that should be required to make the wrench indicate. So say the distance you measured between drive and handle was 20". Divide 1140 by 20 to get 57lbs. Clamp a bolt in the vise. Fasten the wrench to the bolt using the correct socket. Get a digital "fish scale" from someplace cheap like Harbor Freight. If you hook the fish scale onto the center of the handle and pull on the fish scale, the wrench should indicate 95ft-lbs of torque when the fish scale reads 57lbs.

Complicated, yes, but it sounds like something you need to do.

that's good enough to be a faq. thanks!

 

[GSteg]

95ftlbs should be pretty darn tight. Are you sure you're in ft-lb mode and not N-m? 95 N-m would be about 70ftlbs...

 

[bentwrench54]

95ftlbs should be pretty darn tight. Are you sure you're in ft-lb mode and not N-m? 95 N-m would be about 70ftlbs...

agreed, i'd double check your setting.