MINIATURE SELF TAPPING SCREWS

08/31/2010

Thread forming self tapping screws are a more economical fastening method in many applications when inserting into ductile materials such as plastics and die cast as well as to some extent in brass, aluminum and very thin sections of stainless. They save tapping costs and can also be used in many situations where tapping is not feasible. Sometimes the thread hole can be moulded in when making the part. They also have the advantage of being self locking due to the full engagement of the assembly. They should be used only in instances where removal is not required or only a couple of times at most. They insert more readily as they do not need to mate with tapped holes and the BP point makes it easier to line up with the hole. Self drilling and thread cutting self tapping screws are not usually practical in these tiny sizes.

MORRIS makes miniature thread forming screws with type BP-pointed (stock) or B-chamfered (to order) starting ends in sizes 000 thru 2. These are stocked in Slotted modified Flat Fillister and 90 deg. Flat heads with BP points made from #303 stainless in many lengths. The slots are deburred to meet exacting instrument requirements. Dimensions are shown on our website when you select a specific item. Specials can be made to order in many other materials, lengths and head styles with slotted drives only.

It is essential that a hole be made to receive the screw and the diameter is determined by many factors including thread size, material and length. Holding strength and ease of asembly are other considerations. In all cases the hole diameter must be larger than the screw maximum minor diameter for clearance. You should experiment with many hole diameters to determine the optimum condition for a specific application. Use the smallest hole diameter possible. Hole depth should be slightly longer than the screw length. There should be at least .025" of material around the hole to prevent a bulging surface or break through due to the movement of the material and pressure caused by the screw insertion. Call John at 508-764-4394 for hole size range recommendations to try.


Copyright J.I. Morris Co. 2010



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