torque wrench
- Thread starter DOOD
- Start date
5-90
NAXJA Forum User
- Location
- Hammerspace
Accuracy/tolerance and repeatability.
Accuracy/tolerance - the "torque force" method is already fairly inaccurate for determining fastener preload - on the order of +/-15% or so, as I recall. Why introduce additional error using a cheap torque wrench? Spend the money and do it right.
Repeatability - this takes two basic forms, in this case...
1) Repeatability would govern how accurate it would be when torquing a number of screws to a similar value. I'd rather see cylinder head screws torque to 101/102/99/103/100/100/98/101 pound-feet than see a spread of, say, 97/110/89/104/95/80/115 pound-feet. This is sort of a "subset" of the accuracy/tolerance issue.
2) Assume you have to set and unset the torque wrench to the same value several times in a job. With "high" repeatability, you're going to see minimal to no spread in the set-to readings, and even if the thing is off by a large margin, it's still going to give you right about the same value everytime you set the wrench to a certain level. If repeatability is not there, you'll have a lot more "scatter" in your readings.
I'd consider a decent brand (like Craftsman) to be a bare minimum for any sort of measuring instrument - that includes torque wrenches. Also, take care of your torque wrenches - don't let them get knackered about overmuch, don't loosen screws/nuts with them, follow the maintenance instructions, and keep them in the cases they come with, if they come with cases.
Measuring tools of any sort - when there are moving parts involved in the measuring - are something you should save your nickels for to do right. It's cheaper that way...
Accuracy/tolerance - the "torque force" method is already fairly inaccurate for determining fastener preload - on the order of +/-15% or so, as I recall. Why introduce additional error using a cheap torque wrench? Spend the money and do it right.
Repeatability - this takes two basic forms, in this case...
1) Repeatability would govern how accurate it would be when torquing a number of screws to a similar value. I'd rather see cylinder head screws torque to 101/102/99/103/100/100/98/101 pound-feet than see a spread of, say, 97/110/89/104/95/80/115 pound-feet. This is sort of a "subset" of the accuracy/tolerance issue.
2) Assume you have to set and unset the torque wrench to the same value several times in a job. With "high" repeatability, you're going to see minimal to no spread in the set-to readings, and even if the thing is off by a large margin, it's still going to give you right about the same value everytime you set the wrench to a certain level. If repeatability is not there, you'll have a lot more "scatter" in your readings.
I'd consider a decent brand (like Craftsman) to be a bare minimum for any sort of measuring instrument - that includes torque wrenches. Also, take care of your torque wrenches - don't let them get knackered about overmuch, don't loosen screws/nuts with them, follow the maintenance instructions, and keep them in the cases they come with, if they come with cases.
Measuring tools of any sort - when there are moving parts involved in the measuring - are something you should save your nickels for to do right. It's cheaper that way...
Matthew Currie
NAXJA Member #760
- Location
- Vermont, land of big clay
While agreeing with 5-90 in the main, I would add that it can be very handy to have a cheap beam type torque wrench in addition to the fancier stuff. I have a couple of really nice old dial wrenches for the important jobs, but my trusty old Montgomery Wards beam wrench is just right for things like wheel lugs.
ed to add: Beam wrenches are robust and relatively accurate when used carefully, but very easy to misread owing to parallax. Also for higher torques, the tendency shake a little can make true readings difficult, because you see the needle where it comes to rest, not where it's been. Getting a really good reading with a beam takes practice, and these days, fairly decent clickers are cheap enough to make sense.
ed to add: Beam wrenches are robust and relatively accurate when used carefully, but very easy to misread owing to parallax. Also for higher torques, the tendency shake a little can make true readings difficult, because you see the needle where it comes to rest, not where it's been. Getting a really good reading with a beam takes practice, and these days, fairly decent clickers are cheap enough to make sense.
Last edited:
5-90
NAXJA Forum User
- Location
- Hammerspace
Matthew Currie said:
No argument there - beam types are also handy for getting reasonably accurate preload readings on things like pinion yokes and such - you just can't do that with a clicker.
I'll also agree that you should practise a bit when using a beam type - it's kinda like reading a vernier. Once you've done it, it's easy - but it doesn't make any damn sense until you do it, or have someone show you what you're doing wrong.
