Mastering Mil-Spec Dowel Pins: Fit, Material, and Series Made Simple

What Makes Mil-Spec Dowel Pins Different?

Mil-Spec (Military Standard) dowel pins are precision-ground, solid headless fasteners engineered for exact alignment, location, and secure assembly of components in aerospace, defense, and precision manufacturing.

They are produced under strict Mil-Spec specifications to ensure dimensional accuracy, repeatability, and conformance. Unlike commercial pins, Mil-Spec versions must be tested and certified for mechanical properties, hardness, and finish supported by documentation packages that may include Material Test Reports (MTRs), Certificates of Conformance (COCs), Heat Treat Certifications and DFARs compliance statements.

Dowel pins are commonly used as hinges, shafts, pivots, or locating devices to align or secure parts within precision assemblies or fixtures.

Four Common Mil-Spec Dowel Pin Series

Not all dowel pins are created equal. Each Mil-Spec series follows strict guidelines for fit, tolerance, material and other attributes to ensure accuracy and repeatability in demanding applications. Whether double-chamfered or featuring a radius and chamfer combination, these pins play a vital role in precision alignment. Below we deconstruct the taxonomy and attributes of the four series most frequently used in military and aerospace manufacturing.

1 – MS16555 — Standard Headless Dowel Pin (Press Fit)

Equivalent: Similar to ASME B18.8.2 standard series

Design: Straight, solid headless dowel pin normally made with a chamfered crown on one end and a chamfer on the other
Fit Type: Provides a standard interference/press fit
Tolerance: -0 / +0.0002 over nominal size
Material Options:
- MS16555-1 to -145: Steel (Carbon or Alloy), hardened
- MS16555-301 to -444: Phosphate-coated Steel, hardened
- MS16555-601 to -744: CRES 410/416 Stainless Steel, hardened and passivated
Diameter Range: 1/16″ (.0626–.0628) to 1″ (1.0001–1.0003)
Length Range: 3/16″ to 6″ (lengths over 3″ may be limited)
Applications: Ideal for vibration-resistant, high-strength alignment in aircraft and defense assemblies

➡️ Available for purchase online or RFQ

2 – MS16556 — Oversize Headless Dowel Pin (Extended Length / Oversize Fit)

Equivalent: Similar to ASME B18.8.2 oversize standard series

Design: Straight, solid headless dowel pin normally made with a chamfered crown on one end and a chamfer on the other (Similar to MS16555 with oversize tolerance)
Fit: Oversize interference fit
Tolerance: -0 / +0.001 over nominal diameter
Material Options:
- MS16556-1 to -144: Steel (Carbon or Alloy), hardened
- MS16556-301 to -444: Phosphate-coated Steel, hardened
- MS16556-601 to -744: Stainless Steel, hardened and passivated
- MS16556-801 to -944: Cadmium-plated Steel, hardened
Diameter Range: 1/16″ to 1″
Length Range: 3/16″ to 6″ (extended per spec; over 3″ limited)
Applications: Ideal for worn holes and to replace pins that no longer fit securely.

➡️ Now available for RFQ at mfsupply.com

MIL-P-21143 Series

3 – M21143/1 — CRES 303 Stainless Steel Dowel Pin (Press Fit)

Specification: MIL-P-21143

Design: Straight, headless pin with .015/.010 x 45° chamfer on both ends
Fit: Press fit — standard interference fit (referred to as “Oversize” in spec)
Tolerance: -0 / +0.0002 over nominal
Material: CRES 303 Stainless Steel
Diameter Range: 1/16″ to 1″
Applications: Used to join moving components or in high-precision assemblies requiring corrosion resistance and tight alignment

➡️ Available for RFQ at mfsupply.com

4 – M21143/2 — CRES 303 Stainless Steel Dowel Pin (Slip Fit / Undersize)

Design: Produced similar to M21143/1, straight, headless dowel pin with precision-ground surfaces, generally produces with a .015/.010 x 45° chamfer both ends
Fit: Slip fit — slightly undersized for easy removal or adjustment
Tolerance: +0 / -0.0002 under nominal diameter
Material: CRES 303 Stainless Steel.
Applications: Used in assemblies requiring frequent disassembly or maintenance; ideal for prototypes or variable-fit applications

➡️ Available for RFQ at mfsupply.com

Choosing the Right Material

Material	Key Traits	Common Uses
Alloy/Carbon Steel (Plain, Cadmium, Phosphate)	High strength, durable	Heavy-load or high-temp applications
CRES 410/416 Stainless Steel	Hardened, corrosion-resistant	Aerospace and defense
CRES 303 Stainless Steel	Corrosion-resistant, easy to machine	Slip-fit and/or precision alignment

All Mil-Spec dowel pins from MF Supply include Manufacturer’s Certificates of Conformance. Full certification packages — MTRs, Dimensional Reports, Heat-Treat, Passivation, and DFARS statements — are available upon request and may incur a fee.

👉 Checkout our Mil-Spec Precision Dowel Pins Cross-Reference Charts

Checklist: Sourcing the Correct Mil-Spec Dowel Pin

Before placing your RFQ or order, confirm:

Specification / Part Number – e.g., MS16555, MS16556, M21143/1, M21143/2. Check the diameter, length, tolerance, material and all specs to the Mil-Spec print.
Material & Finish – Match environment and strength needs.
Fit / Tolerance – Choose standard press fit, oversize, or slip fit as required.
Documentation – Determine your paperwork requirements at every stage of the process from initial RFQ to receiving inspection to insure audit readiness.

Mil-Spec Dowel Pins from MF Supply

MF Supply is your WBE/WOSB-certified U.S. distributor for certified, commercial, and custom dowel pins, including:

MS16555, MS16556, M21143/1, and M21143/2 series
Alloy and CRES Stainless Steel options
Certification packages (MTRs, COCs, Passivation, DFARS, Heat-Treat)
Fast RFQ turnaround and domestic stock for quick delivery
Made to order option for parts that are not COTs or for special sizes, materials and tolerances

We’re proud to announce that MS16556 dowel pins are now available for RFQ — joining our comprehensive Mil-Spec, metric, and precision dowel pin lineup.

👉 Visit MF Supply to request a quote or browse our catalog.

We are your Purchasing Department’s Secret Weapon for Mil-Spec hardware!

Book a one-on-one consultation with our President, Robin, to discuss how MF Supply can help you solve your Industrial Sourcing, Fastener, and Safety concerns.

Your Purchasing Department’s Secret Weapon!
Here are 5 reasons to buy from MF Supply

We Source and Deliver What Others Can’t, Faster Than You Imagined – With speedy solutions for elusive parts and lengthy delivery times – We’ve got you covered with both custom-made specials (send us your prints!) and hard-to-source options, quickly and at a fair price.
Cost-Effective Functional Equivalents to OEM Brand Fasteners-Why Pay More? – Reduce lead times and costs with the same quality and same performance. Try us for alternatives to brands like McMaster-Carr, MSC, Misumi, PEM, and RAF and experience unmatched savings! Same form, fit and function for less.
Huge Selection of Certified and Commercial Hardware with Same-day Shipping Available for Countless Items – We source and stock standards, specials, commercial, Mil-Spec & OEM brands in inch and metric sizes. Standards include AN, NAS, MS, IFI, ASTM, ASME, DIN, ISO, JIS. We are sourcing experts for inserts, certified Mil-Spec parts and anything in stainless steel. Many parts are available with manufacturers’ certifications, including DFAR, ROHS and CoC. Trust us to ship on-time from our national distribution centers.
A User-Friendly, 24/7 Online Shopping Experience – Enjoy a 24/7 online shopping experience with easy-to-use filters, detailed product information, and a constantly updated technical directory. Sign up now for a seamless experience!
WBE/WOSB Certified Woman-Owned Small Business – As a certified Woman-Owned Small Business, we support your diversity goals. Trust us to meet your fastener and sourcing needs with expertise and efficiency [Cage Code 58QG4].

MF Supply is a WBE/WOSB certified supply chain partner to business, industry and government. We are sourcing experts and stocking distributors of Hardware, Precision & Mil-Spec Fasteners and Safety supplies. For more than 50 years, we have been supplying manufacturers in the electronics, industrial, commercial, aerospace and military markets with the full range of fastener products and services. Our Cage Code is 58QG4 and our registered name is RL Supply Inc dba MF Supply.

The Buyer’s Guide to Dowel Pins You Must Have Today! Updated for 2023!

Posted: February 23, 2023 | Author: mfsupplyblog | Filed under: dowel pin, Mil-Spec, MS16555, MS16556 and Mil-P-21143., PRECISION DOWEL PIN | Leave a comment

MF Supply is a trusted Supplier of Precision Dowel Pins for manufacturers. Through our extensive assortment of Inch, Metric, Commercial, Mil-Spec and OEM brand names and equivalents, we offer our customers quality imported and domestic dowel options. Our products are competitively priced with fast delivery from multiple distributions centers across the USA. Our goal is to help simplify the buying process for this sometimes complex and confusing category of fasteners.

8 Things to Know When Buying Dowel Pins

If you are a manufacturer working with complex assemblies or fixtures, then you’re likely very familiar with precision dowel pins. Commonly used as a hinge, shaft or pivot to locate or hold assembled parts together, dowel pins can withstand frequent insertion and removal without distortion. They are broadly used across various applications in many industries, including: aerospace, electrical motors, hydraulic equipment, instrumentation, tooling and fixtures, machinery, military and many more.

Our goal is to help simplify the buying process for this sometimes complex and confusing category of fasteners.

1. What is a precision dowel pin?

Dowel pins are solid, headless cylindrical shaped straight metal pins with a centerless ground finish. Manufactured to precise fractional diameters and lengths, dowel pins come in a variety of sizes, styles, designs and materials. This variability can cause confusion among buyers, engineers and end-users alike.

2. What materials and platings are available?

Precision dowel pins are available off the shelf in alloy steel (typically hardened) and stainless steel grades 18-8/303, 316 and 416 (typically hardened). Other exotic materials or special finishes are available for special order with a lead time.

3. What sizes are available?

Standard sizes include inch from 1/16″ to 1″ diameter, and metric from M1 to M20 diameter. Length options vary by diameter. Other diameters and special lengths are available for special order and usually involve a lead time.

4. When ordering, do I need to specify the dowel pin tolerance or call out attributes such as standard, undersized or oversized fit?

Precision dowel pins often show up under their MIL-SPEC numbers, MS16555, MS16556 and Mil-P-21143. Metric dowel pins might show up under the following DINs and ISO numbers: DIN 7, DIN 6325, and ISO 2338 and 8734. Dowel pins might also show up under a manufacturer part number such as Pic, WM Berg, Unbrako or Holo-Krome.

If you are ordering by MIL-SPEC, manufacturer’s part number or DIN, then the general attributes including tolerance and style are known. Here are a few of the other options that will help you order the correct pin:

The most common standard inch or imperial sized precision dowel pin is made to the ASME ANSI B18.8.2 spec and has a diameter tolerance of -0.00 / +0.0002 and length tolerance of +/-0.010. For example, a ¼” (0.25) diameter standard dowel pin will have a diameter between 0.2500–0.2502″.
The standard metric tolerance is related to the DIN. Both DIN 7 and DIN 6325 have a standard m6 diameter tolerance of +0.012mm / +0.004mm and a length tolerance related to the specific pin length.
Undersized series dowel pins are used for inconsistent holes. They have a basic diameter 0.0002″ under the nominal diameter. For example, a ¼” (0.25) diameter undersized dowel pin will have a diameter between 0.2500–0.2498″. The Mil-P-21143/2- falls into the undersized category.
Important note: All pin options may not be available in all sizes and materials.
OEM branded pins have their own tolerances and specifications.
Finally, the Oversized series of dowel pins are usually used to fit into worn holes and are generally used in the aftermarket for repairs. These pins are only available off the shelf in steel in a small range of sizes.

