Wood Screw Thread Types,room and board furniture woodworking plans,Food Storage Made Easy 72 Hour Kit,Computer Desk Construction Plans - Review

04.04.2015, admin  
Category: Rustic Woodworking Projects

Categories : type A, type AB, type B, type BT, type 2A, type 2B type M, type MA and type MT with various kinds of head and drives. The maximum permissible variation in the number of threads per inch shall be plus or minus 10 percent of that which is tabulated for the respective screw size. Cut thread type screws are usually supplied with single lead threads for all screw lengths. Rolled thread type screws may be supplied with either single lead or double lead threads at the option of the manufacturer, however, single lead threads are preferred where the nominal length of the screw is shorter than four times the basic screw diameter.
No extrusion of excess metal beyond apex of the point resuiting from thread rolling shall be permissible a slight rounding or truncation of the point is desirable. Points of screws shall be tapered and fluted or slotted as illustrated above for the respective types .The flute on Type BT screws shall have an included angle of 90 to 95 deg and the thread cutting edge located above the axis of screw.


Screws of these nominal lengths and shorter shall have point taper lengths specified for short screws. Points be sharp, however, no extrusion of excess material beyond the apex of point resulting from thread rolling shall be permissible. It can be traced through four distinct phases of tapping screw design- thread forming, thread cutting, thread rolling and self-drilling.
Type C, with its machine threads and high-driving torques became obsolete with the introduction of thread rolling screws.
The flutes or slots shall extend through first full form thread beyond taper except for Type BF screws on which tapered threads may be complete at manufacturer's option and flutes may be one pitch short of first full form thread. The threads may be either cut or rolled at manufacturer' s option, unless designed by purchaser.


Other details of taper and flute design shall be optional with manufacturer provided the screws meet the specified performance requirements.
Before selecting a thread cutting screw, some thought should be given to the possible effect, if any, of the presence of small chips in the system. Gimlet points center into preformed holes and facilitate thread start, but they are longer and need more blind side clearance.



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