Howto Remove Round Head Machine Screws With No Slot

Types of Nuts and Bolts

Fasteners come in many different forms. To make it easy for you, we’ve compiled the data below as a guide for figuring out what each fastener is called. Scroll down to learn about many different types of nuts, bolts and screws!*

Security screws, also known as one-way screws, are very simple in design. They are available in either flat head or round head design in sizes ranging from #6 to #14. They are slotted screws, and can be installed with a standard slotted screwdriver. Removing them is another matter.

*Note: Bolts are fasteners that require a nut or pre-tapped hole to be installed. Screws use their threads to provide their own holding power. The terms in the industry are commonly mixed so sometimes you will see something that is called a screw or a bolt that is actually the opposite. Example: Lag Bolts and Lag Screws are the same thing. We have broken them down according to their true definition.

Select a category below to view a picture and information on that type of fastener.

Bolts & Screws
NutsWashers
Rivets
Concrete AnchorsInsertsThreaded RodRetaining Rings

Types of Bolts

One-way screws come in all kinds of different shapes, but they're all used for the same purpose: turning one way and one way only. Typically, these screw drives are designed to fit slotted. Referred to as both bolts and screws. Shop Hex Head Bolts. A machine screw is a screw or bolt with a flat point. Available in a variety of drive types and heads, they fit a wide variety of applications. Often driven into tapped holes. Used with nuts and washers, also known as “stove bolts” or “stovers”. Shop our Machine.

Carriage Bolts

Also known as a “coach” bolt, has a domed or countersunk head. The square section under the head grips into the part being fastened preventing the bolt from turning when the nut is tightened.
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Hex Head Bolts

Hex tap bolts, hex cap screws, trim head hex cap screws, and hex serrated flange bolts fall under this category. They share a hexagonal head and are driven with a wrench. Referred to as both bolts and screws.
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Machine Screws

A machine screw is a screw or bolt with a flat point. Available in a variety of drive types and heads, they fit a wide variety of applications. Often driven into tapped holes. Used with nuts and washers, also known as “stove bolts” or “stovers”.
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Shoulder Bolts

Shoulder bolts (also known as shoulder screws or stripper bolts) are machine screws with a shoulder between the thread of the screw and the head of the part. Once installed, the non-threaded portion extends out of the surface of the application site, allowing the bolts to act as dowels or shafts for moving parts. They can be installed by hand or with a socket (Allen) driver.
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Socket Cap Screws

Socket cap screws are available in button socket, button flange socket head, flat socket, and socket cap. Driven with a socket wrench or a hex Allen key. The term socket head cap screw typically refers to a type of threaded fastener whose head diameter is nominally 1.5 times or more than that of the screw shank diameter.
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Fo4 slot machine prototype. In Act 1, the first half-pipe is instead made of two 0C chunks.Simon Wai protoBeta 4 onward. Though there is a 128×128 chunk that would be used for a slot machine at 60, slot machines have yet to be placed in the Zone proper.

Socket Set 'Grub' Screws

Set screws are most often headless (aka blind), meaning that the screw is fully threaded and has no head. A blind set screw, known in UK as a grub screw, is almost always driven with an internal wrenching drive, such as a hex Allen key. Socket set screws are installed in threaded holes or inserts.
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Square Head Bolts

Square Head Bolts are similar to hex cap screws but with a 4-sided head. This head style allows for a wrench to grip more easily onto the head of the bolt. The head also provides a larger gripping area as compared to a standard 6-sided hexagonal head.
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Fastener Varieties Menu

Types of Screws

Deck Screws

Our deck screws feature a type 17 point (notched point at the tip) to aid in chip removal during thread cutting which allows for an easy installation in wood and composite deck materials. A bugle head and square drive help to eliminate the stripping effect sometimes experienced with other types of drives.
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Hex Lag Screws

Lag screws, also called lag bolts, are large wood screws. The head is external hex and are driven with a wrench. Used for lag together lumber for framing, machinery to wood floors, and other heavy duty applications.
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Self-Drilling Screws

