Episode 66 — Nuts and Bolts


NutsAndBoltsWe discuss some of the considerations that go into choosing a threaded fastener in this episode of The Engineering Commons podcast. It can be more complicated than you might think!

  • Carmen has a tendency to make up words every now and then; this leads to quizzical reactions from his co-workers.
  • For many years, Jeff has used the Machinery’s Handbook as his reference for most issues related to threads and threaded fasteners.
  • We let slip a million-dollar idea; a blank book that lights up with content when turned on. How many years until this becomes a reality?
  • The primary reason for using a threaded fastener is to allow for the assembly and disassembly of components.
  • If disassembly is not required, one might be better off by welding, soldering, brazing, riveting, swaging, or casting components together.
  • Common threaded fasteners include bolts, screws, nuts, and studs.
  • Despite the differing definitions about what constitutes a screw and what constitutes a bolt, we go with a distinction in usage: a bolt needs a nut, while a screw does not.
  • When selecting a screw or bolt, one usually starts by looking at the strength needed in two places; the fastener itself, and the threaded connection.
  • Plain washers are used to distribute forces that might deform or mar one of the clamped components.
  • The cylindrical portion of a bolt that extends from the underside of the head to its point or end is called a “shank.”
  • Lead is the linear advance of threaded fastener as it makes one complete rotation about its longitudinal axis. Pitch is the spacing between adjacent threads on a threaded fastener.
  • RightTighty, Lefty Loosy” is a mnemonic device for remembering which way to turn a threaded fastener so as to tighten or loosen the connection.
  • Measuring the diametric distance across the tops (or “crests”) of an external thread reveals the “nominal” or “major” diameter of that thread.
  • A notation of “M10 x 1.5″ designates a thread that has a major diameter of 10 mm, and a lead of 1.5 mm.
  • While metric fasteners identify the lead directly, English threads give the inverse of the lead. Thus, the notation “1/4-20″ indicates a thread having a major diameter of 0.25 inches, and 20 threads per inch (a lead of 0.05 inches).
  • In the United States, the primary thread reference is the Unified Thread Standard.
  • Most of the world uses the ISO standards for thread forms and sizes.
  • When selecting a threaded fastener, it’s good practice to use a coarse pitch unless you have a good reason for not doing so. Fine pitch threads are normally reserved for those cases when vibration might tend to loosen the threaded connection.
  • In the American system, sizes below 1/4 inch are identified by numbers that decrease as the nominal diameter decreases.
  • External threads may be machined or rolled; internal threads on machined parts are typically drilled and tapped.
  • A rule of thumb is that the axial thread engagement should be at least 1x the nominal diameter for steel, 1.5x the nominal diameter for cast iron, brass or bronze, and 2x the nominal diameter for aluminum or zinc.
  • A “blind” tapped hole allows for an internal thread that doesn’t go all the way through a component.
  • Many different head types are available in threaded fasteners.
  • A countersink is a cone shaped hole, while a counterbore is a flat-bottomed hole.
  • Establishing the proper preload is an important part of designing a threaded connection.
  • The bolting process can be modeled as going through the stages of rundown, alignment, elastic clamping, and post-yield.
  • Much of the torque applied during bolt tightening goes to underhead and thread friction, rather than bolt preload.
  • One means for determining proper bolt torque is the turn-of-the-nut method.
  • Jeff’s father taught him the criss-cross method for tightening bolts in a circular pattern.

Thanks to Scott Robinson for use of the photo titled “Jetty Bolts.” Podcast theme music by Paul Stevenson.

Episode 65 — A Whole New Engineer


AWNEcoverIn a lively discussion of how to best prepare today’s engineering students for tomorrow’s engineering challenges, we talk with Dave Goldberg and Catherine Whitney about their new book, A Whole New Engineer.

  • Any “dot-com” dreams that Brian harbored during his college days have long since dissipated.
  • Carmen suggests that ridiculous buyout amounts are now measured in units of “Instagrams,” with one Instagram equaling one billion US dollars.
  • Engineers must constantly expand and refine their skills; Jeff notes that over his career he has moved from drawing prints on a drafting board, to working with 2D CAD packages, to implementing 3D models.
  • Our first guest for this episode is Dave Goldberg, who appeared previously on Episode 37, in which he talked with us about the evolution of engineering roles over time. Dave leads ThreeJoy Associates, a consulting firm that advises educational institutions.
  • Our second guest is Catherine Whitney, a New York-based writer who has previously written or co-written more than forty books on a wide range of topics, including nutrition, social issues, and entrepreneurial success.
  • Dave argues that the “old engineer” was entirely appropriate in a time of expertise and narrow technical focus. However, a “new engineer” must reach across disciplinary boundaries, and solve problems in domains that lack recognized experts.
  • Domenico Grasso has written about the importance of taking a holistic approach to engineering education and practice.
  • Catherine mentions the myth of the “lone genius.”
  • Dave makes a passing reference to disruptive innovation, a term coined by Clayton Christensen to describe the manner in which existing markets and institutions may be displaced through the introduction of new technologies.
  • Current technological trends have led to people “bowling alone,” a phrase the describes how individuals are disengaging from the social and political networks that comprise local communities.
  • Richard Feynman’s physics lectures are mentioned by Dave.
  • The story of Jack Andraka is offered as an example of how academic expertise is being undermined over time.
  • Jeff notes differences between “just-in-time” and “just-in-case” learning.
  • Dave notes that more than one version of the Grinter Report (pdf) was proposed back in the mid-1950s.
  • Our guests mention a study by Kristen Wolfe, later referenced by Woodie Flowers of MIT, that looked at the skills used by mechanical engineers five years after they graduated from college.
  • Carmen references one of his favorite books, The Art and Science of Analog Circuit Design, by Jim Williams.
  • An engineering leadership program at the University of Texas El-Paso is cited by Dave as an example of aspiration-specific education.
  • Fernando Flores has written about the power of words in motivating action and establishing commitments.
  • Dave was involved in establishing iFoundry at the University of Illinois, while co-author Mark Somerville was (and is) a faculty member at Olin College.
  • References are made to Daniel Pink’s book Drive, and to Edward Deci’s work on intrinsic motivation (one example of which is his book Why We Do What We Do: Understanding Self-Motivation.
  • A TED talk by Sugata Mitra describes how Indian children were able to teach themselves when provided nothing more than a computer.
  • Harvard University’s Eric Mazur has championed the concept of peer instruction, in which college students teach one another.
  • Dave introduces us to the concept of Junior Enterprise, a student-led consulting firm.
  • In the coaching world, there exists the notion of polarity management, in which distinctions are made between problems and unsolvable paradoxes.
  • Big Beacon is a social movement for transforming engineering education.
  • More information about the book can be found at wholenewengineer.org.
  • Catherine can be reached via email: catherinewhitney -=+ at +=- mac.com.
  • Listeners can contact Dave via email: deg -=+ at +=- bigbeacon.org. He is also active on Twitter and Facebook.
  • Finally, one can follow the happenings at Big Beacon via their website, on Twitter, or on Facebook.

Thanks to Dave Goldberg and Mark Somerville for use of their book cover image. Podcast theme music by Paul Stevenson.

Episode 64 — Reddit Questions


questionsignWe answer nine questions about the engineering profession, gathered from a quaint little website called Reddit, in this episode of The Engineering Commons. You may notice a common thread in our responses, as there is rarely a clear-cut solution, and the answer often depends on the situation!

Thanks to Colin Kinner for the photo titled “Question mark sign.” Podcast theme music by Paul Stevenson.

Practical insights for the engineering crowd