Back to Companies

PH Tool Reference Standards

Meeting the demands of the increasingly complex and quality-conscious NDT marketplace is a challenge we gladly accept.

Product, Service

United States

Visit Website

PH Tool Reference Standards, headquartered in Pipersville, PA, has supplied the Nondestructive Testing (NDT) industry with high quality Reference Standards and Test Blocks since its founding by Phil Herman Sr. in 1973. Whether you need EDM notches, Flat-bottom holes, Micro-holes, or Test Blocks, PH Tool can handle your order.

The entire staff of skilled toolmakers, machinists, technicians, and professional management personnel is dedicated to the development and manufacture of the finest quality Reference Standards available today. Our robust growth and excellent reputation in the NDT world can be attributed to our emphasis on quality, attention to detail, and innovative approaches to the most challenging requirements of our valued customers.

Meeting the demands of the increasingly complex and quality-conscious NDT marketplace is a challenge we gladly accept. We welcome your inquiries and look forward to serving you.

Products & Services
Calibration Test Blocks

ph tool 146Calibration test blocks are nonrepresentative tools, meaning that they are not manufactured from actual parts. Rather, they are of simplified design and contain manufactured discontinuities such as holes, angles, radii and more. Calibration Test Blocks serve the purpose of standardizing and calibrating test equipment to ensure that it is functioning properly.

Calibration Test Blocks are machined in the same manner as other metal parts, using normal machine shop equipment such as saws, milling machines, lathes, surface grinders and engravers. There are many organizations that govern the manufacture of standard test blocks, such as IIW, ASME, ASTM, ISO, and many others. 

As with any good manufacturing process, there are several important things to consider when manufacturing test blocks. Good quality raw materials of the correct alloys are the place to start. Most specifications list the desired alloy, or leave it up to the manufacturer of the blocks and the client to make the right decision. PH Tool™ always performs a pre-machining ultrasonic inspection of the raw material to determine that the stock is free from pre-existing discontinuities.

IIWWhat kind of paperwork comes with the blocks?  All calibration test blocks ship with a NIST-traceable Certification Report stating that the block meets applicable specifications.  A Material Test Report (MTR) is also included to maintain heat or lot traceability of the raw material to the producing mill.  PH Tool also includes a Positive Material Identification (PMI) Test Report with all standard blocks, showing the results of a chemical analysis obtained in-house with our XRF analyzer. The PMI report adds an extra level of certainty that the correct materials were used in manufacture.  If this is not enough, customers also have the ability to purchase a Full-dimensional Inspection Report, showing all of the as-built dimensions of the block.  This is not merely a close approximation of accuracy; the dimensions must be carefully obtained and compiled into a report detailing all of the critical dimensions of the block design.    

Reference Standards for NDT

PH Tool Reference Standards has been the recognized leader in the manufacture of Reference Standards used in the Non-Destructive Testing (NDT) industry. We are the only company who makes standards, and nothing but standards. As a result, our expertise is second-to-none, as is our commitment to producing the finest notch standards available today. Let’s face it, without professionally manufactured, NIST traceable standards, how reliable are the results of your inspection? In the quality-conscious age we live in, it is increasingly important to trust your critical masters to the company who can deliver on the promise of making “the standards of excellence.”

Selecting a Reference Standard

To ensure accurate and repeatable inspection, testing equipment must be standardized and calibrated so that data taken by different operators are comparable and can be matched against inspection norms. Selection of a reference standard is determined by testing technique, type of material to be inspected, type of discontinuity to be detected, and any additional application or industry-specific requirements. Reference standards are representative tools designed to ASTM, ASME, AMS, ISO, and many other specifications. They are used to standardize responses from testing equipment. Samples with EDM Notches and Flat-bottom Holes are often used to standardize amplitude of the detected signal with respect to the size and/or position of known reflectors. Side-drilled holes are also an effective target for such standardizations. 

Preparing a Reference Standard

In cases where reference standards are made from scratch, care needs to be taken to use materials as similar to the component under test as possible. It is often preferable or required to prepare a reference standard from a piece of the same material as that to be tested. This is most often accomplished by introducing EDM notches or machined holes into the actual test object. The advantage of such a reference standard is that the test object and the standard will have the same composition, manufacturing history, surface condition, and geometry.  

