Torque indicator for Hex "L" Key 2

[geesamand]

I have an application in which a socket head set screw is placed essentially next to a wall. I need to develop a way to torque that set screw measurably. Due to the level of desired torque, ball-end keys are not adequate. The only tool that really fits and torques securely is an L-key.

I've seen clip-on devices (plastic) that slide over the short end of the key and rely on the bending of the long side of the L-key to indicate torque. I'll make my own if necessary but I'd love to find a commercially available solution. Where can I find these?

 

[SwinnyGG]

What size is the hex?

I've used a piece of hex stock in the head, with a torque adapter on the wrench, to apply the required torque. This setup won't work if the cap screw is a small size, or the torque required is extremely large.

 

[EdStainless]

When we had high torque close fitting bolts we went to 12 point cap screws (aka Ferry).
We had enough room to then use a torque wrench.

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P.E. Metallurgy, Plymouth Tube

 

[BUGGAR]

Why not just put the torque wrench at the end of the L leg. Torque here equals torque there plus that torque from the extra lever arm.

 

[geesamand]

The hexes are 5mm (M10) and 6mm (M12), torqued to 230 in-lb and 380 in-lb respectively.

These are close enough to the "wall" that anything larger than the hex bit itself will not fit. (!?!) Even a 3/8" square drive with 5/6mm hex bit is far too wide. To clear the wall I tried a 8" long 5mm and 6mm hex bit from Bondhus but at that length they twist a whole bunch and bend too easily. I don't blame Bondhus at all - it seems to be the reason why t-handles aren't used for large torques.

A torque wrench won't physically fit.

While an L-key device isn't the most accurate device, I'll be happy with 20% accuracy and it's very affordable and much better than nothing.

 

[geesamand]

PS: Note that I'm not defending this design as a good design. I'm supporting it.

 

[EdStainless]

Geesamand, What bolts are these? Not socket head cap screws that is for sure.
But how can you have less than 12mm clearance for a 12mm shank bolt? And the head must have a larger bearing area than 12mm......

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P.E. Metallurgy, Plymouth Tube

 

[geesamand]

Hex Head Set Screws in M10 and M12

The obstructing "wall" is a separate component so in the area of the set screw there is slightly more clearance. But move up a few mm from the screw head and that wall begins.

I believe that the original designers a hand-tightened L-key was sufficient. I can no longer agree with that and see torque to spec is necessary.

 

[hendersdc]

A quick google search found a few options for wrenches that have hex key interchangeable heads or hex key adapters that allow you to place a regular hex key on the torque wrench.

Looks like these may not go as high as you would like on torque but could be a good starting point.
[URL unfurl="true"]http://www.mountztorque.com/products/torque-wrenches/hex-key-adapters[/url]

These guys seem to only offer inch sizes but I could be missing something or you could buy one slightly oversized and grind it down.
[URL unfurl="true"]http://omegatec.com/utica-torque-wrench-interchangeable-heads-a-size-series.aspx[/url]

 

[zeusfaber]

Almost certainly not the way to do it - but always worth keeping the absurd alternative at the back of your mind.

Buy a large bag of Allen keys.

Cut a slot most of the way through one, then use it to break a torque wrench repeatedly, increasing the torque setting at each attempt until the key finally snaps

Prepare another key, adjusting the slot depth to get the failure torque closer to the desired value: repeat until you get it right.

Now do the same to the rest of the keys and use them as one-shot torque wrenches.

Or how about switching to Hi-Loks?

A.

 

[Tmoose]

1 foot long pipe and one of these -

http://www.basspro.com/Bass-Pro-Shops-Fish-Scale/product/13327/

 

[pylfrm]

geesamand,

The only tool I've seen like you describe is the 9point8 TorqueKey, but it's only 4 mm.

According to Bondhus, their tools should have been fine. Torque capacities are listed as 483 in*lbf for 5 mm and 855 in*lbf for 6 mm. Even the ratings for ball end tools are barely sufficient at 247 in*lbf and 396 in*lbf.

I wouldn't expect the length of the tool to affect the strength. When you say they twist and bend, do you mean permanently or just while the load is applied? If the latter, why is it a problem?


pylfrm

 

[geesamand]

pylfrm: yes, that's exactly what I'm describing. I think it could be easy to make but just the same it could be much cheaper and easier to buy elsewhere. SKF supplies this type of indicator with an L-key when you buy a Concentra bearing assembly. But I think there the size is always 1.5 or 2mm.

The bondhus hex stock can do the torque load, but when I tried a very long piece under full torque it bent (permanently). Not badly, but I was barely approaching the desired torque and it was twisted over 90 deg. I was supporting the head of the wrench but when it's noodling around that badly it's difficult to avoid bending it. I was standing in front of a torque calibration dial; I really doubt any mechanic in the field will trust it.

 

[MintJulep]

http://www.keltektool.com/preset-torque-wrenches.htm

 

[geesamand]

MintJulep: that's a great option, and it looks like they have internals that can handle up to 500in-lb. This could be a great option for the assembly floor.

I'm thinking more about the plastic indicator and I think it would be easy to test and "calibrate" with a good 3D printed prototype. I could probably afford to supply an L-key and plastic torque indicator to my customers as a courtesy.