metric thread size chart

Apollo International is the leading manufacturer and exporter of Brass, Copper & Other Metal Components in India. The third and final number is the screw's length which equals 30 mm. threads. production fields of machining. When the diameter smaller than 1/4, the value is indicated by a number, like #1 or No.1. 1) For metric threads pitch is the distance between threads. Fluids Flow Engineering For Metric parallel threads, taking a caliper reading of the threads outer diameter in millimetres (mm) will give a reading of the exact thread size but not the thread pitch. The following table chart are standard metric internal thread sizes M 0.25 - M 8 per. In practice this means that one can measure the diameter over the threads of a bolt to find the nominal diameter Dmaj, and the inner diameter of a nut is Dmin. The designation of a screw thread gives the thread symbol, the nominal size, the pitch, and the thread tolerance class (Ex: M6 x 1 - 5H6H). Flat Plate Stress Calcs Tables of the derived dimensions for screw diameters and pitches defined in ISO 261 are given in ISO 724. Please read AddThis Privacy for more information. <> Design & Manufacturability Fastener and Screw / Bolt Design, Formula and Calculations. Welding Stress Calculations The second number is the screw's pitch which equals 1.25 mm. Threads & Torque Calcs tPHY~Xwaj({ dn (=9#?+@U Excel App. For the size M6 1 mm, the pitch is coarse; while the size M6 0.75 mm has a fine Fasteners; C-Class Components; Sofrasar Tunnel Solutions; . The pitch varies from coarse to extra fine with up to 5 different pitches for some dimensions. All units in inches. If you don't know the pitch, choose coarse threads; they're the industry standard. Number of Starts - One. <>/OutputIntents[<>] /Metadata 1646 0 R/ViewerPreferences 1647 0 R>> referenced in the table below (e.g. Thread Dimensions - Imperial Thread Sizes Chart Here are two imperial thread sizes table defines thread dimensions of coarse threads (UNC/UNRC) and fine threads (UNF/UNRF). of Threads/Inch UNC UNF UNEF mmUNM NPT METRIC Dia. Pitch mm p. Root Radius mm r. Pitch Diameter mm d2=D2. stream [2] Each thread is characterized by its major diameter, D(Dmajin the diagram), and its pitch, P. ISO metric threads consist of a symmetric V-shaped thread. <> Conversely, in an internal (female) thread (e.g. The coarse pitch is the commonly used default pitch for a given diameter. Thread sizes are not directly interchangeable. d3. ISO 965-2: Limits of sizes for general purpose external and internal screw threads. 0000005426 00000 n ISO 261: ISO general purpose metric screw threads General plan. endobj 5 0 obj ISO 261 specifies a detailed list of preferred combinations of outer diameter and pitch for ISO metric screw threads. ANSI/ASME B1.13M-1995. ISO 262 specifies a shorter list of thread dimensions - a subset of ISO 261. These thread sizes and classes represent bolts and screws, as well, as other standard internal threads. Metric Internal Thread Chart Limiting Dimensions for M Profile: Thread . Feedback Advertising Metric fasteners are specified with a thread pitch, instead of a thread count. Bearing Apps, Specs & Data In addition to coarse and fine threads, there is another division of extra fine, or superfine threads, with a very fine pitch thread. 8 corresponds to 0.164"). The design principles of ISO general-purpose metric screw threads ("M" series threads) are defined in international standard ISO 68-1. For example, a M6 x 1 mm has a 6 mm thread diameter and has 1 mm between threads. Japan has a JIS metric screw thread standard that largely follows the ISO, but with some differences in pitch and head sizes. Lubrication Data Apps x[7r;@/,V7k K }A INFf:""_/|e_Q\4lh9\)uxO~~yoo/^~yw{)/??>}{9]/^*_?[0\u$LM|~g5UdMBjq,FOm;9CmBe^bEa) j_WcuSC!ly-_l_|}m>7=MGYk~Nu;{9*GUiX=0MdTuT/]l+EG3]>~}mDFN5A7!?&J^bhn3{s}bjhi%f&1itO5>meKNbN-Fw1u{q!O{|)l/YfO._+.mkx>~w*]lL2:/a>r(`{D#9aMFm[a%HJLJzQ$Fh{kX&'q9Pva^Y$3Ll]IXamEx;Jf#J|, |by6dU\bO:,0TyVQqdb_MnU6'@OFA!Vm8SjqDSFI{.^M``KYyl3A9EJh@2S ! 