In all cases, reference standards must be prepared and used in accordance with well-designed specifications that cover the material selection, the manufacture of artificial defects, and of course, instructions for the specific testing application.

For more details visit: Reference Standards for NDT | PH Tool 

EDM Notches

What is EDM?

Electrical Discharge Machining (EDM) is a nonconventional metal removal machining method that employs the use of an electrode to machine the desired shape into a workpiece under carefully controlled conditions. EDM offers several advantages over conventional, “chip-making” machining methods including:

  1. The ability to machine extremely narrow notches.
  2. The ability to access hard-to-reach locations such as pipe/tube IDs without the need to section the workpiece.
  3. The ability to hold very close dimensional tolerances.
  4. The ability to machine harder materials and exotic alloys.
  5. The ability to machine irregular shapes not otherwise possible.

All conductive materials are able to be EDM’d. EDM notches can be machined on both the OD and ID of pipe and tube. Notches can be machined on IDs as small as 0.040”. Transverse (circumferential) notches are normally made with electrodes precisely ground to the respective radius of the workpiece. This ensures uniform notch depth along the notch length. Notches can also be made to match an irregular surface or have a thumbnail (semi-elliptical) profile.

What are EDM Notches?

Electrical Discharge Machined (EDM) notches are produced by PH Tool using both Sinker and Wire EDM technology. Sinker EDM utilizes a carefully-made electrode to machine the desired notch. Wire EDM uses a traveling wire as the electrode. Think of the wire EDM like a sophisticated band saw, where the wire is the blade. The limitation with wire is the inability to machine captive notches – i.e. those that do not break out to the edge of a part. For captive notches, Sinker EDM is required. PH Tool has one of the largest concentrations of EDM machines in the country, with over 40 sinker machines and 6 modern, CNC-controlled wires. Many of our machines have undergone considerable modification and retrofitting in order to handle the unique needs of the NDT industry. These modifications include alterations to the power supply to allow cutting at extremely low aperages, thereby eliminating the recast layer normally associated with EDM technology. They are no longer general-purpose EDM’s, but rather highly-specialized, low-energy “Notch-makers.”

This means that we can handle a wide range of items, from tiny parts that fit in the palm of your hand to 10,000 pound components that would not fit within the envelope of a traditional EDM machine. We are not limited to what will fit in the work tanks. Tubular, bar, and rail standards can be as long as 40 feet.

What can be Notched?

Notches can be placed in any conductive material and can be shaped in a variety of ways. Hollow cylindrical items (tube and pipe) can be notched on the OD and ID, in axial, circumferential or off-angle orientations. Notches can be placed in welded components in the weld, toe, heat-affected zone, base metal, or even embedded in the weld. A wide range of items can be notched including, but not limited to: tube, pipe, bar, plate, wire, rod, engine components, structural aircraft parts, automotive parts, pistons, turbine blades, impellers, disks, hubs, springs and surgical implants.

What Widths are Possible?

EDM Notches used for Eddy Current, Liquid Penetrant and Magnetic Particle testing are typically very narrow, perhaps in the .004 - .005” wide range. Notches used in Ultrasonic Testing normally do not require notches this narrow. PH Tool has developed a proprietary method of machining Nano Notches as small as 0.0006” (15 microns) wide for applications requiring widths as narrow as possible. Refer to our page on Nano Notches for more details on this capability.

NIST Traceability

All of our EDM Notch Reference Standards are 100% inspected, traceable to the National Institute of Standards and Technology (NIST), and include a comprehensive certification report. At PH Tool, our dimensions are carefully obtained via replication and observation using video measurement systems, and contain reliable/repeatable dimensions which are NIST traceable.

More Info on EDM Notches:

See our pages on:

OnestopNDT OnestopNDT OnestopNDT

Step 1 - please enter your Personal details.

Step 2 - please upload your Resume.

Thank you for submitting.

Tree PNG back


Tree PNG back




Tree PNG back


Application Notes


onestop ndt application

NDT Trends #83 is out!!
Grab your FREE copy now.