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T Slot Nut Dimensions

7/11/2022
  1. Browse T-Slot Nuts in the TE-CO catalog including T-Slot Nuts Imperial,T-Slot Nuts Metric,T-Slot Nuts Imperial (Tapped Through),T-Slot Nuts Metric (Tapped Through),Quarter Turn T-Slot Nuts,Stainless Steel T-Nuts.
  2. The last thread is incomplete on T-Slot Nuts to prevent the stud from turning through the bottom of the nut. Many sizes conform to TCMAI standards; Special sizes quoted upon request; Standard package quantity: 25 pcs. Please use the image viewer to see the product line drawing.
  1. Norelem 07060-164 T Slot Nut Dimensions
  2. T Slot Table T Nut Dimensions

T-Slot / T-Slot Nuts; T-Slot Nuts. Jergens Table-Saver design provides a safety-stop feature to prevent turning stud into tableways. Material: C-1018, 303 Stainless. Some of the T-nuts didn't quite fit the slots being a tiny bit oversize. Ten minutes with a file and a sanding wheel cured them as they weren't that hard. What I'm saying is the 5/8 T-nuts are supposed to be undersize to fit a 5/8 slot but even if they're not it's not a big deal, just file to size.

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.

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.

Norelem 07060-164 T Slot Nut Dimensions

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M-LOK
TypeAttachment System
Place of originUnited States
Production history
DesignerMagpul Industries
Designed2007–2014
Produced2014–present
Magpul MOE handguard on a user-assembled AR-15 semi-automatic rifle

T Slot Table T Nut Dimensions

A STNGR USA 15 in (381 mm) HWK M-LOK handguard on an AR-15

M-LOK, standing for Modular Lock, is a free licensed[1]firearmrail interface system developed and patented by Magpul Industries.

M-LOK allows for direct accessory attachment onto the 'negative space' (hollow slot) mounting points, and is a competing standard to VLTOR's open sourcedKeyMod system for replacing the ubiquitous Picatinny rail in some applications.[2] Compared to the Picatinny rail system, both M-LOK and KeyMod enable the user to have a slimmer, lighter, smoother and more fenestratedhandguard/fore-end with accessories mounted only where needed, whereas a Picatinny handguards typically will have rail slots for its whole length resulting in a heavier and bulkier handguard with sharp edges and poorer barrel ventilation.

The M-LOK system can be seen as an evolution of the Magpul Original Equipment (MOE) system, but the two are not fully compatible. Though newer M-LOK accessories can be used on older MOE slot handguards if an adaptor plate is used, there is no adaptor available for using older MOE accessories on the newer M-LOK handguards.


History[edit]

A prototype of the MOE slot was revealed by Magpul in late 2007 together with their Masada Concept Rifle (which would later be known as the Adaptive Combat Rifle). The MOE slot system was released by Magpul in 2009 as a feature on their MOE handguards, and at the same time compatible accessories such as Picatinny rail sections, direct MOE mounted light mounts, grips, bipod studs, etc. were released.

The MOE slot standard was never officially released, and a drawback to the system was that the rear side of the panel had to be accessed in order to mount accessories, limiting its application. The MOE slot system uses a weld nut which has to be placed manually on the inside of the handguard before mounting, making the slot system unsuited for applications such as free-floating handguards. Also, depending on the accessory item, the spacing increments between the MOE slots were not small or uniform enough to adjust the desired placement of accessories.

Acknowledging shortcomings of the MOE systems, Magpul drafted M-LOK as a new and improved mounting standard which was released in 2014 replacing the existing MOE slot. 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 on free-floating handguards. It was designed to work with both metal and polymer parts.

M110A1 SDMR featuring a Geissele M-LOK rail handguard

In 2016, Colt Canada developed and released the Modular Rail Rifle (MRR) that uses a monolithic upper receiver with the M-LOK attachment system.[3] In 2017, several companies produce M-LOK handguards as well as accessories like Picatinny rail strips, vertical foregrips, bipods, sling adaptors, and flashlight mounts.[4]

Nut

In 2017, a summary report of testing conducted by NSWC-Crane for USSOCOM indicated that, while comparable in endurance and rough handling testing, M-Lok greatly outperformed Keymod in repeatability, drop testing and failure load testing.[5]

Licensing[edit]

While M-LOK is free licensed, it is not open source, and thus manufacturers must acquire a license from Magpul before making products using the M-LOK standard. Magpul claims this gives them more control in assuring that all M-LOK products are made to specifications ensuring compatibility. Program participation is open to any interested manufacturer.

