Author: Joe Jackson

ARTICLE – Cold Drawn Steel Bar Stock: How it is Manufactured, Benefits to Your Shop

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Cold Drawn Steel Bar Stock: How it is Manufactured, Benefits to Your Shop

Understanding the benefits provided by cold drawn steel bar stock can help you optimize the work that you quote by maximizing benefits to your manufacturing process and customer

by Miles Free III

Director of Industry Affairs, PMPA

Published June 1, 2023

How Are Steel Bars Cold Drawn?

Hot rolled steel bars, either in cut lengths or in coils, are first cleaned by shot blasting or acid pickling to remove the hard abrasive oxide scale on the surface. Then they are pulled through a carbide die in the presence of high-pressure lubricants which reduces the bar’s cross section. This process is called cold work (no heat is added in the process). The cold work trues up shape and holds diameter size to a very tight tolerance. The process also improves strength (increasing both yield and tensile strength) and hardness while reducing ductility (% elongation and % reduction in area). The drawn bar is then straightened and cut to length. Further testing for surface imperfections if specified. Bars then have rust preventive applied and are packaged and labeled for shipment.

Why Cold Drawn Steel Bars?

The process of cold drawing, is done at ambient temperatures, transforms the material properties by a process called cold work. This cold work increases yield strength, substantially; the tensile strength somewhat; as well as the hardness. At the same time, the ductility is reduced, which improves the steel’s machinability. Because the cold drawing work is done at ambient temperatures, the tolerance achieved for size and out of round is held to just a few thousandths of an inch. By convention, tolerances are held to the minus, nothing to the plus. This makes loading into workholding more
convenient and the material diameter and shape are often useable as is for many mechanical components.

Specifications for Cold Drawn Carbon and Alloy Steel Bars

Cold drawn carbon and alloy steel bars are specified in ASTM A 108 Steel Bar, Carbon and Alloy, Cold-Finished. Size tolerances for Level 1 Carbon Steel Cold-Finished Round Bars (Cold Drawn, or Turned and Polished) can be found in Table A1.1 of ASTM A108. For alloy grades, the size tolerances are found in Table A1.2. Tolerances are based on bar diameter, and carbon content and thermal treatment specified, if any. Tolerances are unilateral (to the minus only) from the specified size. Out-of-roundness in these products is half the size tolerance — per footnote D for both tables. The chemistry which identifies the material as a particular grade as well as other requirements such as product analysis tolerances and grain size can be found in ASTM A 29, Specification for General Requirements for Steel Bars, Carbon and Alloy, Hot Wrought, which is included by reference in ASTM A 108.

The reasons to select a cold drawn steel bar are few but compelling:
• The hard abrasive scale has been removed — preserving tool life as well as metalworking fluid utility. The cold drawing operation improves the as received surface finish of the bar.

• The cold working strain imparted by cold drawing improves the machinability of the material (not only the ease of removal of chip but also the resulting surface finish.)

• The tight dimensional and out of round tolerance may result in a reduction in processing needed.

• The straightness (lack of runout) as well as the better concentricity and dimensional tolerance allows for higher rpms. The higher surface feet per minute, increases output.

• The higher mechanical properties mean that the part may withstand higher stresses and forces in the customer’s application. This makes cold drawn steel bars ideal for shafting and power transmission applications.

• Standard grades are widely stocked and available for prompt delivery.

While the cold drawn bar as shipped has a bright, smooth, workmanlike surface, since no stock removal was taken, it is not warranted for surface finish. However, the bright drawn finish is often suitable without any additional processing. Typically, surface finish is in the neighborhood of 125- 32 microinches using normal processes. (Machinery’s Handbook) However, many of today’s mills have specialized processes that can deliver better.

What don’t you get with cold drawing?

As no stock removal has been taken, there is still the possibility of seams and other surface imperfections. This possibility increases when the steel is resulfurized. While the sulfur promotes better machining, it also increases the possibility of seams and other surface imperfections. ASTM A 108 table A1.8 provides the surface discontinuity
tolerances for carbon and alloy bars, based on sulfur content and bar diameter.

Material may be in stock available for prompt delivery.

