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Speaking of Precision

Speaking of Precision is a knowledge preservation and thought leadership blog covering the precision machining industry, its materials and services. With over 36 years of hands on experience in steelmaking, manufacturing, quality, and management, Miles Free (Milo) Director of Industry Research and Technology at PMPA helps answer "How?" "With what?" and occasionally "Really?"

Machining for Hobbyists: Getting Started

Posted August 28, 2015 1:00 PM by Milo
Pathfinder Tags: Book hobby machining manufacturing

Surprisingly complete and easy to understand book that can be used to supplement training on the job for beginners, and a nice reference for those with a year or so on the job. Machining and measurement principles and techniques clearly explained.

A nice easy to understand supplement for newcomers to machining.

I was genuinely surprised to find some really great nuggets like "the Basic Nomenclature of Measurement " which clearly defines:

  • Nominal size
  • Allowance
  • Limits
  • Tolerance
  • Basic Size
  • Unilateral Tolerance
  • Bilateral Tolerance
  • Precision
  • Accuracy

…in just a little over a page.

Nice graphics, sample calculations, and well done explanations on how to read a micrometer, vernier, as well as tables with feed and speed data for various types of materials for specific machining operations. very focused coverage of the essentials of the topics.

Do not confuse this book for a hobbyist project catalog.

This is a very clear and understandable text that explains the "how, why, and what" of machining and the use of tools of our craft.

Nice photos too.

What I like the most is how the author really distills the information down to useful essentials. And makes them understandable.


Editor's Note: CR4 would like to thank Milo for sharing this blog entry, which you can also read here.

3 comments; last comment on 08/28/2015
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Plan Do Study Adjust--The Engine of Continuous Improvement

Posted July 21, 2015 12:00 AM by Milo

Continuous improvement is of necessity in the very DNA of our shops.

Continuous improvement is in our DNA

In ISO 9000:2000 Section 8.5.1 read :

The organization shall continually improve the effectiveness of the quality management system through the use of the quality policy, quality objectives, audit results, analysis of data, corrective and preventive action, and management review.

In TS16949:2009 it read:

8.5.1.1 Continual Improvement of the Organization

The organization must define a process for continual improvement .

8.5.1.2 Manufacturing Process Improvement

Manufacturing process improvement must continually focus on control and reduction of variation in product characteristics and manufacturing process parameters.

The standard defined continual improvement as : "recurring activity to increase the ability to fulfill requirements."

Recurring activity. To me that means cycle.

It is not a wheel, PDSA is a continuous cycle of cycles!

Karen Martin shared this graphical representation of PDSA in her book The Outstanding Organization.

Plan. Do. Study. Adjust.

This is the process of continuous (continual) improvement.

Plan. Do. Study. Adjust.

It's what we do.

If this sounds familiar, it is because I first wrote about this here Karen Martin

DNA Photocredit


Editor's Note: CR4 would like to thank Milo for sharing this blog entry, which you can also read here.

1 comments; last comment on 07/24/2015
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Buy American: What Does That Mean?

Posted July 14, 2015 11:00 AM by Milo

Industry Week Reports that "Ford Plans Move for Compact Car Production Out of US." What exactly does "Buy American" mean these days?

In 2009 , While two of the three bankrupt thinking Detroit firms were using the government to bully their way through Bankruptcy, running roughshod on their suppliers and creditors, I wrote a piece about "The New Domestics."

Here are a few points that I made in that article:

  • More than 70 percent of the value added in a new car is provided by the suppliers, not the assemblers;
  • More than 300 companies have created jobs in Ohio as a result of the state's "New Domestic" auto industry;
  • Honda has plants or major operations in Alabama, California, Connecticut, Colorado, Georgia, Indiana, Iowa, Michigan, New Jersey, North Carolina, Ohio, South Carolina, Tennessee and Texas.
  • Mercedes has a plant in Alabama too.
  • And BMW has a plant in South Carolina.
  • Volkswagen has broken ground for an assembly facility in Chattanooga, Tennessee. (It's been making cars since 2011, employs 2000 people)

So what is an American Car?

  • One made by my friends and neighbors;
  • Made from materials and parts purchased locally;
  • One that the first digit of the VIN is a "1";
  • One that has more than 50% "domestic content;"

Want to know more about American Cars in 2015?

The MOST AMERICAN CARS

What is the US's leading auto exported abroad?

Surprise Answer

Industry Week Article

Thanks to Draplin Design for the neat graphic.

Camry Photo

Postscript- Not to diminish the role of Canadian Manufacturers- nor their vehicle assembly plants. PMPA members in Canada produce high volumes of high technology systems parts for the automotive markets- fuel injectors, anti-lock brake parts, fluid power system components and much, much more. But the irony of the whole Ford "Wrap ourselves in the flag while we really export your jobs" marketing is really the "driver" behind this post.


Editor's Note: CR4 would like to thank Milo for sharing this blog entry, which you can also read here.

8 comments; last comment on 07/17/2015
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6 Reasons Steel is Vacuum Treated

Posted May 15, 2015 10:00 AM by Milo
Pathfinder Tags: harden oxygen steel Vacuum

Vacuum treated (vacuum degassed) steel is used for critical applications that require steel with an exceptionally high degree of structural uniformity, internal soundness, and other characteristics which may be impaired by the effects of uncontrolled amounts of dissolved gases. Vacuum degassing treatments, along with various deoxidation practices are specified to control the amounts of dissolved gases in the steel. This post describes 6 benefits of vacuum treatment of steel.


Liquid steel after treatment in a Siemens RH degassing plant achieves improved properties.

