Got a welding question. Does grinding the weld bead (i think that's the right word) down so it is flush with the surface a good/bad idea? Will it effect the strength of the weld?
bad idea, the bead is what holds everything together if you grind it you will significantly weaken it.
cannondale used to grind down their welds and thats how they got the term crack n' faill
Grinding the bead shouldn't affect the strength, even though I'd keep it, personally. The strongest part of a weld is the bead, the weakest is the thermally affect zone beside the bead.
Cannondale were one one the first bike manufacturer to tig weld aluminium. High frequency AC welding was still new technology then and the bead were quite rough. They did a second pass without filler and polished the rest to have a nice smooth surface. Through the years they were associated with the smooth welds and kept doing it.
They do crack, I don't think they crack more than others, but if they did it would make sense since they thermally affect the metal twice with their second pass.
You sir, are wrong. Grinding the bead WILL weaken the weld, the filler material being thicker and over the top of the joint materials is what gives strength to the weld. Giving a double pass welding will not affect the heat affected zone "more" it will just heat it again, there will be no decrease in strength by doing so.
bad idea, the bead is what holds everything together if you grind it you will significantly weaken it.
cannondale used to grind down their welds and thats how they got the term crack n' faill
Grinding the bead shouldn't affect the strength, even though I'd keep it, personally. The strongest part of a weld is the bead, the weakest is the thermally affect zone beside the bead.
Cannondale were one one the first bike manufacturer to tig weld aluminium. High frequency AC welding was still new technology then and the bead were quite rough. They did a second pass without filler and polished the rest to have a nice smooth surface. Through the years they were associated with the smooth welds and kept doing it.
They do crack, I don't think they crack more than others, but if they did it would make sense since they thermally affect the metal twice with their second pass.
You sir, are wrong. Grinding the bead WILL weaken the weld, the filler material being thicker and over the top of the joint materials is what gives strength to the weld. Giving a double pass welding will not affect the heat affected zone "more" it will just heat it again, there will be no decrease in strength by doing so.
Not what I've been taught in school, or by every other welder I've worked with since I've started working as a welder, and that was 8 years ago. But I might be wrong.
Grinding the bead shouldn't affect the strength, even though I'd keep it, personally. The strongest part of a weld is the bead, the weakest is the thermally affect zone beside the bead.
Cannondale were one one the first bike manufacturer to tig weld aluminium. High frequency AC welding was still new technology then and the bead were quite rough. They did a second pass without filler and polished the rest to have a nice smooth surface. Through the years they were associated with the smooth welds and kept doing it.
They do crack, I don't think they crack more than others, but if they did it would make sense since they thermally affect the metal twice with their second pass.
You sir, are wrong. Grinding the bead WILL weaken the weld, the filler material being thicker and over the top of the joint materials is what gives strength to the weld. Giving a double pass welding will not affect the heat affected zone "more" it will just heat it again, there will be no decrease in strength by doing so.
Not what I've been taught in school, or by every other welder I've worked with since I've started working as a welder, and that was 8 years ago. But I might be wrong.
As long as the weld has good penetration you can grind it smooth but if you don't know what you are doing you are more likely going to cause more harm than good. If you're going to grind an Aluminum weld you need to have wider more overlapping stacks in your weld in order to do this properly so you get a smooth transition to the tube and avoid stress raisers.
Having said that there really is no good reason to grind a weld- it's purely cosmetic. If I'm not mistaken the FAA forbids it and I have never seen a ground weld in any structural application in either aerospace or motorsport use. Most of the time you see ground welds in the food processing industry. Bikes are one of the only structural applications where I have seen it used- and a lot of manufacturers use quite a bit of filler to smooth the joints. If you want smooth joints and are using steel tube just fillet braze it instead.
As long as the weld has good penetration you can grind it smooth but if you don't know what you are doing you are more likely going to cause more harm than good. If you're going to grind an Aluminum weld you need to have wider more overlapping stacks in your weld in order to do this properly so you get a smooth transition to the tube and avoid stress raisers.
Having said that there really is no good reason to grind a weld- it's purely cosmetic. If I'm not mistaken the FAA forbids it and I have never seen a ground weld in any structural application in either aerospace or motorsport use. Most of the time you see ground welds in the food processing industry. Bikes are one of the only structural applications where I have seen it used- and a lot of manufacturers use quite a bit of filler to smooth the joints. If you want smooth joints and are using steel tube just fillet braze it instead.
As long as the weld has good penetration you can grind it smooth but if you don't know what you are doing you are more likely going to cause more harm than good. If you're going to grind an Aluminum weld you need to have wider more overlapping stacks in your weld in order to do this properly so you get a smooth transition to the tube and avoid stress raisers.
Having said that there really is no good reason to grind a weld- it's purely cosmetic. If I'm not mistaken the FAA forbids it and I have never seen a ground weld in any structural application in either aerospace or motorsport use. Most of the time you see ground welds in the food processing industry. Bikes are one of the only structural applications where I have seen it used- and a lot of manufacturers use quite a bit of filler to smooth the joints. If you want smooth joints and are using steel tube just fillet braze it instead.
Got a welding question. Does grinding the weld bead (i think that's the right word) down so it is flush with the surface a good/bad idea? Will it effect the strength of the weld?
bad idea, the bead is what holds everything together if you grind it you will significantly weaken it.
cannondale used to grind down their welds and thats how they got the term crack n' faill
I thought the two parts are fused together with the steel wire as a filler
saw that on PSbmx a while ago. pretty sweet video. i find it interesting how much frame construction has changed since then. never knew they made bolt on chainstays.
Got a welding question. Does grinding the weld bead (i think that's the right word) down so it is flush with the surface a good/bad idea? Will it effect the strength of the weld?
Above the surface of the metal - no. You can pile metric shit tons of excess on top of a bead and it won't make it stronger. It's penetration, not height that gives a weld it's strength.
I always got a kick out of that bravado when I used to weld. The criteria for being a welder is having access to a welding machine which isn't exactly a task that reflects knowledge. I was a certified welder for 4 years and I can definitely say that just because someone welds does not make them worth listening to regardless of how many years they've been doing it or however they choose to quantify their expertise. Hell even a lot of certified welders spend half their time talking out of their ass.
I still remember the day I had a guy with somewhere around 15 years welding experience tell me in no uncertain terms that you can't run a vertical weld up because it will fail every time.
That being said I agree with what you're saying, its just that frame of mind irks me.
On grinding welds, if possible weld both sides of the joint then grind down the outside. Then again that would only be possible if it was a butt joint between two plates.
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