torque wrench

[DRH]

Hi Guys......Has anyone checked the calibration of your torque wrench lately? How did you do it? I recently found that my 'snap' type wrench was not up to the dialed foot pounds on the handle. I was leaving the engine without enough torque on the head bolts. I'm pretty lucky I didn't blow another head gasket before I found out.......I ended up buying a new wrench---but then, is it calibrated correctly?? How do we know?

 

[RaserX]

Most of the mobile tool guys, (snap-on, cornwell, Mac etc) usually have checking tools
On there trucks. If you see one flag him down. The check is usually free... It cost to send to have calibrated. At least that's my experience

 

[dklawson]

I have the unfair advantage that we have some torque checking equipment at work so periodically I take my wrench in and "note" where it is inaccurate. I don't actually calibrate it, I just keep tabs on where (and by how much) it has errors.

Prior to that I would at least do a sanity check calibration. You can do this yourself if you have a bench vice, a long screwdriver, and a bathroom scale.
1) measure from the center of the wrench drive to a point 2 feet out on the handle and put a tape mark there.
2) set the wrench to the torque value you are interested in (lb-ft).
3) hold the square drive of the wrench in the jaws of the vice so it is securely held when you pull up on the handle.
4) stand still on the bathroom scale and write down your weight.
5) hold the long screwdriver between both hands and put it "under" the tape mark you made on the wrench handle.
6) lift 'UP' on the screwdriver slowly increasing the load until you hear the wrench click.
7) hold the wrench in the at position and look down at the scale. Write down the new scale reading.

Repeat steps 6 and 7 about a half dozen times then average all the scale readings.
Subtract your weight from the average reading.
Multiply the value by "two" since you were pulling at the 2 foot mark.
The resulting value will be the torque in lb-ft that caused your wrench to click.

To those reading this and saying "hey... my bathroom scale isn't accurate"... it only needs to be accurate between your weight and the applied force. You are not using the scale's displayed value in your calculations, only the change in the reading. For most scales, this is more than accurate enough. It is at least accurate enough to know if your wrench has serious calibration issues.

 

[rlwhitetr3b]

I do not understand what the long screwdriver is for.

 

[Nelson]

The screwdriver allows you to apply pressure to the wrench at the two foot distance. With it sitting across the wrench at that point you will be able to know how much torque is being applied.

 

[OopsClunkThud]

I do not understand what the long screwdriver is for.

With a hand on each end of the screwdriver, you use it to apply the force to the wrench right at the tape mark. This assures that the lever arm is accurate.

 

[dklawson]

Thanks. That's exactly what I meant. I should have elaborated.

 

[rlwhitetr3b]

Oh, I was thinking the screwdriver was parallel to the wrench. Now I see.

Thanks, I will have to check my wrenches.

 

[DRH]

Hey dk....great idea. I'll try it. I seldom see the 'Mack' tool guy.

 

[dklawson]

Just remember that my method is only a sanity check to tell you if your wrench is "sorta" right. It's hard to get a steady reading from the bathroom scale when standing on it and pulling up on the screwdriver.

There is a similar use for this method that my family members have used on really big applications... like the axle nuts on air cooled VWs. You can stand on the bathroom scale and pull up on the wrench until you get the scale increase needed for the required torque. From memory, I believe some of those nuts were supposed to go to around 250 lb-ft... well beyond what most of us have for torque wrenches.

 

[Bayless]

Right Doug, 256 ft-lb on the axle nuts and the flywheel gland nut. I have broken a few tools dealing with those evil things. BTW, thanks for the bathroom scale idea. I'll do that before using the wrench again.

 

[DRH]

DK....But, wouldn't one have to have a bathroom scale that goes up to ...maybe 500 lbs? It would, considering a 'fat' guy like me. my scale only goes to about 250lbs.

 

[dklawson]

Not really. If you are already using a long breaker bar (for argument let's say it is 3 feet long) then 250 lb-ft would require 250/3 = 83 pounds of force. The longer the breaker bar, the lower the required force. So if you personally weighed 500 pounds you could use a scale that was good to 600 pounds.

Realistically though, if you weighed 500 pounds and your scale only went to 500 pounds, then instead of lifting/pulling the breaker bar to apply the torque, you would probably find it easier to have someone steady the breaker bar while you stepped on it. Then you would just need to subtract the force from the scale reading, not add it. In short, if you have a scale that you can weigh yourself on, there is a way to make the method work.

 

[nomad]

I use my old bending beam, I believe sturdevant style, Craftsman torque wrench. I believe they are fool proof and last forever. Do have the click wrench for really big stuff.


Kurt.

 

[AN5Sprite]

I use my old bending beam, I believe sturdevant style, Craftsman torque wrench. I believe they are fool proof and last forever. Do have the click wrench for really big stuff.
Kurt.

Thats the same one I've got. Passed down from my father. I second your sentiments Kurt.

 

[Sopwith_Camel]

ok dumb question time im usein a torque wrench for the first time
and it has marks for 42 and 56 and i need to get it to 50
but as i turn the handle the scale is 0 to 12?? so as i turn it the ten lines up with were I would guess 50 is but I fiuged i would ask as i still have to put on the carborators so i have sometime

by the way the Manifold gasket the metal silver side faces the block?

in over my head
steve

 

[dklawson]

That does sound a bit odd. However, being in Europe, what are the units the wrench is calibrated in? lb-ft, Nm, kg-m? Can you post a picture of the scale?

 

[Sopwith_Camel]

newtons
im suppose to torque the head to 50

 

[dklawson]

I have your answer. The picture really cleared this up.

Your torque wrench was designed originally to be calibrated in lb-ft and when marketed in Norway they have stamped it in Nm.

Your "rotary" scale is not 0-12, it is 0-14. Note that there is another scale graduation between the 0 and 12 marks. That middle mark is "13" One full revolution takes you from 0 to 14.

Up the handle, your major graduations are in 28 Nm steps. Two revolutions of the rotary scale will move "up" 28 Nm in torque.

You can tell this is a lb-ft wrench marked in Nm because 14 Nm is "close" to 10 lb-ft. Torque wrenches in lb-ft have 0-9 stamped around their rotary scale and each mark "up" the handle is typically 10 or 20 lb-ft.

Anyway, for your setting of 60 Nm, go to where the top of the rotary scale crosses the handle at 54, and the 0 on the rotary scale lines up with the axial scribe line on the handle. Then turn the rotary scale in "6" more units.

EDIT: Ignore the 60 Nm reference. You said 50 Nm so go to the mark below 54 (26?) then turn the rotary scale up 24 more marks (1 full revolution + 10 more marks).

 

[Sopwith_Camel]

14!!! who counts by 14s
its this new math
ok so the head torques to 50?
just got the carbs on
Ive never atempted any thing this big
steve