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Bolt-Engineer Co., Japan Farewell to Electric or Hydraulic Tools; Large-size Bolt Fastening with Patened “Tension Nut”
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by Dean Tseng, Fastener World

Bolt-Engineer is a specialized maker of fastening tools for large-size bolts (M30 and above) with 30 years of history, selling hydraulic torque wrenches, bolt tensioners, electric nut runners and gear wrenches domestically. It has newly-developed and began global sales of the patented “Tension Nut”, the first of its kind in the fastening tools industry that allows users to fasten large bolts without using hydraulic or electric tools. Fastener World magazine interviewed the company’s overseas manager, Mr. H. Saeki on more details of this groundbreaking product.

Trio-structure design, No Electric or Hydraulic Force Required
Regarding the design of Tension Nut, the manager explained it is composed of a round nut, a bevel disc, and hexagonal socket screws (tension screws). The bevel disc has some upward slopes at a θ° angle to the loosening direction. The round nut is inserted with multiple tension screws inclined at the same θ° angle. The tension screws are in right angle contact with the bevel disc. With the tension screws inserted to the round nut, the loads are dispersed, and therefore it is possible for users to use low torque to fasten. For M30 bolts, with Tension Nut the required torque will drop from 1260Nm to 35Nm; for M42 this will be from 3600Nm down to 70Nm; for M56 this will be from 8666Nm down to 120Nm. By fastening the tension screws with a hand torque wrench or impact torque wrench (10-260Nm), the target bolt can be fastened at a force range of 55-2000kN, which means no electric force (e.g., hydraulic bolt tensioner) is required and users can correctly manage bolt tension.

Counter-Loosening Fucntionality
“The inclination of the bevel disc works with the inclined tension screws,” said the manager, “so the loosening of the nut will conversly create more tightening effect. It is not friction but through the increase of axial force that creates counter-loosening fucntionality.” Any slight displacement of the nut will push up the tension screws on the slopes of the bevel disc and increase the bolt’s axial force, which causes the disc to be pressed against the seating surface and increases the friction on the rough surface of the disc. This is the mechanism that keeps the nut from loosening. On a side note, Tension Nut can couple with the “Counter-loosening Cap” for dust prevention.

The manager said Tension Nut is galling-proof and seizure-proof and can resist high temperature up to 250℃. The company is looking for dealers and recommends this product to large compressor, pressing/forging/extrusion forming/metal forming machine users.

Bolt-Engineer’s contact: Overseas manager, Mr. H. Saeki  

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