Self-drilling screws have a sheet metal thread with a self-driller cutting (TEK) point to pierce through 20 to 14 gauge metals. The higher the TEK number, the larger the drill point to pierce heavier gauge metals.
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Sheet Metal Screws

Sheet metal screws (SMS) have sharp cutting threads that cut into sheet metal, plastic or wood. They have a fully threaded shank and sometimes have a notched point at the tip to aid in chip removal during thread cutting.
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Wood Screws

Wood screws are partially threaded with large cutting threads and a smooth shank. They are designed to slide through the top piece of wood and tightly pull all boards together.
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Fastener Varieties Menu

Types of Nuts

Cap Nuts

The cap nut, also known as the acorn nut, gets its name from its shape. The nut has a domed top to prevent contact with the external thread.
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Castle Nuts

Used with cotter pins to prevent loosening, a castellated nut, also called a castle or slotted nut, is a not with slots cut into the top. Used in low-torque applications such as holding a wheel bearing in place.
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Coupling Nuts

A coupling nut is a threaded fastener used for joining two male threads, most commonly threaded rod. The outside of the fastener is a hex so it can be driven with a wrench.
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Flange Serrated Nuts

A flange nut is a nut that has a wide flange at one end which acts as an integrated washer that does not move or spin. The serrated flange distributes the pressure of the nut over the part being secured and creates a locking action to prevent loosening.
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Hex Finish Nuts

Hex finish nuts are used for fastening to a hex cap screw, socket cap screw or bolt. The most common nuts, hex finish nuts are hex shaped with internal threads and driven with a wrench.
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Hex Jam Nuts

A jam nut is often used when a nut needs to be locked in place without clamping to another object. Hex jam nuts are hex shaped with internal threads, but they are thinner than hex finish nuts.
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Heavy Hex Nuts

Larger, heavier, and thicker than a standard hex nut. Heavy hex nuts are hex shaped, internally threaded, and driven with a wrench. Often used with hex cap screws and carriage bolts.
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Hex Machine Nuts

A machine nut is hex shaped with internal threads. Smaller than a hex jam or hex finish nut, they are used with machine screws under 1/4' diameter.
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Hex Machine Nuts Small Pattern

A machine nut is hex shaped with internal threads. Smaller than a hex jam or hex finish nut, they are used with machine screws under 1/4' diameter.
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Keps-K Lock Nuts

Also known as a keps nut, a k-nut or a washer nut, a keps-k lock nut has an attached free spinning lock washer. Keps nuts are designed to make assembly more convenient.
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Knurled Thumb Nuts

A knurled head thumb nut or thumb nut has a knurled outside surface rather than a hex, which facilitates tightening by hand. Often used in decorative finishes or applications.
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Nylon Hex Jam Nuts

A low-profile lock nut is hex shaped, internally threaded with a nylon insert. The nylon material prevents loosening from vibration and cross threads to stop the nut from backing off of the fastener.
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Nylon Insert Lock Nuts

A nylon insert lock nut is hex shaped, internally threaded with a nylon insert. The nylon material prevents loosening from vibration and cross threads to stop the nut from backing off of the fastener.
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Prevailing Torque Lock Nuts (Stover)

Commonly known as stover nuts, prevailing torque lock nuts have chamfered corners and a conical top. The distortion in the top threads resists loosening from vibration. Also called one-way nuts, they can only be installed one way and are often used in high temperature application because they are all metal with no nylon insert.
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Slotted Hex Nuts

Slotted hex nuts are nuts with portions cut out designed to be used with a cotter ping to create a locking mechanism. These nuts are similar to a castle nut but have a lower profile which sometimes makes them a better option.
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Square Nuts

A four-sided nut that may be flat or beveled on top. Square nuts provide a greater surface contact area which provides more resistance to loosening. Typically mated with square head bolts.
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Structural Heavy Hex Nuts

Structural hex nuts are comparable to finish nuts but are made to be thicker and much stronger. They are typically used in steel to steel structural connections.
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T-Nuts

A t-nut or tee nut is used to fasten wood, particle or composite board leaving a flush surface. A long thin body with a flange at one end resembles a T in profile. T-nuts often have 3 or 4 prongs that sink into the surface providing better retention.
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Break Away or Shear Nuts

