FAQ | Technical & Design Questions
Do we have to engage the minor diameter of the male thread?No. The locking characteristics of Spiralock engage the crests of the threads on the OD of the bolt/screw with the wedge ramp of the internal thread. Back to top ↑ What is the minimum length of engagement required for Spiralock to work?Generally, a length of engagement equal to one diameter is sufficient, but this may vary depending on the application. Back to top ↑ Is Spiralock a directional thread form?Spiralock is a uni-directional thread form. It works only when the crest is pulled up against the 30º wedge ramp. Since the wedge ramp is only on one side, the process works from only one direction. Back to top ↑ Is the Spiralock thread form stronger than the standard thread form?The shape of the thread form, in and of itself, does not produce a stronger thread. However, the fact that Spiralock distributes the load over a greater length on the bolt tends to produce a stronger joint and one which is less susceptible to stripping and fatigue failure. Back to top ↑ Will the off-torque increase with the use of Spiralock?No. Experience has demonstrated that in most cases the off-torque is generally equal to or less than the on-torque. In any event, the characteristics of Spiralock are such that no factors are present which would cause an increase in the off-torque relative to the on-torque, unless galling has taken place. Back to top ↑ Can Spiralock be used in an adjusting screw application?In most cases, no. Spiralock is a free-spinning thread form that relies on tension to produce its self-locking characteristics. So if the application for the adjustment screw is such that the tension load is very light and/or removed completely, Spiralock is not suitable. However, if the screw is kept in constant tension (i.e., a lock nut or strong spring), then Spiralock may be applicable. Back to top ↑ Is more applied torque required with Spiralock?Generally, if your goal is to achieve the same amount of tension in the bolt with Spiralock as you previously developed with standard threads, then more torque may be required when using Spiralock. In most cases, however, the same amount of torque applied to Spiralock as to standard threads will result in better holding power. Back to top ↑ How does the life of a Spiralock tool compare to the life of a standard 60° tool?Spiralock tool life is generally better than standard tool life for several reasons: Back to top ↑ What happens to Spiralock if proper torque is not applied?As with any bolted joint, if the proper torque is not applied during assembly, the integrity of the threaded joint is compromised. Back to top ↑ What torque is required for assembly?Spiralock Corporation provides a guideline of torque values for most thread sizes and bolt grades. We generally recommend a higher torque value than what is used for a standard 60° thread form. Back to top ↑ Can Spiralock be used for assembly when a gasket is used?Yes, Spiralock can be used in a gasket application if it is a hard or thin gasket. Since soft gaskets can compress and relax the tension of the fastener, they should be avoided when using Spiralock. Back to top ↑ Is Spiralock a sealing thread form?No, Spiralock is not a sealing thread, but it can be used with thread sealants. Back to top ↑ Is there a military specification for Spiralock?Yes. Spiralock is incorporated in the specifications # MIL-N-85353 through MIL-N-85353/2A. Back to top ↑ Can Spiralock be used in soft materials?Yes. Another significant advantage to Spiralock is how well it works in soft materials due to its uniform load distribution. By spreading the load over the entire engagement and redirecting the forces radially into compression, significantly higher loads can be achieved without stripping threads. As a result, inserts may be eliminated. However, it should be recognized that soft materials can be deformed under the local contact stresses and that reusability may be affected. |
