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The Switchblade bolt

Yes, it’s got bolts

I am surprised by the reaction of some drilling engineers to bolts when presenting the functional benefits of the Switchblade drillstring stabilization system.

The technical benefits are readily accepted, the only adverse remark is It’s got bolts.

Yes, it’s got bolts, like the cars we drive, the aircraft we fly and the spacecraft that went to the moon had bolts; in fact, everything from fighter jets to the farmer’s plough is assembled by bolts.

The question should not be about bolts but rather the research and the results of the tests conducted on the system.

Each blade of the Switchblade range of tools from the 17” series to the 12” series is designed to withstand a force of 500 KN i.e. 50 tons.

The tangential forces on the blade are absorbed by an integral pin machined into the stabilizer body. The axial loads are absorbed by angular walls of the blade pocket.

The function of the bolts is to restrain the blade in the blade pocket (not to absorb axial or tangential forces); the bolts are secured in place by Nord-Lock washers/bolt securing system.

Fatigue Test

A series of fatigue tests have been conducted on the retention mechanism of the blade to the body.

The tests were conducted in the materials laboratory of WMC, a knowledge centre in The Netherlands ( The pre-tension in the bolts was monitored real-time throughout the tests with instrumented measurement bolts.

The mechanism was tested for 650000 cycles at a frequency of 2 Hz, with a pull force of 320 Kn. = 32 tons and a push force of 60 Kn. = 6 tons. The maximum load recorded on the bolts was 3Kn.

The final stress analysis on the retention mechanism was conducted by Reden, a research & development company in the Netherlands (