The Self-Clinching
Fastener Handbook

DISCOVER THE DIFFERENCE

CONTENTS

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

3How, why and where self-clinching works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

Reliability in service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5

Anatomy of self-clinching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6Types of self-clinching fasteners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7Importance of quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8Installation procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9Installation problems and solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10-11

Common Design Challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12

Other considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13

Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14

Glossary of terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15

Identification Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16© 2021 PennEngineering.
PEM® is a brand name and a registered trademark for fasteners manufactured exclusively by PennEngineering.

HB-2

THE IDEA THAT REVOLUTIONIZEDPRODUCTION FASTENING

When K.A. Swanstrom founded Penn Engineering & Manufacturing
Corp. in 1942, he did so with a revolutionary new product: aneasy-to-install, self-clinching fastener that provides load-carrying
threads in metal sheets too thin to be tapped.

At first, Mr. Swanstrom
produced his innovative
design with four machines ina Doylestown, Pennsylvania
garage. This simple
operation soon gave way
to a modern facility in
Danboro, Pennsylvania as
manufacturers and engineers
alike recognized the benefitsof self-clinching fasteners.
They not only reduced time,labor, weight and inventory

on many assembly jobs, butthey also opened up a whole
new world for engineers anddesigners, making a wide
assortment of thin-metal designs
possible for the first time.
Industry-wide acceptance led
to earnest production of selfclinching fasteners shortly afterWorld War II. As industry’s needto hold together ultra-thin andultra-light metals grew, so did

the product line. Over the years
the original self-clinching fastenerdesign evolved to meet hundreds of
new design applications.
Today, nuts, studs, spacers,
standoffs, access hardware,and other components areused worldwide by a variety of
manufacturers, including producers
of telecommunication, computer,medical, automotive, and aerospaceequipment and systems.

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.

© 2021 PennEngineering®

HB-3

HOW, WHY & WHERE
TO USE SELF-CLINCHING FASTENERS
Broadly defined, a self-clinching fastener is any device,usually threaded, that when pressed into ductile metal,
displaces the host material around the mounting hole,causing it to cold flow into a specially designed annular
recess in the shank or pilot of the fastener. A serrated
clinching ring, knurl, ribs, or hex head prevents thefastener from rotating in the host material once it has
been properly inserted (see page 6). Thus, self-clinching
fasteners become a permanent part of the panel, chassis,
bracket, or other item into which they are installed.

be more economical to use self-clinching fasteners
with gaugeable threads. They can be installed during
fabrication to eliminate loose hardware during final
assembly. In fact, the use of self-clinching fasteners often
will allow the use of a thinner sheet. Because of theircompact design and low profile, they provide for a neat
appearance, too.

They also have greater reliability and more holding
power than extruded/tapped or stamped threads. They
are used chiefly where good pullout and torque loads
are required in sheet metal that is too thin to provide
secure fastening by any other method. Even if the
sheet is thick enough to sustain tapping, it may actually

As a rule, a self-clinching fastener should be specified
whenever a component must be readily replaced andwhere “loose” nuts and hardware won’t be accessible. If
it appears that the attaching “nuts” and “screws” can’tbe reached after a chassis or cabinet is assembled,
self-clinching fasteners can be installed during metal
fabrication and can simplify and expedite component
mounting and assembly operations, including those
performed in the field.

DESIGN FOR MANUFACTURE
AND ASSEMBLY

SELF-CLINCHINGFASTENERS REQUIRE:

Self-clinching fasteners help designers
meet DFMA parameters which include:• Fewer parts to handle. Hardware such as
washers, lock washers, and loose nuts are
no longer required in final assembly.
• Fewer assembly steps. Since the taskof hardware installation is done during
fabrication, the number of steps required
for final assembly is reduced.
• Less total assembly time. Fewer parts andless steps mean shorter assembly time.
All of which lead to shorter time to market,
improved quality through assembly
simplification, and reduced overhead.

