Ode to Machinists Handbook

The Machinery’s Handbook is a wonderful tool.  Although it is often called the machinists handbook, it is a tool that every engineer should also own.  Beyond machinists and engineers, it is a tool that everyone should be aware of its existence.  I came across the handbook early in my career when a colleague pulled out the book and looked up something.   I was hooked at that moment.  I borrowed his book and looked through the myriad of offerings in the book.

I learned what a grade 8 bolt was.  Not only that it was not a grade A bolt – but what it strength was, and when to use them.  I learned how to look at the markings and identify grade 8;  6 dashes with the circle.

Grade 8 Bolt - 5 Radial Lines

I also learned that bolt strength designation is much like women’s clothing sizes: 2, 5, 5.2, 7, 8.   Although these numbers appear random, the handbook walks through the math to explain how these numbers are calculated, and why they are not sequential.  No such standard or logic exists for women’s clothing sizes.

Fastener types and specification, material properties, gear information – all that can be found in the handbook.  Bearing fits and tolerances are critical and specifically spelled out in the handbook.

When I tour a machine or rebuild shop, one of the things I look for is the machinery’s handbook on desks or in toolboxes.  If I don’t see one, I ask about how tolerances are calculated.  Occasionally the shop will reference posters published by the component or OEM manufacturer.  But often, the answer is ‘everyone just knows’.  Even if someone has been rebuilding the same equipment for 20 years, I still want to see the charts that they are referencing.  Even if they remember the tolerance requirements for equipment they see regularly, no one has memorized everything in that handbook.  Machinists, rebuilders, and engineers who do not regularly check to confirm their assumptions and calculations are disrespecting their craft and customers.

There are other tools that provide the same information, but there is nothing as neatly packaged as the handbook.  I urge everyone to have a copy and regularly glance through it, or reference it when needed.  The 30th edition is available and it comes in hardcopy or e-copy.  There are older versions available on line, and there is even an app to help with calculations.   The point is, this is a wonderful reference book, do not go through life “just knowing” confirm what you know, and maybe even learn something new, by using this book.

Does anyone have other must-have reference books that they looking for when auditing shops?



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