Finally, a less important but often overlooked factor is that cold drawn steel bars are the most widely used feedstock in most of our precision machining shops. As a standard raw material, produced to standards for chemistry and tolerances, our shops are able to gain experience and understand what to expect when ordering cold drawn bars. Cold drawn steel bars cost more than hot rolled steel bars of the same grade, due to cost of manufacturing as well as yield loss in the manufacturing process. However, the benefits afforded to our precision machining shops are the absence of hard abrasive oxide scale, improved mechanical properties which lead to better machinability, improved dimensional
control, concentricity, surface finish and straightness. It is easy to see that the benefits of using cold drawn steel
bars outweigh their increased cost of production. Careful handling will preserve surface finish and straightness, minimizing perishability of quality. It is no accident that cold drawn steel bars are a preferred material for many precision machined components. Now you know some of the reasons why.

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Author

Miles Free III is the PMPA Director of Industry Affairs with over 50 years of experience in the areas of manufacturing, quality and steelmaking. Miles’ podcast is at pmpa.org/podcast. Email Miles

 

CRIBSHEET – #116: Twist drills for success

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PMPA Craftsman Cribsheet #116:
Twist drills for success

Drilling holes is one of the most fundamental operations we do in machining.

Published June 1, 2023

By David Wynn, Technical Services Manager, PMPA

In today’s world it seems that all information is tailored toward carbide drills. Carbide drills are great, but how many do you really use every day? Especially in our small-to-medium quantity job shops? It is likely that we use mostly standard HSS twist drills. It is not economical to buy expensive carbide drills for shorter-to -intermediate runs. The problem is that most of the available data and recommendations are tailored toward carbide drills. It is important that we still understand the basics of twist drills. How do you know when to use what type of drill? What is the geometry you want to have? What type of flute do you want to use?

In carbide drilling it is recommended to pilot instead of spot drilling. On the other hand, with standard twist drills it is generally recommended that we spot drill. Following with
angles that are greater than or equal to the last drill point. For instance, follow a 90-degree spot with a 118-degree drill. If you drill with a 135-degree parabolic you can’t follow
with a 118-standard drill – it will walk off center. This can be especially important for parts with multiple ID dimensions, and using non-carbide drills.

When drilling in tougher materials such as stainless, high-carbon steels and most alloys, multifaceted grinds help reduce the cutting forces at the tip and help to pull the chip. This is where parabolic drills shine. Today almost all parabolic drills are made with split points allowing them to be self centering. I have found that it is better to spot drill even when using a split point drill. The parabolic drill allows chips to flow out of the hole rapidly while still allowing coolant to reach the tip.

If the hole is greater than 3 to 4 times the drill diameter, I would recommend pullouts. With HSS twist drills, pull all the way out of the hole to allow the coolant to flood the hole and remove chips. This will also allow the tip of the drill to cool before reentering the cut. On CNCs with modern G83 peck cycles, I like to pullout to .100” in front of the hole. There is a small dwell on the pullout of the peck cycle, but if you are drilling tough material it would be beneficial to increase the dwell. Write your own cycle-increasing dwell times. Also, you can get the optimum pullouts going 3.5x drill diameter first peck, 2x drill diameter on the second peck then about 1x drill diameter (1-1.5x diameter) on all pecks after the second peck. The deeper the drill goes the more difficult it is to remove chips and get coolant to the cutting tip.

It is not recommended to try to achieve tolerances less than +/-.002 without reaming or boring. Here are some recommendations for twist drills for different materials often machined in our shops. In the light metals and those having high thermal expansion, it is recommended to use standard drills because holes cut tight. See chart below.

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PODCAST – Preview of the 2023 Mastery Program

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PMPA Speaking of Precision Podcast:

Preview of the 2023 Mastery Program

Miles Free, Carli Kistler-Miller and David Wynn give our listeners a peek into at what to expect on PMPA’s upcoming Mastery Program including five PMPA member shops, four machine tool/equipment builders, two toolmakers, one steel mill, one bar grinder, one machine monitoring company, one CAD CAM company, one industry media company, one electroplater and one metalworking fluid compounder.

 

Published May 29, 2023

 

 

BREAKING NEWS – Waters of The United States – Clarity for Our Shops

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BREAKING NEWS

Waters of The United States – Clarity for Our Shops

 

The United States Supreme Court just released their opinion on Sackett v. EPA written by Justice Alito. The opinion was unanimous, with other justices submitting concurring opinions while also arguing against certain points made in the Court’s opinion.

 

The opinion narrows the reading of the Clean Water Act- determining that the law only extends to wetlands that have a “continuous surface connection” with regulated waters of the U.S. (a relatively permanent body of water connected to traditional interstate navigable waters). This clarifies and objectively defines what is in fact a “water of the United States,” eliminating the ambiguity of the prior language and enforcement.

