Bleeding washers... 1

[jaykay]

We are going to start building highway sign structures which usually have in excess of 1000 nuts and bolts on average and we have hundreds of structures to build. I am looking for the most efficient way to torque bolts and nuts. The usual way is tightening manually, marking and then using a torque wrench, which seems time consuming. I have heard of bolts that break off at a certain torque value or even bleeding washers that bleed ink when torqued. If any one out there knows where to gets these items from or has a better procedure please let me know, your help will be greatly appreciated.
JK

 

[CWIC]

There are several methods of verifying fastener tension:
1. A calibrated torque wrench and Skidmore.
2. DTI's or direct tension indicators which use a feeler gage to check tension.
3. Twist off (ASTM F1852) or "break off" bolts which shear the stub on the threaded end once the required tension is applied.
4. "Squirters" which expel a liquid under the washer when the correct tension is applied.
5. Turn of the nut which provides theoretical tension performed after the fasteners are snug tight.

Contact the companies you normally purchase your fasteners from, I'm sure they can provide guidance. The company that manufactures "Squirters" were promoting these recently in most of the trade publications.

 

[MechEng13]

What about the possibility of using an impact wrench with adjustable torque. You can set it to the torque you need and verify by checking a few nuts with a torque wrench.



Alan M. Etzkorn
Manufacturing Engineer
Hoffco/Comet Industries Inc.

http://www.hoffcocomet.com

 

[CWIC]

Just an update on the squirters, these devices do have not an approval by the any of the organizations who perform such acitvities including RCSC, AASHTO, ICC ES, etc. as told to me by one of my contacts in the fastener industry. The company who manufactures these devices is Applied Technologies (so I am told). Check for them on the web.

You may want to consider one of the standard fastening systems and methods of tension verification.

 

[Pekelder]

As you are making Higway signs, I suppose you will have to install them on site. Why not use battery powered torque-wrenches (impulse type or direct torque, depending on wanting low or high accuracy of the torque) which you can use for fastening and which will stop or rattle at reaching the right torque. Installing 1000+ bolts will require a electric tool anyway, doesn't it?

It all comes down to the level of accuracy you are required to produce or guarrantee. Ask around with some tool-suppliers. A simple battery-wrench will be fairly priced.

Regards,

Pekelder