Vacuum treatment of molten steel

  • Reduces Hydrogen content. This reduces the tendency of steel to "flake" or become "embrittled."
  • Reduces Oxygen content. This makes it easier for the steel to conform to restrictive microcleanliness requirements.
  • Improves the recovery and uniformity of distribution of alloying elements and other additives.
  • Helps control the composition of the steel closer than without vacuum treatment.
  • Results in higher and more uniform transverse ductility, improved fatigue resistance, and improved high temperature performance.
  • Can be used to achieve exceptionally low carbon content that are otherwise unobtainable by conventional means.

What are some situations where vacuum treatment is employed?

  • Large forgings and large cross sections where hydrogen would otherwise remain and contribute to flaking and embrittlement.
  • Bearings where uniformity throughout the section is important for critical performance.
  • Inverted delta, human critical safety applications where steel toughness and performance place high demands on the steels properties in all directions.

The removal of Oxygen by degassing is a challenge for the steelmaker, because this element is extremely reactive- it can exist in the steel in many forms, such as free oxygen, dissolved in the melt as a soluble nonmetallic oxide, can combine with carbon to form gaseous oxides, and it can exist as complex oxides in the accompanying slags and refractories in the process.

In post will describe some steel deoxidation practices and the types of vacuum degassing that are used in the North American steel Industry.


Editor's Note: CR4 would like to thank Milo for sharing this blog entry, which you can also read here.

2 comments; last comment on 05/17/2015
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Ra Is Different Than Rz

Posted April 10, 2015 11:15 AM by Milo
Pathfinder Tags: measurement Ra Rz surface finish

The methodology of measurement and what is measured are quite different. this is critical to understand if you will not be paid for your parts because the Ra you measured is not in fact the Rz surface profile that customer specified.

"Ra is calculated by an algorithm that measures the average length between the peaks and valleys and the deviation from the mean line on the entire surface within the sampling length. Ra averages all peaks and valleys of the roughness profile and then neutralizes the few outlying points so that the extreme points have no significant impact on the final results.

"Rz is calculated by measuring the vertical distance from the highest peak to the lowest valley within five sampling lengths, then averaging these distances. Rz averages only the five highest peaks and the five deepest valleys-therefore extremes have a much greater influence on the final value."- George Schuetz, Modern Machine Shop

"Ra is the arithmetical average value of all absolute distances of the roughness profile from the center line within the measuring length. Rz is the average maximum peak to valley of five consecutive sampling lengths within the measuring length. Ra averages all measurements and does not have any discriminating value in separating rejects from acceptable cylinders."- Swedev

And by the way the definition of Rz has also changed over the years. Which definition of Rz exactly is your customer using? How do you know?

You will find "Conversion Ratios" on the internet provided by well meaning people. But how useful can these be when the range said to be equivalent goes from 4:1, to 7:1 to 2-:1?

4:1 is equivalent to 20:1? Really? Not in my math class!

Smart shops will avoid using these "approximations in name only" and communicate with their customers to determine the customer's true need. Gambling on conversion factors that you found on the internet is not professional, it is an example of poor engineering practice, and it fails to serve and protect your customer.

Don't Do It!

Read this well written, not terribly mathematical treatment of the subject on MMSOnline

It's a classic.

Authoritative standards : Surface finish measurement procedures, general terminology, definitions of most parameters and filtering information can be found in American Standard ASME B46.1 - 2009, Surface Texture, and in International Standards, ISO 4287 and ISO 4288.


Editor's Note: CR4 would like to thank Milo for sharing this blog entry, which you can also read here.


Top 10 Facts About Leaded Steel Bars

Posted March 30, 2015 11:00 AM by Milo
Pathfinder Tags: leaded steel machining top 10

Leaded steel bars historically have been a mainstay raw material in the screw machining industry. As more applications and newer technology move away to non leaded steel applications, we thought that a brief refresher about Lead and its role in our shops might be timely.

The 0.15- 0.35 weight percent of lead contained in these bars helps them machine 25% faster with less power required.

  1. Leaded steel bars are standard steels and widely available. In the U.S. 12L14 is the predominant grade. 11SMnPb30, 11SMnPb28, 9SMnpb28, and 9SMnPb36are German designations nominally equivalent to 12L14.The Chinese version of 12L14 is Y15Pb; Japanese nominal equivalents include SUM22L, SUM23L, andSUM24L.
  2. Leaded steels are selected for use for the savings achieved in producing parts by machining.
  3. Leaded steels are not appropriate for all parts- and parts with low amounts of stock removal may not create any noticeable savings.
  4. Today's Leaded steels are more consistent, more uniform, than they were when produced by the ingot process.
  5. The decision to use Leaded Steels for a specific part must be based on the economics for that part- volume, stock removal, part complexity, tolerances required, surface finish needed are all factors that contribute to that economic calculation.
  6. There is no sacrifice in mechanical properties when adding lead to steel. neither longitudinal nor transvers mechanical properties are affected by the addition of lead to steel.
  7. Leaded steels are currently permitted under European Union Regulations covering End of Life Vehicles, RoHS.
  8. The reduction in energy required and time needed (about 25%!) to machine a part make leaded steels environmentally friendly by reducing Carbon Dioxide emissions to create parts compared to using unleaded materials.
  9. In order to be dangerous to humans, lead must be in a soluble form. The lead in steel bars is a separate solid phase. IARC lists lead under its Group 2B category - "possibly carcinogenic to humans".
  10. Lead, as well as Chromium, Copper, Manganese, Nickel, and Phosphorous is required to be reported under Sara 313 (40 CFR 372.65) when above thresholds.


Editor's Note: CR4 would like to thank Milo for sharing this blog entry, which you can also read here.

2 comments; last comment on 03/30/2015
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