As you likely already know, dowel pins play an important role in precision assembly for holding, pivoting, locating, and hinging parts in fixtures and more. These parts can be manufactured in different sizes and specifications as well as materials and finishes.

Today, we’re looking specifically at metric dowel pins and in particular the MA4018 and MA4109 dowel pins.

Did you know the MA4018 and MA4019 series metric dowel pins differ only by material (this includes the hardness as required by each material’s specification)?

As you may recall from an earlier post, the M21143/1 and M21143/2 series dowel pins differ only by diameter. The MA4018 calls for material AMS 5688 (spring tempered 302 Stainless Steel), and the MA4019 calls for AMS 5732 or AMS 5737 (both A286, consumable electrode melted, solution and precipitation heat-treated).

Both drawings/specifications are published by the SAE International (Society of Automotive Engineers…yes, Automotive) as is the procurement specification MA4070, required by both.

The MA4070 specification covers “aircraft quality metric pins, such as straight, headless, headed, shouldered, and dowel, in metric sizes.” Its application is primarily for use in “aerospace propulsion systems requiring metric size pins for use as locks, positioners, guides, plugs, and other similar uses.”  And, just as the NASM21143 procurement specification carried a boatload of extra requirements, so does the MA4070.

While we’re talking about MA4070, let’s briefly look at some of its requirements:

• Surface texture in accordance with (IAW) ANSI/ASME B46.1
• Hardness tested IAW MIL-STD-1312-6 (for AMS 5732 and AMS 5737 material)
• (Double) shear strength tested IAW DOD-STD-1312-113 (for AMS 5688 material)
• Plating, product marking, and non-destructive testing are not required for the MA4018/MA4019 but may be called for on other pins that refer to this procurement specification.
• Non-destructive (visual and dimensional) testing classification of defects:
  • The OD (outside diameter) and the OAL (overall length) are considered Major A and subject to a 1.0% AQL (acceptable quality limit)
  • Surface texture (e.g., .8-micron [~32-microinch] Ra finish on the OD) and other dimensional characteristics (e.g., .015 mm [~.0006”] FIR [full indicator reading] straightness) are considered Major B and subject to a 4.0% AQL.
• Raw material certifications, including test results that demonstrate conformance to the chemical and physical specifications of the material.

And that’s not even the deep dive…these folks obviously mean business!  So, what’s the takeaway?  There’s more to these dowel pins than the “cutting of chips” …there’s an obligation to demonstrate compliance after manufacturing.

Just as with so many of the other dowel pins that we manufacture, when you encounter a requirement for a MA4018 or MA4019 metric dowel pin, don’t dismiss it as “just another commercial dowel pin”; as you can see, there’s much more to it when you read the fine print.

Let Horberg Industries be your trusted source for all things MA4018/MA4019…don’t you have enough on your plate?