Formerly Emhart Teknologies & Infastech


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What is Spiralock?

Spiralock is a unique, proprietary, preload locking internal (female) thread form. It is exceptionally resistant to the effects of vibration loosening and substantially reduces the potential of fatigue failure when compared to standard, symmetrical thread forms.

Spiralock does not require any secondary methods (e.g., lock washers, thread adhesives, crimping, inserts, etc.); rather, it relies entirely on the unique geometry of its thread form.

How does Spiralock work?

The female thread form produced by Spiralock incorporates a unique 30° "wedge ramp" at its root. When clamp load is applied during assembly, the Spiralock thread form locks the standard male threads tightly against the 30° wedge ramp, preventing any transverse movement of the male thread in respect to the female thread.

How do we apply it?

Simply by changing the internal thread to Spiralock through tapping, thread milling, single point threading, electrical discharge machining, molding, or casting through the use of Spiralock tools. Alternately, if you are using fasteners such as nuts or inserts, you can simply substitute a same-size nut or insert incorporating the Spiralock thread form.

How can we test Spiralock?

Field-testing Spiralock has proven to be the most reliable method. We also recommend vibratory testing whenever possible. To check thread geometry, we offer a three-gage member system: a GO Pitch Diameter/Ramp Gage that checks the maximum material limits, plus a Hi-Limit P.D. Gage and a Hi-Limit Ramp Gage that checks the minimum material limits of the threaded hole. For applications with more than 32 threads per inch (e.g., saw-tooth designs), we offer a two-gage member system. Spiralock test reports are available upon request.

What tools are required?

For internal thread form applications, you will need a Spiralock threading tool and Spiralock thread gages. For fastener applications, you can simply switch to Spiralock fasteners.

Are other locking devices required for use with Spiralock?

No, the Spiralock thread form eliminates the need for secondary locking devices such as lock washers, thread adhesives, or special inserts.

Are special screws or bolts required for use with Spiralock?

No, Spiralock was designed to mate with a standard 60º bolt or screw, made to a 2A/3A fractional or 6g/6h metric class of fit.

Can Spiralock be reused? And, if so, how many times?

The Spiralock thread form is reusable. In fact, some products using Spiralock have been disassembled and reassembled more that 50 times without any appreciable loss in holding power. Of course, the degree to which any particular part may be reused is dependent upon material hardness, the length of thread engagement, surface roughness, the coefficient of friction, and the tightening torque.

How do extreme temperature changes affect the performance of Spiralock?

The vibration resistance characteristics of Spiralock are not influenced by extreme changes in temperature as long as they are within the engineered working limits of the materials used in the joint; the mating materials share similar thermal coefficients, and there is no significant time delay in the expansion of the components which could use a temporary loss or reduction in bolt tension.

Can we look at a hole and know if it has a Spiralock thread form?

The smaller the hole the more difficult it is to distinguish a Spiralock thread form from a standard 60° thread form.
However, there are devices and methods available, such as bore scopes, Spiralock thread plug gages, and silicone impressions which will help you determine if the hole is threaded with the Spiralock thread form.

When using Spiralock, can the bolt be assembled from either direction?

You will only experience the locking feature from one direction. Spiralock is a uni-directional thread form.

Can we get Spiralock on the male thread?

No, the Spiralock concept was designed and intended only for use in the internal, female thread.

How long has Spiralock been available?

Spiralock products have been offered to the marketplace since 1979 and we are today continuing to add new Spiralock products.

How do we know if Spiralock will work?

Spiralock has been tested in thousands of applications and is currently being used in solving loosening problems for aerospace, automotive, truck, defense, medical implants, appliance, hydraulic/pneumatic, HVAC, material handling, construction and farm equipment, recreational equipment, oil exploration machinery, and other industries. We have an extensive library of successful application stories.

Why does Spiralock result in more uniform load distribution?

The Spiralock thread form distributes loads more uniformly than a conventional thread form for two reasons:

  1. With Spiralock, contact is concentrated at the crest of the male thread, rather than near the center of the flank. This results in greater compliance of the thread form.
  2. With Spiralock, the crest of the male thread is pulled into a 30° "wedge" rather than onto a 60° flank, permitting greater axial movement before achieving full load, thereby substantially reducing the potential of fatigue failure.