• Ductile panel material softer than thefastener. (Generally a 20 point difference
on the Rockwell B scale is required). See
tables on page 6.
• Adequate sheet thickness.
• Pre-punched holes.
• Access to both sides of the sheet for
installation.
• An insertion press with adequate throat
depth to reach the installation point.
If these conditions can be met, then selfclinching fasteners are the best solution
for strong, clean, permanent threads inthin sheet metal. If material is not ductile
enough, see “Fasteners for Non-ductile
Materials” on page 13.

SPECIAL NOTE FOR INSTALLING INTO STAINLESS STEEL SHEETSOne 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

RELIABILITY IN SERVICE OF A
SELF-CLINCHING FASTENER
The reliability of a self-clinching fastener in service
often with values exceeding the ultimate torsional
depends on many factors, beginning with a properly
strength of the mating screw or nut.
sized hole, the thickness and hardness of the hostA second reliability measure is pushout. Pushout values
panel, proper installation and design ofindicate the axial resistance of a fastener
the fastener, and the application where theto remove it from the sheet opposite to the
RELIABILITY
fastener is used.
direction from which it was installed, and
FACTORS:should be roughly 5 to 10% of the force–––––––––––––––––––––
There are three tests applicable to aused to install the fastener.
self-clinching fastener to determine its• Properly sized holereliability in service. The first, called torqueA final test is pull-through.(1) Pull-through• Sheet thickness
out, determines the fastener’s ability tois the resistance of a fastener to pulling• Sheet hardness
resist rotation within the panel. This test
through the metal sheet when a clamping
often is made at the head of the fastenertorque is applied.
• Proper installation• Quality of fastener

GENERAL PUSHOUT AND TORQUE-OUT VALUES FOR PEM®
BRAND SELF-CLINCHING NUTS.(1)(unified and metric data)

TEST SHEET MATERIAL

2-56

M2

Type S Nut Installed Into
Cold-rolled SteelType S Nut Installed Into5052-H34 Aluminum

ThreadSize

Installation

Pushout

Torque-out(lbs.)(kN)(lbs.)(N)(in.lbs.)

1500-2000

6.7-8.9

90

400

10

Type SP Nut Installed Into
300 Series Stainless Steel(2)Installation

Pushout

Torque-out

Installation

Pushout

Torque-out(N•m)(lbs.)(kN)(lbs.)(N)(in.lbs.)

1.13

2500-3500

11.2-15.6

125

550

15

(N•m)

(lbs.)(kN)(lbs.)(N)(in.lbs.)

(N•m)

1.7

8000-1000035.6-44.5

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

8000-1000035.6-44.5

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 TESTTorque-out tests shall be performed
from the shoulder or head side of
the installed fastener. Torque shallbe applied to the fastener in themanner illustrated, using a hardened
test screw and washer, while firmly
holding the test strip. Test screws
should be of sufficient tensile
strength to resist thread stripping. A
minimum of two screw threads must
extend beyond the fastener.

© 2021 PennEngineering®

Driver for applied torqueInstallation Force

Test Strip(parent material).
Held firmly in a vise.

Washer Approximately 1
to 2 pitches. Thickenough to preventneck of screwfrom contacting
threads.

Pushout

Hardened Test Screw/
Bolt Grade 5 or better

HB-5

THE ANATOMY
OF SELF-CLINCHINGMAXIMUM SHEET HARDNESS FORFASTENER MATERIALS
Fastener Material

Sheet Hardness

Aluminum<HRB 50 / HB 89

Unhardened Steel<HRB 60 / HB 107

300 Series Stainless Steel<HRB 70 / HB 125

Hardened Steel<HRB 80 / HB 150

Hardened Stainless Steel<HRB 88 (92) / HB 183 (202)

