Framebuilders - Filing/Sanding/smoothing TIG welds

As the title suggests, I'm thinking about smoothing the welds on an Aluminum frame I have, to give it that "Cannondale look". I'll then have it powdercoated.

However, I'm concerned that this may be a terrible idea as taking material off those welds could likely weaken the frame. I've looked at some C'dale frames and they look like perhaps they had some excess materials to work with.

Thoughts?

Cheers!

I remember talking to a customer last year who had brought his old Cannondale in to get the Suntour derailleurs adjusted. Mentioned to him that some people used to refer to them as "crack 'n' fails", but he said that he had never had a problem. He was pointing out the smooth filed-down welds around the seat collar, and right in front of me put his fingernail right through the top of the seatstay. That little spot had been filed down so much that it was less than paper thin.
Not a big fan of filing weld beads. A good one should be pretty in its own way.

In theory one is not supposed to reduce welds. It is pretty obvious that not all of the beads contribute to weld strength in the sense of the lumps not load sharing very well. But it seems to be the case that cutting through these beads in order to smooth them is detrimental. Fairly random grain structure may be exposed. Also from a practical perspective, it is hard to level the often harder weld beads without reducing adjascent walls. There might be a break with aluminum since I am not sure the beads are harder.

If a smooth look is needed, welds are normally built up, not reduced. With steel, brass braze is often used as the leveling material, or bondo. There are bondo products that can be powdercoated. I think Eastwood may catalog them.

Thanks for the advice, guys. I'll look into the bondo products if I decide to do something like this...that sounds a LOT safer.

Sorry for the thread resurrection; since I'm about to strip down the frame in question for a rebuild, I wanted to re-attack this issue one last time before building back up. More thoughts on this? Is it really that detrimental to, effectively, remove the "peaks" on the big fat Aluminum TIG welds to leave a smoother finish? Obviously nothing as seamless as a fillet braze, but at least without the obvious chunkiness.

Thanks for your replies. The moving parts come off this week, and I'll decide then whether to "dress" the frame, or just rebuild with the new components.

cannondale uses 'double pass' welds so that they can grind them smooth. if welds are not smooth on another frame are would doubt that they use that technique and i wouldn't grind them down

If you chemically strip the finish, make sure the stripper has no lye in it. Lye will destroy the aluminum. Lye is also known as Sodium Hydroxide or Potassium Hydroxide.


http://revver.com/video/67469/why-aluminum-and-lye-do-not-mix/

All welded joints undercut the tubing to some degree; when you file on the weld bead it is almost impossible to avoid further undercutting. On relatively thick aluminum tubes you may be able to get away with it, but on the new ultra-thin TIG welded steel I'd advise against it.

If you want really smooth joint, either fillet braze the whole thing instead of welding, or build up the weld bead with bondo or solder to make it smooth.

John,

This is a fat-tubed Aluminum frame; one from a factory. Since I'm about to tear it down for a rebuild, I was considering doing some "dress" work to the chunky TIG welds on it.

Bondo-ing the weld bead is an option as well, I suppose. I just figured filing or grinding would be a more...elegant...solution if it was possible to do so.

It isn't more elegant because it would tend to indicate you didn't know what you were doing (not true I realize, you asked the right questions etc...). At a craft level the work done is a form of communication. The reason bondo is looked down on (not universally) is because it is realized that more skill is required to either lay a weld that requires no subsequent treatment, or build it up with metal to smooth it out. Bondo is still a technically good solution. In my order some projects are better done with grinding and filing while others would be better done with bondo. Not all grinding of welds is wrong, just undesirable in certain materials and structures. Let's say you are making a coffee table out of 2" square tubing, and you want it to look melted together, there is so much surplus strength that you can grind as freely as you want to.

I think a lot of frames get sprayed with a high build epoxy primer or they get powdered. So there will be some platic make-up used in any case. Might as well go whole hog. :)

If you plan to paint this frame, you can even get a good result from something like 5 minute epoxy mixed with some talc or WEST 410. But the point is that epoxy and talc are both dollar store items around here. Just be sure the epoxy isn't dry.

JB weld is fine to powder coat over. Did someone already say that?

Yup...but I'm not going to powder. A local auto body shop quoted me $120 for a solid color plus clearcoat. Not too bad. I'm going to ask them, while I'm at it, what they would charge to strip and take care of those joints for me. Something like bondo or a fiberglass filler, and sand it smooth. If it's another $80 or so, it could be worth it. After all, the supplies were going to run me close to $50 anyway, not to mention the labor.

I realize that this answer sounds really weird after my original post. Sorry about that. I resurrected this old thread of mine, but after cross-posting in "Mechanics" this time around I've also changed my plan of attack. This idea first occurred to me when I originally posted, but the opportunity is only presenting itself now.