"Smoothing" aluminum TIG welds
#1
Jet Jockey
Thread Starter
"Smoothing" aluminum TIG welds
I posted something similar in the framebuilders forum, but I wanted to get a few more opinions.
Is there any danger in smoothing/filing/sanding/Dremel-ing TIG welds to achieve that smooth "Cannondale look"? I mean...a number of companies do it, but do they make the welds with a load of extra material to sand down, or do they just use the weld as it is?
I'm considering doing some cosmetic work along these lines to my commuter bike and then powdercoating in a single color. My commuter is the matte black Nashbar "X" Cyclocross frame...it's a plenty "beefy" frame, and I've been told the welds look like very good, very strong welds.
Opinions appreciated before I go do something catastrophic!
Cheers!
Is there any danger in smoothing/filing/sanding/Dremel-ing TIG welds to achieve that smooth "Cannondale look"? I mean...a number of companies do it, but do they make the welds with a load of extra material to sand down, or do they just use the weld as it is?
I'm considering doing some cosmetic work along these lines to my commuter bike and then powdercoating in a single color. My commuter is the matte black Nashbar "X" Cyclocross frame...it's a plenty "beefy" frame, and I've been told the welds look like very good, very strong welds.
Opinions appreciated before I go do something catastrophic!
Cheers!
__________________
Good night...and good luck
Good night...and good luck
#2
Really Old Senior Member
I have to admit, a lot of welds look like they were performed by someone in their 2nd day of welding class that was being paid by the piece.
A skillful welder can reduce the amount of "finishing" needed by a great amount.
The danger in grinding etc. is removing metal from the tubing.
A skillful welder can reduce the amount of "finishing" needed by a great amount.
The danger in grinding etc. is removing metal from the tubing.
#3
Jet Jockey
Thread Starter
These welds are big...but they're symmetric and even. To be safe about the tubing, I don't think I'd be able to totally blend in the welds. (But I've heard that there's a powdercoat capable "Bondo"...) But I think with a Dremel and some time I could turn the welds into a smooth ring around the joint without damaging the tubing.
Luckily the frame was not expensive. If I trash it I can buy another...though Mrs Banzai will be rather upset about that!
Luckily the frame was not expensive. If I trash it I can buy another...though Mrs Banzai will be rather upset about that!
__________________
Good night...and good luck
Good night...and good luck
#4
Senior Member
Join Date: Feb 2004
Location: St Peters, Missouri
Posts: 30,225
Bikes: Catrike 559 I own some others but they don't get ridden very much.
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1572 Post(s)
Liked 644 Times
in
365 Posts
I don't have the technical background to know but I'd do it if it was my bike. That's how you learn. At the very worst (which I doubt) you'll have to find another frame. If that happens, chalk the cost up to "Education".
#5
Junior Member
Join Date: Jan 2007
Posts: 11
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
I was at one time a certified structural steel and pipe welder. My welds would at times be x-rayed in order to pass inspection...not trying to impress you, just letting you know I'm not pulling this stuff out of thin air.
When dealing with joints that require structural integrity, Tig welds are not usually ground down for cosmetic purposes. All hand welders try to achieve the "off-set dime stack" look that you're talking about. If my Tig welds did not come out clean, I'd either toss the metal or break the weld, grind ALL the weld off and start over again. Needless to say, this was a rare occurance after a while. On the other hand, it is not uncommon to see stick welds (arc) grounded down, but there is a reason for that. Stick welds are more prone to leave voids.
You can grind the weld down, but use caution that you don't compromise the structural integrity of the weld. If you do grind any significant amount away, you may lay a new bead over the old weld, again that's not the norm with Tig.
When dealing with joints that require structural integrity, Tig welds are not usually ground down for cosmetic purposes. All hand welders try to achieve the "off-set dime stack" look that you're talking about. If my Tig welds did not come out clean, I'd either toss the metal or break the weld, grind ALL the weld off and start over again. Needless to say, this was a rare occurance after a while. On the other hand, it is not uncommon to see stick welds (arc) grounded down, but there is a reason for that. Stick welds are more prone to leave voids.
You can grind the weld down, but use caution that you don't compromise the structural integrity of the weld. If you do grind any significant amount away, you may lay a new bead over the old weld, again that's not the norm with Tig.
