Stress Indicators Inc. > Products

	SmartBolts® DTI SmartBolts® HR SmartBolts® Technical Information Order Samples Client List Download our brochure (PDF format) Stress Indicators, Inc. 6307 Wiscasset Road Bethesda, MD 20816 Tel: (240) 631-7246 Fax: (301) 320-3303 inquiries@smartbolts.com		High-Accuracy Direct Tension Indicators
			HR SmartBolts® have been engineered to maximize indicator sensitivity and to position this maximum sensitivity response at the "fully-tightened" or high end of the tension range. The bright yellow indicator begins to turn color at 70% of proof load, is a grass green color at design tension (typically 90% of proof) and has completely turned to a deep blue-black at 100% of proof load. The sensitive microindicator is capable of visually resolving a deflection of only 60 microinches, which allows tensioning to an unprecedented precision, specified at 5%, but often as precise as 2% of fastener minimum tensile strength. This represents the highest precision available in any self-contained commercial direct-tension-indicating fastener product. (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