FTM 114: Fully Threaded Metric

Fastener Training Minute 114: Part Threaded & Fully Threaded Metric Cap Screws

This edition of the Fastener Training Minute with Carmen Vertullo was originally published March 9, 2017 as “10 things you need to know about Hydrogen Embrittlement” during episode 114 of Fully Threaded Radio.

Well, hi everybody, this is Carmen Vertullo with the Fastener Training Minute coming to you from the Fastener Training Institute and the Carver FACT Center here in beautiful San Diego, California.

Just recently I received the email request from a client who had a confusing issue regarding proper description for metric hex cap screws when they are fully threaded or not fully threaded and when we return I’m going to give you a few pointers on how to properly describe that fastener and which ISO specifications cover them.

We’re talking about metric hex cap screws and fully threaded ones versus not fully threaded ones. There are two specifications which are very similar that cover these fasteners dimensionally, and it does not really matter what the material or property class is. It could be Class 8.8, Class 10.9, Class 12.9, whatever, it does not matter. The dimensional standards are ISO 4014 if the product is not fully threaded, and ISO 4017 if the product is fully threaded. So ISO 4017 products will always be fully threaded. However, with ISO 4014, products will only be fully threaded if they’re short, for example M10 x 30. So if the product in question is relatively short it would be fully threaded regardless of whether the specification was ISO 4014 or ISO 4017.

As a matter of fact in ISO 4014 the length where an M10 becomes no longer fully threaded is somewhere around 35mm to 40mm. If you look at the ISO 4014 chart, there is a table that describes this with diameters down the left side and the lengths along the top, and it has a thick black line that looks like a staircase. Above that line at the top of the chart, we see fully threaded fasteners. So choosing a diameter, we can come across and see exactly where the length of the product determines that it will no longer be fully threaded. They recommend that if you are going to choose a product that is fully threaded from ISO 4014 that you specify ISO 4017 instead. They’re exactly the same product specification except the call out would be different. They’re fully threaded when they’re short, but as they get longer they no longer become fully threaded and then it’s an ISO 4014 product.

Now my client had an issue because the product was called out as partially threaded and ISO 4014 is the specification for non fully threaded products. However, it was so short that it was fully threaded. I know that sounds a little bit confusing. But if you have both of those specifications available, you should take them out. Look them up look at table one and you’ll understand how to know when a ISO 4014 product is fully threaded and when it’s not.

This has been Carmen Vertullo with your Fastener Training Minute talking to you about metric hex cap screw thread length.

Thanks for listening.

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