Im making an A frame to tow a quad bike behind a car, i need to know something because it affects the design. Imagine a steel tube of an arbitrary length of 1 inch diameter, and 2mm thick walls.. It will have a specific inherent strength before load causes it to buckle or deform. now drill a 6mm hole all the way through at some point along it. You have now created a weak point, which will fail before any other point on the tube when under excess load, generally by the hole deforming inwards on itself, or the steel between the holes crumpling up. if i now fill the holes by placing a 6mm steel bolt of equal strength steel as the tube is made from, to what extent do you now restore the strength and load bearing limits of that point in the tube. I reason it must now be at least the same as the rest of the tube, since the tube has no free movement within the hole to deform into, and the amount of material at a cross section of the hole is now more than an undrilled and filled point on the tube. To put this into practical context: if i drill and place a 6mm bolt in one wishbone arm on the quad bike, do i fatally weaken the 32mm dia arm ?