20 35 startxref Do not use these values for standard metric external thread design. For detailed explanations about classes, see the class section below. [5][6] ISO 262 specifies a shorter list of thread dimensions a subset of ISO 261. Where: H = P ( 3 1/2 / 2 ) = 0.866025 P or 20 0 obj <> endobj 0000023239 00000 n Thread Sizes (Dimensions) Explained Imperial & Metric Thread Sizes Chart | CNCLATHING, Thread Types, Terms, Designation, and How to Identify & Measure Threads | CNCLATHING, Bolts Types and Sizes: Metric & Imperial Bolt Dimensions Chart | CNCLATHING, What are UNF Threads and UNC Threads? METRIC THREAD - Drill & Tap Chart Coarse Thread Sizes. For the formal values, use the below chart or standard ISO 965-1. Inch thread sizes are specified by the nominal major diameter and the number of threads per inch. A metric ISO screw thread is designated by the letter M followed by the value of the nominal diameter D (the maximum thread diameter) and the pitch P, both expressed in millimetres and separated by the multiplication sign, (e.g. The above formulas are approximations. In general, smaller fasteners have finer threads, so they have a lower thread pitch. In general, smaller fasteners have finer threads, so the thread count is higher. These applications will - due to browser restrictions - send data between your browser and our server. Download and print metric coarce threads clearance and tap drill chart. endobj Note that the ISO 724 standard specifies threads up to M 300. 0000003684 00000 n sales@apollointernational.in. Videos Design Manufacture Class - 6g for external threads and 6H for internal threads. If the pitch is the normally used "coarse" pitch listed in ISO 261 or ISO 262, it can be omitted (e.g. (See above table). <> endobj 8 0 obj endobj 11 0 obj TPI stands for Threads Per Inch, which means the total number of threads per inch measured along the length of a fastener. For metric screws, this is the number of millimeters preceded by the letter M In tolerance class designation, the pitch diameter tolerance is followed by major diameter tolerance. A table to help find the nearest sized metric coarse, metric fine, BSF, BNW, UNC and UNF fasteners. Once the Td, TD, es & EL values are known the final limits can be calculated according to the below formulas. 1.Thread sizes in inches are specified by diameter and threads per inch. on a bolt) will pass through easily to create a well-located connection to an internally threaded component (e.g. threads in thin-walled pipes). You case use them directly, utilize our ThreadCalculator[ , or browse the below charts. our selection of screws. Measure screw diameter, or screw size, by measuring the width of the threaded part of the screw. This means that the external thread must end flat at Dmaj, but can be rounded out below the minor diameter Dmin. All rights reservedDisclaimer | This data can be found in ISO 951-1 or in the Limits and Dimensions section below. <> To view Metric translation click the Thread Link UNF Series Basic Dimensions chart Click the Thread Link to get the Full Thread Data for all classes in Inch and Metric units. To view the purposes they believe they have legitimate interest for, or to object to this data processing use the vendor list link below. Electric Motor Alternators Metric fasteners are specified with a thread pitch, instead of a thread count. Note - Metric screw diameters usually start with "M" (M3, M4, M5. ). <>/XObject<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/Annots[ 11 0 R 12 0 R 15 0 R 24 0 R] /MediaBox[ 0 0 612 792] /Contents 4 0 R/StructParents 0>> In this guide, we demonstrate how to measure screw thread size for inch and metric systems of measurement. 0000011192 00000 n ANSI/ASME B1.13M-1995. They are based on standard ISO 68-1. The M4 screw size has a diameter of 7/64 inches. Power Transmission Tech. No. The thread pitch is the distance between threads expressed in millimeters. The basic dimensions are nominal dimensions of a metric thread profile without allowance and tolerances (The thread class defines that). endobj 13 0 obj The M8 screw size has a diameter of 5/32 inches. M4 x 0.5. All units in mm. or hb```b``b,ka!n`@W2:^5JR;~lu}snKsk~8Uv}XC+: !4%,F8 i V(300aG"YK:pD\c\u %KYI. Engineering Standards It was one of the first topics standardized by the ISO committee as early as 1947 and is still used today. Thread Form Type. These thread sizes and classes represent bolts and screws, as well, as other standard external threads. Metric Thread Type Chart Thread Seal Tape and Alternative Solutions. 