1. Plastic Overview
The two main categories of plastics where threaded inserts
a. Thermoset Plastics
Thermoset plastics cannot be re-melted using heat or pressure
once they are formed into their desired shape, These plastics tend
to be hard and brittle. Since they will not re-melt, inserts installed
by heat or ultrasonic can’t be used in these materials.
Recommended insert types include:
» Self-Threading » Expansion » Press-In designs
» Phenolic » Epoxies » Vulcanized rubber » Polyamide
Thermoplastic materials can be re-melted and re-formed once
formed into their desired shape.
Heat and Ultrasonically installed inserts perform best in
thermoplastic types of materials however Self-Threading, Expansion
and Press-in style inserts may also be utilized in these materials.
» ABS » PVC » Polycarbonate » Nylon
Thermoplastic materials may be unfilled or may have a wide variety
of fillers added to them to increase the stiffness or toughness
properties of the material for specific applications. These fillers
may include nylon or carbon fiber, mineral or even metal.
2. Insert Characteristics
Dodge Inserts for Plastics are designed to provide the strength necessary
to allow bolts and screws to be tightened to the levels required to stretch
the fastener and maintain a sufficient bolted joint assembly.
The insert must also provide resistance to rotation and pull-out under
a wide variety of load and atmospheric conditions in a given assembly.
The optimum insert design depends on several factors including:
» Plastic resin
» Type and percentage of fill
» Preferred insert installation method
» Application strength requirements
» Environmental concerns
3. Material And Plating
Dodge inserts are traditionally made from 360 brass which falls
under the designation UNS C36000 ½ hard free-cutting brass.
The CDA specification is C360, ½ hard per ASTM B-16.
Dodge inserts are also available in alternate materials including
Steel and Aluminum. Contact Applications Engineering for further
Inserts and Compression
Limiters may be processed with
a variety of finishes from nickel
plates and automotive finishes
to colored dyes to distinguish
insert types or installations.
Please consult our Applications Engineering team for assistance with
To accommodate the best overall balance of rotational and pull-out
strength of an insert, the knurl bands are combined with undercuts,
fins or a combination of both.
b. Knurl Patterns
The most common design methods used to increase rotational
strength of an insert include increasing body diameter or increasing or
changing the knurl pattern on a given insert design. The rotational
resistance of an insert design can change dramatically by altering
the coarseness or fineness of a knurl.
Coarser knurl patterns can provide a significant increase in rotational
strength but can also induce significant stress into the insert/plastic
assembly which could ultimately lead to cracking and premature failure.
Effective in applications focused on high rotational strength.
» Multiple Knurls
It is common practice to utilize more than one knurl style
and direction on the same part to reach the most optimum
combination of rotational and torque resistance.
To eliminate installation issues, many inserts are designed to
be installed into a tapered hole. This allows for the insert to
“self-align” during installation and requires less heat energy
as the mass of plastic resin that is required to melt is less than
with other hole designs. A tapered insert must always be
used in a tapered hole.
In certain applications, it is advantageous to have a large
bearing surface to distribute the load applied when fastening
mating parts. A large flange not only increases the bearing
surface but also allows for adjustment of the mating part
without a negative effect on insert strength.
e. Custom Capabilities
Dodge Threaded Inserts can also be custom designed for specific
applications. Examples include undercut configurations, closed ends,
platings, flange modifications, etc. Contact your Sales Engineer
or Applications Engineering at (866) 364-2781 for assistance.
5. Best Practices
a. Hole Preparation Considerations
Each Style of insert listed throughout the catalogue
Straight vs. Tapered Holes - Straight hole preparation
allows for a taper that should not exceed a 1 degree included
angle. Tapered holes require an 8 degree included angle.
Tapering permits easy release of the core pin, aids in insert
alignment, which in turn reduces installation time.
» Counterbores – Traditionally are not
recommended as they may interfere with
proper insert alignment. Self threading
inserts, or flanged inserts which should be
installed flush, are the exception to the rule.
» Recommended Hole Depth - Allows for proper insert
set down (flush to 0.005 inch below the surface), prevents
excessive flash, and prevents back filling of plastic from
entering bottom threads.
In some applications, a large flange insert is installed from
the opposite end of the part and when the screw or bolt is
assembled, the tensile load is applied to the flange, increasing
resistance to pull-out.
b. Boss Diameter/Wall Recommendations
Traditionally a boss diameter is two times the insert diameter for
inserts ¼” and under, 3mm wall thickness applies for all inserts
that are larger. Exceptions include applications incorporating
supported bosses, reinforced materials, and heat installation.
Special consideration should be given to cold press installations
where stress will be increased and will require larger boss diameters.
c. Assembly Guidelines For Mating Parts
Clearance Holes – It is important that the insert bear the load and
not the plastic to avoid jacking the insert out. The mating component hole
should be smaller than the face of the insert yet allow the connecting
threaded fastener ample space to function normally.
Strength – The head of the bolt being used in the assembly
must seat against the compression limiter to avoid potential
failure due to plastic creep.
Mating Components – The mating component must also
withstand the stress generated by the clamping force. In
instances where the mating component will also be plastic,
the use of a secondary insert should be considered.
Types of Applications
» Insert is equal to or larger than the flange
» Provides higher axial strength
» Failure mode is the bolt
» Insert is smaller than the flange
» Has simple OD configuration
» Applies to smaller inserts under ½” OD
a. Heat Installation
Heat installation involves positioning the insert into the molded or
drilled hole. A heated tip is then inserted into the inside diameter of
the threaded insert.
Localized melting begins to take place and with the downward
pressure, the insert begins to install. Plastic flows into the varying
undercuts and knurls.
Benefits of thermal installation include:
» installation of multiple inserts at a given time
» ability to install inserts beyond ¼”
» superior strength assemblies
b. Ultrasonic Installation
Ultrasonic Installation involves positioning the insert into a molded
or drilled hole.
An ultrasonic horn then contacts the insert and begins to vibrate
the insert. This vibration creates frictional heat which melts
the plastic allowing the horn to lower the insert into position.
Once installed to the appropriate depth, the cycle is repeated for
the next insert.
c. Self -Tapping/Self Threading, Spred-Lok,
Expansion Inserts and Mold-In
Designed for ease of installation. Primarily involves preparing straight
holes and driving the insert into place, pressing the insert into place,
or pressing and then expanding the insert into place. Minimal tooling
c1. Self Tapping
Economical and easy to install. Provides excellent pull out
resistance. Insert design features a cutting edge slot which
assists in installation.
Dodge Inserts are designed for post mold and molded-in installations.
Post molding is cost effective in that it generally shortens cycle time
of the molding process, reduces rejects and damage from inserts
that could potentially come loose and damage the mold.
Molded-In inserts offer higher torque and pull-out resistance.
Several Dodge insert designs are available for Post-Molding
using Ultrasonic installation or Heat installation.
c2. Spred-Lok Inserts
Economical and easy to install. Designed for non-critical applications.
Insert is pressed into a straight prepared hole, expansion of the insert
is accomplished through the installation of the mating fastener. Mating
bolt should be long enough to extend at least two full threads beyond
the insert length to ensure insert retention.
c3. Expansion Inserts
» Standard Expansion
Economical and easy to install. Expansion inserts feature
a two piece design consisting of a threaded insert and a
captivated spreader plate. The insert is installed into a
blind, straight hole and the spreader plate is then depressed.
As the spreader plate is engaged, the knurled portion of the
insert expands, anchoring the insert into place.
» Clinch Expansion
Clinch inserts feature a pilot and a flange and have the same
design characteristics as Standard Expansion Inserts. The
inserts are used extensively in the electrical industry.
The pilot can be clinched over a terminal connector with
the flange providing a large surface for electrical contact.
The installation and clinching operations are simultaneous
using a simple press-in type tool. Like the Flange Insert, much
of the installation force is absorbed by the flange allowing for
use in thin-section applications.
» Flange Expansion
The Flange Insert, in addition to having all of the design
features of the Standard Insert, has a flange with a large
bearing surface. The flange can be used to make an
electrical contact or to fasten a terminal connector. The flange
can also be used to join mating parts by inserting the body of
the insert through the mating part and into the receiving hole
in the parent material. The insert is excellent for use in thin
section applications since the flange absorbs much of the
c4. Mold In Inserts
While the trend is to install inserts into Thermoplastics by post
mold, some highly filled plastics (above 35% fill) will benefit from
a mold-in insert design. The Dodge Ultramold insert is a unique
two-piece insert providing full thread to the bottom of the insert.
This design also features a controlled minor diameter and
innovative counterbore design to insure proper placement on
molding pins. This insert design provides optimum strength
in a space saving design.
» Ultra-Mold® Inserts
The unique two-piece concept allows full and complete threads
throughout the entire length of the insert. This saves space
and weight and reduces costs. Below is an image of a conventional
insert (on left) and the unique design of the Ultra-Mold (at right).
c5. Sealing Inserts
When an insert is heat or ultrasonically installed into a plastic
component, the difference in cooling rates of the metal and plastic
create a “stress relief zone” or microscopic void between the insert
external geometry and the plastic. While this is beneficial in reducing
the stress between the two materials, it can pose challenges to those
applications requiring a leak-proof interface between the insert and
Dodge has addressed this situation with the Ultraseal® insert. The
Ultraseal utilizes an O-ring as an integral component of the insert design.
When heat installed into the proper geometry hole, the O-ring seals
against the plastic and provides a leak-proof assembly.
» ISO/TS 16949: 2009 certified
» Lot control ensures product traceability
» Statistically controlled manufacturing processes
» PPAP, IMDS, Material Certifications
Sales & Applications Engineers
» Strategically located throughout North America
» Offer expertise in insert design, applications
engineering and current assembly technologies
» Offer cost effective fastening solutions; includes:
– Modifications to our standard products
– Custom solutions for your specific applications
– Conduct Line Walks, Value Analysis / Value Engineering
» Our Technical Center offers review of your application,
product evaluation, analysis and recommendations to
help reduce your assembly costs
» Development support includes conceptual ideas,
preliminary designs and drawings
» Engineering prototypes and pre-production sampling
Technical Product Seminars
» Lunch and Learn Seminars offered to engineering,
manufacturing, purchasing and quality teams
» Instructors include representatives from our sales
engineering, applications engineering and/or
At STANLEY Engineered Fastening we believe in seeking ways to serve our customers better. We create the future by anticipating our
customers needs. Through diversifying our product lines, creating unique assembly technologies and offering a breadth of service to meet the
demands of industry worldwide, STANLEY Engineered Fastening provides technological solutions to over 100 different industries.
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systems since 1936 and offers a
comprehensive range of fasteners
With a focus on high-quality threaded
inserts for plastics products, Dodge has
been a leader in the fastening market
since the 1950s.
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threaded assembled products since 1904.
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the aerospace industry, Heli-Coil offers a
vast range of high-quality.
iForm® continues a proud heritage since
1969 and represents over 40 years of
creative threaded fastener application
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rivets, POP blind rivets meet the needs of
STANLEY Assembly Technologies supplies
production solutions to the global
Spiralock is a technologically superior
fastening system ideally suited for
threaded joint applications subjected to
heavy shock and vibration.
A one-sided drawn-arc welding process
is the foundation of the Tucker No-Hole
Whether it's plastic, metal, or a
combination of the two, Warren can
design a product that will suit your