Topic: Let's talk torque wrenchs

[jeffg]

is there anyway to test that your torque wrench is still accurate?

Cal Tech does calibration to (DEAD ON BALLS ACCURATE) that's an industry term                   (check with Marisa)

I always wanted a 1/4" drive, I felt I would do allot more torq ing, have 3/8, & 1/2. Wouldn't mind a screw driver grip style 1/4" drive also.

[dhall57]

You get what you pay for, like we've all be told since we were kids. If you depend on tools to make a living of course you need high quality stuff. Ive got some Craftsman, Kobalt, etc. But the tw's I've got are from HF and serve my purposes very well. For me spending more money on them was not necessary.

[ChopSticks]

Some manuals say to store at lowest setting so I'm assuming if you're wrench is a 10-90ftlbs the lowest setting would be 10 not below that

[mystic_1]

BTW, the "right" way to check a torque wrench for calibration involves hanging very precise weights off of a calibrated wheel like one of these:





These setups are however prohibitively expensive.  Often companies will send in a digital torque transducer and have that calibrated to NIST standards and then use that as a reference standard to check calibration of their in-house tools. 

In a DIY scenario you can do things like clamp the drive of the wrench in a vise and then hang known weights off the handle at a predetermined distance and then see if the wrench clicks.  Working out the weights and distances is pretty straight forward, torque is an expression of weight and distance, so 10 ft lbs is 10 pounds at a distance of 12 inches, or 20 lbs at a distance of 6 inches (120 inch pounds), or 5 pounds at a distance of 24 inches (again 120 inch pounds).

You can check against other wrenches but then you'll need at least two other wrenches and with luck at least two will match, otherwise there's no way to know which one is the accurate one.

What ever method you use, it's important to check the wrench at several points within it's range of operation. 

Your best bet to be absolutely sure is to send it in to a place that'll check it on a rig like the one below.  This particular wrench was off by about 3% near the top of its range, but the deviation was linear and repeatable, so the wrench would still be usable so long as one corrected for this when setting torque.




mystic_1

[Sockeye]

Another option I haven't seen mentioned is CDI brand. I have a 3/8" that covers most needs for these bikes. It's advertised as a "Snap-On brand", whatever that means. No plastic except for the case it came in. I consider it a middle of the road option. Not terribly cheap, but still half what a Snap-On or MAC costs and is a good quality tool that works as well as when I bought it a couple years ago.

Ok, so I've decided to go with a CDI 2502MRPH 3/8-Inch Drive 30 to 250-Inch-Pounds for my low end needs and a Harbor Freight 1/2" 20-150 ft/lbs for the top end. Eventually I plan to replace the HF with a CDI equivalent.

I'm sure the HF will serve its purpose and pay for itself the few times I'll require it, plus it will leave me with a beater/loaner tool for the odd/misc jobs that pop up.

For this first year I'm only going to work on getting the bike road worthy, then I'll tear into everything next year.

[seanbarney41]

I have found that I almost always need to borrow my bud's 1/4" drive 5-200(somewhere around there) inch pound wrench for these bikes.  The 1/4 drive is much more useful for getting at these little engine's hard to get at stuff, and torque values are relatively low...these are not tractor engines.

[calj737]

Right, you need an 8# - 50# wrench. Head nuts and studs are below 20# and they're most of the critical torque values aside from crank and rods.