0000004531 00000 n The class is written after the pitch. However, for manufacturing and machining, you need the allowable range of each dimension. endobj 17 0 obj in a nut), the major and minor diameters are minimum dimensions; therefore the thread profile must end flat at Dmin but may be rounded out beyond Dmaj. Four long charters mean a separate class for the. <<92DA1EFE4BCA9340A2250E06A512D1FA>]/Prev 50340>> Since we also talked about imperial screw callouts, let's read this screw thread callout as well: #6 x 1 x 1/2. It is specified using the nominal major diameter and the number of threads per inch. 0000000996 00000 n Downloads 0000018204 00000 n 0000023618 00000 n The basic dimensions can be used for design. In stock and ready to ship. We don't collect information from our users. ISO Hardware Engineering Data Engineering Book Store Manage Settings Note that the ISO 724 standard specifies threads up to M 300. Only emails and answers are saved in our archive. The metric thread sizes are generally expressed as M2 0.25, the thread diameter is 2mm and pitch is 0.25mm. .com Inch and Metric Pouce et Mtrique Thread Size Comparison Chart R8 Comparisons . TPI is used only with American fasteners. <> There are two common methods to write the thread dimensions. The thread depth is 0.54125 pitch. ISO 68-1: ISO general purpose screw threads Basic profile Metric screw threads. Manufacturing Processes Metric Coarse Metric Fine BSF/BSW UNC UNF; M2 x 0.4--1-64: 1-72: M2.5 x 0.45--3-48: 3-56 . In the plane of the thread axis, the flanks of the V have an angle of 60 to each other. These thread sizes and classes represent bolts and screws, as well, as other standard external threads. [ 13 0 R] In internal thread tolerance class designation, the pitch diameter tolerance is followed by minor diameter tolerance. Dimensions refer to the basic profile in accordance with ISO 68. Engineering Forum 0000002104 00000 n Metric External (Fasteners) Thread Designations Sizes M1.6 - M18 Metric External (Fasteners) Thread and Fastener Sizes M20 - M50 Screw Thread Designations, Minor Diameter, Major Diameter, Pitch Diameter UN Inch Internal Screw Threads Formulas and Calculator per. All units in mm. To view Inch translation click the Thread Link, To manufacture or measure a thread, one has to know the maximum and minimum permissible values of the basic dimensions. For instance, when a screw or bolt measures 5.9mm, it is called a 6mm thread. Engineering Mathematics In addition, one or two smaller fine pitches are defined, for use in applications where the height of the normal coarse pitch would be unsuitable (e.g. Hardware, Metric, ISO For example, for M8 X 0.75 5g6g, the class is 5g6g. 4 0 obj The thread pitch is the distance between threads expressed in millimeters. Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications! These values are calculated according to the thread class (See below). f[rTw*b]w}5gxs:2S9G3@nx= O8~bS{dIh`nl. M8). 22.5. Section Properties Apps All units in inches. They were one of the first international standards agreed upon when the International Organization for Standardization (ISO) was set up in 1947. All dimensions are in inches. If you want to promote your products or services in the Engineering ToolBox - please use Google Adwords. In an external (male) thread (e.g. M10 x 1. endobj 15 0 obj This corresponds to the first number of the thread size. Downloads 0000001531 00000 n Products. Dared, Jamnagar, Gujarat, India. Engineering Mathematics The allowance EL for internal threads and es for external threads is derived from the class. The next step in identifying your thread type is to determine the pitch size. Metric thread marks: M20-6H, M201.5LH-6g-40, where M means metric common thread, 20 means the nominal diameter of the thread is 20mm, 1.5 means the pitch, LH means left-handed, 6H, 6g means the thread accuracy grade, The uppercase precision grade code represents the internal thread, the lowercase precision grade code represents the external Tolerances should be considered when designing products. ISO 965-1 Calculator, Fastener Thread Designations and Definitions Pitch, Minor, Major Diameters, Standard External Metric Thread and Fastener Sizes M 0.25 - M 1.4, Metric External Table Chart Thread Sizes M 20 - M 55, Metric External Table Chart Thread Sizes M 56 - M 78, Metric External Table Chart Thread Sizes M 80 - M 100, Metric External Table Chart Thread Sizes M 105 - M 135, Metric External Table Chart