Seeking source for torque wrench extensions

Looking at the documentation from most of the quality manufacturers of
torque wrenchs (Proto, Snap-on, Norbar, etc..) I see that I can
increase the "range" of a torque wrench by putting an "in-line"
extension on the *drive* end(not the handle end. By scaling the
reading/click setting accoring to a formula which accounts for the
length of the extension, one can apply a torque that is greater than
the wrench would do if there was no extension. (Just so I'm clear,
this is not the typical sort of extension that goes perpendicular to
the wrench, but is instead in line with the axis of the wrench.)
Now - I've searched far and wide and cannot find anyone who actually
makes or sells a simple extension that I can buy. I'm looking for one
that has a 1/2" square female socket on one end (where the drive end
of the torque wrench fits) with a 1/2" male square drive on the other
end. I've seen ones where the drive ends are open-ended spanners, box
ends, etc, but can't find a simple square-square adapter.
Here'a a link to a guy who's built a homemade version:
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Of course, I could build one or have one built, but this seems so
obvious that somebody's got to be making such a thing. Lengths from
6" to 24"(+) would be OK for my needs.
Anybody have a source for such a thing?
-Dave
Reply to
djl
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Are you referring to a "torque multiplier"? If so, search Google for plenty of sources. Here's one, but I have a feeling the link won't work:
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Reply to
AL
I seem to recall an adapter much like you describe with a gearing multiplier inside. I don't remember who made it. It was basically a transmission of sorts with planet gears.
Hmm.. my internet search brought up this.
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-Bruce
Reply to
Bruce Chang
I think the example in the spooky-torque design is probably considerably inaccurate for a couple of reasons.
Beam deflection, like the principle of a beam-type torque wrench. Depending upon the choice of material, the amount of deflection could change with use. As the deflection changes (from a straight line), so does the distance to the center of the far end. The breaker bar swivel pin and yoke deflection.
Maybe the best chance at achieving a predictable multiplier would be a single piece of very strong material (no fasteners or joints), and the centerline kept perfectly straight, while keeping the axis of the torque wrench drive at precisely 180 degrees to the drive socket.
I don't think an accurate torque reading/indication can be achieved with a breaker bar and/or the extension shown in the example. There wouldn't be an easy way to test the accuracy of a homemade extension without having it checked against a calibrated standard.
WB .................
Reply to
Wild Bill
If your interested I have a 3/4" drive for sale reasonable, haven't used it much.. if interested e-mail me Paul
Reply to
ph17314
Sure, beam deflection, and other "slop" in the setup does induce error. As you suggest, I'm intending to minimize that error by having it deflect as little as possible - both mimimizing length (I only need 6-10 inches, really, to get to the torque ranges I'm after) and making sure it's as stiff as possible.
That said, even if the setup were to deflect, say, 15deg, cosine error induced would be about 3.5%. Overall effect on the system is dependent on the relative length of the extension compared to the wrench. If I were to really worry about it, it's pretty a pretty simple trig problem to figure out exactly how much cosine error I have (by measuring actual beam deflection) and factor that back into my torque wrench click setting. Also consider that my *calibrated* wrench is only certified to 4% accuracy anyway. All said, it's well within the range of accuracy I need where the torque specs required are on the order of +/- 15% - it's just not that critical of an application.
As to verifying torque, one can get a good check by clamping the setup in a solid vise and applying known weights to the extension/wrench combo. Measure the distance and you know if you're in the ballpark or not.
"Wild Bill" wrote in message
Reply to
djl
Nope - not looking for a geared multipler. Just a simple bar with socket adapters at each end.
"Bruce Chang" wrote in message
Reply to
djl
Why don't you just buy a right sized torque wrench? If it's important enough to be torqued to spec isn't it important enough to have the proper tool?
I have to wonder if your an engineer (unlikely) or in management (that's my guess).
Reply to
Mark
Mark -
Whoa - the personal dig is uncalled for. That aside - the inquiry is legit.
Given that Proto, Norbar, Sturtevant-Richemont, and Mountz - all of which are highly respected manufacturers of torque equipment - document procedures and calculation formulas for using such extensions, it is only reasonable that this general approach is valid. This is not just a hack - see some links below. The principles involved, the limitations (sources of error) and, most importantly, the needs of this particular application are understood, including those of cost. This *is* good engineering practice.
So - I'm just looking for a source. Get it?
-Dave
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- supplier for Ferrari F1 race team
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- supplier
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- supplier of torque calibration equipment
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(there's lots more out there, check for yourself)
Reply to
djl
I would consider purchasing two 1/2 inch breaker bars, the kind with the round sliding male half inch square drive.
Then grind off the retaining balls on one side of each one, and slide the square drive unit off of one, and onto the other.