TYPICAL SELF-CLINCHING STANDOFF
ScrewComponent
or Panel

TYPICAL HARDNESS OFSHEET MATERIALS
Host Metal Flows
into Undercut

Fastener Material

Sheet Hardness5052-H32/34 Aluminum

HRB 15-30 / HB

Cold-rolled SteelHRB 40-75 / HB

6061-T6 Aluminum

HRB 50-55 / HB 89-96

304 Stainless Steel (Annealed)

HRB 80+ / HB 150+

HSLA Steel (does not follow typical rules)

HRB 80-85 / HB 150-169

TYPICAL SELF-CLINCHING NUT

Flush Mounted

Direction of
Installation ForceHex Head Provides
Torque Resistance

TYPICAL SELF-CLINCHING STUD

Direction of
Installation
Force
Head
Serrated Clinching
Ring Provides
Torque ResistanceComponent

Back
TaperedShank

Host Metal
Host Metal
Cold Flows into
UndercutComponent
Flush Mounted
Ribs Provide
Torque Resistance

Flush Mounted

Host Metal
Flows into Undercut

Direction of Installation Force

HB-6

BASIC TYPES OF
SELF-CLINCHING FASTENERS
A self-clinching feature can be applied to many types of fasteners as shown below to combine the benefits of selfclinching with a broad raxnge 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 notsubject to torsional loading and do not require an anti-rotation feature.

NUTS: Nuts with thread strengths

CONCEALED-HEAD:

greater than mild steel screws
are commonly used whereverstrong internal threads are needed
for component attachment or
fabrication assembly.

Installed into milled, blind holes sothat one side of the panel remains
unmarred. Studs and standoffs
are generally available in theconcealed-head type.

STUDS AND PINS: Threaded

BLIND: Have closed ends that
limit screw penetration and areuseful for protecting internal
components from damage by
inadvertent insertion of extra longscrews. Threads are also protectedfrom damage and foreign matter.

and unthreaded fasteners which
are used where the attachment
must be positioned before being
fastened.

SPACERS & STANDOFFS:
Used where it is necessary to stackor space components away fromthe panel. Thru-threaded or blind
types are generally standard.

RIGHT ANGLE: Provide

FLUSH FASTENERS:

strong right angle attachment
points. These fasteners are acost-effective replacement for:bent edge tabs; bent center tabs;
bent flanges; angle brackets; tackwelds; and loose hardware.

These fasteners are installed
completely flush within the sheet.

CABLE TIE-MOUNT:FLOATING NUTS:
Compensates for mating holemisalignment by having a floating
threaded element.

THREADED ACCESSHARDWARE: Generally used on
enclosures where the screw mustremain with the door or panel.

Provide secure attachment points
for mounting wire to electricalchassis or enclosures without
the problems associated withtraditional mounting methods.

SHEET JOINING FASTENER:
Joins two sheets of metal or
metal to PCB/plastic. The fastenerinstalls smooth with the top sheet,and flush or sub-flush with thebottom sheet.

LOCKING FASTENERS:
Provide a locking feature to restrict
the rotation on the screw underadverse conditions of vibration.
Locking features may include
metal or plastic types.

NON-THREADEDFASTENERS:
Allow for quick assembly or
removal of components without
the need for screws or additional
fastening hardware.
© 2021 PennEngineering®

CUSTOM DESIGNS––––––––––––––––––––––––––––
Since there are a great many types of standard
self-clinching fasteners available, it is usuallypossible to choose one to meet your design
requirement. There are times however that acustom designed and manufactured fastener isnecessary. If this is the case, PennEngineering can
assist you with your requirement to provide youwith the best solution to your design.

HB-7

QUALITY
OF SELF-CLINCHING FASTENERS
An order request comes to the desk of the buyer or
procurement individual for self-clinching fasteners.
Although a review of the manufacturer’s basic
specifications will undoubtedly turn up a shopping list of
suppliers, a purchase made on the basis of lower pricealone may prove more costly in the long run.

