What the GDTP Exam Tests That 2009-Era GD&T Books Miss

The free Kindle days have started, and they run for five days only. If you are preparing for the GDTP with notes written for the 2009 standard, today is the day to fix that for nothing.

The quiet trap in older study material

The GDTP exam follows ASME Y14.5-2018. Plenty of training material, and plenty of second-hand books, still teach the 2009 edition. Most of the two editions agree, which is exactly why the differences hurt: a candidate who learned the older rules answers confidently and loses the mark.

Three changes come up again and again. The symmetry and concentricity symbols were removed from the 2018 standard, so a drawing that needs the median points of a feature controlled now does it another way. The independency symbol arrived, a small circled I that tells the reader Rule #1 does not apply to that feature of size. And the dynamic profile modifier, a small triangle, lets profile refine the form of a surface without also tightening its location.

One short example

Picture a shaft with a keyway that must sit centred on the shaft axis. A 2009-style drawing might put a symmetry tolerance of 0.1 on the keyway, referenced to the shaft as datum A. Under 2018 that symbol no longer exists. The same intent is written as a position tolerance on the keyway width, 0.1 to datum A, and because position applies to a feature of size the designer may now add the maximum material condition modifier when the fit allows it. That bonus tolerance was never available with symmetry.

An exam question built on this does not ask you to recite the change. It shows the old callout and four ways to express it, and only one of them is valid under the standard the exam uses.

How to use the free copy this week

Start with the chapter on what changed between the two editions, then work its questions before anything else. If you already own an older book, keep it for the fundamentals it explains well, but mark every page that uses symmetry or concentricity so you stop practising a callout the exam will treat as invalid. Then sit one of the full practice exams under time, because the 2018 questions are rarely about a single rule and usually about two rules meeting on one drawing.

What the book gives you

The guide has 21 chapters on the 2018 body of knowledge, each with an original drawing for every concept showing what a callout allows and what it forbids. Every chapter ends with 12 exam-style questions that explain why the tempting wrong answer is wrong. Two original 150-question practice exams, one for Technologist and one for Senior, close the book, along with a formula sheet, a 159-term glossary and a study tracker.

It is an independent study guide by a working engineer, not an ASME publication, and it supports your preparation rather than promising a result.

All four books in the promotion

• GD&T Professional Exam Guide Kindle ebook on Amazon
• Practical Airframe Stress Analysis, Vol. 1 Kindle ebook on Amazon
• Practical Airframe Stress Analysis, Vol. 2 Kindle ebook on Amazon
• Python for Aerospace Stress Engineers Kindle ebook on Amazon

More for GDTP candidates

The book’s card is on the books page, with the paperback and the free reader’s companion of chapter quizzes. For timed practice beyond the book, the ASME GDTP Complete Exam Kit adds full practice exams scored by topic. Every announcement of this promotion is collected on the announcements page.