Torque Wrench Calibration

[DCMY #92]

This post is not Hatteras related, except that I use this wrench on my DDs. I have had the Craftsman 20 - 250 ft lb click type torque wrench (Digtork model 9 44546) for many years. Photo attached.
I have the means to check its calibration and today discovered that it is off (high) about 10 ft lbs. I found references on how to adjust the calibration, but I can't find any reference on how to remove the handle's end cap to get access to the adjustment screw. This end cap is used to adjust the desired torque value. If I break the handle cap or it's attachment mechanism in trying to gain access to the adjustment screw there is a high potential that I'll significantly degrade the ability to use the wrench. There are 2 holes in the bottom of the cap that I suspect might give access to some internal feature that will release the cap. Also, there is a plastic part visible, when the cap is pulled back to adjust the torque value, that has detents that look designed to accept a spanner wrench. Beyond this point I'm stumped.

Before I ruin the wrench I'll use the equivalent of a compass correction card when setting the torque value.

So, do any forum members (or lurkers) know how to get the handle end cap off?

 

[DCMY #92]

Sorry - forgot to upload the photo.

 

[jim rosenthal]

Asked Sears/Craftsman about this one? I would.

 

[MikeP]

10 lbs out? At what point in its range? No torque wrench is equally accurate throughout it's range and the wider the range, the more inaccurate it will be at the ends of the range. Clicker-type wrenches are inherently the least accurate of torque wrenches, though the easiest to use, hence their popularity. Frankly, 20-250 is an impossible range to maintain any sort of accuracy and one could, at best, expect reasonable accuracy maybe in the 75-150 range.

The narrower the range of the wrench, the more accurate it will be which is why most machine shops will have at least 3 different torque wrenches, 1/4" drive, 3/8" drive, and 1/2" drive, each covering a fairly narrow range. If you are serious about torque accuracy, a beam or dial wrench is what you want. As one of the engine building shop owners I once worked for used to proclaim, "Clickers are for lug nuts; I better never see you use one on an engine."

 

[DCMY #92]

I have a drawer full of torque wrenches of various ranges and drive sizes. All but this one are beam type, some precision beam wrenches that click at the set torque value.

This click-stop wrench is off 10 ft-lbs at 80 ft-lbs. For the last 20 or so years this wrench has maintained reasonable accuracy. I was recently using it to install some new wheels on our bike hauler and thought that the click came with too much pull. Sure enough, when I checked the calibration it was high. I should have checked it first, but fortunately I didn't do any damage.

It's no problem to adjust the calibration once I have the handle's end cap removed. But I've never had it off and would prefer not to destroy the wrench in trying to do so. Craftsman made wrenches of various sizes in this style for many years. I've found instructions and exploded view for many other wrenches, but oddly not for this one.