For My 2c worth! I'd go along with John. The tensile strength is going to be that of the smallest cross section area left after you've cut away the holes. Therefore, in order to minimise the weight you need to work out how much tensile strength you are going to need (with a safety factor) and remove metal leaving only as much as is required. (The strength of a chain theorem). To maximise the metal removed, a combination of large holes or slots and some small holes may be optimal. If you are also worried about compression, smaller holes may be preferable to slots (or larger holes ?) to minimise the possibility of any lateral forces causing buckling. Richard P John Ferrell cc: Sent by: pic Subject: Re: [EE]: Drilling a square tube?? microcontroller discussion list 16/10/01 07:21 Please respond to pic microcontroller discussion list I would think that the distribution of the stress vectors would dictate the size of the holes. I would guess it is not the holes that are important, it is the size/location of what ever is left? John Ferrell 6241 Phillippi Rd Julian NC 27283 Phone: (336)685-9606 Dixie Competition Products NSRCA 479 AMA 4190 W8CCW "My Competition is Not My Enemy" ----- Original Message ----- From: "Roman Black" To: Sent: Monday, October 15, 2001 1:42 PM Subject: Re: [EE]: Drilling a square tube?? > Bob Ammerman wrote: > > > > On a milling machine, of course ;-) > > > > But, you can approximate the effect by the arrangement of your holes, > > perhaps something like this: > > > > * * * * * * * * * * * * * * * * * * * * > > * * * * * * * * * * * * * * * * * * * * > > > Thanks Bob, now we are getting somewhere. :o) > > Using my "very fuzzy logic" brain, what you > are proposing is a hole structure with minimised > walls between holes in the left-right direction. > So it doesn't matter whether we have groups of > 5 holes (as you drew) or just reduced the distance > left-right between each hole, you are suggesting > that the tension/compression strengths remain > similar?? > > In some other commercially drilled members i've > seen something like this: > > --------------------------- > * * * * * * * * * * * * * * > * * * * * * * * * * * * * > --------------------------- > > on each side wall of the square tubing, which > makes sense to me for a number of reasons. > Any suggestions? > -Roman > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics