The

Self-clinching
Fastener
Handbook
 contents

Brief fastener history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

How, why and where self-clinching works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Reliability in service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Anatomy of self-clinching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Types of self-clinching fasteners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Importance of quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Installation procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Installation problems and solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-11
Common Design Challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Other considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Glossary of terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Identification Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

© 2018 PennEngineering.
PEM® is a brand name and a registered trademark for fasteners manufactured exclusively by PennEngineering.

HB-2 PennEngineering • www.pemnet.com

 the idea
that revolutionized
production fastening

w hen K.A. Swanstrom

founded Penn Engineering &
Manufacturing Corp. in 1942,
he did so with a revolutionary
new product: an easy-to-install, self-clinching fastener
that provides load-carrying threads in metal sheets
too thin to be tapped.
designers, making a wide assortment of thin-metal
designs possible for the first time.
Industry-wide acceptance led to earnest production of
self-clinching fasteners shortly after World War II. As
industry’s need to hold together ultra-thin and ultra-light
metals grew, so did the product line. Over the years the
original self-clinching fastener design evolved to meet
hundreds of new design applications.
At first, Mr. Swanstrom produced his innovative
design with four machines in a Doylestown, Today, nuts, studs, spacers, standoffs, access
Pennsylvania garage. This simple operation hardware, and other components are used worldwide
soon gave way to a modern facility in Danboro, by a variety of manufacturers, including producers of
Pennsylvania as manufacturers and engineers alike telecommunication, computer, medical, automotive, and
recognized the benefits of self-clinching fasteners. aerospace equipment and systems.
They not only reduced time, labor, weight and
inventory on many assembly jobs, but they also
opened up a whole new world for engineers and

Advantages of self-clinching fasteners:

• Provide strong threads in metal as thin as .012”/0.3 mm.
• Installs into a plain, round hole.
• Installed using any parallel acting squeezing force.
• Provide high pushout and torque-out resistance.
• Do not require special hole preparation, such as chamfering and deburring.
• Reverse side of metal sheet remains flush.
• No retapping necessary after application.
• Low installed costs.

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 how, why & where
to use self-clinching fasteners

b
roadly defined, a self-clinching fastener sheet is thick enough to sustain tapping, it may actually
is any device, usually threaded, that be more economical to use self-clinching fasteners
when pressed into ductile metal, with gaugeable threads. They can be installed during
displaces the host material around the fabrication to eliminate loose hardware during final
mounting hole, causing it to cold flow assembly. In fact, the use of self-clinching fasteners
into a specially designed annular recess in the shank often will allow the use of a thinner sheet. Because of
or pilot of the fastener. A serrated clinching ring, knurl, their compact design and low profile, they provide for a
ribs, or hex head prevents the fastener from rotating neat appearance, too.
in the host material once it has been properly inserted
(see page 6). Thus, self-clinching fasteners become a As a rule, a self-clinching fastener should be specified
permanent part of the panel, chassis, bracket, or other whenever a component must be readily replaced and
item into which they are installed. where “loose” nuts and hardware won’t be accessible. If
it appears that the attaching “nuts” and “screws” can’t
They also have greater reliability and more holding be reached after a chassis or cabinet is assembled,
power than extruded/tapped or stamped threads. They self-clinching fasteners can be installed during metal
are used chiefly where good pullout and torque loads fabrication and can simplify and expedite component
are required in sheet metal that is too thin to provide mounting and assembly operations, including those
secure fastening by any other method. Even if the performed in the field.

DESIGN FOR MANUFACTURE SELF-CLINCHING

AND ASSEMBLY FASTENERS REQUIRE:
Self-clinching fasteners help designers meet DFMA • Ductile panel material softer than the fastener.
parameters which include: (Generally a 20 point difference on the Rockwell B
• Fewer parts to handle. Hardware such as washers, scale is required). See tables on page 6.
lock washers, and loose nuts are no longer • Adequate sheet thickness.
required in final assembly. • Pre-punched holes.
• Access to both sides of the sheet for installation.
• Fewer assembly steps. Since the task of hardware • An insertion press with adequate throat depth to
installation is done during fabrication, the number reach the installation point.
of steps required for final assembly is reduced.
• Less total assembly time. Fewer parts and less If these conditions can be met, then self-clinching
steps mean shorter assembly time. fasteners are the best solution for strong, clean,
permanent threads in thin sheet metal. If material is
All of which lead to shorter time to market, not ductile enough, see “Fasteners for Non-ductile
improved quality through assembly simplification, Materials” on page 13.
and reduced overhead.

