How ISO Metric Standards Cut Manufacturing Costs

The ANSI preferred metric sizes are identical to those in the ISO 497 R"20 rounded series selected years ago. The intent of the number series shown is to reduce the number of standard sizes for screw threads, steel plates, steel sheets, round steel bars, lifting capacities, hydraulic cylinder diameters, etc.

The preferred size range from 4 through 40 millimeters may be extended to cover smaller or larger sizes by just multiplying or dividing sizes shown by 10.    For instance, 60-mm sizes would be a preferred choice as would 2.5-mm devices.

For example, the eleven first choice fastener sizes shown in Figure 2 are all metric coarse thread. They are recommended to replace the 53 other thread sizes listed. Furthermore, the four sizes shown in bold are according to the R5 series of preferred sizes shown in Figure 1. The cost reduction becomes substantial when you figure thousands of dollars savings for each unique fastener size that can be eliminated from the product design.

The metric coarse thread pitch is slightly smaller (finer) compared to the customary unified coarse thread pitch. For example; the metric coarse thread M8 has the thread pitch 1.25 mm and the inch thread 5/16 – 18 has the thread pitch 1.41 mm.

Preferred metric, standard metric and customary inch steel plate sizes are shown in Figure 3. It is recommended selections be made from the preferred metric column marked first and second choice. Selection of first choice sizes will further reduce the number of plate sizes from eight to four. This is a huge cost reduction compared with the 19 inch plate sizes that used to be stocked by a large USA company.

You probably do not have to reduce the numbers of ropes used to hold balloons , but the Renard series of sizes gives you a great tool to help cut cost in manufacturing.

Preferred Tolerances

ISO tolerancing standards offer industry a savings opportunity. New software programs make those standards more easily available and can maximize those opportunities and save time as well. Rating basic sizes and tolerances helps reduce the number of hole and shaft sizes specified.

Hole basis fits with hole tolerances identified by ANSI and ISO as H11, H9, H8 and H7 help rationalize on standard cutting tools and gages, whereas shaft basis fits with shaft tolerances h11, h9, h7 and h6 help rationalize on standard round steel bars available in all major industrial countries. See Figure 4.

The ANSI standard and software have ten preferred hole and shaft basis fits ranging from LOOSE RUNNING to FORCE fits shown in Figure 5. It is recommended you use shaft basis fits in most applications since it helps you reduce the cost of cutting tools and gages. However, it may be to your advantage to use shaft basis fits where you have a standard shaft size in the machine with bearings, couplings, sprockets, gears, and other components attached to it. Examples include knitting , printing , and farm machines.

Each preferred fit has the same clearance or interference for hole or shaft basis fit listed on the same line.

The system needs no particular CAD software. Users still must use standard hole or shaft sizes in order to save in manufacturing. Engineers in the EU countries have taken advantage of the system for over 60 years, and many users there still use published tables or recall the allowances from memory.

The ANSI B4.2 standard shows tables of allowances for the ISO tolerance zones, and limit dimensions for the preferred hole, shaft tolerances and the first choice sizes. In the USA, these tables are published in the Machinery's Handbook and the METRIC STANDARDS for Worldwide Manufacturing books . You can save a lot of time searching tables and trying to understand the system by using the two programs that have been developed. You also save time comparing the new metric fits with the old customary inch fits, and you can quickly modify proposed fits to give similar conditions as those proven in use. For more information about the ISO tolerancing system and software's, just enter one of the web pages listed below on the Internet. Software’s are easy to install and use, and run on computers with Windows 95 or NT.

ISO screw thread tolerances are the medium tolerance class 6H for nuts and 6g for bolts as shown in Figure 6. The identical nut tolerance 6H is used for both close- and medium-fit nuts. The close bolt tolerance 4g6g is recommended for set screws and socket head screws and the fastener user taps identically threaded holes for all threaded fasteners,

Tolerances for other steel products are typically greater in many ISO product standards, and may sometimes be twice as large as those used for customary inch products. Refer to specific standard in order to find the tolerance applicable. A large number of ISO steel product standard tolerances are shown in the referenced metric standards book, and a major steel producer use it to prepare bids for sales outside USA.

