This edition of the Fastener Training Minute with Carmen Vertullo was originally published September 18, 2021 as “When can I use a socket set screw as a stud?” during episode 168 of Fully Threaded Radio.
Well, hi everybody., this is Carmen Vertullo with your Fastener Training Minute, coming to you from the Fastener Training Institute and the AIM Testing Laboratory in beautiful El Cajon, California.
Today’s topic has to do with two different types of products. One of these products are socket set screws. And the other one of these products are studs. You may have occasionally seen an end-user think it’s with a good idea to use a long socket set screw in place of a stud. Now, in some cases. That’s an absolutely disastrous idea. Fraught with risk. In other cases, it’s an absolutely excellent idea filled with cast savings. When I come back, I’ll tell you when you can use a set screw as a stud, and when you better not do it.
Well, welcome back everybody. This is Carmen Vertullo with the Fastener Training Minute, talking about using set screws as studs.
Alloy steel socket set screws are very hard, and as fasteners go among our most brittle. Well, I would say brittle is really not a fair word, but they’re the most prone to failure if you put any kind of a side load, or a tensile on them, or any kind of a shock load, because they’re so hard. Rockwell mid-forties for the socket set screws. And so they’re designed to be used in compression, not in tension, and not in shear . Often times, someone will say, oh I need a stud and I think I’ll take a 1/4-20 x 2 socket set screw and use it as a stud. And when they put it in tension, it fails either during installation or shortly thereafter.
Worse than that, they might zinc plate it, and then we really have a recipe for failure. Because they’re such high hardness, hydrogen embrittlement will surely occur with that Fastener. Often times, socket set screws which are zinc plated, do not get baked. They do not get tested for hydrogen embrittlement because they’re compression Fasteners and therefore, theoretically not subject to a hydrogen embrittlement condition. So condition number one that you should never use an alloy steel socket set screw as a stud. It’s just a bad idea or in the metric world of property class 12.9.
In another instance, if the material is stainless steel, you could save a lot of time, a lot of money, and a lot of effort by using a stainless steel socket set screw as a stud because stainless steel socket set screws are not exceptionally hard, they’re just like any other stainless steel Fastener. They’re relatively inexpensive. As a matter of fact, it’s probably less expensive to cut studs out of a piece of stainless steel threaded Rod than it is to use a socket set. Screw, especially if the quantity is not exorbitantly high.
Now, obviously when you need a gazillion studs, the right way to do it is just make a stud. If you need some number of stainless steel studs and a socket set screw will do the trick in the numbers. Not high, saying the thousands, not the hundreds of thousands, that might be a good inexpensive solution to your problem.
So once again, alloy set screws, don’t use them for studs.
Stainless steel set screws, it’s okay to use them for studs.
Be aware though, that long socket set screws may have a relatively deep socket. So you need to make sure that when you use a socket set screw as a stud, that you keep the socket portion out of the tensile part of the application. And in fact that socket may come in handy, so you can seat the stud well into a tapped hole.
Well, I hope this was helpful for you and that you can put it to good use.
This has been Carmen Vertullo with the Fastener Training Minute.