Calibrating micrometer torque wrench

[dwighty390]

Good afternoon!

I have a pair of micrometer torque wrenches that I need to calibrate. Please see the attached picture. What do I need to do here? Is that a jamb nut that I need to loosen and then run the allen bolt down to add tension to spring?

These are both Husky branded torque wrenches but are a previous made in US model, probably 10 years old or so. IIRC they'd be the "same" as maybe some Matco stuff from the time.

Thanks

 

[merkyworks]

Best advice is do nothing. Just cause a torque is older doesnt mean its out of calibration, properly stored it could sit for 20 years and still be in spec.

How do you know it needs to be calibrated?

 

[dwighty390]

Best advice is not to do nothing. It is out of calibration by around 10-11% which is far beyond OK. It needs calibrated. The age was more in the context of "these are good torque wrenches" not related to the need to be calibrated. There's a place that will do it locally but it is over $90 per.

The nut is indeed a jamb nut as I expected. Finally found the info I needed and will get it taken care of.

 

[PCustoms]

Best advice is not to do nothing. It is out of calibration by around 10-11% which is far beyond OK. It needs calibrated. The age was more in the context of "these are good torque wrenches" not related to the need to be calibrated. There's a place that will do it locally but it is over $90 per.

How do you know it's off/out of calibration?

Once you adjust it, how will you verify it is correct?

What are you using it for? Does this calibration require traceability?

The nut is indeed a jamb nut as I expected. Finally found the info I needed and will get it taken care of.

Adjusting it isn't hard, it's the rest that matters

 

[merkyworks]

Best advice is not to do nothing. It is out of calibration by around 10-11% which is far beyond OK. It needs calibrated. The age was more in the context of "these are good torque wrenches" not related to the need to be calibrated. There's a place that will do it locally but it is over $90 per.

The nut is indeed a jamb nut as I expected. Finally found the info I needed and will get it taken care of.

1st post its "What do I need to do here?" and then 2nd post your an expert.

I will ask again how do you know it is out of calibration? Not how much is it out, but what method are you using to verify.

 

[dwighty390]

I have another snap on torque wrench that I recently acquired, a brand new digital torque adapter, and a digital scale. The snap on and the adapter are spot on with each other. 51.0 lbs of weight confirmed via digital scale calculated to the length of the handle of the pictured torque wrench yields an identical discrepancy in cross checking. The husky wrench is about 10% low in torque across the range.

The husky wrench must be set to 99 ft lbs to achieve 90 ft lbs on either the adapter or with the weight calculated, while the snap on checks out with flying colors. (I guess that's about 9%, I did my actual/measured backward in my head before...not super relevant.)

No adjusting it is not hard. Finding confirmation that I was looking at a jamb nut took some time as will turning down a socket on my lathe to fit in there.

No I do not need proof of calibration.

I do appreciate the concern that I might be wasting my time. It is a pretty simple process to confirm that it is out and it has been cross checked threefold. I would find it highly unlikely that a torque adapter, a snap on wrench, and a digital scale all give an identical conclusion if the husky wrench were not the culprit.

 

[PCustoms]

The husky wrench must be set to 99 ft lbs to achieve 90 ft lbs on either the adapter or with the weight calculated, while the snap on checks out with flying colors. (I guess that's about 9%, I did my actual/measured backward in my head before...not super relevant.)

What is the max range on the husky wrench?

These things aren't meant to be super accurate the top/bottom of their ranges. A certified calibration will verify the tolerances full scale and withing the recommended, usable range. IIRC it's 80%, but don't quote me on that it's been about 10yrs since I've had direct responsibility for calibrations.

 

[dwighty390]

1st post its "What do I need to do here?" and then 2nd post your an expert.

I will ask again how do you know it is out of calibration? Not how much is it out, but what method are you using to verify.

No. I did not ask the "what do I need to do here" that broadly.

Me knowing it's out of calibration has very little to do with a simple confirmation on that picture being a jamb nut. Obviously these are able to be calibrated, but as the method is different depending on design, I didn't want to move something unnecessary, or the like. The nut was epoxied to the side of the tube...I didn't want to break it free and dig that out if I was going down the wrong path.

 

[dwighty390]

What is the max range on the husky wrench?

These things aren't meant to be super accurate the top/bottom of their ranges. A certified calibration will verify the tolerances full scale and withing the recommended, usable range. IIRC it's 80%, but don't quote me on that it's been about 10yrs since I've had direct responsibility for calibrations.

Yes it's between 20% and 100% of full scale on these and I checked at various settings. This one in particlalar is a 25-250 and is pushing the 10% mark. I believe it is rated at 3% tolerance.