SPECIAL NOTE FOR INSTALLING INTO STAINLESS STEEL SHEETS

One of the very basics of self-clinching is that the fastener must be harder than the host sheet. Only then will the fastener
perform as intended. This is particularly challenging when installing fasteners into stainless steel sheet metal.
If your application requires that the fastener clinches into stainless steel, be sure you use the fasteners specifically designed
for this purpose. Consult PEM® Bulletin SS for information on these types of fasteners.

HB-4 PennEngineering • www.pemnet.com

 reliability
in service of a self-clinching fastener

t
he reliability of a self-clinching fastener in the fastener often with values exceeding the ultimate
service depends on many factors, beginning torsional strength of the mating screw or nut.
with a properly sized hole, the thickness and
hardness of the host panel, A second reliability measure is pushout.
proper installation and design of RELIABILITY Pushout values indicate the axial
the fastener, and the application where the FACTORS: resistance of a fastener to remove it
fastener is used. from the sheet opposite to the direction
–––––––––––––––––––––
from which it was installed, and should
There are three tests applicable to a • Properly sized hole be roughly 5 to 10% of the force used to
self-clinching fastener to determine its • Sheet thickness install the fastener.
reliability in service. The first, called
• Sheet hardness
torque-out, determines the fastener’s A final test is pull-through.(1) Pull-through
ability to resist rotation within the panel. • Proper installation is the resistance of a fastener to pulling
This test often is made at the head of • Quality of fastener through the metal sheet when a clamping
torque is applied.

General pushout and torque-out values for PEM® brand self-clinching nuts.(1)
(unified and metric data)
Test Sheet Material
Thread Type S Nut Installed Into Type S Nut Installed Into Type SP Nut Installed Into
Size 5052-H34 Aluminum Cold-rolled Steel 300 Series Stainless Steel(2)
Installation Pushout Torque-out Installation Pushout Torque-out Installation Pushout Torque-out
(lbs.) (kN) (lbs.) (N) (in.lbs.) (N•m) (lbs.) (kN) (lbs.) (N) (in.lbs.) (N•m) (lbs.) (kN) (lbs.) (N) (in.lbs.) (N•m)
2-56 M2 1500-2000 6.7-8.9 90 400 10 1.13 2500-3500 11.2-15.6 125 550 15 1.7 8000-10000 35.6-44.5 165 725 17 1.92
4-40 M3 1500-2000 6.7-8.9 90 400 10 1.13 2500-3500 11.2-15.6 125 550 15 1.7 8000-10000 35.6-44.5 165 725 17 1.92
6-32 M3.5 2500-3000 11.2-13.5 95 400 17 1.92 3000-6000 13.4-26.7 130 570 20 2.3 8500-10500 37.8-46.7 170 755 24 2.7
8-32 M4 2500-3000 11.2-13.4 105 470 23 2.6 4000-6000 18-27 145 645 35 4 9000-11000 40-49 180 800 37 4.18
10-32 M5 2500-3500 11.2-15.6 110 480 32 3.6 4000-9000 18-38 180 800 40 4.5 9500-11500 42.3-51.2 230 1025 45 5.08
1/4” M6 4000-7000 18-32 360 1580 90 10.2 6000-8000 27-36 400 1760 150 17 13500 60 450 2000 150 17
5/16” M8 4000-7000 18-32 380 1570 120 13.6 6000-8000 27-36 420 1870 165 18.7 14800 66-80 470 2100 170 19

(1) Pull-through generally applies only to self-clinching studs and standoffs and is not shown in this chart.
(2) See special note about installing into stainless steel on page 4.

Applied Torque

TORQUE-OUT TEST
Driver for applied torque
Torque-out tests shall be performed
from the shoulder or head side of
Installation Force
the installed fastener. Torque shall
be applied to the fastener in the Test Strip Washer - Approximately
manner illustrated, using a hardened (parent material). 1 to 2 pitches. Thick
test screw and washer, while firmly Held firmly in a vise. enough to prevent
holding the test strip. Test screws neck of screw from
contacting threads.
should be of sufficient tensile
strength to resist thread stripping. A Pushout

minimum of two screw threads must

extend beyond the fastener.
Hardened Test Screw/Bolt
Grade 5 or better

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 the anatomy
of self-clinching
Maximum Sheet Hardness for Fastener Materials Typical Hardness of Sheet Materials
Fastener Material Sheet Hardness Sheet Material Sheet Hardness
Aluminum <HRB 50 / HB 89 5052-H32/34 Aluminum HRB 15-30 / HB
Unhardened Steel <HRB 60 / HB 107 Cold-rolled Steel HRB 40-75 / HB
300 Series Stainless Steel <HRB 70 / HB 125 6061-T6 Aluminum HRB 50-55 / HB 89-96
Hardened Steel <HRB 80 / HB 150 304 Stainless Steel (Annealed) HRB 80+ / HB 150+
Hardened Stainless Steel <HRB 88 (92) / HB 183 (202) HSLA Steel (does not follow typical rules) HRB 80-85 / HB 150-169

