DIY: Getting accurate torque from a cheep torque wrench!

[dbsharp]

Try this at your own risk! I am not responsible if you drop the weight on your foot or damage yourself or your property in any way!

So lets say that you have a bolt that you want to get torqued just right. For me that is my main caps and arp head studs. Here is how I get an accurate torque on them.

I used:

engine hoist
adjustable wrench
vise grip pliers
weights (good idea to verify the weight of these)
rope
ruler

Rig everything up like this:


Get the torque wrench level! This is important!

Measure 12" from the center of the 3/8" or 1/2" drive on the wrench. This is the spot to hang the weight from. If your wrench is too small to hang the weight 12" out, then you will have to do some math to get this right. For instance my small torque wrench had the weight at 9" out. for a 35lb weight that would mean: 35x9= 315 in-lbs. to convert that into ft-lbs just divide by 12. 315/12= 26.25 ft-lbs.

Now adjust the torque setting on the wrench until the weight just barely gets the torque wrench to click. Look at the torque wrenches current setting and compare that to how much force is actually on it.

Here is a picture of my setup to get a true 90 ft lbs out of my wrench. The adjustment had to be turned to 104 ft-lbs on this particular torque wrench.


Got it?

[bcjammerx]

or you could just buy a toque wrench...after all, those weights are all est. not exact...torque wrench will be more accurate...and even a cheap wrench will suffice...also...this would only work if your part can hang so that your wrench is at a 90* angle with the ground.

but a cool way to check your wrench to see if it needs replacement

[mj213]

I'm not sure if you realized it or not, but he is using a torque wrench. He's just trying to find out if it's accurate or not because it's cheap.

And yes, free weights are estimated, rarely exact.

[bcjammerx]

i did

*ninja edit*
pics don't load at work...now at home...pics explain what words did not...I seee now.

[short1]

Is it just me, or does it look like that car is in his bedroom?
short

[dbsharp]

no not in a bedroom lol. Its in a very messy cramped garage. If you notice, I said to verify the weight of the weights. I used an accurate scale at work to do this.

[Tippey764]

. I used an accurate scale at work to do this.

But i have a cheap scale. How can i ensure its accurate?

[dbsharp]

Lol I don't know man.

[Losiracer2]

at discount tire, we've got a torque wrench calibration checker....WAY easier than that contraption you made haha. It just checks the calibration though, can't really fix it.

[Jon]

Not a bad DIY, seen this done to some extent plenty of times with fairly accurate results.

I know my 25 lb free weights weigh in at 26.5, 28, 24.9, and 25.7, same with the 20 and 25 lb dumbbells, off about 5-8%.