PEM® Fasteners

Are your fasteners (or specific fastener) RoHS compliant?

The RoHS-compliant status of all PEM®, SI®, and ATLAS® cataloged fasteners can be found in the RoHS Lookup Tool.

Can I install a self-clinching fastener with a hammer blow or similar force?

No, a self-clinching fastener must be installed using a squeezing action. A quick impact installation will not allow sufficient time for the sheet material to cold flow.

Can I install these blind, from one side, if I don’t have access to both sides of the sheet?

Generally, you must have access to both sides of the sheet to properly install self-clinching fasteners. However, there are some 1/4’” / M6 or larger nuts which can be drawn in from one side using an impact-torque wrench. For information on blind threaded inserts for one-sided access installation go to ATLAS® Fasteners Product Information.

Can PEM fasteners made from 300 Series stainless steel be used in aluminum panels without having to consider contact corrosion from galvanic reactions?

This is a question that comes up on a regular basis because passive 300 series stainless steel and aluminum are some distance apart in a galvanic series and there is the potential for galvanic corrosion if an electrolyte is present. Whether or not using our 300 series fasteners in the aluminum panel is acceptable depends on the specifics of the application. The two important factors of the application are as follows:

1. What type of electrolyte, if any, is present, including the type of flow and amount of oxygen present.

2. How critical to the function of the product is the fastener to panel interface? Or stated another way, will a small amount of corrosion at the interface be a concern? Typically the mechanical holding power is not the critical concern. Factors such as electrical conductivity or cosmetics are often the more critical issues.

The customer’s technical staff must ultimately make the decision on the acceptability of using our passive 300 series stainless steel in aluminum panels. If they decide it is not acceptable, we have the following three options, presented in decreasing order of effectiveness.

Our first recommendation is to consider the use of aluminum self-clinching fasteners. Aluminum nuts are our type CLA, made from 2024-T4 aluminum alloy. Aluminum studs are our type FHA, also made from 2024-T4 aluminum alloy. Aluminum standoffs are our type BSOA/SOA, made from 7075-T6 aluminum alloy. All of these aluminum fasteners will clinch into panels with a hardness of HRB 50 or less. This option is preferred whenever the aluminum panel hardness is below HRB 50. Non-heat treatable aluminum alloys will almost always be well below this hardness. Some heat-treatable alloys may also be below HRB 50.

If this option is used, it must be verified that the aluminum fastener strength is adequate for the application. Externally threaded fasteners will have the greatest strength reduction when the fastener material is switched from stainless steel to aluminum.

A second option we have used in the past for critical military applications is to create special parts of 300 series stainless steel with cadmium plating. This is an effective solution because cadmium and aluminum are very close in the galvanic series. We can still offer this solution, but the parts will need to be YC3 specials to produce the required thread size allowance to accommodate the cadmium plating. An additional point on a cadmium plated part is that we can currently offer cadmium with trivalent clear chromate, in case there is an objection to the use of hexavalent chromate typically used with cadmium plating. This option will work in panels up to a hardness of HRB 70, which will cover almost all heat-treated aluminum alloys. Also, there is no reduction in fastener strength with this option.

The third option is to apply zinc plating to special stainless steel fasteners if the customer determines that zinc is close enough to aluminum (depending on the alloy) in the appropriate galvanic series. Many published galvanic series with voltage values are for flowing seawater which may not apply to some applications. This option should only be considered if cadmium is not acceptable.

Can we strip and re-plate a panel after the plated fasteners are installed?

Stripping and re-plating is not recommended. Stripping a panel after plated fasteners are installed can damage the fastener. The recommended alternatives to this are The first choice – Plate the panel and then install the plated fasteners. The second choice is – Install “X” finish (un-plated) fasteners into an un-plated sheet and then plate altogether.

Do any of the self-clinching fasteners offer a water-tight seal?

The only self-clinching fasteners that will provide a complete water-tight seal are the CH line of concealed head studs and standoffs. These fasteners are clinched (pressed) into a blind hole, thereby keeping the reverse side of the sheet undisturbed and free of any voids that might allow any liquid to seep through. Please see PEM® data sheet CH for specifications.

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

No. Self-clinching fasteners are installed using any type of parallel acting press which will squeeze the fastener in place.