Shear nuts are cone nuts with a hexagonal gripping point. They are designed with an intentional flaw to snap the hexagonal head off once the maximum torque is reached. Leaving behind a protective cone nut that cannot be easily removed.
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Tri-Groove Nuts

Tri-groove security nuts have a tapered diameter making them difficult to grip with grabbing devices such as adjustable wrenches or pliers. These nuts require a special unconventional gripping device to install them making them more secure than a typical nut.
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Wing Nuts

Wing nuts are threaded nuts with wings on each side of the body allowing for manual turning and installation. Easy hand assembly and used when the nut needs to be removed often.
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Fastener Varieties Menu

Types of Washers



Backup Rivet Washers

Rivet backup washers are used to create a larger install diameter giving the rivet a better hold and more support. Backup washers can help to prevent pull-through of a rivet.
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Belleville Conical Washers

Belleville conical washers are a type of washer that adds extra tension to a fastener assembly. They are commonly used in stacks to increase the load, deflection or both to an assembly depending on the stack. These washers can be considered lock washers because they add tension and absorb vibration to an assembly.
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Dock Washers

Dock washers are heavy duty washers, often used to build docks. Also used in heavy duty construction where a thick washer is needed, dock washers are similar to fender washers with a small inside diameter hole.
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Fender Washers

Fender washers are round washers with a small inside diameter hole. Fender washers are used to prevent pull-through and provide a greater bearing surface under the fastener.
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Fender Washers - Extra Thick

Fender washers are round washers with a small inside diameter hole. Extra thick fender washers are thicker than standard fender washers and are used to prevent pull-through and provide a greater bearing surface under the fastener.
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Finishing Cup Washers

Finishing cup washers form a cup for the head of the screw or fastener to fit in, creating a finish flush with the top of the head. Used for finishing, cup washers are shaped like a cup.
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Flat Washers

Flat washers are round outer diameter thin plates with a center hole punched to the size of the bolt or screw. Flat washers are used to distribute loads of threaded bolts, screws and nuts evenly as the fastener is tightened.
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Flat Washers - Extra Thick

Extra thick flat washers thicker than standard flat washers. These washers are round outer diameter thin plates with a center hole punched to the size of the bolt or screw. Flat washers are used to distribute loads of threaded bolts, screws and nuts evenly as the fastener is tightened.
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Flat Washers - Military Standard

Military standard (MS) flat washers go through extensive inspection for chemical, physical and dimensional qualities. MS washers must meet specific inner diameter and outer diameter specifications.
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Flat Washers - 900 Series

Flat washers in the 900 series are round and thinner than a standard flat washer with a smaller inside and outside diameter.
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Lock Washers - Split Ring

Split ring lock washers are used to prevent nuts, bolts and screws from vibrating loose. These washers are rings which are split at one point and bent into a helical shape.
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Lock Washers - High Collar

High collar lock washers are designed to fit under the head of a socket cap screw. Split ring lock washers are used to prevent nuts, bolts and screws from vibrating loose. These washers are rings which are split at one point and bent into a helical shape.
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Lock Washers - External Tooth

External tooth lock washers are used for locking and tension. Round washers with teeth on the outside, used for maximum holding power. Must be used with fasteners with adequate head diameter.
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Lock Washers - Internal Tooth

Internal tooth lock washers are used for locking and tension. A round washer with internal teeth, designed to prevent a nut or screw head from loosening with the strut action created by the teeth.
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NAS Washers

NAS washers are round washers with a smaller inner and outer diameter. Often used in military applications because of the strict measurement specifications.
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Neoprene EPDM Washers

Round washers that are slightly beveled with a neoprene lining. Often used with sharp point and self-drilling TEK screws to make a watertight seal around the screw or metal roofing or siding.
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Structural Washers

Structural washers are thick and strong, built for heavy duty applications such as construction. These washers can be found in steel beams and girder fastener assemblies.
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Square Washers

Square washers are square in shape and may be flat on both sides or flat on one side and beveled on one side. Often used with square head bolts, square washers prevent pull through and provide a larger surface area and greater hold than standard round flat washers.
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Fastener Varieties Menu