Material Quality

Due to extensive work and negotiations by the fastener industry, we have worldwide agreements on threaded fastener standards. The ISO 898/I on strength classes for fasteners was published years ago, and it covers the most frequently used classes ISO 5.8, 8.8, and 10.9, which correspond to our customary grades SAE 2, 5, and 8 as shown in Figure 7.

Other important ISO strength classes; ISO 4.6, ISO 4.8, ISO 9.8 and ISO 12.9

Unifying steel material quality standards worldwide is a tremendous task. ISO has done an outstanding job through its many technical committees. Over 60 standards on the subject have been published and more are being developed. The EU has eliminated many differences between German, French, British, Italian and other European steel designations by issuing EN (European Norm) standards designated DIN EN, NF EN, BS EN, UNI EN, etc. and published in each country’s language. For specific details about the ISO fastener strength classes or material quality standards see the referenced metric standards book.

Industry Users of Metric Standards Book, Software’s or Training Program

1.   Daniel Graham wdgraham@hfsdayton.com ; Phone 937 278 2651; Fax 937 274 5719 Standards Engineer (User of all metric products; Global metric program, book and software's) Heidelberg Finishing Systems, Inc 4900 Webster Street Dayton OH 45414         

2.  Richard Breton bretonr@mail.hwpi.com ; Phone 603 743 5515 x2246; Fax 603 749 5219
Associate Principal Engineer (User of metric book and software's)
Heidelberg Web Press, Inc
121 Broadway
Dover NH 03820

3.  Gian L Argentati gian_argentati@ingerrand.com ; Phone 908 859 7524; Fax 908 859 7707
Manager, CEIS (Sponsor and user of metric book and software's)
Ingersoll-Rand Co
942 Memorial Parkway
Phillipsburg NJ 08865

4.  Robert W Noth rn49734@deere.com ; Phone 309 765 4072 ; Fax 309 765 9860
Manager, Engineering Standards (Sponsor and user of metric book and software’s )
Deere & Company
John Deere Road
Moline IL 61265-8098

5.  LeRoy C Prichard lprichard@nucor.com
VP Steel Technologies ; Phone 704 366 7000 ; Fax 704 362 4208
Mr. F Kenneth Iverson ; Phone 704 366 7000 ; Fax 704 362 4208 (Sponsor and user of metric book and software's)
Chairman
NUCOR Corporation
2100 Rexford Road
Charlotte NC 28211

6.  Rick Novara ricknovara@compuserve.com ; Phone 704 921 0303 ; Fax 704 921 0304 , Novara Engineering
12325 Mallard Ridge Drive
Charlotte NC 28269
Rick wrote the following about the ISOTOL; "ISOTOL interfaces just fine with AutoCAD. The software works just fine with MDT. It is straight forward and easy to use. It is a simple program that would be of great value to anyone that needs to figure tolerancing".

7.  Mike E Yamat myamat@cooperpower.com ; Phone 414 768 8303 ; Fax 414 768 8236 (User of metric book and software’s) Cooper Power Systems , 2800 9th Ave , S Milwaukee WI 53172

8.  Stan I Jakuba sijakub@aol.com ; Phone 860 521 7924 ; Fax 860 561 4662 (User of both editions of metric book and ISO tolerancing system) Metric Consultant , S. I. Jakub Associates  43 Westbrook Road  West Hartford CT 06107

References

The newKOK ISOTOL ™ Computer Tolerancing Software    (Price $85   Part no. RKOK-CDTOL ) provides the powerful tool you need to reduce cost in manufacturing and engineering.   The new KOK ISOGAGE ™ Computer Software for Gages    (Price $135   Part no. RKOK-CDGAGE ) provides the powerful tool you need to reduce cost of gaging. This software provides limit dimensions for plug and ring GO-NOGO gages for all tolerances in the ANSI and ISO standards.

Place your order on the Internet  or mail the Order Form to  Maryland Metrics