 

[KnurledNut]

A couple years ago I posted about an Armstrong that I recalibrated with a similar setup. Yours might be similar.
I'll copy and paste it below:

I picked up one of these wrenches recently and calibrated it using a known-good torque adaptor.
This requires a super-duper thin-wall 11/16 deep socket, which I custom made using a Snap-on 12-point.
I turned it down with a drill and angle grinder.
It also takes a 7/32 hex key. I used a t-handle.
Remove the end cap in the handle. Just pry it out.
To adjust, lock the handle, loosen the nut (standard thread), and then turn the hex to the left to decrease/to the right to increase torque output.
Tighten the nut (no need to go full gorilla here), unlock the handle and test.
The adjuster is fairly sensitive. Unless its way out of calibration (which could mean bigger issues/internal damage), start with quarter to half turn increments.
A very basic job with the right tools.
If your gonna make your own socket, the O.D. needs to be .875” or less, necked down for 1.2”.
(I wish someone manufactured a set of extreme thin-wall sockets.)

 

[dwighty390]

A couple years ago I posted about an Armstrong that I recalibrated with a similar setup. Yours might be similar.
I'll copy and paste it below:

I'd guess they are identical or one is a copy of the other based on this, and I appreciate pointing out the thread direction!

 

[PCustoms]

Years back I bought a 3/8 and 1/2 lightly used Craftsman set for a really good price. Both checked OK when I got them.

Went to use the 3/8 one day and couldn't adjust it. The internals had come completely unscrewed. Same exact guts as what you're showing. One of these days I need to remember to bring it to work and adjust/verify it against our calibrated check station. I really haven't had mush use for it Soni haven't bothered

 

[merkyworks]

It sounds like you have a sound method for verification, and with those new details yes it sound like your wrench is out of calibration. Yes you need to loosen the jam nut and then turn the screw with an allen wrench in or out. Screw in to increase torque and screw out to decrease torque. In your case turn the screw in, tighten the jam nut, and then verify the new setting.

Please understand our questions are to make sure we give you the best advice, need to know all the variables to work the equation if you will. Your message history indicates that was your 1st post ever and its not uncommon for people who have no clue what they are doing to join and ask questions like this.

 

[KnurledNut]

Please understand our questions are to make sure we give you the best advice, need to know all the variables to work the equation if you will. Your message history indicates that was your 1st post ever and its not uncommon for people who have no clue what they are doing to join and ask questions like this.

I don't underestimate a guy with rough hands and a dirty workbench.

Welcome to the Journal @dwighty390.

 

[merkyworks]

@KnurledNut Touché

 

[dwighty390]

It sounds like you have a sound method for verification, and with those new details yes it sound like your wrench is out of calibration. Yes you need to loosen the jam nut and then turn the screw with an allen wrench in or out. Screw in to increase torque and screw out to decrease torque. In your case turn the screw in, tighten the jam nut, and then verify the new setting.

Please understand our questions are to make sure we give you the best advice, need to know all the variables to work the equation if you will. Your message history indicates that was your 1st post ever and its not uncommon for people who have no clue what they are doing to join and ask questions like this.

It sounds like you have a sound method for verification, and with those new details yes it sound like your wrench is out of calibration. Yes you need to loosen the jam nut and then turn the screw with an allen wrench in or out. Screw in to increase torque and screw out to decrease torque. In your case turn the screw in, tighten the jam nut, and then verify the new setting.

Please understand our questions are to make sure we give you the best advice, need to know all the variables to work the equation if you will. Your message history indicates that was your 1st post ever and its not uncommon for people who have no clue what they are doing to join and ask questions like this.

I get it and apologize that I didn't give you much to go off of. No worries.

 

[dwighty390]

I don't underestimate a guy with rough hands and a dirty workbench.

Welcome to the Journal @dwighty390.

I just cleaned!

I'll see if I can find an introduction page.

 

[dwighty390]

What is the max range on the husky wrench?

These things aren't meant to be super accurate the top/bottom of their ranges. A certified calibration will verify the tolerances full scale and withing the recommended, usable range. IIRC it's 80%, but don't quote me on that it's been about 10yrs since I've had direct responsibility for calibrations.

It was bothering me that the calibration sheet included in my 1/2 drive showed tests at 50/100/150, but the manual with it said that the accuracy be verified between 20% and 100% of the *range*. 20% of a range between 25 and 250 would be 70. Looking up the actual asme standard indicates that was a typo, and it is between 20% and 100% of *capacity* be accurate.

Interestingly, BELOW that range is actually called out as MORE accurate. So by the standard, they are indeed designed to be very accurate.

Pfa

edit: I intended to look through that chart one more time before posting, and didn't until afterward. I see that it's a percent of of full capacity under 20%, so it becomes less and less accurate from there down, reaching 8% accuracy at the bottom of the scale. Interesting!