Types of Rivets


POP Rivets (Open End)

POP Rivets, also known as blind rivets, are used to connect two pieces of material in quick, efficient way. POP Rivets are tubular, comprised of a hat and mandrel; the length of the mandrel is snapped off when installed.
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Closed End POP Rivets (Sealed)

Closed End Rivets differ from a standard blind pop rivet in that they feature a closed end which creates a watertight seal.
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Large Flange POP Rivets

Large flange, also called Oversize, pop rivets have a larger washer on the hat than standard POP Rivets. Also known as blind rivets, they are used to connect two pieces of material in quick, efficient way. Large flange POP Rivets are tubular, comprised of a hat and mandrel; the length of the mandrel is snapped off when installed.
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Countersunk POP Rivets

Countersunk, also call Flat, POP Rivets, are used to connect two pieces of material in quick, efficient way. The hat of the rivet is almost inverted, with a 120-degree countersink in the integrated washer. POP Rivets are tubular, comprised of a hat and mandrel; the length of the mandrel is snapped off when installed.
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Colored Rivets

Colored rivets are open end pop rivets. Colored rivets have a hat that has been painted wither brown, black or white. These colors are used either to hide rivets and create a finished look or to make them extra visual by using the opposing color from the installation material.
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Multi-Grip Rivets

Multi-grip rivets are often used to substitute conventional rivets where the thickness of installation materials can vary. The rivet simply expands to the size(within its range) and holds the two materials together.
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Structural Rivets

Structural rivets are used to create a stronger assembly than standard stainless-steel pop rivets. They generate an intense amount of force and require a different tool to apply than a regular rivet.
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Tri-Fold Rivets

Tri-Fold rivets, also called exploding rivets, have three cuts in the hat that cause the hat to fold outward when installed into three distinct wings. A tri-groove rivet has better strength and holding power than standard pop rivets.
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Machine
Fastener Varieties Menu

Types of Concrete Anchors

Acoustical Wedge Anchors

Masonry acoustical wedge anchors are used to anchor and secured suspended wire to solid or hollow masonry materials. The fastener is inserted into the pre-drilled hole and then struck with a hammer which extends the wedge to hold the anchor in place.
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Drop In Anchors

Drop in anchors are internally threaded anchors that are commonly installed overhead and flush with the surface of the concrete. These anchors are commonly used to create handrails, lighting fixtures and many other fixtures. They require a setting tool for installation.
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Double Expansion Shield Anchors

Double expansion shield anchors are made for installing in softer materials or those of questionable quality. Their entire length expands in the hole to create a very secure hold. This expansion maximizes friction and hold on the installation material.
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Hammer Drive Pin Anchors

These anchors are used for lighter loads than other types of concrete anchors. Drive pins attach fixtures to masonry materials. A hammer is driven into the exposed head of the drive pin. This expands the base inside of the masonry material creating a hold.
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Kaptoggle Hollow Wall Anchors

Kaptoggle hollow wall anchors are installed through a hole in walls or block. Then a machine screw is screwed into the provided threading resulting in a secure hold. Kaptoggle wall anchors are proven to have better holding power than conventional types of hollow wall fasteners.
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Lag Shield Expansion Anchors

These anchors are shielded expansion anchors used to hold lag screws. They expand outwards as lag screws are driven into them. This expansion presses against the installation surface creating a tight, secure hold. They also have a very precise internal threading to allow the installation lag bolt to turn easily.
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Machine Screw Anchors

Machine screw anchors are installed into masonry materials in a pre-drilled hole. Once placed inside the hole, a machine screw is threaded into the anchor and tightened. As the machine screw is tightened, a coned portion is pulled into the sleeve causing it to deform. This deformation of the sleeve results in a tight wedge inside the hole that cannot be easily removed.
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Masonry Screws

Concrete masonry anchors, also known as Tapcons, cut threads into concrete, brick or block when installed. Extended corrosion protection is gained from the blue climaseal coating. No hole spotting or inserts required.
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Plastic Toggle Anchors

