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.

T-Slot nuts enable the user to add clamps to a fixture without tearing down existing clamps. Slot Size Length. (lbs/kit) Size Size WITH 25MM THICK STEP BLOCKS 68001 18.5 12MM M10 x 1.5 68002 18.5 14MM M10 x 1.5 68003 24 14MM M12 x 1.75 68004 24 16MM M12 x 1.75 68005 24 17MM M12 x 1.75 68006 29 18MM M16 x 2.0 68007 29 20MM M16 x 2.0 Super Clamp Kits 52-piece Kit Contains:. 4 Coupling Nuts. 6 Flange Nuts. 6 T-Slot Nuts.

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

M12-1.75 Thread 18mm Slot 32mmL x 19mmH T-Slot Nut Fastenal Part No. The M-LOK rail specification included metric dimensions instead of imperial, and utilizes a T-slot nut capable of only 90-degree rotation, reinforced by thread-locking fluid, making it suited for applications. Browse T-Slot Nuts Metric (Tapped Through) in the TE-CO catalog including Item #,Thread Size (A),Slot Size (B),Total Height (C),D,Total Length (E),Total Width (F),List Price 800.543.4071 Show Menu.

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.

T Slot Nut Dimensions

^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.

^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.

Other Machining Articles

More from Hardware

Thomas Industry Update

Lug Nuts M12 1.25

Stay up to date on industry news and trends, product announcements and the latest innovations.

Related Resources

• Happy Hanukkah from Space!

• 7 Ways to Say No to Your Manager

• Amazon Investing in 8 New Nevada Facilities, Creating 2,000 Full-time Jobs

• PPG Acquiring North Carolina Coatings Manufacturer in $1.15 Billion Deal

• 2020 Gift Guide: 10 Best STEM Gifts for the Tech Enthusiast Adults on Your Holiday List

• Metric T Slot Aluminum Profiles

• Connectors

• Fasteners

• Accessories

• Frame to Floor

• Panel Accessories

• CarboSix Carbon Fiber

With T-Slot Aluminum, you get more value than you ever would with welded steel. Need flexibility? You've got it with t-slot aluminum. Need Versatility? Extruded aluminum has that too. Strong in the hot or the cold, corrosion resistant, extruded aluminum has everything you need to get a project done quickly and efficiently. No need to paint or weld unlike steel parts. Get whatever you need built fast and strong with our metric series profiles of extruded aluminum framing.

The T-slot Extruded Aluminum Advantage

For thousands of years humans have been fabricating useful, pleasing furnishings and other structures for the home and workplace out of an impressive range of materials, including straw, mud, stone, wood, brick, iron, steel, and other metals of various sorts. But it is only within the last hundred years or so that aluminum the most abundant metal in the Earth's crust has been utilized in an ever-increasing number of day-to-day applications. Partly this is because a cost-effective process for extracting aluminum from bauxite ore was not perfected until about 1920.

So there is one great advantage of employing aluminum for structural design purposes: it is plentiful. Its other advantageous properties include strength, lightness, formability, high ductility, and excellent corrosion-resistance. The innate utilitarian value of those properties is vastly magnified when the metal is formed into T-slot aluminum extrusions.

In a nutshell, T-slot aluminum forms the basis of a framing system for creating three-dimensional structural assemblies made with a variety of extruded and fabricated aluminum parts. With this system, each length of extruded aluminum contains one or more T-shaped indentations, or slots, into which various attachments (with ends also shaped like a 'T'?) conveniently fit and can slide up and down as needed. This allows you to interconnect other T-slotted aluminum parts into even the most complex configurations without having to clamp and weld them together as you would have to do with steel components.

Here are a few of the key advantages of adopting T-slot aluminum solutions to meet your structural design needs.

Strength

True, steel is harder and 'stronger.' But by the same token, aluminum is among the lightest of metals used for modern engineering purposes, with a molecular density one-third that of steel. As a result, it possesses a strength-to-weight ratio that is actually superior to that of steel . Contrary to what you might think, extruded aluminum is strong enough to handle most structural design and assembly applications.

