This edition of the Fastener Training Minute with Carmen Vertullo was originally published December, 19th 2023 as “Is there such a thing a tamper-proof fastener?” during episode 195 of Fully Threaded Radio.
Well hi everybody, this is Carmen Vertullo with your Fastener Training Minute coming to you from Carver Labs in beautiful El Cajon California, and the Fastener Training Institute.
I am feeling wonderful because I am just back from a 7-day trip to Disney World with my kids and my granddaughter and my wife, and we had a marvelous time even though I hate Disney all together. I hate the place, I hate the people, I hate the characters, I hate everything, but they have cool rides that we went on. And while I was walking around that place, as I always do, I looked at fasteners, and one thing I noticed is they use a butt load of tamper resistant fasteners of all kinds. Throughout the park tour, every part we went in and the hotel and the bathrooms. And took some pictures of them (not the bathrooms). Anyway I have dealt with tamper-resistant fasteners ever since I first came into the industry in about nineteen eighty-nine or so, and though I know a whole lot of things about them, I am not really up to speed on the state of the art of tamper-resistant fastening. But through the process of solving problems and doing some application stuff, there’s a couple things that I think are worth knowing. And there is one thing in particular that is worth knowing in your strategy when you need a tamper-resistant fastening solution, that a lot of people don’t think about, and when I come back I’m going to share that with you.
Well welcome back everybody this is Carmen Vertullo with the Fastener Training Minute coming to you again from beautiful El Cajon California at Carver Labs and of course the Fastener Training Institute.
Today’s topic is tamper-resistant fastening. Notice I did not say tamper-proof fastening, because there really is no such thing as tamper-proof fastening. If somebody wants to get in your stuff they’re going to get in one way or another, with a drill or a hammer or a chisel or a grinder ,or whatever. However we can make things more tamper-resistant than if they were just held together with normal fasteners using normal tools.
I’m going to describe a few tamper resistant fasteners to you, I’m not going to describe all of them but just enough to give you the concept.
The most common one that you’re probably familiar with is the pin in the socket tamper-resistant fastener. We have something that would normally be a button socket cap screw either hex or Torx, and it would have a pin inside the socket, and then the driver that we would use with that would have to have a hole in the middle of it to accommodate that pin.
Another common type is a Snake-Eyes fastener and it’s got sort of a smooth button head or sometimes it might be more like a pan head, and it’s got two tiny little holes in it. It is usually called a snake-eye of spanner head, and we need a driver that engages those two tiny little holes.
And other common type is the Tri-Wing tamper-resistant fastener, and it’s got a conical head or a conical nut and there are three little grooves on it and you need a proper tool or driver to engage those grooves.
And another type is the One-Way where you essentially have a slot but it only will go one way cuz it’s slopes the other way and you need no special tool to put that in that just goes in with a normal flat-head screwdriver but you need some special tool to get it out.
Now most of these tamper-resistant fasteners are removable if you have that right tool, and sadly nowadays you can go to any faster distributor and you can buy a box that has all the tamper-resistant drivers that you can imagine in it, with one exception, and that is the custom tamper-resistant fasteners . There’s a few Brands out there, I won’t mention them, where they need a special shape socket with a pin and not a socket it would be actually a drive with a pin, and and only you would have the key to that particular tamper-resistant fastener.
One other type is the Breakaway tamper-resistant fastener, and this essentially is a conical shaped head and it’s conical so you can’t get a wrench on it or a conical shaped nut, and then attached to that is a hex drive that has no threads on it, and if it’s a nut in it’s just attached to the head of the bolt, and there’s a groove there between that thing and the head or the nut, and you tighten it until it breaks off and you throw that part away.
They all have an Achilles heel of one type or another. Most of them can get loose pretty quickly with a hammer and a chisel so they’re not that hard to get off. Also, they sort of don’t work that well when you get two very large Fasteners because the drivers have lower strength than a normal driver so if you need a tamper-resistant Fastener that’s just holding a cover on to protect your IP or to keep somebody from meddling in your stuff, they work fine. But if you need it to be a structural fastener where it’s going to hold something together and you need to tighten it like it was a Grade 5 or a Grade 8 bolt above about a 3/8 or a half inch, those drivers at that point they don’t work that well. Now I will tell you one thing about the pin in the head of the fastener that lessens the strength of those drivers. Obviously, even though those drivers are very hard and strong, now you essentially have a hollow driver.
It’s very weak in fact, but if you design your tamper-resistant pin-in-head fastener, (and kind of listen carefully to this because it’s a little complicated), such that the depth of the hole in the driver is arranged, and the pin in the head is arranged, in such a way that we get some cross-sectional area of the driver in the screw that is solid. That is, we’re not just trying to turn it with a tube you have a much better chance of being able to transmit higher torque. Now these come in all materials: alloy steel, stainless steel, zinc plated steel of all grades. They are not cheap though. Tamper-resistant fasteners costs two to three times as much as normal fasteners in my experience.
I may have seen others but I’m going to tell you the one thing that will give you the highest level of tamper resistant fastening though most people don’t think about this. If you’re going to walk up to a tamper-resistant fastener and you want to undo it and you happen to have a hammer and a chisel, you’re in pretty quick. If you have a grinder you’re off pretty quick, unless it’s a flat head. So if you use a flat head tamper-resistant screw in a countersunk hole, or if you can put your tamper resistant fastener into a counter-bored hole, you have a much harder time getting into that without the proper tool. Because you can’t knock it off with a hammer and chisel or get at it with a grinder as easily.
And that’s sort of my experience with tamper-resistant fastening and all fastener distributors sell them. It’s a very common product and it’s a very high gross profit product and there’s lots of development work that can be done. I didn’t tell you about some other types that we can talk about some other time, and there are some other tricks like making your tamper-resistant Fastener left-hand threaded. That’ll blow a couple peoples process away if they try to get them out, but again that won’t defeat the hammer and chisel tamper-resistant fastener removal tool.
Well that’s about all I can think of about tamper-resistant fastening for now, this has been your Fastener Training Minute, I’m Carmen Vertullo, thanks for listening