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Old 06-01-2013, 15:01   #16
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Re: drilling hole in s/s square tube weakening tube?

Hi I was told as a youngster that TO SATISFY coal mining requirements a hole drilled for a bolt had to have 1.5 times the diameter of the hole either side of it so a 12mm bolt would require 18 mm either side =36mm plus the hole at 12mm = 48 mm. so your 40mm needs a sleeve welded inside it if your going coal mining but if you can do it with a 10mm hole it should be ok. 10x1.5 = 15x2=30 +10=40mm and a 10mm bolt should be strong enough surely? happy mining
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Old 06-01-2013, 15:27   #17
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A 18mm hole in the center of a 40mm will reduce it's load caring capacity by 30 %. The smaller the hole the less proportionately you will be the lose. Also as hole gets closer to a end the stronger it will be. A 10 mm bolt would be stronger than the tube so why use a a 18 mm bolt. It would be more desirable for the bolt to break not the tube. Unless you weld reinforcement plates to surfaces that you drill into your loss is 30%.
I am not a cat sailor but my understandment is cats need to be designed light to deliver promised performance. Did the designer allow for a hole to be drilled in this critical component ?
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Old 07-01-2013, 15:37   #18
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Re: Drilling Hole In S/s Square Tube Weakening Tube?

hi doug, I never meant to drill an 18mm hole? the meaning was that in engineering specs an 12mm hole drilled in 40x40mm box section should have steel 1 and a1/2timesthe diameter of the 12mm hole ie 18mm surrounding the HOLE IN THE STEEL! so if u drill the 12mm hole in the centre line of 40mm box it will only have 14mm of steel left either side of the hole?If on the other hand you drill a 10mm hole it will have 15mm of steel either side of it? I am sorry if I did not explain it fully the first time? 15mm of steel left around the 10mm bolt will satisfy the 1 and a 1/2 times the diameter of the hole spec's but you make sure u are far enough from the end as well .Well folk's that's the end of the whole story fo now.
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Old 07-01-2013, 16:26   #19
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Re: Drilling Hole In S/s Square Tube Weakening Tube?

Carpenter's rule of thumb, you can drill a hole up to about 1/3 of the width of a beam or support, without seriously compromising it if the hole is in the middle. Chop the same size hole at the edge--and it fails.

Of course if the designer thought they didn't need the full width of the beam, they'd have used a smaller cheaper piece of tubing in the first place. These days, you can't assume anything has been built a hair stronger than it absolutely had to be, for limited functions.
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Old 07-01-2013, 17:30   #20
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Re: Drilling Hole In S/s Square Tube Weakening Tube?

Don't over think it. Use K.I.S.S. Keep it simple stupid. This works almost always.
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