INSTALLED COST
THE BOTTOM LINE––––––––––––––––––––––––––––
When a designer investigates the desirability ofusing self-clinching fasteners, his calculations
must offer a true picture of cost. If integral
fasteners are now being welded, the cost of
materials, labor and overhead must be factored
into the final cost per fastener to grant an
accurate comparison with the final calculated
cost per self-clinching fastener. Rejects andspoilage due to failure of poorly designed
fasteners will contribute to high production
costs, so be certain that the fasteners actuallypurchased meet your engineering specifications.

There are significant variations in the materials
used, manufacturing processes, quality controls
and component dimensions that make the “same”
product, made by different manufacturers, very
different from one another.
Wire stock is used for the manufacture of many
self-clinching fasteners. Basic blanks are formed oncold headers or cold formers; subsequent operations
such as piercing, drilling, tapping, thread rolling, andslotting may be required.
Self-clinching fasteners are also made from freemachining, cold-drawn, low-carbon bar stock, avariety of free-machining and cold-drawn stainlesssteels, aluminum and phosphor bronze. They areformed on automatic bar machines and generally
have secondary operations such as slotting, tapping
or lock forming.
Finishing operations such as heat-treating andplating are equally sophisticated, and quality control
measures must be monitored throughout the
manufacturing process.
With so many manufacturing variables to control,
there are several quality areas which must be
examined before choosing the supplier of selfclinching fasteners for your application.

THESE INCLUDE:
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 threadtolerances. 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 failduring 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 theappearance 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

INSTALLATIONPROCEDURE
Fast, simple installation saves time and money on the assembly line. In just three easy steps, self-clinching fasteners canbe installed with any parallel acting press that can be adjusted to optimum installation forces.
First, place the fastenerinto the anvil hole andplace the mounting hole(preferably the punchside) over the shank of
the fastener.

With installation punch
and anvil surfaces parallel,
apply squeezing force
until the head of the nut
comes in contact with the
sheet material.

Finally, install themating piece fromthe side opposite
the head of thefastener.

ADDITIONAL NOTES
1. Mounting holes may be punched or drilled; they should not be chamfered or have broken edges in excess of.005”/.127 mm. Hole tolerances of +.003, -.000/+0.08 mm must generally be held. The fastener should be installedon the punch side if the sheet is .09”/2.29 mm or thicker because of the piercing break-to-die diameter. In all cases,
the manufacturer’s recommended “minimum centerline of hole to edge of sheet” (see page 12) distance should beobserved. No deburring or countersinking is required.
2. Installation typically results in a flush surface on one side of the panel. Conversely, staked or crimped fasteners
require special counterboring to obtain a one-sided flush surface.

3. When installing, the most important criterion is that the fastener must be squeezed into place with any parallel
acting press.
4. Because the installation equipment generates no excess noise or pollution, the fasteners can be installed anywherein the production process. No special facilities, ventilation equipment, or safety procedures are required.
5. When installed using the recommended squeezing force (depending on the size of the fastener and hardness of the
sheet metal), there is little or no distortion of the sheet or damage to the finished surface. Fasteners generally should
be installed after plating, finishing or anodizing.
6. Sheet material must be softer than the fastener. If the fastener is not hard enough, it will deform (crush) instead ofcold flowing the sheet material. Some operations will locally harden a sheet, i.e., punching 300 series stainless or laser
cutting a mounting hole (see note on page 4).
Fastener Installation “Do’s”

Fastener Installation “Don’ts”

Do provide mounting holeof specified size for eachfastener.

Don’t attempt to install a 300 series stainless steel fastener into a stainless steel
sheet.

Do install fastener into punchside of sheet.
Do make certain that shank(or pilot) is within hole before
applying installation force.
Do apply squeezing force
between parallel surfaces.
Do apply sufficient force tototally embed clinching ringaround entire circumference
and to bring shoulder squarely
in contact with sheet. For
some fasteners, installation will
be complete when the head isflush with the panel surface.

