Bicycle Mechanics - New Craftsman Torque Wrenches Don't Work

I bought a brand new 25 to 250 in-lbs clicker type Craftsman torque wrench today so that I could properly torque down the 4mm bolts on my handle bar stem. The Ritchie directions said to tighten to 5 N-m and I set the wrench to 4-N-m to kind of ease into it. I snapped the bolt off before it clicked. So I played around with it a little bit and I was able to snap off another 4mm bolt before there was a click or any indiction that I was over torque. OK so I took that wrench back and got a replacement, set the wrench to 40 in-lbs and tested it on some bolts on my car. No click or any indiction of when I got to torque.

The directions say "At low settings the release is gentle and there is no audible click. Learn how different amounts of torque feel . . . . " I don't need to buy their torque wrench to get this result.

What is going on here? Does 25 to 250 in-lbs really mean 100 to 250 in-lbs? This was the smallest they had in the store although the directions seem to indicate smaller ones exist. Do I need to get a smaller wrench for 40 to 80 in-lbs range? Or did Craftsman make a bad batch of wrenches and are wasting my time with this?


About the bike. I apparently over torqued the stem onto the handle bars. When I realized this I backed off of the torque. The bar does not appear to be crushed. There is a scratch on it but it appears to be superficial. I was just going to get a couple of new bolts and keep the same parts. I hope this will OK?

The bummer is this is my only bike and it puts me out of service for commuting.

Click type torque wrenches have a lighter click at the bottom of their range. You feel it rather than hear it.

I teach a mechanics course as my second job. You'd be surprised at how many students fail at their first attempts to torque something correctly in the lower ranges of the torque wrench scale.

Trust the feel young rob.

Clickers are tricky to use and can get out of calibration rather easily. They are valuable when you are torquing hidden bolts and can't see the wrench but nothing on a bike fits that description.

My advice is to return the clicker and get a 1/4"-drive beam wrench for the small bolts and a 1/2"-drive beam wrench for the big stuff like crank arms and bottom brackets. Together they should cost less than the clicker and will be more reliable and easier to use at low settings.

Clicker-wrench also don't address the issue of creep. That is, when you reach the specified torque and hold it, the bolt will actually turn a little more. With the clickers, if you re-torque the bolt again, you'll find that the point where it clicks will be a couple degrees further than the original click.

Better would be the beam-type wrenches where the needle can be held at a specific torque for a couple of seconds. The wrench will continue to turn little at that torque value, then stop. Snap-on makes really good torque-wrenchs with dial-indicators: ebay - Torqometer TQ-6 (http://cgi.ebay.com/ebaymotors/SNAP-ON-TORQOMETER-TQ-6-INCH-POUNDS-TORQUE-WRENCH_W0QQcmdZViewItemQQcategoryZ43991QQihZ002QQitemZ120111081393QQrdZ1)

http://i15.ebayimg.com/01/i/000/9a/0f/9f84_1_b.JPGhttp://i8.ebayimg.com/03/i/000/9a/0f/a689_1_b.JPG

Pick a torque wrench such that the torque you're applying is near the middle of the range of the wrench. Craftsman stuff hasn't been decent for many years.

Clickers are tricky to use and can get out of calibration rather easily.
That may be true of cheap Craftsman wrenches but my 30 year old Snap-on clicker wrenches have never needed re-calbration, and yes I have them checked regularly.


They are valuable when you are torquing hidden bolts and can't see the wrench but nothing on a bike fits that description.
True. They are also valuable when you're in an awkward position and straining to tighten a bolt to 120ft-lbs while trying to read the shaking needle on a beam type. Once I used a click type I never looked back. ;)

idcruiserman's and ScrubJ's advice is on the money... use torque wrenches whose range is in the middle of what you are torquing, and develop a feel for the torque required. In the case of the click type on such a light torque as the OP was attempting, the wrench will make more of a bump than a click and it will happen so quick a novice may not notice it.

