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What is a screw?

A screw is an externally threaded fastener capable of being inserted into holes in assembled parts, of mating with a preformed internal thread or forming its own thread, and of being tightened or released by torquing the head. An externally threaded fastener which is prevented from being turned during assembly and which can be tightened or released only by torquing a nut is a bolt. (Example: round head bolts, track bolts, plow bolts.) Additionally, any externally threaded fastener that has thread form which prohibits assembly with a nut having a straight thread of multiple pitch length is also defined as a screw. (Example: wood screws, tapping screws.)

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Flat Phillips Concrete Screws
Hex Washer Head Concrete Screws
Hex Cap Screws Grade 5 - Zinc Plated
Plastite Style Screws
Taptite Style Screws
Deck Screws Philips Drive

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Screw Types

Some basic information regarding screws that Aspen Fasteners offers from inventory.

Dowel screws

A double ended fastener with two tapered and threaded ends often used in furniture manufacturing to create a hidden joint. Half the length of the dowel screw is driven into each of the two pieces making up the joint. Available in zinc plated steel and up to 6" in length.

Drywall/framing Screws

These screws are specialty drywall & framing screws and are designed specifically for use in drywall applications. The bugle head style, sharp point and threading of these screws are made to attach drywall to wood or metal studs and provide the greatest holding power in drywall. Available in hardened steel with a black phosphate finish and with either phillips or square drives.

Eye Screws

Also known as screw eyes - a wire form with a looped head and threaded end tapered to a point. Larger ones are often referred to as lag eye screws. Designed to be used as attachment point, particularly for something that is hung from it. Available in zinc plated steel .

Hi-Lo Self Tapping Screws

These specially threaded screws designed to cut threads as they are driven into untapped holes. Hi-Lo self tapping screws have a double lead thread where one thread is high and the other low thread for easier penetration into the substrate. The smaller minor diameter thread increases contact with the substrate resulting in a stronger grip and increased resistance to pull out. These screws are available in carbon steel in a number of finishes (clear zinc, black zinc, black oxide) and stainless steel. Available in a variety of head styles (flat, hex washer, pan and truss) and drives (phillips, slot, 6-lobe, hex) Available in sizes from #2 to #14 diameters and lengths from 3/16" to 2".

Lag Screws/Bolts (US)/Coach Screws UK

similar to wood screws but usually much larger with lengths up to 12" and diameters from 1/4" to 3/4" Lag screws are designed to fasten heavy lumber together, or wood to masonry/concrete. Hex head lag screws are stocked in steel with zinc or galvanized finishes.

Machine Screws

A full threaded screw with a blunt end and usually used with a nut or driven into a pre-tapped hole. Always match your screws to the job, considering both the finished result and the materials being used. Available in steel with a variety of different head styles (binding, fillister, flat, hex, hex washer, oval, pan, round and truss) and drives (phillips, slot, 6-lobe, square, hex) and finishes (clear zinc, yellow zinc, black zinc, green zinc, black oxide, nickel plated) and in stainless steel and in nylon. Steel machine screws also available with metric threading. All machine screws feature standard 'machine' points, and are available in sizes from #2-56 to 1/2" and lengths from 1/8" to 6".

Plastite 48-2 alternative screws

48-2 Plastite alternative screws are specially designed trilobular™ thread-rolling screws for use in plastics.

Maximum holding power

48-2 Plastite alternative Trilobular™ screws have a twin lead thread design offering quicker and more effective screw penetration into the substrate. They also have a deep and narrow 48 degree thread profile with extra wide spacing between threads. This thread profile improves thread-forming and thread engagement within the plastic. In addition these screws have a Trilobular™ thread configuration which improves displacement of material into relief areas when driven into the plastic. This further increases the resistance to vibrational loosening forces. The higher quality internal threads produced by these specialized screws also reduces material failure and improves holding power in plastic materials. It also reduces stripping, pull-out and allows for repeated removal and insertion into the same tapped hole.

Easier to drive

The three lobed design of the Trilobular™ thread with full relief of the thread form takes advantage of the properties of plastics by allowing recovery and filling-in between the lobes, decreasing driving effort. 48-2 Plastite alternative screws are available in steel with the following head styles: flat head, pan head, truss head and hex indented washer head, drives: Phillips drive, 6-lobe drive and hex head, and with either a clear zinc finish, or black zinc finish or black oxide finish. 48-2 Plastite alternative screws are also available in stainless steel 18-8 and 410 with pan head, flat head and hex indented washer head and either phillips or 6lobe drives. Because of the variations in grades of plastics, depth of engagement and usage requirements, it is highly recommended that tests be performed for each application by a competent engineering laboratory to determine the ideal pilot hole size.