#6
Jet Jockey
Thread Starter
So. How DO manufacturers achieve that smooth look? Do you know anything about the powdercoat friendly Bondo?
__________________
Good night...and good luck
Good night...and good luck
#8
Really Old Senior Member
I was at one time a certified structural steel and pipe welder. My welds would at times be x-rayed in order to pass inspection...not trying to impress you, just letting you know I'm not pulling this stuff out of thin air.
When dealing with joints that require structural integrity, Tig welds are not usually ground down for cosmetic purposes. All hand welders try to achieve the "off-set dime stack" look that you're talking about. If my Tig welds did not come out clean, I'd either toss the metal or break the weld, grind ALL the weld off and start over again. Needless to say, this was a rare occurance after a while. On the other hand, it is not uncommon to see stick welds (arc) grounded down, but there is a reason for that. Stick welds are more prone to leave voids.
You can grind the weld down, but use caution that you don't compromise the structural integrity of the weld. If you do grind any significant amount away, you may lay a new bead over the old weld, again that's not the norm with Tig.
When dealing with joints that require structural integrity, Tig welds are not usually ground down for cosmetic purposes. All hand welders try to achieve the "off-set dime stack" look that you're talking about. If my Tig welds did not come out clean, I'd either toss the metal or break the weld, grind ALL the weld off and start over again. Needless to say, this was a rare occurance after a while. On the other hand, it is not uncommon to see stick welds (arc) grounded down, but there is a reason for that. Stick welds are more prone to leave voids.
You can grind the weld down, but use caution that you don't compromise the structural integrity of the weld. If you do grind any significant amount away, you may lay a new bead over the old weld, again that's not the norm with Tig.
Typically, aluminum isn't used for the reactor parts, but refueling equipment (staging, ladders etc.) can be.
Welds must also be smooth enough to test with dye penetrant for piping systems.
#9
Senior Member
Join Date: Jul 2005
Posts: 3,268
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 118 Post(s)
Likes: 0
Liked 50 Times
in
25 Posts
Grinding or "dressing" frame welds was very popular with the street rodders I used to hang with. Later, after a few thousand miles, the welds would start to crack. Since then, I've never ground any welds, ever. Yes, I get my welding done by someone who is really good at it. Yeah, aluminum welds are a little on the fat side. Your best bet is to leave them alone. bk
#10
Senior Member
A lot will depend on the penetration. Steel tends to penetrate nicely and you can easily and safely profile the weld lines. Also it's not all that hard for a good welder to get the smooth fillet look in steel and with stainless steel.
However when welding thin walled aluminium I think you'll find that the welders or the machine setup folks don't go so much for full joint penetration. With joints of that sort the bead is needed to bridge the structural gap.
For example I've read of two stories where guys with japanese sportbikes sent in their aluminium frames for polishing. The polisher, being used to working with steel and castings more than welded assemblies, "helpfully" ground down the welding beads and then lovingly brought the metal to a mirror like finish. The frames were ruined in the process as cracks occured almost immediately when put back into use.
However when welding thin walled aluminium I think you'll find that the welders or the machine setup folks don't go so much for full joint penetration. With joints of that sort the bead is needed to bridge the structural gap.
For example I've read of two stories where guys with japanese sportbikes sent in their aluminium frames for polishing. The polisher, being used to working with steel and castings more than welded assemblies, "helpfully" ground down the welding beads and then lovingly brought the metal to a mirror like finish. The frames were ruined in the process as cracks occured almost immediately when put back into use.
#11
Jet Jockey
Thread Starter
The consensus seems to be leaning towards "Don't!".
So.
Who can tell me, at least generically, how they think Cannondale does it? Or, does anyone know a powdercoat compatible Bondo type product?
So.
Who can tell me, at least generically, how they think Cannondale does it? Or, does anyone know a powdercoat compatible Bondo type product?
__________________
Good night...and good luck
Good night...and good luck
#12
Senior Member
If the welder knows their stuff they can lay the bead down in such a way and with the right penetration to form a pretty nice looking bead in the first place and in a way that will allow for some profiling. But if the bead isn't done that way from the outset then you're best off to leave it alone.
My old school R series touring Canondale has huge filleted beads. But since mine is the lower range "cheapie" of the series my frame didn't get the nice profiling done to it. So my welds look as if they were done with a caulking gun.