They are also valuable when you're in an awkward position and straining to tighten a bolt to 120ft-lbs while trying to read the shaking needle on a beam type. Once I used a click type I never looked back. ;) .

The next time I'm in an awkward position trying to tighten a bolt to 120ft-pounds on my bike, I'll be sure to borrow your clicker. Until that need arises, my "cheap" beam wrenches work more than adequately. :)

BTW, what does the current version your Snap-On wrench cost these days?

So is there a decent torque wrench for low range work such as carbon parts? I'm still looking for one that does not cost an arm and a leg.

So is there a decent torque wrench for low range work such as carbon parts? I'm still looking for one that does not cost an arm and a leg.
I have posted this several times already, once with a picture. I made my own torque wrench with a ten inch steel bar and a five dollar dial indicator fisherman's scale from Wal-Mart. I made one end of the bar so I can insert hex key wrenches of various sizes. The scale is attached to the other end. Torque is force over distance. Fifty inch pounds is a five pound pull over ten inches. You get the idea.

I did find the scale was six percent low in its readings. That would have resulted in too much torque. So, I lessened the distance between the hex key and the scale by six percent. It is now very accurate.

Check the scale for accuracy by weighing something of a tested, known weight. Your grocery store prints the exact weight of a package of meat on the label. The scales used to weigh the meat must pass state inspection.

Thanks everyone for the replies. I guess I have been taught a lesson. I sucessfully used a bigger clicker wrench last year on my crank and BB so I did not think the stem bolts would be that hard. The Craftsman 0 to 250 in-lb wrench has like a 12 in handle on it, which makes it hard to get a feel on something small. Anyway I took the clicker back to Sears but they do not seem to cary a smaller beam type right now. I may get a Park Tool one at some point but I don't like the scales they come with (0 to 60, 0 to 600). I got some more M5 bolts and and just tighten them down with an allen wrench.

I recently bought a BB w/ external bearings and the torque setting for the crank arm bolts was 15Nm (130kgf.cm). I am only familiar w/ in-lbs. Can someone explain this and does this require a more precise torque wrench?

So is there a decent torque wrench for low range work such as carbon parts? I'm still looking for one that does not cost an arm and a leg.

syntace makes the best one as far as i'm concerned, but it's still pretty expensive, and not necessary most of the time after you learn what different torques feel like from using the wrench for a week or so.

there was a sweet digital torque wrench that someone linked to a very long while back that looked promising, but i think that one was hella dollas.

I recently bought a BB w/ external bearings and the torque setting for the crank arm bolts was 15Nm (130kgf.cm). I am only familiar w/ in-lbs. Can someone explain this and does this require a more precise torque wrench?

15N-m = 132.8in-lbs = 11.1ft-lbs

Torque units conversion (http://www.convert-me.com/en/convert/torque)

I am an engineer and deal with torque in my job. You must realize the way that these torques are calculated. The torque is generated ONLY from friction in the threads. So, if the bolt material, roughness, foreign material in the threads, any wear on the threads, ANY of these things change, then the true tension on the bolt changes. In other words, torqueing a bolt is only trying to achieve a certain TENSION on the bolt (pull longwise). Torque is a very very very rough estimate of tension.

In my humble opinion (not expert), lower torque stuff (up to about 20 ft.lb.) is not worth wasting time on a torque wrench. Anything above that is worth your time.

Again, just my humble opinion.

What I do is get a foot long wrench, and pull up until it feels about right. If you ever pick up 5lb, 10lb weights in the gym, you should get close enough for comfort.

Again, it won't hurt to torque it, but please realize the limitations.

my 30 year old Snap-on clicker wrenches have never needed re-calbration, and yes I have them checked regularly.
They are also valuable when you're in an awkward position and straining to tighten a bolt to 120ft-lbs while trying to read the shaking needle on a beam type. Once I used a click type I never looked back. ;)
In the case of the click type on such a light torque as the OP was attempting, the wrench will make more of a bump than a click and it will happen so quick a novice may not notice it.
I fully agree with this. You must understand though that a whole lot of these people on this board do not know how to use/apply tools to the work. Oh yeah , they can talk/type up a good story... say like the engineers of the board :rolleyes:

I fully agree with this. You must understand though that a whole lot of these people on this board do not know how to use/apply tools to the work. Oh yeah , they can talk/type up a good story... say like the engineers of the board :rolleyes:

Thanks porky for your valuable addition.