Thread Sizes M 140 to M 175, Metric External Table Chart Thread Sizes M 180 to M 255, Metric External Table Chart Thread Sizes M 260 to M 1060. a nut) on the other side. #0 DIA = 0.059 #1 DIA = 0.073 #2 DIA = 0.086 #3 DIA = 0.099 #4 DIA = 0.112 0000003268 00000 n Metric thread sizes are specified by diameter and pitch, which is the space between The M6 screw size has a diameter of 9/64 inches. If you would like to change your settings or withdraw consent at any time, the link to do so is in our privacy policy accessible from our home page.. For example, in the screw size 10-24, the first digit refers to the thread diameter, the and second digit is threads-per-inch (TPI). Engineering Book Store All these parameters are derived from simple formulas based on the threads nominal diameter and pitch. 0000001956 00000 n 0000002218 00000 n Materials and Specifications 0000002833 00000 n Hardware, Imperial, Inch Other (usually smaller) sizes may occur to reduce weight or cost, including the small series flange bolts defined in ISO 4162 which typically have hexagonal head sizes corresponding to the smaller 1st choice thread size (eg. Thermodynamics The table below is not complete. The designation of a screw thread gives the thread symbol, the nominal size, the pitch, and the thread tolerance class (Ex: M6 x 1 - 4g6g). The approximate allowance can be calculated according to the below formulas: Unfortunately the above formulas are approximations only. The clearance drill sizes listed are the most commonly used sizes. Machine Design Apps , Finishing and Plating The following table chart are standard metric internal thread sizes M 0.25 - M 8 per. (@xML{|Oe)SN)^p7'oBi0T:r_Q3. of Threads/Inch BA BSW BSF BSP Major Dia. While a ruler could be used to calculate the pitch size, a pitch gauge is highly . UN - Constant pitch (##-UN) thread. For metric screws, this is the length in millimeters between threads. Metric Metric thread sizes are specified by diameter and pitch, which is the space between threads. Physics The engineer can select any class for the male and female threads to achieve his design goals. | Difference Between UNF and UNC Thread | CNCLATHING, Guide to Design and Machining Thread: How to Cut an Internal & External Thread? endobj 6 0 obj 0000010391 00000 n endobj Thread Size: Tap Drill (mm) Thread Size: Tap Drill (mm) Thread Size: Tap Drill (mm) M4 x 0.35. [citation needed]. as screw size. The terms coarse and fine have (in this context) no relation to the manufacturing quality of the thread. %PDF-1.7 Metric Thread: Metric is one of the first internationally agreed general-purpose thread types. 3 0 obj ISO metric threads consist of symmetric V-shaped thread. You can target the Engineering ToolBox by using AdWords Managed Placements. on a bolt), the major diameter Dmaj and the minor diameter Dmin define maximum dimensions of the thread. H = P ( 31/2 / 2 ) = 0.866025 P Metric External Thread Chart Limiting Dimensions for M Profile: Thread Designation: Pitch, p . Some of our calculators and applications let you save application data to your local computer. (e.g. An example of data being processed may be a unique identifier stored in a cookie. This is also referred to as the "major" diameter in the information below. Beam Deflections and Stress The ISO metric screw thread family is a series of general-use, 60 straight threads. Let us take an example now - a 3/8-16 (coarse) thread size has a 3/8" nominal major diameter and 16 thread per . number (e.g., #10 or No.10). ASME B1.1 If no characters follow the M and diameter, it means that all the other parameters are according to the default as defined in ISO 965-1: The ISO Metric Thread System consists of two series: The below charts show all the possible thread size combinations of diameters/pitch as defined in ISO-261. Civil Engineering Finishing and Plating (adsbygoogle = window.adsbygoogle || []).push({}); Copyright 2000 - 2.Thread sizes in metric are specified by diameter and pitch. This is to ensure compatibility with mating components. Civil Engineering M16 x 1. United Inch Screw Threads Per ASME B1.1. 