Once you factor in the inconvenience of moving and positioning heavy pieces of steel not to mention the added labor cost of welding or riveting them together, drilling and tapping holes for mounting bolts, and then cleaning, prepping, priming, and painting the surface of the metal then T-slot aluminum becomes an increasingly attractive option if you are seeking cost-effective structural framing solutions.

Durability

If it's tough enough for trucks, military combat vehicles, and commercial airliners, then rest assured that aluminum is tough enough for more prosaic, everyday purposes. One key aspect of this durability is its resistance to rusting. Rust is to steel as rot is to wood. Unlike steel, for all intents and purposes aluminum doesn't rust at all. A microscopic layer of oxide (which is responsible for the silvery-gray color of anodized aluminum) naturally forms on the surface of the metal and prevents that from happening. You don't even have to prime and paint it in order to protect it! If any of your project's aluminum extrusions or other parts never rust, then you'll never have to replace them saving you money and down-time in the long run.

Versatility

Finally, one of the most important advantages to using T-slot aluminum extrusions and accessories is that, unlike permanently welded steel, the system is modular by design i.e., it is easily changeable. You can connect, position, and fasten together the aluminum profiles however you'd like, using the appropriate fasteners , connectors , and desired accessories . Later on, as needed, you can then adjust and rearrange them in any configuration you like.

The most common type of aluminum fastener used to fasten parts together is the T-nut: just drop it into the T-slot and then twist it into a locked position. That is so much easier than welding!

But where the real magic happens is in the versatility of our aluminum connectors. Just a partial list would include:

• quick connectors
• T-connectors
• tilt connectors
• milling connectors
• bolt connectors
• cube connectors
• angle connectors
• slotted gussets
• corner brackets

Once you've put the finishing touches on the assembly with end caps, casters, cable blocks, machining jigs, tool hangers, cabinet siding, doors, or any of a number of other accessories that we carry, you're good to go!

For maximum versatility for both both our international and domestic customers, be aware that our T-slot aluminum extrusions come in both metric profiles and inch profiles .

From carts to aquarium stands , from shelves to enclosures , and from ergonomic workbenches to eye-catching signs , Framing Tech T-slot aluminum extrusion systems are designed, machined, and assembled for versatility—and they are built to last.

T-Slot Aluminum FAQs

• What is T-slot Aluminum Extrusion?

  T-slot aluminum extrusion is a structural fabrication material that utilizes an engineered cross-sectional profile that is both strong and versatile in its use.

• Will T-slot Aluminum Extrusion corrode?

  Our aluminum extrusion is non-corrosive. This is mostly due to the clear anodized finish that comes standard on all of our extrusion, but also due in part to aluminums natural ability to oxidize. The oxidation process creates a secondary layer of protection from corrosion, similar to how copper will patina.

• Is T-slot Aluminum Extrusion considered a “Green” material?

  Yes! Due to excellent recycling practices most of the aluminum ever produced is still in use today. In fact, aluminum is 100% recyclable and of the most common materials recycled aluminum is the ONLY material that is infinitely recyclable. It is also much lighter than glass and steel per cubic inch, and has a much smaller carbon footprint during fabrication, processing, and shipping.

• Why choose aluminum extrusion over steel?

  The main advantages are that aluminum extrusion is more versatile, modular, easier to work with, and costs less than steel. Building with aluminum extrusion is as simple as inserting a connector into the t-slot and tightening it into place with standard hand tools. No need to clamp, weld or paint aluminum extrusion. T-slot aluminum extrusion makes it easy to re-locate pieces or add onto your current structure at any time.

  What is aluminum extrusion used for?

  Currently, T-slot aluminum extrusion is widely used in automation, material handling, safety guarding, manufacturing and laboratory applications. However, many people are adopting t-slot aluminum extrusion for use in a wide variety of projects. Some have even built their own machines such as 3D Printers and CNC machines using our aluminum extrusion.

• What is a T-slot, and how do I use it?

  A T-slot is what we call the channel that runs the length of our aluminum extrusion shapes. The T-slots are designed to a specific depth and width depending on the material. The T-slot is used mostly for mounting and fastening a wide variety of accessories and panels to the aluminum extrusion. Often, panels will be inserted into the T-slot to quickly create a wall or enclosure.