Discussion in 'Workshop Tips and Secrets / Tools' started by wanttobuild, Nov 5, 2018.
Can anyone recommend a quality torque wrench for small AN bolts?
I use this one:
Cheap and light, but you need to be able to look at it.
I couldn’t find one locally at the time, so I used a 6” long 1/4” break over handle and a small fish scale that I calibrated. Made a little loop from a bread tie and pulled with the scale perpendicular to the handle.
Just what I was lookin 4
Good deal. I use a similar type with the floating handle (as opposed to the ball) and it reads inch pounds. Beam type wrenches are consistently accurate unless somehow the beam gets damaged. The pointer is a pointer and if it gets out of line it's easy enough to fix. If anyone decides on a "click type" torque wrench be sure to buy a good high quality one. A cheap click type will most likely cost you much more than you save.
I agree on the "being able to look at it" part. Sometimes the position makes it difficult to get a clear look at the scale ... and sometimes the older eyeballs some of us have don't want to focus. :gig:
Do you correct your torque readings on the scale for the length of the break over handle? If not, at inch pound readings, you can be way off actual torque at the bolt head. You could be applying way too much torque. Torque wrenches take the reading by flexing at the pivot point (bolt head), not a dead pull handle end.
Here is the math:
A. Here is the formula: M1 = M2 x L1 / L2
M1 is the torque setting of the wrench.
M2 is the actual torque applied to the nut
L1 is the normal length of the wrench
L2 is the extended length of the wrench (Length of wrench + length of adapter)
M1=torque wrench setting ?
M2=80 FT-LBS (Desired torque)
L1=18" (Length of torque wrench)
L2=22" (Total length of wrench with 4 inch extension added to wrench)
80x18/22=65.45 M1 therefore = 65.45; In other words if you want to torque a fastener to 80 FT-LBS using an 18 inch torque wrench with a 4 inch torque extender you will set the wrench to 65.45 FT-LBS
If you measure the distance from the center of the bolt to the point that the force is applied and measure the force correctly you will get an accurate torque measurement. Distance in inches x force in pounds = inch pounds of torque. Doesn't matter what type of wrench/tool is used.
Does the use of an extension effect the reading?
Only if the extension changes the effective length of the arm (as defined by the distance between the center of the bolt and the force applied at the handle). So in the context of an "extension" that makes the socket deeper/longer, no. If the "extension" is a long crows foot, yes. For crows foot extensions, the industry standard is to apply a correction factor if its over an inch long; so a standard (short) crows foot does not get a correction.
Should have clarified, just taking about distance between wrench and fastner.
Just wanted to ✔
The harbor freight ones are surprisingly accurate. Easy to test: run an bolt through a pipe clamped to the workbench, use two nuts to hold a lever arm, put weight on the end at a known distance. Set the torque wrench to the calibrated torque, see when it clicks. I did this for the 3/8 one for doing connecting rod bolts, it was within a couple percent, and completely repeatable (which is more important).
You mean there's not a constant 0.8 correction factor?
I didn’t specify, but was driving a socket from the breakover bar. When considering torque, a formula containing a force and distance is implied. More important is how that torque is applied and condition of the fastening hardware it is used on. Further, there is a rather large range of torque values acceptable to AN hardware. Your mileage may vary, but it is worth your time to study recommendations from multiple sources and decide for yourself.
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