Typical self-clinching nut

Direction of
Installation
Force

Head

Serrated Clinching
Ring Provides
Torque Resistance

Back Tapered
Shank

Typical self-clinching standoff Host Metal

Host Metal
Cold Flows into Component
Screw Undercut
Flush Mounted

Typical self-clinching stud

Component
or Panel

Component

Host Metal Flows

into Undercut

Flush Mounted Direction of Hex Head Provides

Installation Force Torque Resistance

Ribs Provide Host Metal

Torque Resistance Flows into Undercut

Flush Mounted
Direction of Installation Force

HB-6 PennEngineering • www.pemnet.com

 basic typesof
self-clinching fasteners
A self-clinching feature can be applied to many types of fasteners as shown below to combine the benefits of self-clinching with a broad
range of fastener functionality. All of these self-clinching features are a variation of one on the three basic styles shown on page 6. Some
unthreaded fasteners use plain round displacers because they are not subject to torsional loading and do not require an anti-rotation feature.

nuts: Nuts with thread strengths concealed-head: Installed

greater than mild steel screws are into milled, blind holes so that one side
commonly used wherever strong of the panel remains unmarred. Studs
internal threads are needed for and standoffs are generally available in
component attachment or fabrication the concealed-head type.
assembly.
blind: Have closed ends that limit
studs and pins: Threaded screw penetration and are useful for
and unthreaded fasteners which are protecting internal components from
used where the attachment must be damage by inadvertent insertion of
positioned before being fastened. extra long screws. Threads are also
protected from damage and foreign
spacers & standoffs: matter.
Used where it is necessary to stack
or space components away from the right angle: Provide strong
panel. Thru-threaded or blind types right angle attachment points.
are generally standard. These fasteners are a cost-effective
replacement for: bent edge tabs;
flush fasteners: These bent center tabs; bent flanges; angle
fasteners are installed completely brackets; tack welds; and loose
flush within the sheet. hardware.

floating nuts: Compensates cable tie-mount: Provide

for mating hole misalignment by secure attachment points for mounting
having a floating threaded element. wire to electrical chassis or enclosures
without the problems associated with
threaded access traditional mounting methods.
hardware: Generally used on
enclosures where the screw must sheet joining fastener:
remain with the door or panel. Joins two sheets of metal or metal to
PCB/plastic. The fastener installs
locking fasteners: Provide smooth with the top sheet, and
a locking feature to restrict the flush or sub-flush with the bottom
rotation on the screw under adverse sheet.
conditions of vibration. Locking
features may include metal or plastic
types.
CUSTOM DESIGNS
non-threaded Since there are a great many types of standard self-clinching
fasteners: Allow for quick fasteners available, it is usually possible to choose one to meet
your design requirement. There are times however that a custom
assembly or removal of components designed and manufactured fastener is necessary. If this is the
without the need for screws or case, PennEngineering can assist you with your requirement to
additional fastening hardware. provide you with the best solution to your design.

PennEngineering • www.pemnet.com HB-7

 quality

a
of self-clinching fasteners
n order request comes to the desk of the many self-clinching fasteners. Basic blanks are formed
buyer or procurement individual for self- on cold headers or cold formers; subsequent operations
clinching fasteners. Although a review of such as piercing, drilling, tapping, thread rolling, and
the manufacturer’s basic specifications slotting may be required.
will undoubtedly turn up a shopping list of suppliers, a
purchase made on the basis of lower price alone may Self-clinching fasteners are also made from free-
prove more costly in the long run. machining, cold-drawn, low-carbon bar stock, a variety
of free-machining and cold-drawn stainless steels,
Installed cost . . . There are significant aluminum and phosphor bronze. They are formed on
the bottom line variations in the automatic bar machines and generally have secondary
When a designer investigates the
materials used, operations such as slotting, tapping or lock forming.
desirability of using self-clinching manufacturing
fasteners, his calculations must processes, Finishing operations such as heat-treating and plating
offer a true picture of cost. If integral quality controls are equally sophisticated, and quality control measures
fasteners are now being welded,
the cost of materials, labor and
and component must be monitored throughout the manufacturing
overhead must be factored into the dimensions that make process.
final cost per fastener to grant an the “same” product,
accurate comparison with the final made by different With so many manufacturing variables to control, there
calculated cost per self-clinching
fastener. Rejects and spoilage due to
manufacturers, very are several quality areas which must be examined
failure of poorly designed fasteners different from one before choosing the supplier of self-clinching fasteners
will contribute to high production another. for your application.
costs, so be certain that the
fasteners actually purchased meet
Wire stock is used for These include:
your engineering specifications.
the manufacture of

DIMENSIONAL TOLERANCES: A self-clinching fastener requires very tight tolerances to maximize it’s performance. In a
part that is specified with a dimension .010”/0.254 mm a variation of only .002”/0.051 mm can make a 20% difference.