Plastic toggle anchors are used in hollow wall or cinder block to create a fastening point for sheet metal screws. These anchors have legs that fold to enter a pre-drilled hole that expand when a screw is driven into them. Once the legs are fully expanded, the toggle anchor is securely in place.
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Sammys Screws

Sammy Screws are used with threaded rod and save time by drilling into masonry materials. They have a female threaded portion to accept the threaded rod into it. Sammys are installed either vertically or horizontally and are commonly used due to their lower installation costs, flexibility and ease of use.
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Sleeve Anchors

Concrete masonry sleeve anchors consist of a threaded stud with an outwardly flared cone-shaped end, with a nut and a washer on the end. Tightening of the nut pulls the stud end into the expander sleeve, wedging it outwards and locking the anchor into the base material. Made for hollow concrete applications (ex. cinderblocks).
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Shop Phillips / Slotted Combo Head Sleeve Anchors

Toggle Wing Hollow Wall Anchors

Toggle Wings are used in situations when installing through a material. The wing can be bent in half and pushed through the material. Once it is all the way through the material it expands and can be screwed into to hold things in place against the rear side of the material.
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Wedge Anchors

Concrete masonry wedge anchors are used to anchor and secure material and equipment to solid concrete masonry surfaces (ex. concrete slabs). Comprised of an anchor, a nut and a washer. Used to fasten concrete to equipment, materials, generators, motors, pumps, pipe, strut, plastics and wood.
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Fastener Varieties Menu

Inserts

Dowel Pins

Dowel pins are manufactured on pneumatic dowel equipment and come in pre-cut lengths and diameters. They are cylindrical with slightly beveled ends. Used in many applications and industries such as aerospace, joint reinforcement, shelf support, furniture building, and hobbyists use them to build toys and models.
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Helicoil Threaded Inserts

Helicoil inserts are precision formed screw thread coils worked into a diamond shape and wound into a spiral coil which is installed into helicoil tapped holes. They provide permanent conventional 60-degree internal screw threads. Helicoil inserts are larger in diameter prior to installation, during installation the inserting tool applies torque to the tang reducing the diameter of the leading coil permitting it to enter the tapped thread. Helicoil inserts are measured in installed length.
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E-Z Lok Threaded Inserts

Unlike helicoil inserts which require a special drill, E-Z Lok threaded inserts for metal are installed using standard tools. Drill the appropriately sized hole with a standard drill, tap the hole with the matching size tap and turn the insert to install. Stainless Steel Threaded Inserts are used for metal applications, and Brass Threaded Inserts are used for wood and soft material applications.
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Shop E-Z Lok Threaded Inserts Brass

Keystock

Keystock is a solid rectangular shaped solid barstock. It is often formed or machined into a machine key, Keystock usually serves as a wedge or locking device in shaft keyways once it has been formed into the proper shape.
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Threaded Rod

A threaded rod is threaded with no head, available in many grades and materials. Often referred to as redi-rod, fully threaded rod and ATR, threaded rod is used for fastening anything from an anchor bolt, to suspending electrical or plumbing equipment from a ceiling. Often used in drop ceiling application.
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Unthreaded Rod

Unthreaded rod, also called round rod, is used in framework, shafts, braces, supports and axles.
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Fastener Varieties Menu

Retaining Rings

Bowed-E Retaining Rings

External Bowed E radially assembled Rotor Clips or retaining rings are designed to be installed into a groove on a shaft. Once snapped into a groove, these clips exert a force or –preload on retained parts, in order to compensate for accumulated tolerances. Externally bowed are radially installed.
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E-Style Retaining Rings

External E Radially assembled Rotor Clips or retaining rings are the most popular and widely used style of radial retaining ring. They are called “e” rings because of the three prongs on the inside of the shaft which make contact with the bottom of a groove on a shaft to create a shoulder for effective assembly retention.
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External Shaft Retaining Rings

Axially installed External Rotor Clips or retaining rings are designed to be installed into a groove or shaft. Once installed in a groove on a shaft, a portion of these retaining rings protrude from the groove in order to create a shoulder to keep an assembly.
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Internal Housing Retaining Rings

Axially installed Internal Rotor Clips or retaining rings are designed to be installed into a groove on a shaft. Once installed in a bore or housing, a portion of these retaining rings protrude from the groove in order to create a shoulder to keep an assembly.
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Fastener Varieties Menu

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American National Standard Machine Screws and Machine Screw Nuts

This Standard ANSI B18.6.3 covers both slotted and recessed head machine screws. Dimensions of various types of slotted machine screws, machine screw nuts, and header points are given in Tables 1 through 12. The Standard also covers flat trim head, oval trim head and drilled fillister head machine screws and gives cross recess dimensions and gaging dimensions for all types of machine screw heads. Information on metric machine screws B18.6.7M is given beginning on page 1708.