Do you have a complete list of fastener installation forces?

A complete list of fastener installation forces is available on our website at:

Does the shape of the self-clinching fastener change during installation?

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

How far apart from each other can I reliably install PEM fasteners?

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.

I notice some of the fasteners have a hexagonal-shaped head. Do I have to punch a hexagonal mounting hole to install these?

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

Is there a maximum sheet thickness I should be concerned with before specifying self-clinching fasteners?

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.

Is there a Military Specification / National Aerospace Standards cross-reference available for PEM® part numbers?

These lists are available on our website:

The FE and PL series calls out a sheet thickness with a range as opposed to “min sheet thickness”. Can they be used and installed properly in sheet thicknesses thicker than the high end shown in the range(s)?

They can be installed into thicker sheets, but you run the risk of drawing the part through the panel with the tightening of the screw. This can cause cracking between the knurl and barrel portion of the shank. If going into a thicker panel, you should pay particular attention to the tightening torque so that you do not cause this type of failure.

What happens if I install a broaching fastener (in P.C. board) closer than the recommended minimum edge distance?

Violating the CL-Edge distance specified in our catalog may cause the board to crack or exhibit some sort of other damage like delamination. Due to the broaching nature of the K-style product, there may also be deformation of the holes in the area. The question will be whether the deformation will cause a problem for attaching other components. It is suggested that you first install the fasteners in some test material to determine the potential risk of board damage.

What happens if I mount a self-clinching fastener closer to the edge of a panel than recommended in the catalog?

By violating the centerline-to-edge feature, you will likely experience bulging on the edge of your panel. Once bulging occurs, one can expect some reduction in the performance of the fastener due to the material not flowing into the undercut of the fastener. What performance to expect is difficult to predict and will depend on the installation and the application. In order to prevent some of the bulge, a tool can be made that braces the edge of the panel. You have to take great care doing this to ensure the product does not stick on the tool during installation. Also, the performance will still be reduced as the hoop stress of the material is compromised by the thinner section of the material. If you can live with the bulge and a reduced performance value, it is likely you can still use the parts in your application.

What holds the fastener in the sheet?

The squeezing force on the fastener causes the sheet material beneath the head to cold flow into the back-tapered shank or undercut of the fastener securely locking it in place.

What is the difference between an S and SS part number and a CLS and CLSS part number? Why is there an additional S in the part number for the #10-24, #10-32, and M5 thread sizes?

The original CLS and S (in the #10-32, #10-24, and M5 thread sizes) were created for a smaller (.234″) mounting hole. Due to many performance issues with these sizes, (because of the thin section between the thread and the undercut portion of the clinch profile) a beefier version was developed for a larger mounting hole. The original design (S and CLS) was eventually made obsolete and we were left with the SS and CLSS for these thread sizes.

What is the property class of a type FH fastener?

Type FH studs are not made to a property class, but the minimum final hardness exceeds the minimum of both the 8.8 and 9.8 Property Classes. However, the type FH studs are neither a “true” Property Class 8.8 or 9.8 for the following reasons:

  1. The 10B16 material we use may not be allowed (subject to customer approval).
  2. Our maximum hardness exceeds the maximum hardness of Property Class 8.8.
  3. Our maximum hardness may exceed the maximum hardness of Property Class 9.8 (depending on the standard used, ISO or SAE).
  4. Parts are not marked with a property class designation.
  5. We do not do all of the testing required on each lot by ISO and SAE standards.
  6. Larger sizes (about M5 and up) of type FH studs fail in the head when tested in tension and therefore will not meet the tensile strength requirement of the standards which are based on the tensile stress area of the thread.

When installing a PEM® fastener into a punched mounting hole, is it best to install the fastener into the punch entry side or the die side?

The fastener should be installed into the punch side of the hole. The die side of the hole has a blow-out effect. This increases the diameter and the size is less predictable.

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

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″ / 1mm is the minimum sheet thickness necessary.

Which PEM® fasteners can I successfully install (clinch) into stainless steel sheets?

Certain PEM fasteners are designed specifically to install into stainless steel sheet. These include types SP, SO4, BSO4, FH4, FHP, and PFC4. You can consult our Fasteners for Use in Stainless Steel Sheets data sheet for details on each type.

Will self-clinching fasteners be damaged if they are welded to the panel for extra security?

