All of the NAAMS Pt. 4: Stop Blocks & Clamp Arms

The United States Council for Automotive Research (USCAR) maintains the NAAMS Global Standard Component Components and Assemblies for manufacturing stamping and assembly operations.  Admittedly that’s a mouthful of acronyms, so some explanation is warranted.  NAAMS is an abbreviation for the North American Automotive Metric Standard and was chartered in 1992 as a collaborative effort among the “Big 3” American automotive companies- Chrysler, Ford, and GM- with the goal of standardizing manufacturing equipment with the hope of leveraging their market size in the U.S. to drive the entire automotive supply chain all the way down the line to standardization.

While there are many different NAAMS standards that were developed for various facets of capital equipment manufacturing/assembly equipment employed to create a myriad of possible subcomponents and assemblies, the focus in this targeted examination is reserved for the standards related to stop blocks and power clamp arms.

Stop Blocks

MISUMI's NAAMS Crowned Stop Block

MISUMI’s NAAMS Crowned Stop Block

Stop Blocks are typically more commonly known as “Setup (or Set)” Blocks.  They serve a very specific purpose in the progressive die stamping tooling setup process.  These blocks are firmly fastened to the stamping dies at strategic locations within the die, and their function is to literally stop the downward motion of the stamping die to ensure an accurate stamping cut is created every time the die stamps a feature in the sheet, thereby prolonging the life of the tool.  During die setup and design configuration, these stop blocks allow the tooling engineer or designer to carefully line up component dies in the operation to ensure that the cut at each stamping operation is accurately made every time the stamping dies meet in the cutting operation.  This is vital due to the extremely high deformation/cutting forces and high cycle rates employed in progressive die stamping operations.

Power Clamp Arms

MISUMI's NAAMS Clamp Arm 60 Series

MISUMI’s NAAMS Clamp Arm 60 Series

Power clamp arms are also employed in stamping fixture and tooling design and are typically referred to as “clamp arms”.  Power clamp arms are typically required wherever a pneumatic clamp actuator is present, typically in a very wide range of assembly or stamping operations.  The clamp arm itself is a simple piece of metal that, much like wrench lever arm, is used to drive the pneumatic actuators of the power clamps in the assembly fixture, thereby providing the clamping functions.  As such, these arms are removable components of pneumatic power clamps and contribute to the end goal of firmly clamping workpieces for assembly operations.

NAAMS Standards

The most critical identifying information on the stop block or clamp arm is the stamped NAAMS code. It provides all of the identifying information required to obtain all the governing specifications on the part.  The Stamping codes contain the entirety of information for the stop blocks (governed by Chapter L) and the clamp arms (governed by Chapter G).  These two chapters are readily available from the assembly specification section of the NAAMS webpage, and as such, they contain more than all the information one could need on these components.

Lastly, and probably most importantly, all NAAMS standards are defined in standard metric units with a base length unit of millimeters.  This is critical to know upfront when designing anything that employs NAAMS components so that there is no confusion about the components.

General NAAMS standards

Power Clamp Arm NAAMS Standard

Stop Block NAAMS Standard

Power Clamp Arm NAAMS Information

Functionally, the power clamp arms are relatively simple pieces of metal, typically cut from tooling steel plate stock using some kind of metal cutting operation.  The NAAMS power clamp arms are available in either a straight profile like a traditional wrench, or an offset “J-shape” to the rectangular drive square in the center of the clamp, “wishbone” clamp arms that engage two-sided drive shafts are also available.  Power clamp arms are also available with some type of offset hole pattern on the top of the clamp arm that can be employed as locating features for alignment pins in the fixture.  The clamps are available in the standard black oxide surface finish, or the safety orange bright color standard which is employed in clamp actuators that physically clamp a part or component for safety purposes and may result in an unsafe condition if the clamp were to be disengaged or tampered with.  The NAAMS code number is etched into the front of every power clamp arm so that the component can easily be identified and matched to the corresponding standard.

Stop Block NAAMS Information

Stop blocks come in two distinct geometries- the flat profile and the crowned profile.  These names are generally self-explanatory- the crowned profile stop block possesses an arced rounded top while the flat profile is a flat top.  The blocks possess countersunk holes for fastening to the die and sometimes possess entire through holes in the body of the block to reduce the weight of the blocks.  NAAMS stop blocks are all fabricated from SAE 1060 hardened tool steel and finished with a black oxide surface coating.  The NAAMS code number is etched into the front of every stop block so that the component can easily be identified and matched to the corresponding standard.

While a bit of background context on the function of the desired component is helpful to a degree; there really is no substitute to simply reading through the NAAMS standard in its entirety to really become proficient in the NAAMS code number designations.  However, memorization of the exact standard numbers isn’t necessary, as the NAAMS code standards are very accessible and easy to understand with ample pictures and illustrations, and it’s therefore extremely beneficial to keep the standard handy whenever questions arise.

Be sure to catch up on our other NAAMS and locating pin posts below!

All of the NAAMS Part 1: What is NAAMS?

All of the NAAMS Part 2: The Shim Sham Shuffle

All of the NAAMS Part 3: Rise Up

What are diamond locating pins and should I be using them?

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