DTI SmartBolts


DTI (Direct Tension Indicating) SmartBolts directly correlate fastener tension with color. Accuracy and reliably is ensured because the color change of the DTI Visual Indication System™ is proportional to fastener stretch — the only true measure of how tight your joint is (torque readings can be misleading since torque only measures how difficult it is to turn the bolt head).

The SmartBolts built-in visual tension indicator turns from red to black when proper tension has been reached — and is completely reversible for the life of the fastener.


Fastener Size Ranges
Hex Flange Socket
Diameter (Minimum) 7/16” (M10) ½” (M12) 1” (M24)
Diameter (Maximum) 2 ½” (M64) 2 ½” (M64) 2 ½” (M64)
Length (Minimum) 1 ¼” (30mm) 1 ¼” (30mm) 3” (75mm)
Length (Maximum) 24″ (600mm) 24” (600mm) 24” (600mm)
If you have a requirement that is not listed in this table, please contact us to discuss availability.


DTI Visual Indication System™

The DTI Visual Indication System™ continuously measures and displays tension information. From loose to tight and back again, the system is reliable and repeatable through countless cycles of operation. It is compatible with a wide range of fastener types, and we can adapt it to fasteners of nearly every available grade, finish, and coating.


Our engineering team can design the DTI Visual Indication System to meet the specific requirements of your application. During the design phase, a Design Tension is specified. The Design Tension identifies a properly tightened SmartBolt.

Accuracy +/- 10% of Design Tension
Design Tension Range 30-90% of Modified Proof Strength
Operating Temperature Range -4F (-20C) to 168F (75C)


DTI Frequently Asked Product Questions 


General Information

How do DTI SmartBolts work?
The visual indicator in a DTI SmartBolt gradually changes color according to the amount of tension that is applied to the bolt. The visual indicator is black when Design Tension is reached and red when loose. This color change provides a real-time indication of bolt tension.

Can the DTI Visual Indicator be designed into any type of fastener?
DTI SmartBolts are available in a wide range of fastener types and sizes. Please review the Fastener Size Ranges table for additional information. If you have a requirement that is not listed in the table, please contact us to discuss availability.

What is included with my order of DTI SmartBolts?
All shipments of DTI SmartBolts will include a DTI Verification Guide, DTI Quick Start Guide, and a Certificate of Compliance. The Certificate of Compliance lists your product specifications (such as dimensions, grade, design tension, and proof load) so that you can verify the product meets your application requirements.

Is there a warranty for DTI SmartBolts?
Yes! All SmartBolts® products are warranted to the original end user for one year from the date of purchase.

Can I use normal tools with DTI SmartBolts?
Yes! DTI SmartBolts are designed to be used with the same tools you’re already using to install and maintain your bolted joints. In cases where the indicator is covered with a tool during use, we recommend tightening the DTI SmartBolt in stages to check the indicator and prevent overtightening.


DTI Visual Indication System

Do DTI SmartBolts indicate tension or torque?
The DTI SmartBolt indicator measures tension. When a bolt is tightened, it is forced to stretch. This stretching force on a fastener is also called tension. Tension creates the clamp force that holds your bolted joints together.

What is Design Tension and how does it relate to the TIGHT color on the DTI Verification Guide?
Design Tension is the tensile load on the bolt at which DTI SmartBolts® are designed to indicate the “Tight” color. “Tight” shows the DTI SmartBolt has been properly installed and preload is established.

What range of Design Tensions are available?
In general, customers can request Design Tensions ranging from 30 – 90% of the fastener proof strength in increments of 5%. Indicating tensions outside of this range are assessed on a case by case basis. All Pre-Engineered DTI SmartBolts have a Design Tension set at 70% of fastener proof strength, which is appropriate for many applications.

Does over-tightening damage the indicator?
No, provided the bolt is not tightened beyond its elastic limit (proof load). As with all bolts, if you tighten beyond the proof load you may permanently deform the bolt, and therefore the indicator will no longer operate correctly. An easy way to check if a bolt has been significantly yielded is to loosen the bolt and check that the indicator matches the “loose” red color.

How should I use the DTI Verification Guide?
Hold the DTI Verification Guide up to the DTI SmartBolts indicator. It’s good practice to put the intersection of two colors next to the indicator. This way you can compare the indicator color with the guide and know that it is darker or lighter than the color on the guide. Once you reach the TIGHT color, the bolt is properly tight.


Durability and Environmental Conditions

Are DTI SmartBolts reusable?
Yes! DTI SmartBolts are designed to operate in the elastic range of the fastener and therefore are reusable for the endurance limit of the bolt.

What is the expected service life of DTI SmartBolts?
DTI SmartBolts have an operational service life of over twenty years when used as specified, comparable to that of a solid steel fastener.

Do DTI SmartBolts reduce the strength of the fastener?
In most cases, DTI SmartBolts do not lose any tensile strength. However, when the modification of the indicator protrudes into the threaded or transition regions of the bolt, a reduction in tensile strength will occur. The amount of strength reduction is determined during the engineering analysis and made available to the customer for evaluation prior to ordering.

What are the operating temperature limits for DTI SmartBolts?
DTI SmartBolts are specified to operate in environments from -4°F to 168°F (-20°C to 75°C). The indicator may not function properly in environments colder than -4°F (-20°C ) but will return to normal functionality when temperatures return within the operational limits. Continuous use above 168°F (75°C) may degrade the indicator permanently.

How do the bolts stand up to outdoor environments, rain, snow, mud, etc.?
Within the specified temperature range, your DTI SmartBolt may be expected to perform through all normal environmental conditions. DTI SmartBolts operate well in outdoor, wet weather exposure as well as metalworking fluid environments. For full submersion or direct blast exposure, please contact us for options.