How often can an APM Hexseal self-sealing fastener (screw, bolt or nut) be used?

The APM Hexseal design (U.S. patent no. 3,175,454) was conceived to generate high pressure fastener sealing that could survive multiple usages. The asymmetrical annular groove design minimizes O-Ring friction, resulting in minimal wear and, in turn, maximizing reusability.

That being said, this question cannot be answered with a simple number, since each application condition is different. Factors such as clearance hole size and reinstallation frequency, in combination with environmental and operating conditions, will have an impact on how many uses a part can withstand. If this is a concern for you, please let us know. We are happy to advise on the best possible solution to maximize part reusability.

Can the APM Hexseal self-sealing fasteners be supplied with painted heads to match equipment color?

Yes we can! Please contact us for more information.

Can these self-sealing fasteners be supplied with self-locking features?

Yes. APM Hexseal Seelskrews® and Seelbolts® can be ordered with a variety of nylon locking features, such as patches and pellets.

Please be aware that we offer this only as an added feature for APM Hexseal self-sealing fasteners. We do not offer this as an independent service.

I noticed that the APM Hexseal Seelnut® does not use an O-Ring like some of your competitors. How does it seal?

Standard nut configurations do not allow for effective O-Ring displacement the way conventional fasteners (such as machine screws, bolts and rivets) do. To meet this challenge, APM Hexseal developed a different method that incorporates permanently molded silicone threads into the nut itself. When torqued, these rubber threads form a high-pressure seal along the mating threads of the corresponding fastener, as well as with the contact surface. Our design also provides metal-to-metal contact, which adds to the Seelnut®’s superior sealing power.


How do I know if my panel-mounted switch needs a sealing boot?

This question is a matter of risk-assessment and good business judgment. The more hostile the environment (the greater the presence of moisture, dust, dirt, lubricants, cleaning solvents, anything that can generate fungus, or corrosion that will impede contact or actuator function like ice build-up) the higher the need for environmental protection sealing boots. Also, if your equipment is sold under warranty, it’s much cheaper to anticipate and protect the internal switch mechanism than to risk a field failure and expensive repair. So, although the initial cost may be greater because of the inclusion of the boot, the real cost is negligible when factoring in security and customer satisfaction.

Are APM Hexseal sealing boots recognized by UL, CSA or the US Military?

Yes, many of APM Hexseal’s sealing boots are UL Recognized Components. Most are also manufactured to meet MIL-DTL-5423, which is the governing specification for electronic component environmental protection. As part of the rating process, both UL and the military have regularly inspected our facilities and products, so you can be confident that you are getting the highest quality parts. We are proud to say that APM Hexseal’s sealing boots are the only boots on the market that have these approvals.

Why do some customers order sealing boots for switches that are already factory sealed?

There are a lot of reasons to add a sealing boot to a switch, and not all of them are obvious at first.

Imagine an environment with a high concentration of fine dust particles, like cement, flour, etc. Any device in an environment like that is susceptible to particulate build-up in the switch actuator well, which would seriously compromise smooth operator function. The same issue can arise in extremely cold environments when ice forms around the actuator, causing freeze-ups. In cases like these, the concern is not about contaminants getting inside the device, but is instead about protecting the outside, maintaining the actuation functionality. A silicone sealing boot acts as a total barrier, preventing any build-up and preserving the movement of a switch. Remember, it doesn’t matter how well protected the inside of a switch is if it’s impossible to flip!

Another thing to keep in mind is that even a hermetically sealed switch needs to be mounted to something. Pre-sealed switches may not be at risk of internal contamination, but their panel mounting holes are still exposed to moisture and leakage penetration. Every APM Hexseal boot is designed with a patented perimeter seal that surrounds and vacuum protects the mounting hole, preventing bad things from reaching exposed circuit boards, etc. Another way to protect a pre-sealed switch would be with one of our Bushing Seals, specifically designed to focus on sealing the mounting hole.

Can APM Hexseal boots be ordered in colors other than black or gray?

Definitely. Our parts can be made in any color your heart desires! We can even match the elastomer material color to your particular color specification. This request is becoming increasingly popular for function/panel color matching.

Is EMI/RFI Suppression an option for any APM Hexseal parts?

Yes. We can provide up to 120dB of shielding effectiveness with select toggle, pushbutton and rotary sealing boots. Many telemetry, medical and military applications call for this enhanced capability. For more information, please contact us directly.

Can APM Hexseal make threaded boots in thread sizes that are not currently offered?

Yes. Please consult factory for assistance.

At first glance most switch boots seem the same. Is there really any difference?

Absolutely! Since APM Hexseal first invented and patented the environmental seal concept for electrical controls back in 1947 we have developed a wide variety of styles and designs based on the specific needs of different environments as well as what works best with different switches. Much of what makes each boot unique is internal, however, and not always easy to see from the outside. For example, we have boots that include a dual chambered interior, which creates a double sealing barrier, boots designed for sensitive switches that require a lighter touch and thus a more flexible boot design, and even boots that contain embedded RFI shielding mesh that is molded directly into the rubber. Each unique design offers additional protections that can be critical to certain application types.

Can APM Hexseal boots be mounted on the outside of NEMA enclosures without compromising the enclosure’s integrity?

Yes. APM Hexseal’s UL Recognized switch and circuit breaker sealing boots meet the requirements of UL Standard 50, and are a cost-effective solution for maintaining the rating of NEMA enclosures. APM Hexseal offers a wide variety of lever, toggle, pushbutton and rocker style boots that are perfectly suited for this type of sealing need.

I have come across switches that have companion boots included… How do those boots compare to APM Hexseal’s boots?

It likely comes as no surprise to hear us say that companion boots on the market really do not compare to APM Hexseal parts. Despite the bias that we obviously have in favor of our products, there are several factors that we consider critical to a truly effective sealing boot that we have not seen in our competitors’ products.

One of APM Hexseal’s most celebrated sealing features on our sealing boots is our patented perimeter sealing rib which creates a secure seal with the switch mounting panel. Our sealing rib adds an extra level of sealing protection that we have not seen in companion boots available on the market.

Secondly, the majority of APM Hexseal’s threaded sealing boots are single-piece designs with the mounting nut molded into the part itself, reducing the number of possible leakage points and making for a more reliable boot overall. Many of the alternate designs we have come across make use of a separate mounting-nut, which does not offer the same level of security and protection. Additionally, the Neoprene elastomer frequently used by outside companies to make boots does not possess the same rugged characteristics or life expectancy of our silicone, making them more susceptible to weathering, cracking and ultimately sealing failure.

APM Hexseal is proud to offer a variety of UL Registered parts that hold IP66/IP68 ratings. The vast majority of companion boots on the market are not UL listed and their IP ratings do not measure up, even when offered in silicone rubber. Though this is not a physical attribute, we believe it to be a very important factor to consider when it comes to product quality and reliability.