Technical specifications[edit]

Rail specifications[edit]

The slot dimensions (used on handguards, etc.) are available on the web.[6] The slots provide metric 20 mm (0.79 in) length intervals, and accessories can be mounted either within a slot or bridging between slots, making it possible to adjust the position of accessories in smaller intervals than the length of the slot. The slots on an M-Lok handguard are approximately 32 mm (1.260 in) long and 7 mm (0.276 in) wide and space 8 mm (0.315 in) from each other. The radius of the corners is approximately 2.38 mm (0.094 in).[7][8][9]

Attachment specifications[edit]

The quarter-turn T-slot nuts have different torque specifications depending on the handguard material:

  • 4.0 N⋅m (35 lb⋅in) for attaching metal accessories to metal handguards.
  • 1.7 N⋅m (15 lb⋅in) for attaching polymer or metal accessories to polymer handguards.
  • 1.7 N⋅m (15 lb⋅in) for attaching polymer accessories to metal handguards.

Attachment screws made by many U.S. manufacturers are often either #8-32 TPI or 10-24 TPI UNC threads, which respectively have major thread diameters of 0.1640 inches and 0.1900 inches (4.166-0.794 mm and 4.826-1.058 mm expressed in metric designation). Many M-LOK screws on the international market instead use either M4 or M5 metric threads to reduce cost.

The tool required for mounting, in addition to the thread size, also depends the screw head type. Hex keys are used extensively in the firearms industry, but metric and imperial hex keys as a general rule are not compatible. It is possible damage the tool and screw by selecting a tool that is too small for the fastener, which can be done by using an Imperial/customary tool on a metric fastener, or the converse. An exception to this is 4 mm hex keys, which are almost the exact same size as 532 in (3.97 mm). In many industries, this makes 4.0 mm (532 in) hex keys preferred for consumer products because end users can successfully use an imperial key on a metric fastener, and vice versa.

Hex key spanner (wrench) size

Thread type

Socket head
cap screw

• Button head cap
screw
• Flat head counter-
sunk cap screw
M43 mm2.5 mm
M54 mm3 mm
#8-32 TPI9/64' (3.57 mm)3/32' (2.38 mm)
#10-24 TPI5/32' (3.97 mm)1/8' (3.18 mm)

While screw and slot dimensions are available on the web, the T-slot nut dimensions are currently under review by the US State Department to determine whether it should be regulated by ITAR, and until it is clarified drawings are only available to US citizens.

  • M-LOK handguard and attachment parts

  • M-LOK approximate slot dimensions. (Primary measurements in millimeters, inches in parenthesis).

See also[edit]

  • Rail Integration System, generic term for a system for attaching accessories to small firearms
  • Weaver rail mount, early system used for scope mounts, still has some popularity in the civilian market
  • Picatinny rail (MIL-STD-1913), improved and standardized version of the Weaver mount. Used for both for scope mounts, and for accessories (such as extra sling mounts, vertical grips, bipods etc.) Major popularity in the civilian market.
  • NATO Accessory Rail- further development from the MIL-STD-1913
  • UIT rail, an older standard used for mounting slings particularly on competition firearms
  • KeyMod - competing standard open standard design to M-LOK for mounting accessories
  • Zeiss rail, a ringless scope mounting standard

References[edit]

Wikimedia Commons has media related to M-LOK.
  1. ^'Magpul Industries - M-LOK'. Archived from the original on 4 December 2017. Retrieved 6 June 2016.
  2. ^KeyMod vs. M-Lok: The Next AR Rail Standard by Chris Baker, November, 19, 2014
  3. ^Colt Canada Modular Rail Rifle (MRR)
  4. ^M-LOK Outselling KeyMod about 3 to 1, 28 January 2016
  5. ^Details On The USSOCOM Sponsored KeyMod vs M-LOK Test Conducted at NSWC-Crane, 5 May 2017
  6. ^Magpul Industries - M-LOK DESCRIPTION AND FAQ DOCUMENT[permanent dead link]
  7. ^'magpul.com - M-LOK 2015 FAQs'(PDF). Archived from the original(PDF) on 7 April 2019. Retrieved 7 April 2019.
  8. ^M-Lok dimensions
  9. ^Magpul M-LOK estimated dimensions
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