SCREWS

Screw Guides/ Technical Information | Sheet Metal | Wood Screws | Drywall Screws | Concrete Screws | Thread Cutting | Thread Forming | Leg Leveling Screw/ Devices | Application Screws |  More information about screws in our catalog

SCREW GUIDES/ TECHNICAL INFORMATION STANDARD THREAD CUTTING SCREWS The figure below shows some examples of standard thread cutting screws. These screws are provided with cutting slots. The type BT (formerly known as type 25) screw is the most common standard thread cutting screw due to its wide thread spacing and generous cutting slot. The type BF screw also has wide thread spacing, but the slotted cutting flights may tend to clog when working with softer materials. The B series screws have been used with materials having a flexural modulus as a low as 1400 MPa. The type T (or 23) is often useful with very high modulus glass reinforced materials with a flexural modulus greater than 7000 MPa. Standard Thread Forming Screws Thread forming screws do not contain cutting slots and do not produce chips. They are generally used with plastics with a modulus smaller than 3000 MPa. The figure below shows some examples. These standard screws with their 60º thread angle generate relatively high radial and hoop stresses. The wider thread spacing of the types AB and B is recommended over the type C for most applications. The gimlet point of the type AB necessitates extra long bosses as the tapered point does not contribute to the strength of the connection. Basic Dimensions for Coarse Thread Series ( click here to view chart ) Basic Dimensions for Fine Thread Series ( click here to view chart ) Guide to Fastener Materials Note : Steel low-carbon is generally the default steel selection when no other steel grade is specified, or when no higher grade steel is required. Please check your application needs if you are not certain. Mechanical Guidelines for Fasteners - Screws, Nuts, Bolts, Washers, Pins ( click here to view guide ) Guide to Finishes & Plating ( click here to view guide ) Guide to Head Dimensions ( click here to view guide ) Guide to Screw Points ( click here to view guide ) > back to top

SHEET METAL Type A : Found on Sheet Metal (Tapping) Screws Type A tapping screws have coarse threads and gimlet points. They are used in thin metal, resinous plywood, and various composite boards. Type AB : Found on Sheet Metal (Tapping) Screws Type AB tapping screws have spaced threads and gimlet points. Like the Type A, they are used in thin metal, resinous plywood, and various composite boards. Type AB screws offer a wider range of applications over Type A screws. Type B : Found on Sheet Metal (Tapping) Screws Type B tapping screws have spaced threads and a blunt point with incomplete entering threads. They are used in thin metal, nonferrous castings, resinous plywood, plastics, and various composite boards. Type 25 : Found on Thread Cutting Screws Also known as Type BT, Type 25 screws have spaced, incomplete tapered threads with a blunt point and tapered entering edges, with one or more cutting edges and chip removal indentations. They are used in plastic, asbestos compositions, and other composites. > back to top

Machine Screws :

WOOD SCREWS Click here to Request a quote Normal Screw Length Tolerance on Length Up to 5/8in., Incl. Over 5/8 to l-1/2 in., Incl. Over l-1/2 to 2-3/4 in., Incl. Over 2-3/4 to 5 in., Incl. -0.03 -0.05 -0.06 -0.09 > back to top

DRYWALL SCREWS > back to top

CONCRETE SCREWS > back to top

THREAD CUTTING Standard Thread Cutting Services The figure below shows some examples of standard thread cutting screws. These screws are provided with cutting slots. The type BT (formerly known as type 25) screw is the most common standard thread cutting screw due to its wide thread spacing and generous cutting slot. The type BF screw also has wide thread spacing, but the slotted cutting flights may tend to clog when working with softer materials. The B series screws have been used with materials having a flexural modulus as a low as 1400 MPa. The type T (or 23) is often useful with very high modulus glass reinforced materials with a flexural modulus greater than 7000 MPa. > back to top

THREAD FORMING   Standard Thread Cutting Screws Thread forming screws do not contain cutting slots and do not produce chips. They are generally used with plastics with a modulus smaller than 3000 MPa. The figure below shows some examples. These standard screws with their 60º thread angle generate relatively high radial and hoop stresses. The wider thread spacing of the types AB and B is recommended over the type C for most applications. The gimlet point of the type AB necessitates extra long bosses as the tapered point does not contribute to the strength of the connection.   Plastic Application Screws Self-tapping screws designed for plastics There are four commonly used screw types: HiLo® Screws, Plastite® Screws, PT ® Screws, Polyfast® Screws   HiLo® HiLo® Screws HiLo® screws are designed with a double lead, consisting of a high and a low thread. The screw thread configuration has a smaller minor diameter than that of conventional screws and the high threads make a deeper cut into the material between the threads, contributing to greater resistance to pullout and stronger fastening. The high thread has a 30º thread angle and the low thread has a 60º thread angle. The screws are available in thread cutting and thread forming varieties and with different point and head styles. Selecting the proper HiLo ® In selecting the proper Hi-Lo ® screw to solve an assembly problem in plastic, wood or other low density materials, several aspects of the fastener must be considered: the diameter, head style, length, type of point, fastener material and plating. The following data provides the information necessary to make decisions in each of these areas. It should be noted that the Hi-Lo ® screw is available in both inch and metric sizes. ( click here to view chart, Diameters- Inches )   Delta PT® Screws PT® screws, supplied by Ejot, are thread-forming screws with a 30º thread angle and a modified shank, which is said to improve plastic flow during the thread forming operation. Delta PT® ( click here for Delta PT Thread Forming Screw Doc. PDF 90kb ) Plastite® thread-forming screws Plastite® thread-forming screws have a trilobal cross-section, which reduces the driving torque. After installation, cold flow of the plastic effectively locks the screw in place, increasing the resistance to loosening and making the screw ideal for vibration applications. Plastite® ( click here for Plastite Doc. PDF 363kb ) > back to top