© 2021 PennEngineering®

Don’t install steel or stainless steel fasteners in aluminum panels before anodizing.
Don’t deburr mounting holes on either side of sheet before installing fasteners –deburring will remove metal required for clinching fastener into sheet.
Don’t install fastener closer to edge of sheet than minimum edge distanceindicated by manufacturer – unless a special fixture is used to restrict bulging ofsheet edge.
Don’t over-squeeze. It will crush the head, distort threads, and buckle the sheet.
Approximate installation forces are listed in performance data tables. Use this info
as a guide. Be certain to determine optimum installation force by test prior to
production runs.
Don’t attempt to insert fastener with a hammer blow – under any circumstances.
A hammer blow won’t permit the sheet metal to flow and develop an interlock
with the fastener’s contour.
Don’t install screw in the head side of fastener. Install from opposite side so thatthe fastener load is toward sheet. The clinching force is designed only to hold thefastener during handling and to resist torque during assembly.
Don’t install fastener on pre-painted side of panel.

HB-9

INSTALLATIONPROBLEMS AND SOLUTIONSPROBLEMPOSSIBLE CAUSESOLUTION

Poor holding power - fastener notseated squarely.

• Punch and anvil faces are notparallel.
• Panel cocked during installation• Ensure that punch and anvil areflat and parallel and hard.
• Ensure that large panels are held
perpendicular to punch and anvil.

Poor holding power – fasteners fallout of panel.

• Inadequate installation force.
• Panel too hard for fastener material.
• Countersunk hole in panel.
• Oversized mounting hole.
• Some operations may locally harden
a sheet, i.e., punching 300 Series
Stainless or laser cutting a mounting
hole.
• Die side of panel thicker than 		.093”/2.36 mm may have hole toolarge for fastener due to necessary
punch and die clearance.

• Seat fastener against shoulder
by applying more force orchanging shut height of press.
• Specify appropriate fastenermaterial for sheet hardness, i.e.,
stainless steel (see note on bottomof page 4).
• Do not countersink or deburr hole.
• Prepare properly sized mounting
hole.
• Punch hole under size and ream tocatalog dimensions or change
tooling to punch from opposite
side of panel.

Poor holding power of fastener nearbend.

• Sheet was bent after fastener was
installed. This may have caused
distortion of mounting hole.
• Hole is punched prior to bend andhole has become elongated.

• Bending should be done prior to
installation.
• Punch hole after bending the sheet

Poor holding power of standoffs orstuds in panel.

• Hole in anvil too large or chamfered.

• Use anvil with hole per catalog
dimensions.

Poor holding power – nut off centerof hole.

• Punch or drill hole to specified• Oversize mounting hole.
dimensions.
• Nut is cocked in hole and shears side
• Check that shank of nut is squarelyof hole when installed.
in hole before squeezing.

HB-10

INSTALLATIONPROBLEMS AND SOLUTIONSPROBLEMPOSSIBLE CAUSESOLUTION

Threads tight – sheet buckles.

• Fastener over-squeezed.

• Reduce installation force.

Tight threads, cracked.

• Shank length extends through sheet.

• Choose fastener with proper shanklength for sheet thickness.

• Undersized mounting hole.

• Prepare properly sized mounting
hole.

Poor holding power of standoffs orstuds in panel.

• Lack of countersink in anvil.

• Provide countersink in anvil to
specified dimensions.

Head of flush-head stud or standoff
cups.

• Punch diameter too small or not
hard and flat.

• Punch must be larger than headof stud or standoff and preferable
equal to anvil diameter.

Edge of panel bulges.

• Mounting hole violates specified
minimum edge distance.
• Nut is over-squeezed.

• Restrain panel or bracket in
fixture during installation or move
mounting hole away from edge.
(See page 12)• Reduce installation force if possible.

Fastener does not fit into hole.

Fastener deforms or shears during
installation.
Sheet metal may extrude into
installation tooling causing tool tostick or crack.

