Quote Originally Posted by Fishy Jim View Post
FK, do you actually build to an engineered design, or is it seat of the pants material spec?



I'm not an engineer if that is what you are asking. Are you?(seriously) You came across quite condescending there. (what's up with that?) Do you need an "engineer" to design/approve everything you do before you can build it?
Just because a design is on a set of prints does not mean a engineer designed it. Believe me I know when I need to get the real engineers involved. In most of my work the "engineers" have usually fallen a little short and that's where I come in. Too many "engineers" don't know jack about using aluminum and don't factor in things like cycles and HAZ's. They try to use shortcuts and use steel welding techniques on aluminum. Maybe they need a little more "seat of the pants" experience.
BTW My father in law is an engineer, my son went 4 years to an engineering university (and has his masters and is presently working on his PHD) and one nephew is an engineer with his masters degree.


Like I said earlier, you need far less volume of steel to accomplish the same strength. So in common practice (build to design strength rather than volume), it is cheaper to use steel than AL. But, if volume is the only comparison (such as a heavy jig made of a solid chunk), AL is cheaper. You need more AL by volume than you do steel to achieve a specific load capacity. At the same strength, the AL will be much lighter than the steel (and will have cost you more).

I got what you said the first time, so you didn't need to repeat it.
Even on the link you just provided size for size, on the sizes I checked, aluminum was NOT cheaper but was almost the same or slightly higher. Big chunks too I don't think it (your link) is a very good way to compare the two anyway...comparing your best deals out there is the real world method. When I do that, for me, aluminum IS higher. In fact I don't recall a time aluminum was ever cheaper than steel.
But I do get what you are saying.
In my area steel is a good bit less than aluminum size for size. I get a very good price on new steel but I buy a LOT more weight of aluminum.
I wouldn't consider buying metal online unless it was very short pieces of an odd size. They always seem too high to me. I have 2 steel supliers within 5 miles of my shop that happen to be on the way to work. I use 2 aluminum suppliers that deliver to my shop and one of them runs a free truck delivery once a week.