3.50. All units in mm. click on the images UNC-UNF SUPPLIERS BSW-BSF SUPPLIERS HISTORY OF THREADS THREAD ROLLING VIDEO quick view The Thread Rolling Process 54 0 obj <>stream All units in mm. Vibration Engineering Electronics Instrumentation Engineering Forum However, here's a quick overview from the chart: The M2 screw size has a diameter of 1/16 inch. Cookies are only used in the browser to improve user experience. These are the M Profile limiting Dimensionings. Gears Design Engineering Thread sizes are given in nominal sizes, not in actual measurement. 15.0. All units in mm. Metric Fasteners use a thread Pitch. Thermodynamics In German, DIN 931: M1,6 to M39 Hexagon head bolts (Product grades A and B), IS 9519: Fasteners - Hexagon products - Width across flats, Metric screw thread profile, dimensions and tolerances, https://en.wikipedia.org/w/index.php?title=ISO_metric_screw_thread&oldid=1137685462. A thread's pitch size is the number of threads per inch or the distance between threads on metric thread types. 0000007146 00000 n Hexagonal (generally abbreviated to "hex") head widths (width across flats, spanner size) are for DIN 934 hex nuts and hex head bolts. Blue Background Default ClassesGreen Background First Choice Classes.Yello Background Second Choice Classes. For example, an M10x1.5 (coarse) thread has a 1.5mm pitch, while an M10x1.25 (fine) thread has a 1.25mm pitch. Vibration Engineering For inches, this is done The "M" designation for metric screws indicates the nominal outer diameter of the screw thread, in millimetres. METRIC BOLT SIZE CHART - Stud Bolt to Nut Size Chart Metric Stud Bolt To Nut Size Chart Our metric stud bolt to nut table is meant to help determine the correct size bolt or nut for your purpose. ISO Hardware Engineering Data xref (Valid above 1.6 mm / 0.063) Direction - Right-hand thread. METRIC THREAD -- EXTENDED THREAD SIZE RANGE http://mdmetric.com/tech/M-thead%20600.htm[2014-04-03 09:32:56] MARYLAND METRICS THREAD DATA CHARTS ISO Metric Thread Charts ISO Metric Thread Chart | Metric Thread Dimension The choice of the recommended class is made according to two parameters: Type your thread description in the Search Box. UNEF - Ultra Fine pitch thread. ANSI/ASME B1.13M-1995. This is because extra fine threads are more resistant to coming loose from vibrations. Machine Design Apps 0000000016 00000 n Siz e Gau ge Si e ge BRITISH No. %%EOF BA threads are used for sizes under 1/8 inch the older British fastener system. <> ]W?ozKWkg7Z):J93N-6.\m[(RNJl%\XM?|^^P?"ruXvAot/guxfa8|dqL$|_^d:|vLW7?y5e.,&~eYie[/+;iV3Uk~DT^67_^,*wAU,|iG{Loug]L4ib]]p`n:(|N ;7lO/mj^0ZKL~bcsT?r/zb&E|/O\V'+Z;qqf~\/x c78Owv^o;$^?_/wq&\n|/ fZ\NQG#O1 yo?@P84J_]nx&_X^Wq]Pf9v t~)H?S>t.ALr.)\. Superfine pitch metric threads are occasionally used in automotive components, such as suspension struts, and are commonly used in the aviation manufacturing industry. Do not use these values for standard metric internal thread design. Below are some common spanner (wrench) sizes for metric screw threads. ), for this chart you can just drop the 'M' from the front and add an extra at the back (M3 = 3mm, M4 = 4mm. <> Measure thread spacing. Fluids Flow Engineering These thread sizes and classes represent bolts and screws, as well, as other standard internal threads. THREAD CHART 10b Thread Charts Screw Threads Threaded fasteners thread detail with eight charts and video showing thread production with a link to a history of threads. 0000001347 00000 n The design principles of ISO general-purpose metric screw threads ("M" series threads) are defined in international standard ISO 68-1. Applications and Design View our thread pitch chart here to get more ideas about different thread sizes. Plot No. <> To understand classes, you first need to understand the terms Allowance (Sometimes referred to as deviation) and Tolerances. Some of our partners may process your data as a part of their legitimate business interest without asking for consent. 0000005898 00000 n Heat Transfer Inch thread sizes are specified by diameter and threads per inch. Plastics Synthetics The formal values must be obtained from ISO 965-1 or from the below chart. Tap size: Basic major dia (mm) Basic major dia (inch) mm per thread: Drill size (mm) Drill size (inch) UNC - Coarse Putch thread. Hardware, Metric, ISO Minor Diameter Female Thd. Do not use these values for standard metric external thread design. [2] Each thread is characterized by its major diameter, D (Dmaj in the diagram), and its pitch, P. ISO metric threads consist of a symmetric V-shaped thread. 