THREAD FIT: A part may be specified because it meets one or more government specifications for thread tolerances. If
equivalents are considered, be sure that they meet the same specifications.

LOCKING TORQUE: If applicable, be sure that parts meet the locking torque specifications required.

HEAT TREATMENT: This is a very critical quality area. Improper heat treatment can cause a fastener to fail during or after
installation. Improper tempering can cause fastener brittleness causing the fastener to crack; inadequate treatment can cause
fasteners to be so soft that they are literally crushed during installation.

PLATING: Plating standards set limits for preparation of the metal, plating thickness, adhesion, rust corrosion protection,
hours of salt spray testing, and other operations. A poorly plated part will diminish the appearance and performance of your
final product.

PERFORMANCE: The fasteners should be tested to meet the manufacturer’s published performance data. In addition to
basic performance testing, be sure the fastener also meets your requirements for vibration resistance, thread locking, heat, and
electrical characteristics.

QUALITY CONTROL: Ensure the fastener manufacturer is ISO 9001 / QS 9000 (or other industry appropriate) compliant.
This will help assure that all the above criteria is being met.

HB-8 PennEngineering • www.pemnet.com

 installation
procedure

f
ast, simple installation saves time and 5. When installed using the recommended squeezing force
money on the assembly line. (depending on the size of the fastener and hardness
of the sheet metal), there is little or no distortion of the
In just three easy steps, self-clinching sheet or damage to the finished surface. Fasteners
fasteners can be installed with any parallel generally should be installed after plating, finishing or
acting press that can be adjusted to optimum anodizing.
installation forces.
6. Sheet material must be softer than the fastener. If
the fastener is not hard enough, it will deform (crush)
First, place the fastener into the instead of cold flowing the sheet material. Some
anvil hole and place the mounting operations will locally harden a sheet, i.e., punching
hole (preferably the punch side) 300 series stainless or laser cutting a mounting hole
over the shank of the fastener. (see note on page 4).

With installation punch and anvil Fastener Installation “Dos”

surfaces parallel, apply squeezing
Do provide mounting hole of specified size for each fastener.
force until the head of the nut comes
Do install fastener into punch side of sheet.
in contact with the sheet material.
Do make certain that shank (or pilot) is within hole before applying
installation force.
Finally, install the mating piece Do apply squeezing force between parallel surfaces.
from the side opposite the head of Do apply sufficient force to totally embed clinching ring around
the fastener. entire circumference and to bring shoulder squarely in contact with
sheet. For some fasteners, installation will be complete when the
head is flush with the panel surface.
Additional notes . . .
Fastener Installation “Don’ts”
1. Mounting holes may be punched or drilled; they
Don’t attempt to install a 300 series stainless steel fastener into a
should not be chamfered or have broken edges in stainless steel sheet.
excess of .005”/.127 mm. Hole tolerances of +.003,
Don’t install steel or stainless steel fasteners in aluminum panels
-.000/+0.08 mm must generally be held. The fastener
before anodizing.
should be installed on the punch side if the sheet
is .09”/2.29 mm or thicker because of the piercing Don’t deburr mounting holes on either side of sheet before installing
fasteners – deburring will remove metal required for clinching
break-to-die diameter. In all cases, the manufacturer’s
fastener into sheet.
recommended “minimum centerline of hole to edge of
sheet” (see page 12) distance should be observed. No Don’t install fastener closer to edge of sheet than minimum edge
distance indicated by manufacturer – unless a special fixture is used
deburring or countersinking is required.
to restrict bulging of sheet edge.
2. Installation typically results in a flush surface on Don’t over-squeeze. It will crush the head, distort threads, and buckle
one side of the panel. Conversely, staked or crimped the sheet. Approximate installation forces are listed in performance
fasteners require special counterboring to obtain a data tables. Use this info as a guide. Be certain to determine optimum
one-sided flush surface. installation force by test prior to production runs.
Don’t attempt to insert fastener with a hammer blow – under any
3. When installing, the most important criterion is that the circumstances. A hammer blow won’t permit the sheet metal to flow
fastener must be squeezed into place with any parallel and develop an interlock with the fastener’s contour.
acting press.
Don’t install screw in the head side of fastener. Install from opposite
4. Because the installation equipment generates no side so that the fastener load is toward sheet. The clinching force
excess noise or pollution, the fasteners can be is designed only to hold the fastener during handling and to resist
installed anywhere in the production process. No torque during assembly.
special facilities, ventilation equipment, or safety Don’t install fastener on pre-painted side of panel.
procedures are required.
PennEngineering • www.pemnet.com HB-9
 installation
problems and solutions

Problem Possible Cause Solution

Poor holding power - fastener not • Punch and anvil faces are not • Ensure that punch and anvil are flat
seated squarely. parallel. and parallel and hard.
• Panel cocked during installation. • Ensure that large panels are held
perpendicular to punch and anvil.