5. Can I specify if I need radius or chamfer on the pin ends?

The pin style will depend upon the spec and the material. Precision dowel pins may come with either a double chamfer or a radius on one end and a chamfer on the other end. Specific style requirements are available for special order and usually involve a lead time.

6. What information do I need to request a quote?

The easiest way to order is by either the manufacturer or MIL-SPEC part number. To order by description, you need the diameter, length and material and if applicable, and any special tolerance, plating or style requirements.

7. Do I need to buy special installation tools?

Just remember, no hammers! When installing dowel pins, never drive the pin into the hole with force. Always press it in for best results. And production favors pins since they require no extra fastening hardware for insertion, no secondary operations, and no mating parts. This ease-of-use adds up to speedier production, which makes everyone in the food chain happy!

8. What level of certification is required?

Generally, a Certificate of Conformance or a COC is sufficient for your customer. Full certification with material certs and test reports are often available for USA made and MIL-SPEC parts and might have an additional fee.

Available Dowel Pins Categories

We are Dowel Pin experts, offering the full catalog of standard Dowel Pins in Inch, Metric, Military and OEM branded options in a wide selection of materials, sizes and specifications. As stocking distributors, many dowel pins are available and ready to ship today from our national distribution centers.

The full range of commercial and MIL-SPEC parts (M21143, MS16555, MS9390), including parts that are USA made, DFARS and ROHS compliant.
Inch sizes to ASME ANSI B18.8.2 standards in Alloy Steel, Stainless Steel 18-8, 316, 400 Series and Hardened
Metric sizes including DIN 7, DIN 6325, and ISO 2338 and 8734 in Alloy Steel, A2 & A4 Stainless Steel
Precision Series and OEM branded equivalents to PIC, BERG, both Inch & Metric Precision Dowel pins including Press-Fit A, B and Slip-Fit C series and all MD series pins in 416 and 303 Stainless Steel.

In addition to our vast selections of standards, we offer Custom-made parts per print in non-standard sizes and exotic materials and finishes made here in the USA with full certifications. Minimums and lead times will apply.

Seeking parts not listed for purchase on our website? We’ve got you covered! Submit your Dowel Pin RFQ and our team of experts will return your quote quickly!

Book a one-on-one consultation with our President, Robin, to discuss how MF Supply can help you solve your Industrial Sourcing, Fastener, and Safety concerns.

Six Reasons To Buy From MF Supply

Full eCommerce Enabled Website With Technical Manual Available 24/7 – Visit our website and Create a New Account, track online orders, browse our product catalog, check technical specs, subscribe to our blog, or buy online. We are adding items and improving functionality daily!
Same Day Shipping From The USA – Our hardware products are in stock and ship to you directly from our USA based distribution centers.
Functional Equivalents To Expensive Brand Names- We stock and source alternatives to brand name fasteners, reducing long lead times and saving you money.
Creatively Solve Problems – We are sourcing experts, offer competitive pricing and specialize in finding hard to find parts and reducing long deliveries.
One-Stop Shopping On Certified Hardware – We stock and source a full line of fasteners including Mil-Spec, DFARS compliant and other industrial products.
WBE/WOSB Woman Owned Certified Small Business – To meet your diversity & set-aside needs.

The Buyer’s Guide to Dowel Pins You Must Have Today!

Posted: August 26, 2022 | Author: mfsupplyblog | Filed under: dowel pin, Mil-Spec, MS16555, MS16556 and Mil-P-21143., PRECISION DOWEL PIN | Leave a comment

MF Supply is a trusted Supplier of Precision Dowel Pins to manufacturers with our extensive assortment of Inch, Metric, Commercial, Mil-Spec and OEM brand names and equivalents.