Questions? Consult our Applications Engineering department at techsupport@pemnet.com© 2021 PennEngineering®

HB-11

COMMON DESIGNCHALLENGES
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 toreinforce 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 asshown by the dotted lines. This distortion will reduce the amountof panel material in the undercut and may significantly reduce theholding 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-Edgesituations.

SPACING OF MULTIPLE FASTENERS

Multiple fasteners installed must be spaced far enough apart toavoid 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 distanceby 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 fastenerperformance.
• 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 slightcolor 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

OTHERCONSIDERATIONSAUTOMATED 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
installations. These presses are specifically designed tofeed self-clinching fasteners automatically into punchedor drilled holes in sheet metal, seating them correctly witha 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 andhardness of the sheet and the height of the fasteners.
Our equipment capabilities incorporate “smart” toolingand software, automation, robotics integration, andin-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 anddramatically improving production efficiencies.

Haeger® 824™ OneTouch™ 5e Lite

FASTENERS FOR NON-DUCTILE AND ONE-SIDE ACCESS INSTALLATION
Self-clinching fasteners are designed to be installed into sheet metal panels only when both sides of the
sheet are accessible. For applications that do not meet this criteria, PennEngineering offers other possible
solutions. These include:
ATLAS® style blind threaded
inserts (rivet nuts) provide strong
threads in applications where
only one side of the assembly isaccessible for installation. Thesefasteners can also be used in mostnon-ductile material applications.

ReelFasT® SMT fasteners
mount to P.C. boards in thesame manner as other surface
mount components prior to theautomated reflow solder process.
© 2021 PennEngineering®

VariMount® bonding fasteners
are assemblies comprisedof standard PEM® fasteners
mounted permanently into baseplates. The assembly can thenbe fastened to assorted panel
types in a variety of ways.

Flare-mount fasteners offer
a combined broach/flarefeature for even greaterpullout performance in P.C.
Board materials.

A broaching fastener is any knurledshank fastening device that is pressed
into a punched or drilled hole toprovide a strong threaded attachment
point in a non-ductile material.
HB-13

ANSWERS TO THE TEN MOST FREQUENTLY ASKEDQUESTIONS ABOUT SELF-CLINCHING FASTENERS
Question: Does the shape of the self-clinching

Question: When using self-clinching fasteners,
what are my panel requirements?

Answer: No, the fastener does not deform in
any way. There is no flaring, crimping, swaging,
peening or riveting necessary.

Answer: Generally, there are two basic
requirements. First, the panel must be a ductile
material softer than the fastener which is going
into it. Second, the panel must meet the minimum
sheet thickness required by the particular fastener.
Some self-clinching fasteners can be installed into
sheets as thin as .020”/0.51 mm, but generally.030”/0.76 mm or .040”/1 mm is the minimum
sheet thickness necessary.

fastener change during installation?

Question: What holds the fastener in the sheet?
Answer: The squeezing force on the fastenercauses the sheet material beneath the head tocold flow into the back-tapered shank or undercutof the fastener securely locking it in place.

Question: Do I need special equipment to install

self-clinching fasteners?

Question: Is there a maximum sheet thickness I

should be concerned with before specifying selfclinching fasteners?

Answer: No. Self-clinching fasteners are installedusing any type of parallel acting press which willsqueeze the fastener in place.

Answer: Generally, there is no specified maximum
thickness for sheets. However, because of their
special design and function, a few fastener types
do specify a thickness range which includes a
maximum.

Question: Won’t these fasteners fall out, twist out,

Question: I notice some of the fasteners have aor spin in their mounting holes if I tighten down
too hard?

Answer: No. Typical torque-out values are
generally quite high compared to the rotational
force that will be put on them. In fact, for mostquality self-clinching nuts, the screw will fail before
the nut rotates in the material.

hexagonal shaped head. Do I have to punch ahexagonal mounting hole to install these?