Poor holding power – fasteners fall • Inadequate installation force. • Seat fastener against shoulder
out of panel. • Panel too hard for fastener material. by applying more force or changing
• Countersunk hole in panel. shut height of press.
• Oversized mounting hole. • Specify appropriate fastener
• Some operations may locally material for sheet hardness, i.e.,
harden a sheet, i.e., punching 300 stainless steel (see note on bottom
Series Stainless or laser cutting a of page 4).
mounting hole. • Do not countersink or deburr hole.
• Die side of panel thicker than • Prepare properly sized mounting
.093”/2.36 mm may have hole too hole.
large for fastener due to necessary • Punch hole under size and ream to
punch and die clearance. catalog dimensions or change
tooling to punch from opposite side
of panel.

Poor holding power of fastener near • Sheet was bent after fastener was • Bending should be done prior to
bend. installed. This may have caused installation.
distortion of mounting hole. • Punch hole after bending the sheet
• Hole is punched prior to bend and
hole has become elongated.

Poor holding power of standoffs or • Hole in anvil too large or • Use anvil with hole per catalog
studs in panel. chamfered. dimensions.

Poor holding power – nut off center • Oversize mounting hole. • Punch or drill hole to specified
of hole. • Nut is cocked in hole and shears dimensions.
side of hole when installed. • Check that shank of nut is squarely
in hole before squeezing.

HB-10 PennEngineering • www.pemnet.com

 installation
problems and solutions

Problem Possible Cause Solution

Threads tight – sheet buckles. • Fastener over-squeezed. • Reduce installation force.

Tight threads, cracked. • Shank length extends through • Choose fastener with proper shank
sheet. length for sheet thickness.

Fastener does not fit into hole. • Undersized mounting hole. • Prepare properly sized mounting
hole.
Fastener deforms or shears during
installation.

Sheet metal may extrude into

installation tooling causing tool to
stick or crack.

Panel buckles badly with stud in .040” • Lack of countersink in anvil. • Provide countersink in anvil to
to .059” (1 mm to 1.5 mm) material. specified dimensions.

Head of flush-head stud or standoff • Punch diameter too small or not • Punch must be larger than head
cups. hard and flat. of stud or standoff and preferable
equal to anvil diameter.

Edge of panel bulges. • Mounting hole violates specified • Restrain panel or bracket in
minimum edge distance. fixture during installation or move
• Nut is over-squeezed. mounting hole away from edge.
(See page 12)
• Reduce installation force if possible.

Questions? Consult our Applications Engineering department at techsupport@pemnet.com

PennEngineering • www.pemnet.com HB-11

 common design
challenges
CENTERLINE-TO-EDGE
When installing too close to an edge, the sheet may bulge or
blow out. Supporting the edge with special anvils can be used to
reinforce the edges and get closer than published values indicate.
Use with caution.

MULTI-SIDED CLOSE-TO-EDGE APPLICATIONS

All minimum centerline to edge distances given in catalog bulletins
apply to one edge only. If this distance is applied on multiple sides as
shown here and the edges are not supported during installation there
will be significant panel distortion as shown by the dotted lines. This
distortion will reduce the amount of panel material in the undercut and
may significantly reduce the holding power of the clinch feature.

PROXIMITY TO A BEND
When installing near a bend, use the “Centerline-to-Edge” value to find
the minimum distance to the outside of the bend radius. Failures that
occur are different from Centerline-to-Edge situations.

SPACING OF MULTIPLE FASTENERS

Multiple fasteners installed must be spaced far enough apart to avoid distorting each other’s holes.
Failures seen can include sheet distortion and “oil canning”. When determining the
distance between two or more fasteners, you can calculate the distance by the
formula, C/L to edge + 1/2 the diameter of the second mounting hole.

See our Tech Sheet for more information on centerline-to-edge challenges.

MATERIAL AND FINISH CONSIDERATIONS

• Do not install self-clinching fasteners after paint or powder coating. This will diminish fastener
performance.
• When using steel panels, install plated fasteners after panel is plated. Otherwise install unplated
fasteners into panel if entire assembly is going to then be plated.
• Do use proper alloy (A286/400 Series) stainless fasteners in stainless steel sheets. 300 Series fasteners
do not provide adequate differential hardness for best performance.
• Anodizing complete aluminum assemblies after installing aluminum fasteners may cause slight color
differences between fasteners and panel.
• Beware of processes such as hard coat anodizing and nitriding that might increase panel hardness. This
might make it more difficult to install self-clinching fasteners.