1) For metric threads pitch is the distance between threads. The ISO metric screw thread is the most commonly used type of general-purpose screw thread worldwide. Pressure Vessel Continue with Recommended Cookies, * Easy access to all the data charts that appear on this page. <> Mechanical Tolerances Specs ISO 68:1973 ISO general purpose screw threads - Basic profile, ISO 261:1973 ISO general purpose metric screw threads - General plan, ISO 262:1973 ISO general purpose metric screw threads - Selected sizes for screws, bolts and nuts, ISO 724:1993 ISO general-purpose metric screw threads - Basic dimensions, ISO 965-1:1980 ISO general purpose metric screw threads - Tolerances - Part 1: Principles and basic data, ISO 965-2:1980 ISO general purpose metric screw threads - Tolerances - Part 2: Limits of sizes for general purpose bolt and nut threads - Medium quality, ISO 965-3:1980 ISO general purpose metric screw threads - Tolerances - Part 3: Deviations for constructional threads, ISO 1502:1996 ISO general-purpose metric screw threads - Gauges and gauging. Friction Engineering Understanding Inch & Metric Thread Callouts. The design principles of ISO general-purpose metric screw threads ("M" series threads) are defined in international standard ISO 68-1. endobj 12 0 obj Metric Thread Size Chart Product Table Tap Size Diameter (in) Diameter (mm) Thread Count (TPI) Thread Pitch (mm) Tap Drill Size M24x1 0.9449 24.0000 ~26 1.000 23 mm M24x1.5 0.9449 24.0000 ~17 1.500 22.5 mm M24x2 0.9449 24.0000 ~13 2.000 22 mm M25x2 0.9843 25.0000 ~13 2.000 23 mm endobj 7 0 obj xms$+B OO Skip to content. The table below indicates some of the most used coarse threads up to size M 68. Metric thread specifications are different because . 0 That is, an M6 screw has a nominal outer diameter of 6 millimetres and will therefore be a well-located, co-axial fit in a hole drilled to 6mm diameter. Diameter is also known Important: Ensure that "Actual size" (no page scaling) is selected when . The ThreaDoctor includes 3 sub-apps: Metric Thread Calculator, UN thread Calculator, and NPT thread Calculator. All rights reservedDisclaimer | Engineering Calculators Hardware, Imperial, Inch In all other cases, calculations must be made manually according to the below formulas or by our Threading Calculator, * For threads over 1.4 mm and classes 5H & 6h for threads up to and including 1.4 mm. Lubrication Data Apps HVAC Systems Calcs | Contact Privacy Policy, Home The tolerances TD for internal threads and Td for external threads is derived from the class. We don't save this data. Materials and Specifications The thread angle is 60o and the thread depth is 0.614 x pitch. 0000019519 00000 n These are the M Profile limiting Dimensionings. To view Metric translation click the Thread Link UNEF Series Basic Dimensions chart Metric thread callouts are fundamentally different because the thread pitch is specified instead of threads per inch or per mm. The ISO Standardisation Authority defines strict specifications metric threads. Section Properties Apps Click the Thread Link to get the Full Thread Data for all classes in Inch and Metric units. ANSI/ASME B1.13M-1995. Major Diameter mm d=D. In the ISO metric system a decimal point is made with a comma instead of a period. M10 x 0.75. Pitch is the distance between adjacent thread crests. endobj 10 0 obj The relationship between the height H and the pitch P is found using the following equation where is half the included angle of the thread, in this case 30:[3]. Manufacturing Processes The printable fastener tools series also includes general charts and tools for identifying and measuring fasteners, including a ruler and thread gauge. The 1st choice column follows the R10 series from ISO 3, while the 2nd choice column is rounded off values from the R20 series from ISO 3. Structural Shapes The M5 screw size has a diameter of 1/8 inch. Plastics Synthetics 0000016080 00000 n Where: H = P ( 3 1/2 / 2 ) = 0.866025 P or The metric thread sizes are different from the inch thread sizes. 2023, by Engineers Edge, LLC www.engineersedge.com [1] They were one of the first international standards agreed when the International Organization for Standardization (ISO) was set up in 1947. pitch. <> Electronics Instrumentation The thread pitch is the distance between each thread in mm. For example, a 10-24 screw has 0.190" thread diameter and has 23 threads per inch.