Smart Manufacturers Use Blanket Purchase Orders to Reduce Risk

Posted: February 28, 2018 | Author: mfsupplyblog | Filed under: dowel pin, Mil-Spec, MS16555, MS16556 and Mil-P-21143. | Leave a comment

BPOS Hedge Against Inflation

Learn to Hedge Against Inflation through Proactive Purchasing

The world of manufacturing is filled with risks. Staff turnover, overseas competition and third party vendor issues can all threaten your service level and put pressure on your organization. But one of the biggest risks in 2018 is inflation.

Rising material prices and inflationary forces are impacting costs at every level. Master suppliers are reporting price increases of 7%+ on steel products and 10%+ on stainless steel. What is a manufacturer to do?

One of the most powerful ways to mitigate the risk of rising prices is through a proactive supply chain strategy that includes issuing Blanket Purchase Orders (BPO). With a stable price for a fixed period of time, the BPO serves as a hedge against inflation.

What is a Blanket Purchase Order?

A blanket Purchase Order is a contract to buy parts at a guaranteed price within a specific time period or schedule (typically one year). For example, a manufacturer forecasts to use 10,000-12,000 pieces of an MS16555 stainless steel dowel pins annually. They issue their supplier a Blanket PO for 12,000 pins a year at a negotiated price with 12 monthly releases of 1,000 pieces. This gives them 12 months of predictable costs at today’s 12,000 piece price, rather than tomorrow’s 1000 piece price. As we start to see double digit price increases in the industrial marketplace, the savings multiply.

What are the benefits of Blanket Purchase Orders?

A Blanket PO can add certainty to a business and can make your production process leaner, guaranteeing the price and availability of parts without the burden of holding the parts in stock. Suppliers also benefit because they have a predictable revenue stream. Both sides have certainty concerning quantity, price, delivery requirements and payment terms.

Beyond certainty, the top benefits of BPOs for manufacturers are:

Reduces unit costs through quantity discounts.
Guarantees pricing & reduces time spent on price negotiation.
Shortens lead time and eliminates stock outs.
Assurance of quality of products and vendors.
Improves efficiency of ordering, receiving and bill paying process.
Leaner operations with reduced stock burden.

During inflationary times, the benefits of locking in today’s prices for up to 1 year multiply.

When should a manufacturer issue a Blanket PO?

When an item has a high minimum annual usage ($500 minimum EAU).
When a quantity discount can be achieved.
When you are already making repetitive purchases from the same supplier within a certain time period (typically 1 year).
When parts are used according to a production schedule.
When parts have a lead time.

When should a manufacturer NOT issue a Blanket PO?

When minimum annual usage of item is low (under $500).
When part is only used for project work and usage in unpredictable.
When price is subject to change without notice.
When quality of product or supplier is questionable.

What other factors should I consider?

The main risks when using Blanket Purchase Orders occur when BPOs are not monitored or extended past their final scheduled release, which can lead to price changes and inventory availability problems. The best way to mitigate this risk is through the use of an effective spend management tool that includes a minimum safety stock level. Collaboration with your supplier is also recommended.

The other main risk occurs when a blanket order is issued for more than the needed quantity of a specific part due to demand forecast issues or product changes. This risk can be mitigated by working with your supplier to set conditions to manage this gap, such as extending a 1 year blanket to 18 months.

Blanket Purchase Orders at MF Supply:

Here at MF Supply, we can help you effectively craft a proactive BPO strategy based on your organization’s unique needs. We offer blanket orders for up to 18 months with flexible terms and low minimums.

For more detailed information about Blanket Purchase Orders, to request a line card, or to send an RFQ, visit our website. And if you don’t see what you need listed, as always, ask us. “Finding the right screw for you” is our tag line after all!

Contact me at robin@mfsupply.com with your questions, comments or helpful hints!

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MF Supply's experts discuss fasteners and electronic hardware

Mastering Mil-Spec Dowel Pins: Fit, Material, and Series Made Simple