See our Tech Sheet for more information on surface finishing sheet metal assemblies.

HB-12 PennEngineering • www.pemnet.com

 other
considerations
AUTOMATED ASSEMBLY

Since all self-clinching fasteners must be squeezed into place, any

press or vise that provides the necessary parallel force may be used
to install them.

An automated press should be considered for high volume Haeger 824

installations. These presses are specifically designed to feed self- OneTouch-4e
Lite.
clinching fasteners automatically into punched or drilled holes in
sheet metal, seating them correctly with a parallel squeezing force.
Feeding rates are five to six times faster than manual insertions,
and installation force is adjustable to compensate for variations in
thickness and hardness of the sheet and the height of the fasteners.

Our equipment capabilities incorporate “smart” tooling and

software, automation, robotics integration, and in-die installation
with our in-die fastener feeding system which brings new
dimensions to stamping capabilities and incorporates the latest
technologies to deliver the performance that is needed to compete
in the highly competitive stamping industry. It eliminates the
secondary operations typically required for fastener insertion,
thus reducing overall labor costs, improving part quality and
dramatically improving production efficiencies.
PEMSERTER®
In-Die fastener
feeding system.

FASTENERS FOR NON-DUCTILE AND ONE-SIDE ACCESS INSTALLATION

Self-clinching fasteners are designed to be installed into Flare-mount fasteners offer a combined
sheet metal panels only when both sides of the sheet broach/flare feature for even greater
are accessible. For applications that do not meet this pullout performance in P.C. Board
criteria, PennEngineering offers other possible solutions. materials.
These include:
ReelFasT® SMT fasteners mount to P.C.
ATLAS® style blind threaded inserts boards in the same manner as other
(rivet nuts) provide strong threads surface mount components prior to the
in applications where only one side automated reflow solder process.
of the assembly is accessible for
installation. These fasteners can also VariMount® bonding fasteners are
be used in most non-ductile material applications. assemblies comprised of standard
PEM® fasteners mounted permanently
A broaching fastener is any knurled into base plates. The assembly can
shank fastening device that is pressed then be fastened to assorted panel
into a punched or drilled hole to types in a variety of ways.
provide a strong threaded attachment
point in a non-ductile material.
PennEngineering • www.pemnet.com HB-13
 answers to the ten most
frequently asked questions
about self-clinching fasteners

Q Does the shape of the self-clinching fastener Q When using self-clinching fasteners, what are my
change during installation? panel requirements?

A No, the fastener does not deform in any way. There A Generally, there are two basic requirements. First,
is no flaring, crimping, swaging, peening or riveting the panel must be a ductile material softer than the
necessary. fastener which is going into it. Second, the panel must
___________________ meet the minimum sheet thickness required by the

Q What holds the fastener in the sheet? particular fastener. Some self-clinching fasteners can
be installed into sheets as thin as .020”/0.51 mm, but

A The squeezing force on the fastener causes the generally .030”/0.76 mm or .040”/1 mm is the minimum
sheet thickness necessary.
sheet material beneath the head to cold flow into the ___________________
back-tapered shank or undercut of the fastener securely
locking it in place. Q Is there a maximum sheet thickness I should
___________________ be concerned with before specifying self-clinching

Q Do I need special equipment to install self- fasteners?

clinching fasteners? A Generally, there is no specified maximum

A No. Self-clinching fasteners are installed using thickness for sheets. However, because of their special
design and function, a few fastener types do specify a
any type of parallel acting press which will squeeze the thickness range which includes a maximum.
fastener in place. ___________________
___________________
Q Won’t these fasteners fall out, twist out, or spin in Q I notice some of the fasteners have a hexagonal
shaped head. Do I have to punch a hexagonal
their mounting holes if I tighten down too hard? mounting hole to install these?

A No. Typical torque-out values are generally quite A No. All self-clinching fasteners are installed into
high compared to the rotational force that will be put a round punched or drilled hole. A hexagonal head will
on them. In fact, for most quality self-clinching nuts, the cause the sheet material to cold flow around the head to
screw will fail before the nut rotates in the material. provide high torque-out resistance. The hex head will be
___________________ flush in the sheet when installed.
___________________
Q I would like to replace some of the welded
fasteners I now use in my stainless steel fabrications. Q Can I install these blind, from one side, if I don’t
Is there a self-clinching fastener that will go into a have access to both sides of the sheet?
stainless steel sheet?
A Generally, you must have access to both sides
A Yes. Self-clinching fasteners for stainless steel of the sheet to properly install self-clinching fasteners.
applications are available. These fasteners are generally However, there are some 1/4”/M6 or larger nuts which
made from specially hardened stainless steel and will can be drawn in from one side using an impact-torque
install into sheets up to HRB 88 in hardness. wrench. For information on blind threaded inserts for
one sided access installation go to www.pemnet.com.

