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Old 25-04-2013, 09:27   #1
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Cable installation through pedestal guard

I need to run some cables through my 1" Edson pedestal guard. Does anyone know what is the largest hole I can drill in the tube without seriously compromising the guard strength?

Mike
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Old 25-04-2013, 09:39   #2
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Re: Cable installation through pedestal guard

If it was a beam, 1/4-1/3 of the diameter would be the limit, so maybe 1/4" to 3/8" for a hole in a tube. Larger than that and I would sleeve the tube to reinforce it, or some up trhough the deck and run alongside it in a conduit.
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Old 30-04-2013, 04:43   #3
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Re: Cable installation through pedestal guard

NavPod recommend to drill 7/8". I don't know if you ever drilled in stainless, but it is hard. Go very slow so you don't overheat the drill bit. When I did mine, I could not go through. Drilling in a stainless tube, the bit start to dance and I could not complete the hole. I have just enough to pass the connectors of some wire (N2K, VHF remote, etc.).
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Old 30-04-2013, 07:08   #4
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Re: Cable installation through pedestal guard

Thanks to both for your informative replies.

Cheers,
Mike
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Old 02-05-2013, 13:21   #5
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Re: Cable installation through pedestal guard

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Originally Posted by captmikecoin View Post
Thanks to both for your informative replies.

Cheers,
Mike
Just to add to what PeterSailor said, drilling through Stainless has a particular issue. I'll skip the metallurgy, because I don't really know it, but this is the gist:

If you go too fast, it will heat up too much. This will cause the stainless to harden, and then you'll never drill through it.
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Old 03-05-2013, 03:08   #6
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Re: Cable installation through pedestal guard

Having contacted Ocean Equipment who supply Navpods and replacement guards, they recommend a rectangular hole to allow connectors to pass more easily. So I plan to do that using a Dremel DSM20 which is like a miniature angle grinder to cut the tube. Like an angle grinder it uses composite abrasive discs to cut steel so it should do the trick nicely.

I plan to do the work in a couple of weeks time and will report back.

Mike
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Old 03-05-2013, 04:59   #7
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Re: Cable installation through pedestal guard

Whatever size and shape hole you drill, be sure to use a plastic grommet to protect the wires from the sharp edges of the metal.

I would select the grommet first to be sure one was available for the size hole I was planning.

If you can get to the back side and the planned hole is 1/2" or larger, drilling a smaller pilot hole and using an electrician's hole punch will produce and easier and nicer looking hole.

I don't know where you would find a square grommet. A square hole will leave stress points in the corners unless you drill holes in each corner and connect them with straight cuts leaving a rounded corner.
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Old 03-05-2013, 06:34   #8
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Re: Cable installation through pedestal guard

When I need to drill a hole larger than 1/8" in SS tubing I make an initial hole with a 1/8" bit. Then I expand the hole to the required size with a step drill bit. That provides a nice clean hole with no burs and the step drill bit goes through the tube wall like it was butter.

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Old 03-05-2013, 07:17   #9
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Re: Cable installation through pedestal guard

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When I need to drill a hole larger than 1/8" in SS tubing I make an initial hole with a 1/8" bit. Then I expand the hole to the required size with a step drill bit. That provides a nice clean hole with no burs and the step drill bit goes through the tube wall like it was butter.

John
Step bits work very well in sheet metal.

You still need a grommet.
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Old 03-05-2013, 11:06   #10
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Re: Cable installation through pedestal guard

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Whatever size and shape hole you drill, be sure to use a plastic grommet to protect the wires from the sharp edges of the metal.

I don't know where you would find a square grommet. A square hole will leave stress points in the corners unless you drill holes in each corner and connect them with straight cuts leaving a rounded corner.
A grommet goes without saying but I thank you for the reminder. As for a square one I think I shall use a suitably large circular one which could be shaped approximately to the rectangular hole. We'll see. Failing that seal up the hole and cables with Sikaflex to prevent movement, leaving some sealant all round between the cables and the pipe.

As for stress points, a pedestal guard is a pretty unstressed component and certainly not subject to oscillating loads which would tend to fatigue it. Just my opinion. As I wrote above, it's what the guard makers suggested.

Mike
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Old 03-05-2013, 11:44   #11
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Re: Cable installation through pedestal guard

You can buy plastic "U" shaped strips that are intended for smoothing the edge of cut materials like this for protecting cables. Sort of "make your own grommet". This would work on square holes although round holes would be much easier to make and protect with off the shelf grommets.
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Old 04-05-2013, 20:10   #12
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Re: Cable installation through pedestal guard

I recently worked on a new Hunter with a Lewmar binnacle. In this one, there was a somewhat irregular hole approx 5/8" wide by about 1" high in one SS tube to admit wires into the compass pod. It was big enough to pass the connector of a Seatalk(ng) backbone cable.The hole in the tube is located close to a support, so strength is less of an issue there.

No grommet on earth would fit this hole, but I did manage to jam a piece of split plastic wire loom around the wires and part-way into the hole.

Good luck with the Dremel... I tend to break about 3 discs a minute. Careful drilling followed by some filing might be faster.
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Old 04-05-2013, 20:22   #13
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Re: Cable installation through pedestal guard

Lake, are you breaking the dark red "sandstone" abrasive discs? Or the good black composite ones? I find the black ones are hard to break unless you're twisting the tool. The sandstone ones, POS on anything except foam or balsa.

They've also got a diamond-impregnated cutting wheel that's even better, but of course, more expensive.
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