If the aluminum is tempered the edge of each hole will lose some of its
tempering when drilled.  That means each hole will have a ring of weak
soft aluminum around it.  This leans me towards fewer bigger holes.
Also drill slowly with a sharp drill.

Sherpa Doug

> -----Original Message-----
> From: Roman Black [mailto:fastvid@EZY.NET.AU]
> Sent: Monday, October 15, 2001 11:07 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]: Drilling a square tube??
>
>
> Hi, I know this is more of a mech engineering
> question than an EE one, but here goes. :o)
>
> I need to drill a square tube, hardened aluminium,
> to make it as LIGHT as possible. The square tube
> is 25mm across each edge, and used on a racing
> motorcycle for a non-critical purpose, ie it's
> not part of the drivechain!! It's about 1.2mm
> thickness wall (25mm x 25mm x 1.2mm) if that
> helps.
>
> From my rather "fuzzy logic" examination of the
> stucture the square tubing is not stressed under
> flexion, but it will be exposed to compression
> and expansion forces, so there is nothing to bend
> it, but it needs good strength for compressing
> and stretching forces... ;o)
>
> I'm not after formulae as the problem is slightly
> more complex than what I have posted, but any
> general ground rules and "reasons why" will be
> really appreciated.
>
> Do we drill the tubing with large diameter
> holes, or lots of small holes, and why/how
> will each method give the BEST STRENGTH for
> the MAX amount of weight lost???
>
> Thanks guys! :o)
> -Roman
>
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