HB-14 PennEngineering • www.pemnet.com

 glossary
of terms

Anvil - An insert, either solid or hollow, which is used on the Pull-through - The resistance of a fastener to a force applied in the
underside of a panel to resist the installation force. same direction to which it was installed.
Blind - A hole, usually threaded, which is open from only one end. Punch - A movable insert, either solid of hollow, which applies an
installation force to the top of the fastener.
Broaching - The act of cutting a shape in any object by using a
mandrel of a similar shape. As applied to fasteners, the way a knurled Pushout - The force required to remove a fastener from a panel in
shank “broaches” its way into the mounting hole. a direction opposite to the way from which it was installed. Note:
Pushout is expressed in pounds or newtons.
Captive - The ability of a fastener to remain securely attached to a
panel. Rockwell hardness - A relative measure of hardness. Rockwell C
Scale is used for hard materials, Rockwell B for softer materials, such
Captive screw - See: panel fastener.
as sheet metal.
Chamfer - A beveled edge or corner.
Self-clinching - The method by which a fastener is securely attached
Cold flow - The movement of a ductile material under pressure. to a sheet of ductile material by causing the material to cold flow
under pressure into an annular recess of the fastener thereby securely
Concealed-head - A type of fastener which, when installed, is
locking it in place.
completely hidden when viewed from the reverse side.
Self-locking - A locking element, formed as an integral part of a
Counterbore - That portion of the axial length of which is drilled to a
fastener, which provides force to restrict the rotational movement of a
larger diameter than the remaining portion of the part.
threaded member.
Ductile - Metal which is not brittle and can be easily formed or bent.
Shank - The portion of a fastener, which is slightly smaller than the
Floating - The ability of a fastener to move in a direction parallel to fastener’s mounting hole and provides a positive location for the
the mounting panel and allow for mating hole misalignment. fastener in the hole. A shank also incorporates an annular groove
which becomes filled with panel material as the fastener is installed,
Flush - The ability of a fastener to be contained completely within the
and the retention of this material provides pushout resistance.
thickness of a panel. Also refers to the absence of a protrusion above
the surface of the panel. Shank length - The actual length of that portion of a fastener which is
embedded in the panel material.
Head - The portion of a fastener which forms its largest diameter.
Shoulder - The surface area of a fastener which contacts the top
Installation force - A term expressed in pounds, tons, or newtons
surface of the sheet material. See: positive stop.
applied axially to a self-clinching fastener to achieve proper
installation. Spring-loaded - A device having a separate moveable component
that is biased in one direction by a spring.
Interference fit - The insertion of one member into another whose
diameter is slightly smaller than the part being inserted. Standoff - A tubular device, usually threaded, for spacing or stacking
components.
Knurled clinching ring - The displacer portion of a fastener which
has corrugations and is used to develop torque resistance when Stud - A male threaded captive post that extends from a panel.
installed in sheet metal.
Swaging - An operation whereby a reduced diameter of a fastener
Locking element - A device employed to restrict rotation of a is deformed to secure it to a panel. Note: the antonym of swaging is
threaded member while operating in adverse environments, such self-clinching where the panel material is caused to deform.
as vibration and temperature. The nut-locking element provides
Thread class - A measure of clearance or fit between the screw and
prevailing locking torque to the mating screw.
the nut taken at the pitch diameter.
Minimum distance - The minimum distance from the center of a
Threaded insert - A threaded device which is installed in a panel
fastener mounting hole to the nearest edge of a panel which will keep
material.
the edge from deforming. This distance may be reduced by suitable
fixturing or increasing thickness of panel material. Through hole - A hole, threaded or unthreaded, which transverses
the entire length of a part and is usable from either end.
Minimum sheet thickness - The thinnest section of a panel, usually
measured in thousandths of an inch or millimeters, into which Tolerance - The absolute amount of maximum or minimum
a fastener may properly be installed. The same fastener may be dimensional deviation allowed that will not affect the performance of
installed in panels having any thickness greater than minimum. a mechanical part.
Mounting hole - A properly-sized round opening in a panel to receive Torque-out - The amount of torque necessary to spin the fastener
the shank of a self-clinching fastener. out of the sheet. This is torque applied to the fastener. No axial load is
applied.
Panel fastener - A threaded screw which is held captive to a panel
and which, when disengaged from its main nut, remains fixed to that Torque-through - The amount of torque necessary to fail the fastener
panel. in axial load.
Pin - A captive post that extends from a panel. Undercut - The reduced diameter of a fastener which receives sheet
material when a fastener is installed. Depending on the type of
Plunger assembly - A spring-loaded device used for latching or
fastener, may be rectangular or back tapered in shape.
indexing purposes.
Positive stop - A visual indication that the proper depth of
penetration of the knurled ring has occurred or when the “head” is in Expanded list of terms can be found on our web site
contact with the top surface of the panel. Synonym: shoulder. www.pemnet.com

PennEngineering • www.pemnet.com HB-15

 PEM® fastener
identification trademarks
To help you identify genuine PEM® brand fasteners, most are marked by one of our registered trademarks. Genuine PEM brand
fasteners can only be purchased from one of our authorized worldwide distributors. For a complete list of these distributors, check
our web site: www.pemnet.com.

