How to measure the straightness of stainless steel allen head cap screws?

The straightness of the stainless steel allen head cap screws also affects the screw-to-screw assembly, so there are also some customers who require the straightness of the screws. So how to measure the straightness of the screw?

The straightness of the stainless steel allen head cap screws is the same as the surface defect, which has a great relationship with the judgment of the inspector, and is different from the measurement indexes of strength and hardness. Therefore, any scientific testing instruments and devices, any perfect testing methods, can not be perfect. Only make the product less defective, or if there is a defect, try to take measures to correct it, such as straightening the long rod screws with excessive straightness.

Straightness measurement method using straightness measuring device:

★Place the stainless steel allen head cap screws to be measured between the fixed rail and the adjustable movable rail. Take care to avoid the standard allowable radius of the screw head or the length of the neck.

★Select the screw by hand to find the maximum bending part of the rod, and then tighten the set screw to fix the adjustment guide. A reading of the distance between two parallel guides is obtained by means of a micrometer. That is, the maximum bending degree of the rod.

★The total bending amount is calculated by multiplying the length of the screw measurement by the allowable limit of the straightness per inch listed in the table. In addition to this, the actual measured value of the outer diameter of the thread during measurement should also be considered. For fasteners, the size of the rolled thread is the outer diameter, which is the maximum value of the circumscribed circle of the thread. It is also possible to select the maximum value of the unthreaded rod diameter as the actual measured value.

★The basis for judging whether the straightness is out of tolerance is: adjust the movable guide rail according to the straightness limit value listed in the table, and tighten the set screw, then rotate the stainless steel hexagon socket screw by hand, if the screw and the rail interfere with each other. Stopping the rotation means that the screw is out of line.

Screw straightness limit

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