The self-clinching feature of a self-clinching fastener makes welding an unnecessary step. Self-clinching fasteners, when properly installed, have adequate holding power in the sheet without welding. In fact, self-clinching technology was originally conceived, and is, a less costly, cleaner and more dependable alternative to weld fasteners.

The negatives of welding include the following. Welding a steel fastener will melt the zinc plating, which would speed up corrosion in the welded area. Welding an austenitic stainless steel fastener increases the risk for sensitization (sensitization can happen to austenitic (300 series) stainless steels from uncontrolled cooling which can allow carbides to precipitate at grain boundaries making the material susceptible to intergranular corrosion). If the fastener is made from 303 stainless steel, welding could lead to cracking due to out-gassing of the low melting point free machining additives. A hardened type 400 series stainless could be re-tempered and weakened by welding.

Won’t these fasteners fall out, twist out, or spin in their mounting holes if I tighten down too hard?

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

What is the FIT (Failure in Time) rate for surface mounted and broaching PEM® fasteners listed in catalog data sheet K?

FIT rate is not applicable to these fasteners. Although they are typically installed onto PCBs and may carry current, they are mechanical fasteners and do not have the same failure characteristics as electronic components, in that they do not possess any electrical characteristic that will change over time.

Installation Machines

Can the manual tools be used on an arbor press or press brake?

Our tools are designed for PEMSERTER insertion machines. An illustration of the tools can be found in our online tooling selector or manual tooling guides. Customers can develop an adapter if required.

Can the MICRO-MATE® hand tool install studs or standoffs?

No, the MICRO-MATE® hand tool is designed to install S / CLS nut product line up to 10-32 / M5 thread size.

Do you sell the Series P3® hand tool in Europe?

No, we do not support the Series P3 hand tool in Europe, as we do not have CE certification for it.

How do the insertion machines operate?

Demonstration videos for PEMSERTER insertion machines are available on the Website in our Operation & Tooling Section.

How do you install automatic tooling on the insertion machine?

Installation videos for automatic tooling can be found on the Website in our Operation & Tooling Section.

In auto stud mode, why won’t the vacuum punch pick up the fastener that is present in jaws?

Check the gap between the vacuum punch and the stud jaws. The gap should measure between .003″ to .005″ (.08 mm to .13mm) maximum.

What are the combinations of the fasteners we can install on the PS2000 Dual Bowl Machine?

We recommend you review each application with the PEMSERTER Engineering group to confirm suitability to install intended combination of the fasteners and advise appropriate installation solutions.

What is the correct tooling length required for the Series 4 insertion machine?

The total length of tooling required for operating the Series 4 & Series 4AF press is 7″ / 177.8mm. The standard lengths of the tools are Punch 4″ / 101.6mm & Anvil 3″ / 76.2mm.

What is the maximum length of a stud or a standoff that can be auto fed on the Series 4AF insertion machine?

The maximum length of a stud or a standoff that can be auto fed on the Series 4AF is 1″ (25mm).

What is the maximum length of a stud or a standoff that can be installed using the Series P3® pneumatic hand tool?

The maximum length of a stud or a standoff that can be installed using the Series P3 is 1/2″ (12.7mm).

What is the tooling part number for my fastener?

Tooling part numbers can be found in the Product Finder.

What is the throat depth of your insertion machines?

PEMSERTER® Series 4® and Series 4®AF have a throat depth of 45.7cm / 18″ and the Series 2000® and Series 3000® have a throat depth of 61cm / 24″. This information is also available on our website under PEMSERTER® Presses.

Where can I find part numbers of spare components for auto tooling?

The Online Tooling Selector lists individual tooling components for each tooling package.

Where can I find what tooling is available for the MICRO-MATE hand tool?

All Available tooling for the Micro-Mate® hand tool is available in the manual.

Where can I find what tooling is availble for the Series P3 portable hand tool?

All available tooling for the Series P-3 portable hand tool is available in the operation manual.

Will the QX4 Turret Tool Assembly for the Series 4 work with other machines?

The QX4 Turret Tool is designed for the Series 4 manual machine only. The tool will not mount on other PEMSERTER insertion machines. There is a QX Turret Tool option designed for the Series 2000 & Series 3000 insertion machines.

