James
You addressed your question to Jim, but I thought I'd give comment..tubing wall thickness you use depends on where and what,what goes for one use might be marginal elsewhere..I'd stick to 3/16 or better tubing,common 1/8" wall thickness for me just doesnt have enough metal there for strength..once you weld it there's even more stresses to be supported my the metal..thicker is better in a hoe that will get pounded along the course of its life..Most of the tubing available at my local steel supplier is 3/16 and some 1/4 and 3/8. I think more importantly is the inch size of tubing and try to go rectangular if you can for strength along longitudinal members like backhoe dippers and booms..sure square tubing will work but rectangular would be stronger along the length..look out when you put holes in it as well,you are adding critical stress points,the holes reduce chord height and strength..and as always dont weld vertically across the member,just like a truck frame welding vertically across one will cause the notch effect,first place to break..try to weld the crack up and you shift the problem,it'l crack right along the weld again and again..anyway my mini loader uses 2x4" frame tubing,1/4wall with 1-1/2" mechanical tubing at the joints with a 1"hole in the middle,gives you 1/4" of meat to weld to all around it and uses 1" 4140 steel pins,i pick 1700lbs with it on a regular basis no issues yet after 10yrs operation..2"bore lift cylinders, they have 3/4"pins in them..some of the main frame pins are bigger,frame articulation pins are 1-1/2", the pin bosses were made from 2"round stock,standard A36 mild steel.You can go a long way with 1"pins,as long as you have pin bosses welded on the outside of the tubing to support the pin it'l work out OK. The bigger you can go the better. It takes a lot to shear a 1"tool steel pin,even mild steel for that matter....hope that helps you
