Making a Thumb

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I have a Yanamar B-50 Excavator and my winter project is to make a thumb for it.  Since it will endure a great deal of abrasion and pressure I figure on making it out of some pretty tought stuff.  T1 or AR400 steel would be nice.  But... a friend offered a (free )cutting edge from a snowplow.  It's 6" wide 1/2" thick and 8' long, plenty of material but I don't know how it will stand up.  I assume that it's tough if it's a cutting edge, but how tough?   Anybody know what they are made of?  I am borrowing a plasma cutter from a friend to cut it out - can't wait to get my hands in that.    Any hints or ideas would be welcomed.
Reply:Its high carbon heat treated steel.   Thats what most snow plows cutting edges are made of.Lincoln 300 Vantage 2008300 Commander 1999SA250 1999SA200 1968Miller Syncrowave 200XMT350MPA/S-52E/xr-15Xtreme 12vs Millermatic 251 w/30A  Millermatic 251 Dialarc 250 Hypertherm 1250 GEKA & Bantom Ironwokers
Reply:I'm not going to attempt to weigh in on the composition of wear bars/cutting bars but I can tell you that they can be very difficult to get a good structural (stout) weld on using normal hobby shop and conventional methods. Depending on choice of filler you're likely to get either tons of heat cracks in the bead or under bead cracking. Soooo if you try to merely slap a bushing retainer on the side, you're maybe good to go. If you want to saddle it onto a a big bushing then it probably won't hold without proper method of procedure and material. Bottom line is some research, advice and a plan of attack will be the pass/fail factor here.Nice thing about things like "thumbs"  and "rock teeth" is they are not necessarily life threatening and can be a good learning experience. If it falls off in front of a crowd you can always claim you got some sour rod.