PEM® Dimple - U.S. Trademark Reg. #1,089,546

CFHA, CFHC, CHA, CHC, FH, FH4, FHA, FHL, FHLS, FHP, FHS, FHX, HF109, HFG8, HFE, HFH, HFHB, HFHS, HFLH, HSCB,
KFH, KSSB, MPP, PF10, PF30, PF31, PF32, PF50, PF51, PF52, PF60, PF61, PF62, PF11, PF11M, PF11MF, PF11MW, PF11PM, PF12,
PF12M, PF12MF, PF12MW, PF7M, PF7MF, PFC2, PFC2P, PFC4, PFHV, PFK, PFS2, PSHP, SCB, SCBJ, SCBR, SF, SFK, SFP, SFW,
SGPC, SKC, SKC-F, SMTPFLSM, SSA, SSC, SSS, T, T4, TFH, TFHS, THFE, TK4, TKA, TP4, TPS, TPXS, and TS fasteners

PEM® Stamp PEM® Skirted Shoulder

PEM® “Single Groove” mark
U.S. Trademark Reg. U.S. Trademark Reg.
U.S. Trademark Reg.
#1,403,759 #4,037,181
#2,028,457
CLS, CLSS, H, HN, HNL, PSHP, PF11, PF11M, PF11MF, PF11MW,
A4, BSO4, LA4, MSO4, PFC4,
S, SFN, SL, SMPP, SMPS, SS, PF11PM, PF12, PF12M, PF12MF,
SO4, SP (Select sizes), and
and WN fasteners PF12MW, PF7M, and PF7MF
TSO4 fasteners
fasteners

PEM® “Double Squares”

mark PEM® C.A.P.S.® Dot PEM® Circle on Pedestal
U.S. Trademark Reg. Pattern U.S. Trademark Reg.
#1,400,893 / #3,404,061 U.S. Trademark Reg. #4,293,597
A4, AC, AS, LA4, LAC, and #4,007,693 RAS fastener
LAS fasteners PF11PM fastener

PEM® Double Notch PEM® Blue Nylon

U.S. Trademark Reg. PEM® Blue Nylon Ring Locking Element
#4,326,083 PFC4, PFC2P, PFC2, U.S. Trademark Reg.
microPEM® SMTSO fastener PFS2, and PFK fasteners #1,449,260
PL, PLC and CFN fasteners

PEM VM® Stamp

PEM® SH Stamp
(Both Sides)
U.S. Trademark PEM® RT Stamp
U.S. Trademark Reg.
Reg. #5,023,068 S-RT fasteners
#5,305,895
SH fasteners
VariMount® Base Plates

PEM® SP Stamp PEM® SMPP Stamp

ATLAS® AE Stamp
U.S. Trademark U.S. Trademark
MaxTite® and Plus+Tite®
Reg. #3,270,807 Reg. #5,055,266
products
SP fasteners SMPP fasteners

PEM® “Two Groove” mark - U.S. Trademark Reg. #2,077,226

B, BS, BSO, BSON, BSOS, CSOS, CSS, DSO, DSOS, HSR, KF2, KFB3, KFE, KFS2, KFSE, PF7M, PF7MF,
SMTSO, SMTSOB, SMTPFLSM, SO, SOA, SOAG, SON, SOS, SOSG, TSO, TSOA, and TSOS fasteners

All PEM® products meet our stringent quality standards. If you require additional industry or other specific quality certifications, special procedures and/or part
numbers are required. Please contact your local sales office or representative for further information.
Regulatory compliance information is available in Technical Support section of our website. Specifications subject to change without notice. See our website for the
most current version of this bulletin.

North America: Danboro, Pennsylvania USA • E-mail: info@pemnet.com • Tel: +1-215-766-8853 • 800-237-4736 (USA)
Europe: Galway, Ireland • E-mail: europe@pemnet.com • Tel: +353-91-751714
Asia/Pacific: Singapore • E-mail: singapore@pemnet.com • Tel: +65-6-745-0660
Shanghai, China • E-mail: china@pemnet.com • Tel: +86-21-5868-3688
Visit our PEMNET™ Resource Center at www.pemnet.com • Technical support e-mail: techsupport@pemnet.com
HB-16 2/17/20