Discussion On The Installation Specification Of Self Tapping Screws

Self tapping screws, or quick thread screws, are steel fasteners with galvanized and passivated surfaces. Self tapping screws are usually used to connect thin metal plates (steel plates, saw plates, etc.). When connecting, first make a threaded bottom hole for the connected part, and then screw the tapping screw into the threaded bottom hole of the connected part. There are many kinds of tapping screws and other functions. For example, how should we install tapping screws? How to operate self tapping screws? What are the specifications for self tapping screws?

Before purchasing self tapping screws, we should first understand the required model and size, and then select high-quality screws with smooth surface, no rust spots, no impurities in the slot head, and no damage or deformation. Before tightening, select the correct tool and adjust it to the correct gear for operation. During the installation of self tapping screws for special parts, in order to ensure the assembly quality of products, the equipment process specification shall be strictly followed and shall not be changed at will.

Before fastening the parts with self tapping screws, in principle, the assembly holes of the parts to be installed should be aligned as much as possible. When the individual assembly holes between two parts are misaligned, and the gap between the two assembly holes is less than 1mm, the self tapping screws cannot be directly used for installation. One of the parts should be replaced or manually corrected so that the gap between the holes is not less than 1mm (or the tail diameter of flat head self tapping screws (Type F)).

When using the air screwdriver, electric screwdriver or screwdriver as the operating tool for fastening the installation of self tapping screws, the operator must fasten the fasteners when they are stationary or moving at a low speed, and must not fasten the fasteners when they are moving at a high speed (such as when the differential roller chain or the fast roller section is moving at a high speed), so as to avoid scratching the sheet metal, other parts or workers.

When fastening parts with self tapping screws, in order to prevent the screws from slipping out of the screw holes and scratching parts or production staff, it is required to align the self tapping screws vertically with the connection holes, and then tighten the screws with operating tools. The direction of fastening screws can be divided into horizontal fastening screws and vertical fastening screws. Generally, inclined fastening is not allowed; When tightening and loosening fasteners, the axis of the air screwdriver and electric screwdriver nozzle must be consistent with the axis of the fastening screw or bolt (concentric) and perpendicular to the surface of the fastener.

The head of the tapping screw shall be fully attached to the surface of the fastened parts before it is fixed in place. If there is a plastic washer between the tapping screw and the parts, the plastic washer shall not be loose. When the screw is fixed in place, the fastening operation shall be stopped to prevent the screw from being screwed off, slipping or the plastic washer from being squeezed and damaged.

In general, the size, mechanical properties and working performance requirements of self tapping screws have the following standards:

1. Self tapping screw size standard

ASME B18.6.3 2010 not only introduces the dimensions of slotted and cross recessed tapping screws and metal drive screws, but also includes the mechanical properties and working performance requirements of carbon steel tapping screws. The appendix gives instructions for measuring various dimensions and application guidance on clamping length and test aperture.

2. Performance standards of tapping screws (including mechanical performance and working performance):

(1) SAE J933: introduces the mechanical properties and working performance requirements of carbon steel ordinary self tapping screws and white cut self tapping screws. The requirements for selection of raw materials, heat treatment, depth of carburized layer, surface hardness and core hardness are further specified.

(2) SAE J81: introduces the mechanical properties and working performance of self extruding self tapping screws (self tapping locking screws).

(3) SAE J78: describes the mechanical properties and working performance of self drilling and tapping screws.

(4) IFl-113: Introduced the mechanical properties and working performance of self drilling and self tapping screws.

(5) ASTM C1513: describes the mechanical properties and working performance requirements of carbon steel tapping screws.

For other special types of tapping screws, there is no corresponding national or industrial standard, nor is there any recognized data for tapping screws made of other metal materials except carbon steel. The technical data of these self tapping screws can be inquired from the manufacturer.

During the installation of self tapping screws, if the fastened fitting holes are misaligned, the specifications and models of the screws do not match, or the gear of the wind driver is too large, the screws may break and the screw heads slip. Once the screws are clamped, they cannot be forced to screw in any more. This screw should be withdrawn, and another screw should be replaced after finding out the cause. There are also many standards for self tapping screws. It is recommended that you use them when installing screws.