Expansion bolting

Utilizing Superbolt technology, Nord-Lock is able to offer tremendous radial expansion and joint clamping power in one bolting system. The Expansion bolts replace traditional interference or force fit bolts. Radial expansion is critical for rotating couplings or alignment systems that require the bolts to be able to transfer forces in shear.

The key to this technology is the split expansion sleeve that mates with the customer’s machined holes. The split sleeve requires less tolerance on mating parts than is traditionally required with interference fit or hydraulic systems, saving critical machining time.

  • Note: Detailed instructions are included with each shipment.


  1. Slide split tapered sleeve (2) onto the tapered stud (1) and place together in the bore.
  2. On side A, place spacer (3) in the bore to center split sleeve between the split line.
  3. On side A, slide washer over the tapered stud (1) and screw on the tensioner (4) by hand.
  4. Tighten jackbolts stepwise according to tightening procedure.
  5. On side B, slide hardened washer over the tapered stud (1) and screw on the tensioner (5) by hand.
  6. Tighten jackbolts stepwise according to tightening procedure
  7. Verify tensioner torque on side A.



  1. According to removal procedures, loosen the jackbolts on side A stepwise and unscrew the tensioner (4) by hand.
  2. Tighten several jackbolts on side B further, in order to release the tapered stud (1) off the tapered sleeve (2).
  3. Unscrew the tensioner (5) by hand.
  4. Remove tapered stud (1), tapered sleeve (2) and spacer (3) from the bore.

  • Easy: Loose fit sleeves (up to .010″ – .020″ in the through-hole) are easily inserted even in holes misaligned due to rotation. Only hand tools are required for installation and removal.
  • Fast: Tightening requires only minutes per assembly.
  • Safe: Eliminates the need for special high powered tools, bolt deep freezing and high pressure hydraulic systems. Torque required is usually under 100 ft-lbs. Entire assembly requires only hand tools.
  • Economical: Save money over hydraulic systems in time and tooling. No need to ream/hone the bolts as normal machine precision is sufficient. Additionally, for precise alignment as little as two Expansion Bolts can be sufficient. Loose fit through-bolts with MJT tensioners, can be used in the remaining holes.
  • Reusable: The split sleeve springs back to original size, use after use. Compared to the close tolerance solid sleeves found in other systems, the loose fit split sleeve is much less likely to hang up during removal.
  • Generates axial and radial force simultaneously. Easier to “pull together” coupling halves.
  • No reaming/honing required: Only line boring of holes is necessary.
  • No coupling face machining is required (where the nuts seat). The multi-jackbolt design compensates for small variations in perpendicularity of the spotface to the hole centerline.
  • Eliminate finish machine of sleeves on site: Generous sleeve expansion permits finish machining in advance.

Expansion bolts have been used all over the world to solve tough bolting challenges.

Expansion bolting is particularly favorable on:

- Couplings on:

  • Ship drives
  • Turbines
  • Engines
  • Generators
  • Compressors

 …and many more!


Further the Expansion bolt for blind holes can replace dowel pins in transmitting transversal loads and ensuring positions.