Knowledge bag for when you're in trouble: Nominal sizes and diameters of pipe threads
Common questions and concerns about screws resolved! Screw standards edition.
YAMAWA will respond to the inquiries received from customers. This document also includes some minor speculations. 【Contents】 ■Inquiry I know how to express unified screws like "1/4-20UNC" and "1/2-13UNC" in inches. For the "1/4-20UNC" external thread, I understand that the outer diameter reference dimension is 1/4 of 1 inch (25.4mm), which is "6.35mm." However, the outer diameter reference dimension for the pipe thread "G1/4-19" (old standard: PF1/4-19) is 13.157mm, which does not match at all. How should I understand this? *For more details, please refer to the PDF document at the link below.
Inquire About This Product
basic information
【Other Published Content】 ■Response ■A Little Speculation ■Comparison Table of Actual Dimensions and Inch Dimensions of Pipe Taps *For more details, please refer to the PDF materials or feel free to contact us.*
Price range
Delivery Time
Applications/Examples of results
For more details, please refer to the PDF document or feel free to contact us.
Company information
Since our founding in 1923, the YAMAWA Group has been dedicated to researching and developing the highest quality cutting tools—such as taps, dies, and center drills—to meet the ever-evolving technological needs of the market. Guided by the founding spirit of contributing to the progress and development of Japan’s machinery industry, we continue to pursue excellence as specialists in cutting tools. YAMAWA products are trusted across a wide range of industries, from space exploration and aerospace to automotive, shipbuilding, machine tools, home appliances, and IT-related sectors—both in Japan and worldwide. Staying true to our philosophy of providing “Reliable Screw Threads”, we constantly refine our technology and quality management systems. As Japan’s first tap manufacturer to obtain ISO 9001 certification, we take pride in our heritage while striving to advance innovation and deliver cutting tools that support manufacturing around the world.
![[Fine U-Nut Delivery Case] Conveyor](https://image.mono.ipros.com/public/product/image/e60/2000427103/IPROS10633359386401646396.jpeg?w=280&h=280)