My old school R series touring Canondale has huge filleted beads. But since mine is the lower range "cheapie" of the series my frame didn't get the nice profiling done to it. So my welds look as if they were done with a caulking gun.
#13
Senior Member
Join Date: Jul 2006
Location: Silver Spring, MD
Posts: 143
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
I'd say at the very worst you'll have to have your face surgically repaired if the joint fails at the wrong time. You're not necessarily going to know if you weakened the joint enough to cause failure until you put some stress on it - it would suck if that stress threshold was during a nice high-speed descent and your head tube decides to separate itself from the rest of your frame.
__________________
bike good
bike good
#14
Senior Member
Join Date: Jul 2005
Posts: 7,490
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 141 Post(s)
Liked 163 Times
in
89 Posts
Sorry, I have no technical info to add to the thread. But I do remember reading an article about Cannondale once, at that time there was a guy (probably quite a few, actually) in the factory who's only job was to grind the welds smooth. My impression was that it was sort of the "new guy" position, after you did that awhile you got to move up the ladder.
Like you, I remember wondering at the time if Cannondale's welds start out with a little more material so they can afford to grind some off-
#15
Senior Member
Join Date: Jul 2006
Location: Oakland, CA
Posts: 1,300
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
#16
Geek Extraordinaire
Join Date: Feb 2006
Location: Long Beach, CA
Posts: 1,769
Bikes: Bianchi Advantage Fixed Conversion; Specialized Stumpjumper FS Hardtail
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Considering that cannondales have a reputation for cracking, i'm not sure that you want to emulate them.
__________________
I'd rather have a bottle in front of me than a frontal lobotomy.
Sintesi Conversion Serotta Track
I'd rather have a bottle in front of me than a frontal lobotomy.
Sintesi Conversion Serotta Track
#17
Jet Jockey
Thread Starter
BikeManDan...neat picture.
I did some internet research on this subject, and it turns out that C'dale welds practically come out that way...they double weld, with the second pass laying down more metal. The few bumps that are left are sanded off, but according to the reading I did those are actually very few, and the double pass achieves higher weld penetration.
I don't weld, but it sounds plausible to me.
So. I'm not going to touch the welds on my bike. I intend to Bondo over them, and then powdercoat. Who present knows a powdercoat safe/compatible Bondo?
__________________
Good night...and good luck
Good night...and good luck
#18
Senior Member
Join Date: Aug 2007
Location: Northampton, MA
Posts: 956
Bikes: Iron Monkey: a junkyard steel 26" slick-tired city bike. Grey Fox: A Trek 7x00 frame, painted, with everything built, from spokes up. Jet Jaguar: A 92 Cannondale R900 frame, powder coated matte black with red and aluminum highlights.
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
I think you should ask your powdercoater that question. I think it's probably a primer, but I'm just guessing.
#19
Cat 6
Join Date: Dec 2007
Location: Mountain Brook, AL
Posts: 7,482
Mentioned: 27 Post(s)
Tagged: 0 Thread(s)
Quoted: 500 Post(s)
Liked 184 Times
in
119 Posts
I don't think powdercoat will adhere well on your typical plastic bondo. Youi may need to find something metallic based. Search for posts by DrDeltron. I'll bet he has answered that question before on here.
__________________
72 Frejus (for sale), Holdsworth Record (for sale), special CNC & Gitane Interclub / 74 Italvega NR (for sale) / c80 French / 82 Raleigh Intl MkII f&f (for sale)/ 83 Trek 620 (for sale)/ 84 Bruce Gordon Chinook (for sale)/ 85 Ron Cooper / 87 Centurion IM MV (for sale) / 03 Casati Dardo / 08 BF IRO / 09 Dogma FPX / 09 Giant TCX0 / 10 Vassago Fisticuff
72 Frejus (for sale), Holdsworth Record (for sale), special CNC & Gitane Interclub / 74 Italvega NR (for sale) / c80 French / 82 Raleigh Intl MkII f&f (for sale)/ 83 Trek 620 (for sale)/ 84 Bruce Gordon Chinook (for sale)/ 85 Ron Cooper / 87 Centurion IM MV (for sale) / 03 Casati Dardo / 08 BF IRO / 09 Dogma FPX / 09 Giant TCX0 / 10 Vassago Fisticuff