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SmartBolts®

DTI SmartBolts®

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Stress Indicators, Inc.
6307 Wiscasset Road
Bethesda, MD 20816
Tel: (240) 631-7246
Fax: (301) 320-3303 inquiries@smartbolts.com		   DTI Smartbolts
High-Accuracy Direct Tension Indicators

  
   
DTI SmartBolts® provide an eye-catching bright indication of a loose or under tensioned condition. The bright red-orange indication of a loose fastener will gradually darken when tightening until it is a deep black at design tension. The accuracy of the indicating tension is within 10% of the design tension. This represents a favorable precision applicable to almost any commercial condition where maintenance or liability is important. The amount of under tension on the fastener may be readily estimated from the color of the indicator.


(Use mouse to operate the SmartBolt®)





Torque vs. Direct Tension Indicators
Tightening Bolts – Bolts are often tightened by applying torque to the head or nut, which causes the bolt to stretch. The elongation results in bolt tension or pre-load, which is the force that holds the joint together. Torque is relatively easy to measure with a torque-wrench, so it is the most frequently used indicator of bolt tension.

Unfortunately, a torque-wrench does not measure bolt tension accurately, usually only about +/- 30%, because it does not take friction into account. The friction depends on bolt, nut, washer-material, plating, surface smoothness, machining accuracy, degree of lubrication and the number of times a bolt has been tightened. Fastener manufacturers often provide information for determining torque requirements for tightening various bolts, accounting for friction and other effects. However, in field applications, this information is often not available, practical or administered poorly.

Size range
SmartBolts® are available in bolts ranging from 7/16" (M10) to 1 1/4" (M32).

Patents
SmartBolts® are manufactured under one or more of the following patents.

U.S. Patent Nos.
3.602,186; 3,987,699; 3,987,668; 4,114,428; 4,904,132

Canadian Patent Nos.
930,619; 1,092,847; 2,048,667