Will the Series 4 Top Mount or Bottom Mount Reverse Flange Anvil Holders work on other machines?

No. These options are available for the Series 4 manual insertion machine only. There is a J-Anvil option available for the Series 2000 insertion machine. Refer to the manual tooling guide.

SI® Threaded Inserts for Plastics

Are inserts available with NPT threads?

NPT threads are not available as a standard. We may be able to do it on special order.

Are these inserts RoHS compliant?

The RoHS compliant status of all SI® cataloged fasteners can be found in the RoHS lookup tool.

Do the inserts work in wood?

We offer metal inserts that are designed to be cold pressed into plastic. Although these inserts are not designed to be pressed into wood, they may work if used with an adhesive. Testing this product in your application is recommended. We will be happy to provide technical assistance and/or samples for this purpose.

Do you have performance data for a certain insert into a certain material or how does the insert perform in a certain type of plastic material?

Performance is dependent on fastener type, installation process and material. Some of this data is available in the SI® data sheet. If the specific information that you require is not shown in the data sheet please contact us at [email protected] for further information. We can supply you with free fastener samples so that you can perform your own testing or depending on the application do the testing for you here in our technical lab.

Do you sell installation equipment?

Currently we do not sell equipment for installing SI® brand threaded inserts for plastics. For your convenience, listed below are suppliers of ultrasonic and thermal insertion presses:

How much installation force is needed to install inserts?

Installation forces are dependent on fastener type, installation process and material. Some of these forces are available in the SI® data sheet. If the specific information that you require is not shown in the data sheet please contact us at [email protected] for further information. We can supply you with free fastener samples so that you can perform your own testing or depending on the application do the testing for you here in our technical lab.

What is the recommended temp for heat staking?

As a general rule, try setting the heat staking machine temperature 50˚F/10˚C higher than the published melt temperature of the plastic. Testing this product in your application is recommended. We will be happy to provide technical assistance and/or samples for this purpose.

What would be the best type of insert for me to use? Molded-in, heat/ultrasonic, or press-in?

View our 4 Ways to tackle threaded inserts for plastics for more information on the types of inserts to consider. If you require further information please send your specific question to [email protected].

When installing a SI® type insert for plastic, what is the recommended wall thickness for the boss?

The boss thickness for an insert is very dependent on the material being used as well as the mold configuration creating the hole. As a rule of thumb, 2X the part diameter is usually sufficient, however, if there is a potential for knit lines along the boss due to the mold configuration, this diameter should be increased.

Why are there two versions of the IUA/IUB/IUC inserts for the M3 and M5 thread sizes?

The M3 thread in the #4-40 body and the M5 thread in the #10-32 body has a very thin wall. Therefore, we offer the IUAA/IUBB/IUCC inserts for applications that require a larger body diameter.


What are the RoHS concerns related to aluminum products?

The issue with aluminum and RoHS is that some aluminum alloys, such as 2011, contain lead in amounts that could exceed the 0.4% allowed by the exemption in clause 6 of the Annex of the RoHS directive. Fortunately, the alloys we use for standard parts do not contain any intentional additions of lead and therefore have always been RoHS compliant. With regards to chromium, any chromium present in aluminum will be in the metallic or zero valence state and is therefore not a RoHS concern since the RoHS directive restricts only hexavalent chromium which only exists in certain compounds in which the chromium has a valence state of +6 (hexavalent). A chromate finish applied to aluminum could contain hexavalent compounds. We do not apply any type of chromate finish to any of our standard aluminum products.

Does the RoHS Directive ban the use of cadmium plating on fasteners?

Yes, cadmium plating is not RoHS compliant. Although clause 8 of the Annex of the original RoHS Directive (2002/95/EC) granted an exemption allowing cadmium plating to be used in some aerospace applications and other safety-critical applications, the current Directive no longer allows any exemption for cadmium plating. Cadmium is also a REACH SVHC and cadmium plating on any of our fasteners will always exceed the allowable REACH threshold of 0.1 % of article weight.

Does the RoHS Directive ban all chromium?

Chromium can exist in four states. Metallic, divalent, trivalent and hexavalant. In some compounds, chromium is in the hexavalent state (valence of +6) and many of these compounds are hazardous. The current European RoHS Directive bans the use of six substances, one of which is hexavalent chromium. The ban on hexavalent chromium targets primarily corrosion-resistant coatings, such as chromate conversion coatings applied to zinc plating. Metallic chromium found in stainless steel is not a RoHS substance.

