SAE/Metric fasteners

[Rick]

Anyone out there have a good link to an elementary discussion of the differences in SAE and Metric?

Rick

[Charlie Bress]

Elementary discussion is: SAE has the body diameter in inches or fractions thereof. The small stuff is numbered, but descriptions of these abound. The larger numbered ones have thicker bodies. They range from number 12 to 000 or smaller. the real small ones get into jewelers sizes the number 12 is usually followed by 1/4". These SAE fasteners will have a second number (the pitch) which is the number of threads per inch. There are coarse and fine threads per inch. Usual use for fine is to enhance vibration resistance.

Metric sizes are in millimeters of body with followed by the pitch. which is in millimeters.

They are not interchangeable.

SAE are generally used in USA and other backward industrial countries. Most of the rest of the world uses the metric sizes.

The greatest joy you can have is working on a supposedly American car like Ford or GM etc. and having a mix of SAE and metric fasteners. Or if it was made in Europe or Asia it might be all metric. This has been a boon for the tool manufacturers who now have duplicate lines of tools, one for SAE and one for metric.

For a comparison of the two systems look at any number of web sites. For openers try

Charlie

[Rick]

Thanks Charlie...

Rick

[Richard J Kinch]

See _Machinery's Handbook_. It's a lot more complex than just different sizes and units of measure.

[John Grabowski]

I don't have anything to contribute to a discussion, but I do have a chart of drill and tap sizes with their metric equivalents that you might find useful. Here's the free link:

John Grabowski