This edition of the Fastener Training Minute with Carmen Vertullo was originally published June 18, 2020 as “Fastener Standards Review Channel” during episode 153 of Fully Threaded Radio.
We’ve been doing an interesting thing on the internet here since the pandemic has been going on and it’s called the Fasteners Standards Review Channel. I spend about half an hour just reviewing fastener standards online and anyone is welcome to join. If you’d like to hear that or see the recordings just contact me.
It turns out that the two standards that we reviewed at first were ISO 898 Part 1 (where all of our common metric bolts come from), and SAE J429 (where most of our common inch bolts come from). SAE J429 deals with Grades 2,5, and 8 and there’s some really complicated tables in that standard. Some of the most complicated ones are the ones that tell us what we are actually required to test, which fasteners have to be tested, and how they have to be tested. We spent some time on it and as a result, I think I came up with an easy way to understand those tables. Or at least a way to think about them that gets you to the answer regarding what to test, or at least what to look for on your certification test reports to make sure that the fasteners are in compliance, because those tables are not just for test labs or anyone that has a registered quality management system, whereby you are keeping track of proper certifications and test reports.
Lets start with ISO 898 Part I because that’s the more complicated of the two and in ISO 898 Part 1 the tables are broken down by category depending upon what is actually required to be tested. They call these tables table FF1, FF2, FF3, FF4, and MP1 and MP2. The FF sort of stands for telling us that it is a fully-formed or finished fastener or a totally finished fastener that can be more less tested complete. And the MP series is for fasteners that for some reason do not provide a complete fastener where maybe we are going to use a machined specimen or a machined part of the fastener to test. Here’s the thing that we have to keep in mind when we’re looking at these very intimidating tables. Think about what the fastener is in terms of three things: it’s size and length, and it’s length to diameter ratio.
Is it a heat-treated Fastener, that is is it just a Grade 2 or a ISO 898 property class 4.8 non heat-treated Fastener or if it’s a heat-treated Fastener property classes 8.8 10.9 and so on, and is the fastener in any way less than a full headed fastener such as a hex head or a socket head. In other words, is it a flat head or does it have a hole drilled in it. Is there something about the fastener that gives it a reduced load ability such that it probably couldn’t withstand the full test. Because when we look at the tables, what we want to know is what do we have to do. Do I have to do a hardness test? Do I have to do a tensile test? Do I have to do a wedge tensile test? Do I have to do to decarburization tests and so on. For example in SAE J429 when we talk about the inch products, we do not need to do a decarburization test or examination on those fasteners that are not heat treated because there would be nothing that happens to the fastener that would cause carburization.
As well, if the product is very short and in ISO 898 and SAE J429 that requirement is generally whether the product has a length that is less than 2 1/2 times its diameter. If it’s less than two and a half times is diameter it’s technically too short to put in a tensile testing machine now here at AIM Test Labs we figure out ways around that because sometimes our clients would like to have it tested anyway, and then beyond that both tables are set up in terms of understanding three possibilities. One possibility is that the Fastener must be tested to look at its strength in terms of whether it is heat treated, its size (length to diameter ratio) and its configuration. What kind of a head does it have, or does it have a reduced body? And we look at the table, and it will say that based on all of that, you must do this one certain test, or based on all of that you cannot do this one certain test. It’s either not possible or not required.
And then finally, there are some options. You can choose an option based on either what your capability for doing the test is. In other words, if you don’t have a large enough tensile test machine you can use an option that allows you to test a machined specimen taken from the large bolt that you can’t test. This is based on not just your capability or the test Labs capability, but maybe what the customer wants.
So those very intimidating tables are not that intimidating when we think of them in those three ways.
What’s the Fasteners strength, is it heat treated or not?
What’s the Fastener size, its length to diameter ratio?
And finally, does the fastener have anything about it that would reduce its load ability in terms of its head configuration or reduced body size?
Well, that’s about all you could say without actually looking at the tables. And if you wanted to look at the tables, you can go ahead and look at episodes 1 through about eight on the faster standards review channel from AIM Testing Laboratory where we actually put the stuff up on the screen and it might make a little bit more sense to you.