PTFE Heat Shrink Tubing: Wall Thickness After Recovery

 

Recently a customer wanted to use some PTFE shrink tubing to cover the shoulder of a bolt as a slip surface and had questions about the wall thickness of shrink tubing. In this customer’s application they were starting with a 0.140” mandrel (the shoulder of the bolt), and the tubing they were considering had a nominal recovered wall thickness of 0.010” with a tolerance of +/-0.003”.

The customer’s main question was: “After going through the heat shrink process, what would you estimate the wall thickness to be and how uniform is it?”

We frequently receive questions like this about estimating wall thickness. In this case, our customer was trying to work out if he would be dealing with a finished outside diameter on the low end of 0.154” (the mandrel plus the two walls, 0.140”+0.007”+ 0.007”) or on the high end of 0.166” (the mandrel plus the two walls, 0.140”+0.013”+ 0.013”). From the highest possible outside diameter to the lowest, a 0.012” swing can make a big difference so the concern is valid and raises two other questions. First, what is allowed in order for the product to be considered within specifications? Second, what do users need to make the product work for their application?

For this post, we are going to make the assumption that the products are going to be in spec because at Component Supply, we distribute quality products and, honestly, we are awesome pretty much all of the time. So, let’s go over the aspect of making the product work for the application. In general, we have found that the wall thickness is fairly true to the nominal or within +/-0.001”. So, for the typical application you can plan on that being the case. In the example we have been using, this would yield an overall outside diameter between 0.158” (the mandrel plus the two walls, 0.140”+0.009”+ 0.009”) or on the high end of 0.162” (the mandrel plus the two walls, 0.140”+0.011”+ 0.011”).

Just a side note: we would not suggest that you do something like design a product with tighter specifications than what is called out in our charts. That’s just a good way to disappoint a lot of people.

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