 

FULL SACKETT ET UX. v. ENVIRONMENTAL PROTECTION AGENCY DOCKET

 

 

PODCAST – 2023 PMPA National Technical Conference Wrap Up

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PMPA Speaking of Precision Podcast:

2023 PMPA National Technical Conference Wrap Up

Miles Free & Carli Kistler-Miller review the recent 2023 PMPA National Technical Conference in Cleveland, Ohio and the positivity it showed us about precision machining!

Published May 8, 2023

 

 

STATE OF MANUFACTURING – Wisconsin Manufacturing

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STATE OF MANUFACTURING – Wisconsin Manufacturing

by Joe Jackson

Marketing & Events Assistant, PMPA

Published May 1, 2023

Fabricated Metal Products Manufacturing is a subsector of manufacturing that makes critical goods from metal components.

Precision Turned Products Manufacturing is a subsector of fabricated metal product manufacturing that makes the components that MAKE IT WORK!

 

WISCONSIN ECONOMIC OUTPUT

Wisconsin Manufacturing
NAICS 31-33
$64,880,000,000

Fabricated Metal Product Manufacturing
NAICS 332
$15,223,624,000

Precision Turned Product Manufacturing
NACIS 332721
$769,376,000

WISCONSIN MANUFACTURING ACCOUNTS FOR

Manufacturing Is Productivity –19% of Wisconsin’s total output (GDP)

Manufacturing Builds Businesses – 9,754 manufacturing establishments in the state of Wisconsin

Manufacturing Creates Jobs – Jobs: 17% of all Wisconsin employees are in the manufacturing sector. (475,300 employees)

Manufacturing Earns Export Dollars – Wisconsin manufactured goods exports were valued at $23.71 billion last year.

 

Manufacturing produces for WISCONSIN!

  • Manufacturing is Wisconsin’s largest industry
  • Manufacturing is Wisconsin’s largest GDP producer and the source of their largest exports.
  • Fabricated Metal Manufacturing is the 3rd largest sector in Wisconsin’s manufacturing economy.

 

Wisconsin is a great place for a career in manufacturing

  • Manufacturing jobs pay, on average, 45% more than the average job in Wisconsin with an average salary of $79,864 per year.

 

Sources: NAM.org, IndustrySelect.com, US Census, wicmp.org

Data selected to show relative values. May not be directly comparable due to differences in sampling, analysis, or date obtained.

 

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Author

Joe Jackson

Marketing & Events Assistant, PMPA

Email: gro.apmp@noskcajj — Website: pmpa.org.

CRIBSHEET – #115: Paint Your Edge to Gain an Edge!

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PMPA Craftsman Cribsheet #115:
Paint Your Edge to Gain an Edge!

Kindergarten skills for the shop. Do you color your inserts?

Published May 1, 2023

By David Wynn, Technical Services Manager, PMPA

This is not a discussion of children coloring their coloring page inserts from a children’s book. I am literally asking how many of you out in the shop color your carbide inserts. If you don’t color them, then how do you know what edge is good? What edge is bad? This is a simple visual management tool to help our shop performers identify the edges that will result in trouble-free production. No matter when you go back to a holder, you always know where that insert stands. Visual management gives an immediate positive report on the status of the tool. No more guessing if the edge has been previously used. It looks good. How do we know?

It is often hard to tell when an insert is worn. The obvious ones are the chipped out or cracked in half. How about when you get a job that requires tight surface finish requirements and a worn insert is totally unnoticeable other than the resulting cut. This is where a paint marker designed to mark on oily surfaces comes in handy. The simplest solution is a one-color system. Red for a bad edge and that is it. But consider a three-colored approach to enable the most life out of your inserts:

Red for bad edge. You are not using this edge again no matter what. Used 90% of the time.

Yellow for reusable edge. You would not use a yellow edge on a part that needs some super surface finish or tight tolerance, but when you have a ± 0.015″ bushing and just need a cutoff insert, this will definitely work. Used about 7% of the time.

Green for good edge but has been used. This is reserved for only those times you go to the lathe and drill a hole in a 12L14 or 360 brass ejector. This drill is still brand new, but the color lets us know it has been used. Used less than 3% of the time.

The next time you go to a drawer and look at a load of holders and wonder which of these inserts are used, look for your colored edge so that you know. Better yet, put the inserts away instead of leaving them in the holder. Now you can go to a box of inserts and easily see how many edges you really have. How many times have you ordered a box of inserts only to find 10 holders with that insert already in it? Visual management by applying simple color codes to your tooling will save you thousands of wasted dollars in inserts of uncertain status, locked up in holders. So, add a little color the next time you go to change an insert. Add a little color and you will always have confidence in the status of your edge. Use visual management to give you an edge!