So now you have two square sliding male fittings. Step one would be immobilize them on the bar with, say, braze. Be sure they are pointing in opposite directions.
Step two is find the correct size 12-point socket that fits a half inch square. I think there is a very close match iirc.
Then the existing torque wrench goes into the 12-point socket, and the socket you want to use goes on the other male end.
Key to making this work is purchasing the items used or otherwise, inexpensively.
Jim
================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ==================================================
Reply to
jim rozen
I knew what you were getting at before you asked the question.
I have more than a passing familiarity with the use of fixtures and extensions on torque wrenches.
Extensions are only used to gain access to fasteners that are otherwise inaccessible. Period.
The use of an extension may be mathematically sound and 'good engineering practice'. That's why it's usually a good thing to keep many engineers away from the work. Keeps them from doing too much damage.
It is an unacceptable practice, or at least extremely poor form for a technician to use an extension solely to increase the range of the torque wrench. We know better.
And the fact your having such a difficult time finding what your looking for should give you a clue.
Get it?
Suck it up. Buy the correct tooling.
Reply to
Mark
Mark wrote: (clip) The use of an extension may be mathematically sound and 'good engineering practice'. That's why it's usually a good thing to keep many engineers away from the work (clip) Get it? Suck it up. Buy the correct tooling. ^^^^^^^^^^^^^ Stubbornness is no substitute for thinking. djl has explained his need, and allowed for the minor inaccuracies that could result from the use of an extension. Let's face it--most of us do not require Bureau-of-Standards accuracy when we tighten a bolt. But, I guess that engineers, using accepted mechanical theory, know less than you do.
Reply to
Leo Lichtman
jim rozen wrote: (clip) Then the existing torque wrench goes into the 12-point socket, and the socket you want to use goes on the other male end. Key to making this work is purchasing the items used or otherwise, inexpensively ^^^^^^^^^^^^^^ That idea might be less expensive to carry out if you just welded a 1/2" drive socket to the end of a 1/2" breaker bar.
Reply to
Leo Lichtman
I could have used one a few weeks ago...
Its been a long time since I've seen the catalogs, but I suspect the Kent Moore tool company - which used to (or maybe still does) make specialty tools for GM - had what you are looking for.
Good Luck!
djl wrote:
Reply to
Stephen Kurzban
It all depends what one has available in the junk box.
But whatever he does, *don't* weld the items together. I've found that the HAZ becomes brittle sometimes that way, and the tool will snap at the weld. Brazing is really better.
Jim
================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ==================================================
Reply to
jim rozen
Many times yes, they do know less.
That's not arrogance, it's an observation.
Seems many engineers think their degree means they know what their doing instead of what it truly is, a learners permit.
Bureau of Standards accuracy? Damned straight. If it didn't matter there wouldn't be calibration expiration dates on our tools.
Reply to
Mark
The induced error comes from the torque wrench you use and the accuracy of the length measuresments on BOTH the wrench and the extentions. Slop and deflections (within reason) do not affect it. But the error is doubled so a +/- 4% of FULL SCALE becomes +/- 8% of full scale. A 150 ft pound wrench at +/- 4% with a doubler extension becomes +/- 12 foot pounds. If that is within your tolerance, go for it.
If you want to argue about calibration, it is always a good thing. But how many auto dealerships take the time to go through all the mechanic's toolboxes and calibrate the various torque wrenches?
In the industrial setting, it is common to send an inspector around to all the tool boxes and ban or confiscate out of tolerance dial indicators, tape mesures, etc.
djl wrote:
Reply to
Roy J
It worked for me (with careful cut and paste work), but this does not look like what the original poster is looking for.
This is a geared torque converter.
What he is looking for is an extension which offsets the socket by a precise distance. When set in line with the bar of the torque wrench, and extending past the head. The effect is to add length to the wrench, so the torque reading is actually lower than the actual torque applied at the end of the effectively longer lever.
As others have pointed out, while this extends the range of the wrench, it reduces the accuracy. And if the extension is not in proper line with the main shank of the torque wrench.
The way this works is that you need to apply a given force on the torque wrench handle (at a precise distance from the socket). The wrench is actually measuring the force. By extending the socket to beyond the head, you are applying that force on a longer lever, you are producing proportionally more torque at the actual socket.
What you found is probably a better choice in reality -- but is certainly more expensive. If the original poster is looking for this to keep costs down, and does not care about the loss of accuracy, what he is looking for is probably the best choice -- btu I'' bet that he could find a torque wrench to cover the range that he needs by a quick eBay search, and keep the costs way down that way.
I'm set, up to 600 ft-lbs, thanks to a surplus sale many years ago.
Enjoy, DoN.
Reply to
DoN. Nichols

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