Threads

Except for sizes 0000, 000, and 00, machine screw threads may be either Unified Coarse (UNC) and Fine thread (UNF) Class 2A (see American Standard for Unified Screw Threads starting on page 1865) or UNRC and UNRF Series, at option of manufacturer. Thread dimensions for sizes 0000, 000, and 00 are given in Table 7 on page 1698.

Threads for hexagon machine screw nuts may be either UNC or UNF, Class 2B, and for square machine screw nuts are UNC Class 2B.

Length of Thread

Machine screws of sizes No. 5 and smaller with nominal lengths equal to 3 diameters and shorter have full form threads extending to within 1 pitch (thread) of the bearing surface of the head, or closer, if practicable. Nominal lengths greater than 3 diameters, up to and including 1 1⁄8 inch, have full form threads extending to within two pitches (threads) of the bearing surface of the head, or closer, if practicable. Unless otherwise specified, screws of longer nominal length have a minimum length of full form thread of 1.00 inch. Machine screws of sizes No. 6 and larger with nominal length equal to 3 diameters and shorter have full form threads extending to within 1 pitch (thread) of the bearing surface of the head, or closer, if practicable. Nominal lengths greater than 3 diameters, up to and including 2 inches, have full form threads extending to within 2 pitches (threads) of the bearing surface of the head, or closer, if practicable. Screws of longer nominal length, unless otherwise specified, have a minimum length of full form thread of 1.50 inches.

Table 1. Square and Hexagon Machine Screw Nuts ANSI B18.6.3-1972 (R1991)

All dimensions in inches. Hexagon machine screw nuts have tops flat and chamfered. Diameter of top circle should be the maximum width across flats within a tolerance of minus 15 percent. Bottoms are flat but may be chamfered if so specified. Square machine screw nuts have tops and bottoms flat without chamfer.

Diameter of Body

The diameter of machine screw bodies is not less than Class 2A thread minimum pitch diameter nor greater than the basic major diameter of the thread. Cross-recessed trim head machine screws not threaded to the head have an 0.062 in. minimum length shoulder under the head with diameter limits as specified in the dimensional tables in the standard.

Designation

Machine screws are designated by the following data in the sequence shown: Nominal size (number, fraction, or decimal equivalent); threads per inch; nominal length (fraction or decimal equivalent); product name, including head type and driving provision; header point, if desired; material; and protective finish, if required. For example:

  • ¼ - 20 × 1 ¼ Slotted Pan Head Machine Screw, Steel, Zinc Plated
  • 6 - 32 × ¾ Type IA Cross Recessed Fillister Head Machine Screw, Brass

Machine screw nuts are designated by the following data in the sequence shown: Nominal size (number, fraction, or decimal equivalent); threads per inch; product name; material; and protective finish, if required. For example:

  • 10 - 24 Hexagon Machine Screw Nut, Steel, Zinc Plated
  • 0.138 - 32 Square Machine Screw Nut, Brass

Table 2. American National Standard Slotted 100-Degree Flat Countersunk Head Machine Screws ANSI B18.6.3-1972 (R1977)

a When specifying nominal size in decimals, zeros preceding the decimal point and in the fourth decimal place are omitted.

All dimensions are in inches.

Table 3. American National Standard Slotted Flat Countersunk Head and Close Tolerance 100-Degree Flat Countersunk Head Machine Screws ANSI B18.6.3-1972 (R1991)

a When specifying nominal size in decimals, zeros preceding the decimal point and in the fourth decimal place are omitted.

b These lengths or shorter are undercut.

c May be rounded or flat.