 

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ARTICLE – Markets Served — Who Knew?

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Markets Served — Who Knew?

PMPA members shared the markets they served in 2022. The top 5 may surprise you.

by Miles Free III

Director of Industry Affairs, PMPA

Published May 1, 2023

Every year, the PMPA does a survey of our membership to determine the critical topics they are seeing as we prepare
for our advocacy in Washington D.C. before Congress and working with executive branch agencies. This year’s survey
showed continued high interest in many areas of concern, particularly around expensing, depreciation and recovering research and development investments. But the surprising takeaway for me was to see how the percentage of shops serving the various market segments has changed just since last year.

Historically, the top five markets most heavily served by our North American precision machining shops have been light vehicle, aerospace, medical device and implant, industrial machinery and equipment, and agricultural equipment/off highway. One of the interesting facts is that in many years, the category “all other” is often the third or fourth largest category — our shops’ high precision, high-performance components empower many different systems in a wide variety of industries. This year, “all other” came in eighth position showing just how strongly the demand from our primary markets has been. This year’s surprise? Oil and gas customers were the second place market served with 61% of survey respondents reporting sales to that industry.

Industrial machinery and equipment came in first position, claiming shipments from 66% or two thirds of respondents.
Automotive light truck came in third position tied with medical with 55% of this year’s survey respondents producing parts for those industries. Agriculture and off road came in fourth place, tied with defense/ordnance at 53% of respondents producing for these industries. Aerospace, typically our shops number two or three industry in terms of
being served by our shops, came in fifth position, tied with heavy truck which is served by half of our survey participants.
Appliances, electronics, telecommunications, new/renewable energy (think solar, wind, hydro) and computer/business machines filled the remainder of named markets served.

Every shop is different, and even though many shops use similar machine tools, equipment and technology, each organization has its own strengths and focus as far as understanding and meeting customer requirements — both explicit and implicit. But what the shifting number of shops serving each of these different markets showed me is
that our shops also have a flexibility, an agility to meet the needs of the greater market. Yes, a shop may be a strong
provider of high-volume, low-mix critical components for autos and light trucks, but that does not mean they cannot
also be a supplier for a variety of other components in smaller quantities for other industries.

The greatest surprise to me, however, from this year’s survey results, was the strong showing of oil/gas as the market served by the second largest cohort of shops in our survey. I would never have thought that oil/gas — aka dinosaur juice, according to the pundits inside the beltway — would be the second most important market for our shops for contract parts production. And yet we are. This flies in the face of all of the policy and legislative initiatives for reducing CO2, climate change and ESG considerations in the federal government — I counted 54 separately listed entries in the Energy Information Administration’s Table 1 Included and excluded Inflation Reduction Act (IRA) provisions in the Annual Energy Outlook 2023 publication.

Despite the reports and forecasts of energy-related CO2 emissions falling 25%-38% below 2005 levels, our shops are
finding components for oil and gas to be the second largest segment of their current book of business. If we were to
add the percentage of shops also claiming renewable and new energy production orders market, the percentage of
shops serving “all energy” rises to number one position — with the largest number of our shops producing components.

Our takeaways? Despite all of the press attention on new and renewable energy, and CO2 reduction, the oil and gas market is surprisingly our industry’s second-ranked market served by percentage of shops responding. It is second to industrial machinery and equipment, ahead of automotive and light truck in third position, with medical and aerospace tying for fourth.  is ranking is quite an upset. All of these markets are human-safety critical, where requirements for safety, quality and integrity of product are of the highest importance.

For the old timers who think our industry is just about hose fittings and high volumes of commodity parts, our latest survey tells a much different story. We are the people that make things. Things that provide all of us with energy.
Energy that makes things go. Without energy there is no supply chain — nor need for one. Take the reports of the
impending death of dino juice and ICE vehicles with a healthy dose of critical thinking. While these markets are
expected to decline, our shops are currently finding plenty of opportunity to add value as they produce needed critical
components. In the long term, our parts count and book of business could shrink. But we were completely surprised
to see that the oil/gas market is, as of 2023, our second largest market served.

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Author

Miles Free III is the PMPA Director of Industry Affairs with over 50 years of experience in the areas of manufacturing, quality and steelmaking. Miles’ podcast is at pmpa.org/podcast. Email Miles