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Old 12-03-10, 12:42 AM   #1
tgrssn
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how to measure torque (nm/lbs per inch)?

i've gotten by for a long time w/o knowing, but i'm curious; how do you make specific torque measurements so you assemble things to "manufacturers specs"?
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Old 12-03-10, 12:52 AM   #2
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torque wrench -- try Sears or Home Depot
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Old 12-03-10, 08:17 AM   #3
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Even a lower cost beam type torque wrench would work if you only need it on occasion. Make sure that the wrench covers the range you need. You could buy one that measures in inch pounds and use a chart like this for conversions.

http://www.thetoolhut.com/Torque-Con...ch-Pounds.html
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Old 12-03-10, 10:22 AM   #4
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I prefer the click action type of torque wrench http://www.harborfreight.com/1-4-qua...ench-2696.html

and on a related note, Torques are measured by a force(newtons, pounds) multiplied by the lever arm, so proper units would be newtons * meters(Nm) or inches * pounds (in. lbs.). Sorry about my being so anal but proper units make everything more clear.
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Old 12-03-10, 10:46 AM   #5
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I prefer click type also and own two to cover the range of work that I do. I get the impression that the OP is inexperienced and thus suggest that using a low cost beam type would be far Superior to guessing. Most inexperienced users are trying to accomplish basic work at a low cost. As far as I'm concerned, a professional should use the best he or she can afford. If you are being payed for your work and an inaccurate reading causes damage to a customer's bike, your "savings" in buying a cheaper tool will pale in comparison to the potential cost of damages.
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Old 12-03-10, 11:02 AM   #6
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Beam type wrenches are not only cheaper than click-type but inherently more reliable.

Decent ones give up nothing in accuracy. They only lack the convenience of being able to set the torque of a fastener when you can't see the wrench itself. That is never true when working on a bicycle.
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Old 12-03-10, 11:13 AM   #7
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I prefer beam wrenches, I use a Park 1/4 inch drive for all the small stuff and a Sears 1/2 inch drive for bottom brackets, casettes, and crank bolts.
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Old 12-03-10, 11:29 AM   #8
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If I'm not mistaken the beam type can also measure both directions. I have a click type I've used for automotive stuff and it doesnt click when tightening reverse threaded things sometimes found on bikes.
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Old 12-03-10, 12:55 PM   #9
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Quote:
Originally Posted by pallen View Post
If I'm not mistaken the beam type can also measure both directions. I have a click type I've used for automotive stuff and it doesnt click when tightening reverse threaded things sometimes found on bikes.
Excellent point and yes, beam wrenches measure torque in both directions with no other adjustments or changes. That's very useful when torquing English bottom bracket cups or cartridges in place.
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Old 12-03-10, 01:30 PM   #10
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And beam-type torque wrenches can be re-calibrated. Click-type wrenches need to be sent back to the factory to be re-calibrated. I think that it is nice to have a racheting mechanism, but truth be told, the beam type is probably a better choice, especially if budget is a factor.
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Old 12-03-10, 05:54 PM   #11
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Quote:
Originally Posted by blamp28 View Post
Even a lower cost beam type torque wrench would work if you only need it on occasion. Make sure that the wrench covers the range you need. You could buy one that measures in inch pounds and use a chart like this for conversions.

http://www.thetoolhut.com/Torque-Con...ch-Pounds.html
Good point about covering the needed range. The majority of torque wrenches have the most accuracy within a percentage if their range, not the entire range they are rated for. For amounts less than 7 lb-ft, an in-lb wrench is better suited, 1 in-lb intervals are great, 2.5 in-lb intervals are OK. For amounts greater than 7 lb-ft, a lb-ft wrench with a range from 5 to 75 lb-ft is good. For large torque values like those found on an Auto, a half inch drive 50 lb-ft to 250 lb-ft is best. Whether a professional or not, you will be better served with the best torque wrench you can afford.

I have dial type, click, and split beams, that can all measure in reverse if needed, so reverse use is not limited to beam types. I have a high end torque wrench I've used regularly for 35 years; I had it calibrated a couple years ago and only gained 1 lb-ft of accuracy. I know an engineer that has his quality shop wrenches tested for calibration regularly for government compliance, and they maintain their accuracy in spite of heavy use & abuse. There's not a downside to purchasing quality equipment.

A handy tool I use all the time for various disciplines http://joshmadison.com/software/convert-for-windows/

Last edited by Werkin; 12-03-10 at 06:06 PM.
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Old 12-04-10, 12:01 AM   #12
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Quote:
Originally Posted by pallen View Post
If I'm not mistaken the beam type can also measure both directions. I have a click type I've used for automotive stuff and it doesnt click when tightening reverse threaded things sometimes found on bikes.
My half-inch (used for bottom brackets) clicks in reverse, 3/8" craftsman clicks in reverse, and I don't think I've ever checked my other 3/8".
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Old 12-04-10, 01:11 PM   #13
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Regardless of which type of torque-wrench used, it will always be more precise than the best mechanic's "calibrated" hand. We had that argument constantly at the shop and we'd double-check the calibrated-hand's work with a torque-wrench afterward. It can be +/- 40% or more off from the perceived torque. Heck, even the bottom-of-the-line Harbour Freight clicky wrench can get within +/-10%.

The results are even worse with newbie mechanics. They tend to over-tighten small bolts and under-tighten big ones. Such as the crankarm bolts which require 25-33 lb*ft. Simply impossible to do with itty-bitty L-shaped allen-keys. You need an automotive-style 3/8" ratchet-wrench to get up to the required torque.
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Old 12-04-10, 08:21 PM   #14
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Originally Posted by DannoXYZ View Post
Regardless of which type of torque-wrench used, it will always be more precise than the best mechanic's "calibrated" hand. We had that argument constantly at the shop and we'd double-check the calibrated-hand's work with a torque-wrench afterward. It can be +/- 40% or more off from the perceived torque. Heck, even the bottom-of-the-line Harbour Freight clicky wrench can get within +/-10%.

The results are even worse with newbie mechanics. They tend to over-tighten small bolts and under-tighten big ones. Such as the crankarm bolts which require 25-33 lb*ft. Simply impossible to do with itty-bitty L-shaped allen-keys. You need an automotive-style 3/8" ratchet-wrench to get up to the required torque.
A big amen to this. Feel is for fools.
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