What type of chromium is in the conversion coating applied to zinc plating?

The substance of concern with regard to chromate conversion coatings on zinc plating and RoHS compliance is hexavalent chromium. The RoHS Directive restricts hexavalent chromium but does not restrict less hazardous trivalent chromium. Historically, both clear and yellow chromate conversion coatings contained hexavalent chromium compounds. In recent years suppliers of chromate conversion coating materials have been working hard to develop chromate conversion coatings that contain only trivalent chromium compounds and provide acceptable corrosion resistance. Presently there are a number of such products available in clear. Yellow chromates have been more difficult to develop because the corrosion resistance requirements are greater. For example, ASTM B 633 requires 12 hours of neutral salt spray to white corrosion for clear chromate, but 96 hours for yellow chromate. With regard to our standard zinc-plated PEM brand steel fasteners, we began using trivalent clear chromate in June of 2002 for all our products with finish suffix ZI. Therefore all -ZI product plated after June 2002 is RoHS compliant. Also, we began using trivalent chromate in our optional zinc and yellow (suffix -ZC) plating on March 1, 2006. Therefore, this finish is compliant as of that date.

How does PennEngineering determine the RoHS-compliant status of the hexavalent chrome used in the conversion coating for zinc and zinc alloy platings?

PennEngineering uses the detection methods defined in the IEC-63321-7-1:2015 to measure hexavalent chrome in the chromate conversion (passivation) layer of our zinc-chromate plated parts to assure they are not hexavalent chromium-based as determined by IEC-62321-7-1:2015 and other consensus standards.

What type of chromium is in stainless steel?

In stainless steel, chromium is in the metallic state, which is not hazardous.

What type of chromium is in the oxide layer created by passivating stainless steel?

Our research has found this layer to be dichromium trioxide or Cr2O3, which is a trivalent compound as opposed to chromium trioxide or CrO3, which is a hexavalent compound.

What does the term “Lead-Free” mean?

The term “Lead-Free” can have two meanings. First. it could simply mean that the product has no lead. Secondly, it could mean that the material is compatible with a lead-free soldering process. In the second case, the process must be specified.

What are the specific lead exemptions that relate to fasteners and how are these exemptions currently addressed by PennEngineering?

The overwhelming majority of PennEngineering’s products are lead-free. Other products are compliant by the exemption. More specifically:

Exemption 6a – Some PennEngineering parts are machined from leaded steel and use European RoHS exemption 6a. In the latest version of the European RoHS Directive, sometimes referred to as the RoHS recast or RoHS II, exemption 6a is still valid with no expiration date currently set. Parts using exemption 6a are therefore fully compliant with the European RoHS Directive and will remain so until such time as exemption 6a expires. We continue to closely monitor the status of exemption 6a and will take prompt action if and when an expiration date is set. However, if you currently require lead-free steel options, they are available with associated costs. Contact [email protected] for more information.

Exemption 6c – Some PennEngineering parts are machined from leaded brass and use European RoHS exemption 6c. In the version of the European RoHS Directive currently in effect, sometimes referred to as the RoHS recast or RoHS II, exemption 6c is still valid. A review of exemption 6c is currently in process and the EC (European Commission) is expected to extend it, but even if they do not, it will remain in effect for at least 12 months from the date of their decision. Parts using exemption 6c are therefore fully compliant with the European RoHS Directive and will remain so until such time as exemption 6c is removed. However, if you currently require lead-free brass or can utilize other lead-free materials such as steel, stainless steel, or aluminum, there are options that we can discuss. Again, there may be associated costs. Contact [email protected] for more information.

Do you use any non-compliant plastics in any of your products?

No. All of the plastic used in our locking and hybrid products are RoHS compliant.

Site Search

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You can search our website in different ways. You can search for inventory or product specifications using the full part number or partial part number. You don’t even need to type the words “inventory” or "product spec"!
Examples of what to type:
Full or partial part number: “S-632-1ZI”, “CLS 632” Type: “CLS”, “FH”, “SO” Website content: “Self-clinching Nuts” or “PEM studs”