Thanks porky for your valuable addition.

Sorry about this, I just get mad when people sneer at the facts because it is not what they are used to / have been told in the past / or just don't want to believe it. E.G. Drivers vs. bicycle right to the road.

HOWEVER, I am giving you the facts about torque calculations. They are very rough approximations. When true bolt tensions are needed in my industry, we stretch the bolt hydraulically, and then run the nut down snug.

Torques probably get the required tension most of the time, so go ahead and use the wrench. I was just pointing out that you shouldn't worry about a 6% error, because the calculation used to get the torque probably has like 30-50% error because it is an approximate calculation using approximate values in the first place. This is especially true for small torques, less so for larger torques, like I said earlier.

I am just trying to give people perspective, so please don't sneer. If you do this stuff for a living and have facts, then please let me know.

Another thing to consider is that most torque wrenches are accurate at best in their mid-range value. Lower and upper end tend to lose accuracy. So if you expect to wrench 50 N/M use a wrench 0-100 N/M range.

Fastener preload using a torque wrench will vary +/- 25%. An experienced "wrencher" using no torque wrench will produce +/-35% error. This information can be found in Machinery's Handbook 26th edition.

I try to use a torque wrench whenever possible. QUESTION to McDave: Where can I get my torque wrenches checked for proper calibration?

Jason

QUESTION to McDave: Where can I get my torque wrenches checked for proper calibration?

Jason

I've always got mine checked on the Snap-on tool truck. Only takes a few seconds with their torque tester.

So is there a decent torque wrench for low range work such as carbon parts? I'm still looking for one that does not cost an arm and a leg.

I have the Park TW1 (1/4" drive), seems decent to me.

No need for a torque wrench, but I think I'm preaching to the wrong choir here.

Clicker-wrench also don't address the issue of creep. That is, when you reach the specified torque and hold it, the bolt will actually turn a little more. With the clickers, if you re-torque the bolt again, you'll find that the point where it clicks will be a couple degrees further than the original click.

Edit: After re-reading the above quote I decided to delete my response as I believe creep to be a non-issue. I think I'm beginning to understand what porky is saying. :-)

BTW Those Snap-on dial type wrenches are sweet, but as my eyesight continues to fade, even with bi-focals, I still prefer my clickers. :)

Fastener preload using a torque wrench will vary +/- 25%.
As does the spec, so shoot for the mean.


An experienced "wrencher" using no torque wrench will produce +/-35% error. This information can be found in Machinery's Handbook 26th edition.
Got a page number? I'd like to look at the fine print. I suspect that that's something akin to an average. I recall a test in which experienced (auto) mechanics frequently mis-tensioned the bolts by 50%+ without a mechanical aid. Maybe 3/4 times it was within spec so the average wouldn't look bad at all, but what level of risk are you willing to accept on critical fasteners?

To DMF a.k.a. mister-fine-print. See the table on page 1480.

Sorry, I should have asked for the section. I've got 27th Ed. and the page numbering is different.

Never mind. Found the section: TORQUE AND TENSION IN FASTENERS starting p. 1495. Good stuff. Lots of crunchy math. Okay, got it. Table 2 on p.1500.

Table 2. Accuracy of Bolt Preload Application Methods
Method Accuracy
By feel ±35%
Torque wrench ±25%
Turn-of-nut ±15%
Computer-controlled wrench
- below yield (turn-of-nut) ±15%
- yield-point sensing ±8%
Preload indicating washer ±10%
Bolt elongation ±3−5%
Strain gages ±1%
Ultrasonic sensing ±1%
* Tightening methods using power drivers are similar in accuracy to equivalent manual methods.

Nah, they don't really discuss the torque methods. Oh well.