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Self-Tapping test of metallic bone screws

The test specifies the axial pressure required to measure metal bone screws with self-tapping properties when screwing into the standard material to confirm the consistency of the product under test or to compare the relevant properties of different products of similar size.

Test Procedure: 

1, Put the test block in the block clamp device. Load the bone screw specimen onto the driver. The specimen and driver are then lowered by the spindle into the pilot hole. 

2, Conduct the test by driving the specimen using a rotational rate (the rotational speed of 30 rpm) . 

3, The axial force is increased by 2.0 N/s during the insertion process until the torque or the axial travel increases significantly. At this point increasing axial-force shall conclude and the system should maintain the axial compressive force at which the self-tap was first noted.

4, Continue the rotation while maintaining axial load until the specified number of complete rotations have been achieved, thereby concluding that the specimen encompasses valid self-tap properties.


Axial Load

Maximum Self-Tap Force

Maximum Torque

Axial Displacement

Torque measuring range




Torque   sensor accuracy

Less   than 0.5%F.S.

Speed   accuracy


Axial   force load cell

200N/1000N   (fulfill axial pull-out test)

Load   cell accuracy

Less   than 0.5%F.S.

Load   cell resolution


Linear   displacement sensor range

More   than 50m

Displacement   sensor accuracy level

Less   than 0.5%F.S.

Displacement   sensor resolution


Torsion   angle sensor

99999   degrees

Torsional   angle accuracy

±0.2   degree

Torsion   speed

1r/min   to 30r/min free adjusting

Effective   travel

400±10mm   (can be increased on demand)

The   coaxiality of the two chucks


Standard   Power

220V,   50HZ, 1 phase, 0.4Kw

Working   system

MS   Win10

Fixture: Bone screw test fixture needs to be customized according to the customer's product According to the sample type, the front end adopts a special chuck clamp specimen outer circle, and the rear end design fixture jackal rod shape is consistent with the center hole of the specimen (configuring a non-standard chuck tooling); adjust the position of the moving seat so that the fixture top rod and the specimen are fully inserted and aligned, and then the scheme can be edited to start the test to obtain the required torque. According to the type and size of the specimen, the clamp top bar of different sizes and specifications is designed.

Standard ASTM F543-07 Test A4: "Self-tapping Performance Test Method for Self-Tapping Medical Bone Nails" specifies the method of evaluating the axial force required for a self-tapping bone nail to drill into a standard experimental material. Although clinically considered a simple process, reproducing this process in vitro is a relatively complex movement due to the interaction between the rotary axis and the linear axis of the test machine. The test requires a continuous rotational speed of up to 30 rpm, with the axial load gradually increasing at a loading rate of 2N/s while drilling in. The purpose of this test is to record the torque curve of bone screws as they drill into and remove material. 

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