Answer: No. All self-clinching fasteners are
installed into a round punched or drilled hole. A
hexagonal head will cause the sheet material tocold flow around the head to provide high torqueout resistance. The hex head will be flush in the
sheet when installed.

Question: I would like to replace some of thewelded fasteners I now use in my stainless steel
fabrications. Is there a self-clinching fastener thatwill go into a stainless steel sheet?

Answer: Yes. Self-clinching fasteners for stainlesssteel applications are available. These fasteners are
generally made from specially hardened stainlesssteel and will install into sheets up to HRB 88 inhardness.

HB-14

Question: Can I install these blind, from one side,

if I don’t have access to both sides of the sheet?

Answer: Generally, you must have access to bothsides of the sheet to properly install self-clinching
fasteners. However, there are some 1/4”/M6 orlarger nuts which can be drawn in from one sideusing an impact-torque wrench. For information
on blind threaded inserts for one sided accessinstallation go to www.pemnet.com.

GLOSSARYOF TERMS
Anvil - An insert, either solid or hollow, which is used on theunderside of a panel to resist the installation force.

Pull-through - The resistance of a fastener to a force applied in
the 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 amandrel of a similar shape. As applied to fasteners, the way aknurled shank “broaches” its way into the mounting hole.
Captive - The ability of a fastener to remain securely attached toa panel.
Captive Screw - See: panel fastener.
Chamfer - A beveled edge or corner.
Cold Flow - The movement of a ductile material under pressure.
Concealed-head - A type of fastener which, when installed, iscompletely hidden when viewed from the reverse side.
Counterbore - That portion of the axial length of which is drilled
to a larger diameter than the remaining portion of the part.
Ductile - Metal which is not brittle and can be easily formed or
bent.
Floating - The ability of a fastener to move in a direction parallelto the mounting panel and allow for mating hole misalignment.
Flush - The ability of a fastener to be contained completely
within the thickness of a panel. Also refers to the absence of a
protrusion above the surface of the panel.
Head - The portion of a fastener which forms its largest diameter.
Installation Force - A term expressed in pounds, tons, or newtons
applied axially to a self-clinching fastener to achieve proper
installation.
Interference Fit - The insertion of one member into another whose
diameter is slightly smaller than the part being inserted.
Knurled Clinching Ring - The displacer portion of a fastener which
has corrugations and is used to develop torque resistance when
installed in sheet metal.
Locking Element - A device employed to restrict rotation of athreaded member while operating in adverse environments, suchas vibration and temperature. The nut-locking element provides
prevailing locking torque to the mating screw.
Minimum Distance - The minimum distance from the center of afastener mounting hole to the nearest edge of a panel which willkeep the edge from deforming. This distance may be reduced bysuitable fixturing or increasing thickness of panel material.
Minimum Sheet Thickness - The thinnest section of a panel, usually
measured in thousandths of an inch or millimeters, into which afastener may properly be installed. The same fastener may beinstalled in panels having any thickness greater than minimum.
Mounting hole - A properly-sized round opening in a panel toreceive the shank of a self-clinching fastener.
Panel Fastener - A threaded screw which is held captive to a panel
and which, when disengaged from its main nut, remains fixed tothat panel.
Pin - A captive post that extends from a panel.

