? about penetration

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Is it considered a bad or weak weld if you don't have penetration coming through the oppositte side of the metal? What if there is just heat marks? Does it have to be 110% penetration to be good? Hope I am clear on the question.
Reply:Only need 100%.  110% just means more to grind off.For the joint to be as strong as the metal it's holding together,  the weld should be as thick as the smallest plate in the joint.  Yes, you should see weld penetrating through to the back side of the joint if the weld fully penetrated.  It does not need to droop through beyond the back surface, but a fully penetrating weld usually does that a little at least in some parts.  If you're welding 1/4" to 1/8", you need a weld 1/8" thick for it to be as strong as the rest of the metal.  If your weld is only 1/16" thick, then you may as well have made the project out of 1/16" plate instead of 1/8" cause you only have the strength of a 1/16" plate.If the weld did not fully penetrate, you can always flip the metal over and weld the other side to complete it as a fully welded joint.That said, if your project does not call for the full strength of the material in that particular area, full penetration may not be necessary.Last edited by DesertRider33; 01-23-2008 at 11:13 PM.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:On fillets there are ways of obtaining adequate strength through fillet size.
Reply:100% pen on everything???? Not on this planet. You don't need 100% on every single little weld you make. Like Sandy said, fillets don't need it all the time. Addicted, it all depends on the application.
Reply:Originally Posted by SandyOn fillets there are ways of obtaining adequate strength through fillet size.
Reply:O.K. thx guys your lots of help I appreciate it.
Reply:AWS D1.1 wants to see fusion to the root and not necessarily  beyond
Reply:So if you got a good heat mark through the back side, it is gonna be fine?
Reply:From the responses you've already recieved to your question you have probably already surmized that it depends on the application. To get an accurate answer for any given application the fine experienced hands here on this board need to know the specific application.Anything worth doing is worth doing RIGHT
Reply:Well at the moment it is just for a cart i'm building which like they said it's practice so weld everything lol. I understand that it varies depending on the situation and such. Your all a bunch of great guys thx.
Reply:You have to think about the carts usage. I've built some rated over a ton that got welded seriously, and many others that would never see 500 lbs. If you're just throwing one together you only need to figure the material and it's maximum intended load and weld accordingly.Anything worth doing is worth doing RIGHT
Reply:Yeah it's just a cart for a Lincoln AC225, some rods, gloves and such. I figured i'd practice on this one cuz the next one is for my HH187 and the big tank of gas so it will have some weight on it. I know that tank of gas is HEAVY!