Self Drilling Screws

Also referred to as TEK screws, self drilling screws are specially designed to drill, tap and seal all at the same time with one driving operation. They are similar to a self tapping screw, but it has a drill-shaped point to cut through the substrate eliminating the need for drilling a pilot hole. The points are numbered from 1 through 5, the larger the number, the thicker metal it can go through without a pilot hole. Stocked in steel in a variety of head styles (flat, hex, hex washer, oval, pan, round, trim, truss and wafer head) and drives (hex head, phillips, slot, square, 6-lobe,) and also in stainless steel in sizes from #2 to 5/16" and lengths from 3/8" to 6".

Self piercing screws

Self-piercing tapping screws are externally threaded screws with designed to self-pierce A metallic material and tap their own mating threads . Self-piercing screws are high-strength, with sharp point angles of 25 to 30 degrees. Available with a hex slotted drive in zinc plated hardened steel. Also available with a bonded washer to self seal once driven into the material.

Self tapping/Sheet Metal Screws

These specially threaded screws designed to cut threads as they are driven into untapped holes. A self-tapping screw requires a pre-drilled pilot hole from the correct size drill. Recommended drill bit sizes vary, depending on the diameter of screw to be used, type of screw (points A, B, AB, and High-Low), and structural thickness of the substrate. These screws are available in carbon steel in a number of finishes (clear zinc, yellow zinc, black zinc, black oxide) and stainless steel. Available in a variety of head styles (flat, hex, hex washer, oval, pan round and truss) and drives (phillips, slot, 6-lobe, square, hex) Available in sizes from #2 to 3/8" diameters and lengths from 1/8" to 4".

Sems Screws

SEMS Screws is a machine screw pre-assembled with a free-spinning lockwasher. The washer is held in place by the major diameter of the screw being larger than the hole of the washer. Available in steel with an external tooth lock washer, internal tooth lock washer, split lock washer or square cone lock washer. Also available in stainless steel.

Thread Cutting Screws

Another type of tapping screw with specialized tips (type 1, type 23, type 25, type F) that physically remove material from the substrate to form the tapped thread path. They are available in carbon steel. this screw is designed to tap its own threads as it penetrates the substrate but requires a pre-drilled pilot hole. Available in points 'F', '1', '23' and '25' with a variety of head styles (flat, hex, hex washer, oval, pan and truss) and drives (hex head, phillips, slot, 6-lobe,), in sizes from #2 to 1/4" and lengths from 3/16" to 3".

Thumb Screws

Thumb screws are specially designed fastener with machine screw threads to be turned into a tapped hole by hand without the use of any tool. Available in steel and in stainless steel with either a knurled (with or without a washer face) or regular head (with or without a shoulder).

Set Screws

A set screw is a headless screw driven into a pre-tapped hole. It is often used as a compression device to hold a sleeve, collar or gear on a shaft in order to prevent slipping to facilitate relative rotation. Various drive types are available to rotate the set screw. These types include hexagon socket, fluted socket, screwdriver slot and square head. Aspen Fasteners stock set screws made of heat treated alloy steel with a hex socket drive in coarse and fine thread. Various point designs are available (the part of the set screw that rotates against the shaft being secured) and include: Cup - Hollowed end, is the most commonly used point style. Used when the digging in of the point is not undesirable. Cone - Pointed end, this type generates the highest torsional holding power and is typically used for a permanent connection. Oval - Rounded end that is typically used when frequent adjustment is required. The oval end prevents/reduces indentation. Flat - Cause little damage to the shaft and are used when frequent adjustment is required. Dog - Flat end with the threads stopping short of the end with the end fitting into a hole. Sizes range from #2 to ˝" and lengths from 1/16" to 1-1/2".

U-Drive Screws

A thread forming screw with a high helical thread to be driven or hammered into a substrate (e.g. plastics, sheet metals, or castings) for a quick permanent assembly. Requires a pre-drilled or punched hole. Available in zinc or black oxide coated steel in sizes ranging from #00 - #8 and lengths between 1/8" and 3/4"