I've got a couple old beam wrenches that I plan to replace with dial types - just haven't gotten far enough ahead to just yet.
However, what I said about accuracy and repeatability will still stand with a beam wrench or a dial wrench, as it would with a click wrench. Buy cheap, get cheap. Tools are (mostly) worth what you pay for them, so it's worth it to spend a little extra to get it done right.
motorcityxj
NAXJA Forum User
- Location
- detroit suburbs
What about servicing torque wrenches? My brother has a few craftsmen, and he was burned by the warranty and a shifty sales men who told him (about 5 years ago when he bought it) that the craftsmen warranty applied to the torque wrenches. His is no longer accurate. Anyways they will not repair or replace it.
What are a good value and most durable style of torque wrench in your guys opinion?
His wrench is this style by the way ... you twist the collar on the shaft to set the poundage.
http://www.sears.com/sr/javasr/prod...OOL&subcat=Torque+Wrenches&BV_UseBVCookie=Yes
What are a good value and most durable style of torque wrench in your guys opinion?
His wrench is this style by the way ... you twist the collar on the shaft to set the poundage.
http://www.sears.com/sr/javasr/prod...OOL&subcat=Torque+Wrenches&BV_UseBVCookie=Yes
5-90
NAXJA Forum User
- Location
- Hammerspace
Yep - that's a "clicker" wrench, where you feel a tangible "click" in the handle when you reach the torque you set on the collar (also sometimes sold under the brand "Micro-Tork" - referring to the micrometer-type collar...)
You can check with outfits like Snap-On and MAC. They offer calibration for their own torque wrenches working on similar principles, so it's a possibility. You could also check the Yellow Section under "Tools" or "Calibration Services," I'd think.
I've been keeping tabs on mine (they've got a torque checker at school...) and they haven't wandered at all. Did your brother happen to drop the wrench, or loan it out?
You can check with outfits like Snap-On and MAC. They offer calibration for their own torque wrenches working on similar principles, so it's a possibility. You could also check the Yellow Section under "Tools" or "Calibration Services," I'd think.
I've been keeping tabs on mine (they've got a torque checker at school...) and they haven't wandered at all. Did your brother happen to drop the wrench, or loan it out?
Matthew Currie
NAXJA Member #760
- Location
- Vermont, land of big clay
motorcityxj said:What about servicing torque wrenches? My brother has a few craftsmen, and he was burned by the warranty and a shifty sales men who told him (about 5 years ago when he bought it) that the craftsmen warranty applied to the torque wrenches. His is no longer accurate. Anyways they will not repair or replace it.
What are a good value and most durable style of torque wrench in your guys opinion?
His wrench is this style by the way ... you twist the collar on the shaft to set the poundage.
http://www.sears.com/sr/javasr/prod...OOL&subcat=Torque+Wrenches&BV_UseBVCookie=Yes
For durability a beam wrench wins. It's hard to hurt one of them unless you run over it or something. I guess you could bend it from overtorquing, but you could probably just bend it back or bend the indicator needle to match.
A dial wrench should hold its calibration pretty well if it's carefully used, because it has only the one moving part - the shaft that holds the socket is twisted, and an arm attached to that actuates the dial, which is zeroed with every use. But it's also easy to break, for the same reason. There's no safety stop to prevent you from twisting it too hard and killing it.
Click wrenches don't seem very forgiving of abuse and dropping and throwing, but they're nearly idiot proof for overtorquing, since after the click occurs there's no further engagement of the mechanism. My guess is that, especially with a number of relatively cheap ones available, this is still the best value for the buck. Edited to add: Click wrenches are more complex than others, and use springs that are more likely to go out of calibration than torsion bars and beams. It's important for long term reliability to remember to zero the wrench setting after you use it.
My favorite torque wrench is one that I don't think is made any more. I can't even remember the brand. It's ancient. It's essentially a beam wrench with the beam enclosed, actuating a dial. The dial is not spring loaded, so it holds the reading. You must zero it for every bolt, but even if your hand shakes or the bolt pops a bit, it will record the maximum torque and hold it.
I've never tried a digital one, so can't comment on that.
Last edited:
