torque wrench question(s)

[mtkst19]

2 questions-- 1 about parts, other about accuracy

a tq wrench is only as good as it's calibration. with that said, i own 4 wrenches- all of them are click style w/ the micrometer type handles. I have 1 for each drive size and a 2nd 1/2 drive for lugnuts only.

what i find odd is all my snap on wrenches are 4% (1/4, 3/8, and 1/2 drive respectively) and my cornwell 1/2 is 3% accuracy when shipped from the factory. they have been re-calibrated or checked since then. so im pretty confident in their accuracy.

if you like, my model numbers and the accuracy when shipped are:
cornwell- ce-c97453 3%
snap-on qjr117f 4%
snap-on qc2fr75 4%
snap on qjr2100c 4%


question number 1 revolves around the ******* of this group--the qjr2100c. Every snap on guy i have run across says this should be a 3/8 tq wrench. Mine has 1/2 guts. As luck would have it, i stripped a tooth on the pawl while torquing wheels. Now what? it is not worth **** to me dead. i'd convert it back to 3/8 drive but i would need everything to do so. i think i will need pictures to explain this one better. so ill try to grab some tonight w/ my cell phone.

to further muddy the waters on torque wrenches--

now my question #2 for anyone to answer is how exactly is harbor freight measuring their accuracy of 4%? As this is on par w/ "better" brand stuff. im assuming the 4% is the mid range of the spectrum. lower and upper ranges would be out even more--but how much more? anyone have a spec paper from a hf clicker? or better yet, anyone actually test one to see how up to par they are?

hell, for 10 bucks i'd pick one up just to keep in the car for lugs or have it as a loaner when people ask to borrow a wrench. I dont like lending out my tq. wrenches, as my friends would destroy them. i could see them using it in the off position standing on it to loosen lug nuts or use it as a ratchet to wind all the bolts down that need torqued instead of using a proper ratchet to get them snugged then the tq wrench to finish them off.

 

[DARKSCOPE001]

Harbor freight tw probably dont fall in the range of 4% it can say calibrated all day long. but that doesent mean ****. things that more high end companies would probably take into consideration hf will not. Things like When was the last time the calabration machine was tested for accuracy? Also when poor sweatshop worker bob who is only trying to feed his family drops the wrench after "certiflying" it do you think he rejects it? or tests it again to see if his mishap has knocked the wrench out of calibration? Probably not. also my answer to your 1st question would be another question. In what form did you use it the most? did you use it as a 3/8 or a 1/2? if you used it as a 1/2 the most rebuild it as that. Just go to snapons website and im sure with a little poking around you can find the parts you need to get that guy working just like he used to

GOOD LUCK
Sean Scott

 

[Merkava_4]

Here's the parts page to the QJR2100C -

http://buy1.snapon.com/catalog/parts/pro_det.asp?Item_id=38255&group_id=8898

 

[Falcon67]

4% is about normal for most torque wrenches. The cal is only as good as the traceability to a known standard. Note - once you use something like a rod stretch gauge to measure fastener stretch instead of torque, you'll realize that torquing a fastener is more like throwing a ball at a barn as far as accuracy goes. 4% is plenty. I really perfer to use my electronic torque gauge that goes between the wrench and the fastener. It beeps with increasing frequency as you approach the set point. Not worth much on small stuff but good on big stuff like main studs, head studs and the like.

 

[Charles (in GA)]

The 4% or whatever accuracy spec they mention is the max error allowed anywhere over the whole calibration range of the tool. Actually its the top 80% of the range up to the max limit of the tool. Doesn't make sense, didn't to me, let me give an example.

A 100 lb./ft torque wrench has range markings USUALLY of 20 to 100 lb/ft. this is the top 80% they are talking about. The tool has a range of zero to a hundred but it isn't accurate below twenty precent of the maximum of the tool, or twenty foot pounds, so they don't bother to mark it down there. Beam type torque wrenches have a scale that goes from zero to whatever, but they are not calibrated as being accurate below that magic twenty percent point, even though they are marked that way (and a beam type probably is accurate way low, but the rules for standards and certification, be it here in the US, Austaralia, or the UK, each have their own rules that all specify 20% of the max to 100% of the max as being the range of certification (top 80%).

I find it interesting that Snap-On doesn't tell you at all what square drive size a QJR2100C is, but then again, the search window will not find qjr2100c for me either, I have to use Google to find it.

Charles

 

[matthew]

The actual accuracy and specified accuracy are different things. The HF wrench might be +/-3%, and rated at +/-4%. The better quality one might actually have output of +/-1%, but be rated at +/-3%.

Also, calibration frequency may also play into it. The better ones might have longer intervals between calibrations to stay within that 3%.

 

[mtkst19]

i seen the repair page for the qjr on snap on's site and it does not say specifically that it is 3/8 drive anywhere in parts. my googling shows it is a 3/8 wrench--yet the one in my box is deff. 1/2 drive. Entire time i have owned it it has been 1/2. i bought it second hand when i 1st started out and have had it calibrated even. i tried to buy used 1/2 wrenches from the time period and struck out finding one to use for the guts.

as for the accuracy, i was always under the impression that if you had a 0-100 wrench w/ 4% accuracy, the upper 20 and lower 20 were not in spec (or atleast not guarenteed to be). but from 21-80 it would be 4%

with that said, i was also told to keep your click type micrometer handle style wrenches stored at the lower 20%. so if i had a 0-100 wrench, store it at 20. i always kept them at 0 but some old timer explaine dot me something along the lines of weaking the spring by leaving it at 0. needs the preload that the 20% gives it or somethign along those lines. i dont remember fully. just figured he knew wtf he was talking about it and just followed his advice.

 

[Merkava_4]

i seen the repair page for the qjr on snap on's site and it does not say specifically that it is 3/8 drive anywhere in parts.

I gave you the link so that you can get the ratchet repair kit. I really don't care whether it's 1/2" drive of not; I've sent you the correct page that applies to your torque wrench.

 

[mtkst19]

so how do i put the "correct" 3/8 guts in it with out the proper backing plate? i dont know the correct term for it (backing plate?) but it is what the drive square sticks out of to connect to the socket. as the plate i currently setup for a 1/2 drive plate. if i order a repair kit (which comes w/ a new pawl mechanism i assume) it is going to be different than the 1/2 drive one in it now.

 

[Merkava_4]

so how do i put the "correct" 3/8 guts in it with out the proper backing plate? i dont know the correct term for it (backing plate?) but it is what the drive square sticks out of to connect to the socket. as the plate i currently setup for a 1/2 drive plate. if i order a repair kit (which comes w/ a new pawl mechanism i assume) it is going to be different than the 1/2 drive one in it now.

Go ahead and order the 1/2" drive repair kit which is RKQJ3A for torque wrench QJR3200C - it should fit.

Your torque wrench is supposed to be 3/8" drive if it's indeed a QJ2100C though...

 

[FordF1]

I bought a used beat up Snap On 1/2 Torque wrench at a pawn shop last year. It was only $60 or $70 bucks, so I figured what the hell, even if it is broken if can't be too much to fix.

There was a torque bench where I used to work so I had it tested before sending it away. It came back within 4% at 200ft/lbs and even less error at 40ft/lbs. I know this torque wrench was beaten up, but it came out testing well within spec. I think 7% (maybe 6%) is the standard they use to work on airplanes, so I wouldn't be looking for the highest accuracy. The tech said that Snap On ones are pretty good long term, especially the older ones he has tested.

 

[Charles (in GA)]

I think 7% (maybe 6%) is the standard they use to work on airplanes, so I wouldn't be looking for the highest accuracy. The tech said that Snap On ones are pretty good long term, especially the older ones he has tested.

The airline I work for uses 4% as a max error for general purpose tools. Some stuff may be less than that. I cannot image anyone wanting to bother with one that is 6% or 7% out. Thats 7 ft lbs variation allowed at 100 ftlbs.

Charles

 

[Monte]

here you can see some test results from a magazine. DIN-ISO norm says maximum difference +-4%. The test results show that there is a difference up to 14,55%.

 

[caper]

I believe it was Nissan Crawler who told us the HF torque wrenches tested at his shop(aviation industry)routinely meet calibration while some supposedly better wrenches don't.

 

[Coach James]

The 4% or whatever accuracy spec they mention is the max error allowed anywhere over the whole calibration range of the tool. Actually its the top 80% of the range up to the max limit of the tool. Doesn't make sense, didn't to me, let me give an example.

A 100 lb./ft torque wrench has range markings USUALLY of 20 to 100 lb/ft. this is the top 80% they are talking about. The tool has a range of zero to a hundred but it isn't accurate below eighty percent of the maximum of the tool, or twenty foot pounds, so they don't bother to mark it down there. Beam type torque wrenches have a scale that goes from zero to whatever, but they are not calibrated as being accurate below that magic eighty percent point, even though they are marked that way (and a beam type probably is accurate way low, but the rules for standards and certification, be it here in the US, Austaralia, or the UK, each have their own rules that all specify 80% of the max as being the range of certification.

I find it interesting that Snap-On doesn't tell you at all what square drive size a QJR2100C is, but then again, the search window will not find qjr2100c for me either, I have to use Google to find it.

Charles

If it's not accurate below 80% of the max, it would only be accurate between 80 and 100 ft-lbs. Do you mean it's not accurate below 20%?

Coach

 

[Charles (in GA)]

If it's not accurate below 80% of the max, it would only be accurate between 80 and 100 ft-lbs. Do you mean it's not accurate below 20%?

Coach

You are correct. Thanks. I'm taking some prescription pain medication and that makes typing on the internet dangerous.

Charles

 

[bmxr4life87]

Gearwrench torque wrenches don't require the dial to be backed off as per the paper work included which is nice because we keep them set for our fleet

 

[mtkst19]

i know it has been two days since this was last discussed. finally got pictures.

as you will see, head is small 3/8 but guts are 1/2. really, i could care less if it stays 3/8 or 1/2. hopefully this week my snap on dealer will have some stuff for me.

 

[caper]

Looks like somebody may have put a kit for sf730 in that wrench.It's Snap on's 1/2"dr in a 3/8"dr head.You'd be looking for kit RKRSF730.