Superbolt mt style mechanical tensioners

How MJT'S Work

The Superbolt multi-jackbolt tensioner (MJT) takes the high preload requirements in large diameter bolting and breaks it down into manageable torques using the jackbolts threaded through the nut body. Superbolt tensioners remain easy to install, even on larger sizes, compared to standard hex nuts.


1) By tightening the jackbolts, a strong thrust (axial) force is generated. This thrust force is directed against a hardened washer. Jackbolts have a small friction diameter and can therefore create a high thrust force with relatively little torque input.

2) The loads are transferred through the nut body which is positioned on the main thread by hand.

3) A hardened washer is used to transfer the force while protecting the flange face.

4) The thrust (axial) force of many jackbolts and the opposite reaction force of the main bolt head create a strong clamping force on the flange.

5) The thrust (axial) force from the jackbolt creates an equally strong reaction force in the main bolt.


The advantage is obvious, but how exactly do our multi-jackbolt tensioners achieve this? As you can see in the animation below, the hardened washer is installed first. Then the nut body is threaded onto the existing stud or bolt, hand tight against the washer. The jackbolts are then tightened and thrust against the hardened washer. Accurate preload is achieved on the stud by torquing the jackbolts.

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Our bolting technologies come in a variety of custom configurations, meeting the requirements of virtually every type of application. MJTs are available in both nut and bolt style, and we also can supply studs, expansion bolts, flexnuts, thrust collars and more. Visit our products page for more information.