Pushout - The force required to remove a fastener from a panel
in a direction opposite to the way from which it was installed.
Note: Pushout is expressed in pounds or newtons.
Rockwell Hardness - A relative measure of hardness. Rockwell C
Scale is used for hard materials, Rockwell B for softer materials,
such as sheet metal.
Self-clinching - The method by which a fastener is securely
attached to a sheet of ductile material by causing the material
to cold flow under pressure into an annular recess of thefastener thereby securely locking it in place.
Self-locking - A locking element, formed as an integral partof a fastener, which provides force to restrict the rotational
movement of a threaded member.
Shank - The portion of a fastener, which is slightly smaller than
the fastener’s mounting hole and provides a positive location
for the fastener in the hole. A shank also incorporates anannular groove which becomes filled with panel material as thefastener is installed, and the retention of this material provides
pushout resistance.
Shank Length - The actual length of that portion of a fastener
which is embedded in the panel material.
Shoulder - The surface area of a fastener which contacts the top
surface of the sheet material. See: positive stop.
Spring-loaded - A device having a separate moveable
component that is biased in one direction by a spring.
Standoff - A tubular device, usually threaded, for spacing or
stacking components.
Stud - A male threaded captive post that extends from a panel.
Swaging - An operation whereby a reduced diameter of afastener is deformed to secure it to a panel. Note: the antonymof swaging is self-clinching where the panel material is caused
to deform.
Thread Class - A measure of clearance or fit between the screw
and the nut taken at the pitch diameter.
Threaded Insert - A threaded device which is installed in a panel
material.
Through Hole - A hole, threaded or unthreaded, whichtransverses the entire length of a part and is usable from either
end.
Tolerance - The absolute amount of maximum or minimum
dimensional deviation allowed that will not affect theperformance of a mechanical part.
Torque-out - The amount of torque necessary to spin thefastener out of the sheet. This is torque applied to the fastener.
No axial load is applied.
Torque-through - The amount of torque necessary to fail thefastener in axial load.

Plunger Assembly - A spring-loaded device used for latching or
indexing purposes.

Undercut - The reduced diameter of a fastener which receives
sheet material when a fastener is installed. Depending on thetype of fastener, may be rectangular or back tapered in shape.

Positive Stop - A visual indication that the proper depth ofpenetration of the knurled ring has occurred or when the“head” is in contact with the top surface of the panel. Synonym:
shoulder.

Expanded list of terms can be found on our web sitewww.pemnet.com© 2021 PennEngineering®

––––––––––––––––––––

HB-15

PEM® FASTENERIDENTIFICATION 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
U.S. Trademark Reg.
#1,403,759
CLS, CLSS, H, HN,
HNL, PSHP, S, SFN, SL,
SMPP, SMPS, SS, andWN fasteners

PEM® Skirted Shoulder
U.S. Trademark Reg.
#4,037,181
PF11, PF11M, PF11MF,
PF11MW, PF11PM, PF12,PF12M, PF12MF,
PF12MW, PF7M, andPF7MF fasteners

PEM® “Single Groove”
mark
U.S. Trademark Reg.
#2,028,457
A4, BSO4, LA4, MSO4,
PFC4, SO4, SP (Selectsizes), and TSO4
fasteners

PEM® “Double
Squares” mark
U.S. Trademark Reg.
#1,400,893 /#3,404,061
A4, AC, AS, LA4, LAC,
and LAS fasteners

PEM® C.A.P.S.® Dot
Pattern
U.S. Trademark Reg.
#4,007,693
PF11PM fastener

PEM® Circle on
Pedestal
U.S. Trademark Reg.
#4,293,597
RAS fastener

PEM® Double Notch
U.S. Trademark Reg.
#4,326,083
microPEM® SMTSO
fastener

PEM® Blue Nylon Ring
PFC4, PFC2P, PFC2,
PFS2, and PFK
fasteners

PEM® Blue Nylon
Locking Element
U.S. Trademark Reg.
#1,449,260
PL, PLC and CFN
fasteners

PEM VM® Stamp(Both Sides)
U.S. Trademark Reg.
#5,305,895
VariMount® Base Plates

PEM® SH Stamp
U.S. Trademark
Reg. #5,023,068
SH fasteners

PEM® RT Stamp
S-RT fasteners

PEM® SP Stamp
U.S. Trademark
Reg. #3,270,807
SP fasteners

PEM® SMPP Stamp
U.S. Trademark
Reg. #5,055,266
SMPP fasteners

ATLAS® AE Stamp
MaxTite® and Plus+Tite®
products

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, IrelandE-mail: europe@pemnet.com
Tel: +353-91-751714

ASIA/PACIFIC
SingaporeE-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

4/25/22