LEG LEVELING SCREW/ DEVICES   Custom   Casters > back to top

APPLICATION SCREWS   Technical Information - Types of screw points Types of Screw Points DIE POINT: One of the least expensive pointing operations applied at the time of heading. This operation provides an end chamfer starting with a diameter smaller than the root diameter of the thread. The minimum reduction of the point is approximately 10% below the maximum minor diameter with an included angle of 40 to 50. DOG POINT: A straight pointed section reduced in diameter slightly below the root diameter of the thread. Usually extending In length about two-thirds the diameter of the thread. Recommended for ease In starting, to insure against stripping fine threaded products, and to increase efficiency along production lines. ROLLED POINT: An efficient method of producing pointed long studs or long screws with an end chamfer similar to the Die Point. The last thread and a half is slightly cupped by the thread roll-over operation. PINCH POINT: (ROUNDED): An Inexpensive method of applying a 40',60' or go' lead-in point having a slightly rounded contour but with pinch-off marks on Its surface. Used for aligning several. sheets or assembling several parts requiring pilot action. NAIL POINT: (PINCHED): Usually supplied with an approximate 45' Included angle having a sharp point and slightly squared surface. Used for Impinging or locking against wood or other solt material. Other degrees of Included angle and sharpness also available. CUPPED POINT: A special cup section supplied on the end of the threaded member having a depression In the end to reduce the area In contact with the surface which increases Its holding and locking power under pressure. ROUND POINT: A dome-like rounded surface applied to the end of a threaded member In order to offer pressure without disfigurement. Used for adjusting, members where friction without cutting action Is desirable. CONE POINT: A precision forming operation to provide any required Included angle. Offers a smooth surface, accurate length, and a sharp point which can be produced to any desired contour to fit your particular requirements. TYPE A POINT: A thread forming screw for use in thin metal .015 to .050 thick. Used with drilled, punched or nested holes in sheet metal, resin impregnated plywood, asbestos combinations, among others. Not recommended for new design. TYPE B POINT: A thread forming screw for use In heavier metal .050 to .200 thick. Larger root diameter with finer thread pitch for light and heavy sheet metal non-ferrous castings, plastics, Impregnated plywood, asbestos combinations, and other materials. TYPE AB POINT: A thread forming screw combining locating type point of Type A with thread size and pitch of Type B. Normal limitations of Type B apply. TYPE C POINT: A thread forming screw with either coarse or fine pitch machine screw thread and blunt tapered point. Eliminates chips and permits replacement with standard screw In the field. Higher driving torque required. Usable In heavy sheet metal and die castings. TYPE U POINT: A thread forming screw with high Helix thread for driving or hammering into sheet metal, castings, fiber or plastics for permanent, quick assemblies. TYPE F POINT: A thread cutting screw with machine screw thread with blunt tapered point. having multi-cutting edges and chip cavities. For heavy gauge sheet metal. aluminum, zinc and lead die castings, cast Iron, brass and plastic. TYPE FZ POINT: A thread cutting screw with a tapping screw thread with blunt tapered point and multi-cutting edges and chip cavities. For plastics, die castings, metal clad and resin impregnated plywood, and asbestos. TYPE 1 POINT: A thread cutting screw with single flute for general use. Produces a fine standard machine screw thread for field replacement. TYPE 17 POINT: A thread cutting screw for wood with a coarse tapping screw thread and a special long sharp point fluted to capture chips. TYPE 23 POINT: A thread cutting screw in the fine thread series offering maximum thread cutting area and excellent chip clearing, with minimum tightening torques. TYPE 25 POINT: A thread cutting screw similar to Type 23 point except with coarse Type B thread. For plastics and other soft materials with large chip clearing and cutting edges. SELF-DRILLING: With special drilling points-lengths-diameters that will drill through '1/4" metal. Eliminates all hole preparation-drills faster than a drill. No punching: drilling or tapping required. Reduces die costs. SELF-DRILLING: Produces more secure sheet metal assemblies faster...used as self-drilling screw or driving thru pre-punched holes. Can be used with or without' pilot holes. Positive rake "forward cutting edge" drills straight thru sheet metal at peak speed. Perfectly mated threads Increase strip and back out pressures.   Cross Threading Problems Material Threading page 1 ( click here for Doc. ) |  Material Threading page 1 ( click here for Doc. )   Self Drilling   Thin sheet Metal - Extruding Screw Extruding Screw ( click here for Doc.PDF 000kb ) |  Undercut Heads ( click here for Doc. ) Roofing Screws Concrete Screws Sems Screws Self Drilling Screws   Thread Inference SSX ( click here for Doc.PDF 411kb) | Custom ( click here for Doc. ) > back to top

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