Slotted fillister head machine screw dimensions are shown in the following chart according to ASME B18.6.3 standard.

The fillister head has a rounded top surface, cylindrical sides, and a flat bearing surface.

Some important notes from the ASME B18.6.3:

- Thread dimensions for the No.0000, No.000 and No.00 sizes are also included in the standard.

- The general data about the head height, bearing surface, gaging of recess, slot, length, tolerance on length, length of thread, points, finish, workmanship and designation of machine screws are given in the standard.

Slotted Fillister Head Machine Screw Dimensions:

Nominal screw size


Dimensions of Slotted Fillister Head Machine Screws
Nom. Size --- ---
Basic Dia. --- ---
Head Diameter (A) max ---
min ---
Head Side Height (H) max ---
min ---
Total Head Height (O) max ---
min ---
Slot Width (J) max ---
min ---
Slot Depth (T) max ---
min ---

Note 1: Dimensions in this calculator are in inches.

Note 2: Machine screws shall have a definite underhead fillet large enough to ensure that full fastener strength is achieved. The radius of the fillet under countersunk head screws shall be no greater than 40% of the basic screw diameter. The radius of the fillet under truss heads and number 6 sized pan heads shall be no greater than 25% of the basic screw diameter. The radius of the fillet under all other head styles shall be no greater than 15% of the basic screw diameter.

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


Gages and Gaging : Specifications and dimensions for the gages used on Unified inch screw thread is defined in the ANSI/ASME B1.2-1983 standard. Types of gages including thread plug gages, snap gages, thread ring gages and plain diameter gages for internal and external threads are covered in same standard. Screw thread gaging systems for acceptability is covered in the ASME B1.3-2007 standard.

Details of gages and gaging about the machine screws heads are given in the appendices of the ASME B18.6.3-2003 standard.

Unified Screw Thread: A thread form used by the United Kingdom, Canada, and the United States to obtain screw thread interchangeability among these three nations. It has 60° thread angle and dimensions are stated in inch units.

UN form screw threads: The UN thread is intended for general purpose fastening operations.

UNC (Unified National Coarse): Most commonly used type for general engineering applications. This thread form is used in materials with low tensile strength which makes threads more resistance against stripping (internal threads) .UNC give possibility for quick assembly.

UNF (Unified National Fine): External threads of this Fine Series have greater tensile stress area than comparable sizes of the Coarse series. The Fine series is suitable when the resistance to stripping of both external and mating internal threads equals or exceeds the tensile load carrying capacity of the externally threaded member. It is also used where the length of engagement is short, where a smaller lead angle is desired, where the wall thickness demands a fine pitch, or where finer adjustment is needed.

Thread class: A classification system to classify the threads for interchangeability and manufacturability. Class 1 threads are loosely fitting thread and used for ease of assembly. Most commonly used class is 2 and this class is designed for general use. Class 3 is used for closer tolerances.


Link Usage
Unified Inch Screw Thread Sizes & Tolerances Calculator Calculates basic major, minor and pitch diameters of the external (bolt) and internal (nut) inch thread according to ASME B1.1-2003 standard. In addition to basic size calculations, limits of sizes calculations of different tolerance classes can be done according to same standard.
Dimensions For No.0000, No.000 and No.00 Thread Sizes Dimensions for unified thread sizes of No.0000, No.000 and No.00
General Data on ASME Machine Screws General data on ASME machine screws


  • ASME B18.6.3 - 2003, Machine Screws and Machine Screw Nuts