All dimensions are in inches.

Table 4. American National Standard Slotted Undercut Flat Countersunk Head and Plain and Slotted Hex Washer Head Machine Screws ANSI B18.6.3-1972 (R1991)

a When specifying nominal size in decimals, zeros preceding the decimal point and in the fourth decimal place are omitted.

b These lengths or shorter are undercut.

a Unless otherwise specified, hexagon washer head machine screws are not slotted.

All dimensions are in inches.

Table 5. American National Standard Slotted Truss Head and Plain and Slotted Hexagon Head Machine Screws ANSI B18.6.3-1972 (R1991)

a Where specifying nominal size in decimals, zeros preceding decimal points and in the fourth decimal place are omitted.

a Unless otherwise specified, hexagon head machine screws are not slotted.

All dimensions are in inches.

Table 6. American National Standard Slotted Pan Head Machine Screws ANSI B18.6.3-1972 (R1991)

a Where specifying nominal size in decimals, zeros preceding decimal and in the fourth decimal place are omitted.

All dimensions are in inches.

Table 7. Nos. 0000, 000 and 00 Threads ANSI B18.6.3-1972 (R1991) Appendix

a Where specifying nominal size in decimals, zeros preceding decimal and in the fourth decimal place are omitted.

b There is no allowance provided on the external threads.

c The minor diameter limits for internal threads are not specified, they being determined by the amount of thread engagement necessary to satisfy the strength requirements and tapping performance in the intended application.

All dimensions are in inches.

Table 8. American National Standard Slotted Fillister and Slotted Drilled Fillister Head Machine Screws ANSI B18.6.3-1972 (R1991)

All dimensions are in inches.

1 Where specifying nominal size in decimals, zeros preceding decimal points and in the fourth decimal place are omitted.

2 Drilled hole shall be approximately perpendicular to the axis of slot and may be permitted to break through bottom of the slot. Edges of the hole shall be free from burrs.

3 A slight rounding of the edges at periphery of head is permissible provided the diameter of the bearing circle is equal to no less than 90 percent of the specified minimum head diameter.

Table 9. American National Standard Slotted Oval Countersunk Head Machine Screws ANSI B18.6.3-1972 (R1991)

a When specifying nominal size in decimals, zeros preceding decimal points and in the fourth decimal place are omitted.

Howto Remove Round Head Machine Screws With No Slot Machine

b These lengths or shorter are undercut.

All dimensions are in inches.

Table 10. American National Standard Header Points for Machine Screws before Threading ANSI B18.6.3-1972 (R1991)

All dimensions in inches. Edges of point may be rounded and end of point need not be flat nor perpendicular to shank. Machine screws normally have plain sheared ends but when specified may have header points, as shown above.

Table 11. American National Standard Slotted Binding Head and Slotted Undercut Oval Countersunk Head Machine Screws ANSI B18.6.3-1972 (R1991)

a Where specifying nominal size in decimals, zeros preceding decimal points and in the fourth decimal place are omitted.

b Unless otherwise specified, slotted binding head machine screws are not undercut.

a These lengths or shorter are undercut.

All dimensions are in inches.

Table 12. Slotted Round Head Machine Screws ANSI B18.6.3-1972 (R1991) Appendix

a When specifying nominal size in decimals, zeros preceding decimal point and in the fourth decimal place are omitted.

All dimensions are in inches.

Not recommended, use Pan Head machine screws.

Machine Screw Cross Recesses

Four cross recesses, Types I, IA, II, and III, may be used in lieu of slots in machine screw heads. Dimensions for recess diameter M, width N, and depth T (not shown above) together with recess penetration gaging depths are given in American National Standard ANSI B18.6.3-1972 (R1991) for machine screws, and in ANSI/ASME B18.6.7M-1985 for metric machine screws.

ANSI Cross Recesses for Machine Screws and Metric Machine Screw

Summary

This article presents information about standard machine screws and nuts, including the different types and tables of sizes with key dimensions. Learn more about fasteners from the Machinery's Handbook, 30th Edition, which is published and available from Industrial Press on Amazon.

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