Penetrator Hole size for Drilling

Hi there!

I’m sorry if this is already obvious but we just really want to be sure on what we should do. We have bought blank penetrators from Blue Robotics and we are unsure of the hole diameters that we should make for drilling. Based on this table from potted cable penetrators, the fourth and fifth columns indicate maximum compatible cable diameter and recommended hole diameter respectively. We would just like to clarify, is the recommended hole diameter the the diameter that we should drill the penetrator? If that’s the case, does it mean that regardless of cable diameter, the hole is a constant 10 mm?

Or is it the diameter of the penetrator itself?

Additionally, we would also like to clarify if the penetrator is hollow inside, like a shell, or it is pure aluminum. And lastly, should the drilling of the penetrator go through from one side to the other? Any help on these questions would be highly appreciated. Thanks!

Hi @yvesyves,

The M10 penetrators have an M10 external thread for mounting, which is 10 mm in diameter. A “10 mm through-hole” hole is recommended for whatever you are mounting the penetrator to. Note that “10 mm through-hole” is something you’re supposed to be able to pass something 10 mm wide through - our end caps use 10.2 mm holes.

It may be helpful to look at the technical details of the blank penetrators, and a 3D model.

It’s solid metal. A “blank” in manufacturing is generally a solid piece of material that’s intended for further processing :slight_smile:

If possible (assuming a sufficiently precise drilling setup), you should try to follow the intended general internal shape:

For the drilling diameters,

  • the throat needs to be at least big enough to fit your wires through it, but small enough to avoid excessive weakening, and should be smaller than the cable jacket diameter
    • I’d recommend staying <8mm, but aim for ‘just’ big enough
  • the shoulder needs to fit the cable jacket, with only a little bit of room to spare
  • the head can be larger - just don’t get too close to the edges

For reference numbers you can measure the diameters on the provided CAD models against the suggested maximum cable diameters :slight_smile:

Note that the chamfers on the corners help avoid the cable (or users) getting cut, and allow the potting compound to move through more freely.

Hi there, @EliotBR. Thanks for the immediate response.

Thanks for this clarification.

Thanks for this. If I am following correctly, Blue Robotics does not specify exact hole diameters, but should however, follow these guidelines in drilling the penetrator holes?

I’m not really sure what you mean. Those guidelines are general things you should consider. If you want to know the hole diameters for our pre-drilled penetrators you can measure them in the 3D models linked in the technical details (which is what I meant by “the provided CAD models”), e.g. I just used FreeCAD to take these measurements for the 4-5 mm cable one:

If you’re asking about custom cable sizes then no, we don’t provide a tool or equation for calculating hole sizes.

This is noted. We’ll look into this. Thanks!

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