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Pushing out a dent in steel frame from the inside?

Old 10-11-20, 10:59 AM
  #1  
estebe
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Pushing out a dent in steel frame from the inside?

So after taking a frame out of storage I was really pleased to find this

Dent
I know it's estetic but I would like to try to fix it and I was thinking to machine a plug from aluminium, grease it, slide it in from the bb and try to hammer it in, maybe it will push the dent out( i can feel a little dimple with my finger in the inside of the tube). Do you think it's doable? Thank you
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Old 10-11-20, 11:12 AM
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If you got the skill to do that without damaging anything else, go for it. Pushing it out might pop more paint and that will result in touch up that you will need to use filler to make it look decent and less noticeable than it is now.

I'd ignore it or just put filler in it and paint.

Last edited by Iride01; 10-11-20 at 11:16 AM.
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Old 10-11-20, 11:18 AM
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estebe
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Originally Posted by Iride01 View Post
If you got the skill to do that without damaging anything else, go for it.

I'd ignore it or just put filler in it and paint.
Unfortunately i don't have access to a lathe but how hard could it be to fabricate a cyclinder to the inner diameter of the tube? Then drill it in the middle, tie a piece of steing to it and pull it out? It's really close to the bottom bracket so i think in theory it would work? Or?
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Old 10-11-20, 11:37 AM
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Never Fix A Running Piece. I'd leave it, or fill the dent with Bondo®-type stuff, and touch it up. Good chance that trying to fix it will make things worse.
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Old 10-11-20, 11:46 AM
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Um...any thing is possible...

So is the risk of:

1) Cracking the braze in the lug joint.
2) Having the a aluminium rod deform at the impact end and 'mushroom'.
3) having the dimple just gouge the aluminium plug having no effect on pushing the dimple out.
4) the extremely tight spaces and inner tude dimensions you are dealing with.
5) how will you get the aluminium plug back out again.
6) if you are this concerned about the dipmple) I'm sure you'll need to get a colour match touch up paint.
7) Hitting the frame with a hammer is you miss your target.

...I'd take a hard pass on the above.

Personal preferance:

1) Touch up paint and leave the dimple.
2) Car body panel filler, touch up paint to hide the dimple.

Hardest part of these latter two options is finding the colour match paint.
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Old 10-11-20, 11:55 AM
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Ignore and cover with a vinyl decal.
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Old 10-11-20, 11:59 AM
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A 4mm downtube ding isn't something I'd even notice, let alone try to fix. But rest assured that if you do, another rock is going to shoot up and give you another one just like it.
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Old 10-11-20, 12:03 PM
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Similar dents in shotgun barrels are "ironed out" as you describe but the plugs used to do it are precision machined hardened steel and have to be hammered or hydraulically forced under the dent. They are not aluminum or pulled with a string. Also, the bore is accessible from both ends and your frame isn't.
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Old 10-11-20, 12:24 PM
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Originally Posted by estebe View Post
Unfortunately i don't have access to a lathe but how hard could it be to fabricate a cyclinder to the inner diameter of the tube? Then drill it in the middle, tie a piece of steing to it and pull it out? It's really close to the bottom bracket so i think in theory it would work? Or?
You got the basics, but how do you get the expander plug up in there, much less pull it out without damaging anything else. Some of which has been mentioned by others, like the the brazed parts of the tube ends where it's lugged.

Also, this dent isn't something just ready to pop out. The metal was re-shaped and will have to be re-shaped if you swage it with your plug. And typically that requires going a little more in the other direction which has you bulging the tube all the way.

Also, inside diameters on tubes used for bikes isn't always the same through the length of the tube. I think the ends are narrower diameter than the middles. Don't know where this changes or if it is unique to double butted tubes or what.
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Old 10-11-20, 12:43 PM
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estebe
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Well, this was quick and unanimous 😃 thank you all, i'll bondo the dent and leave it be then...
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Old 10-11-20, 12:46 PM
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You need to have a ball shaped steel dolly pushing behind the dent, while you hammer -tap around the front of the dent to float the dent out.
A body shop guy who works on motorcycle gas tanks will have this type of dolly or spoon that lets they reach through a hole and get behind a dent.
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Old 10-11-20, 01:42 PM
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Originally Posted by estebe View Post
Unfortunately i don't have access to a lathe but how hard could it be to fabricate a cylinder to the inner diameter of the tube? Then drill it in the middle, tie a piece of string to it and pull it out? It's really close to the bottom bracket so i think in theory it would work? Or?
Seeing as you're near the joint you're likely in the butted section of the tube and the ID may vary.
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Old 10-11-20, 01:48 PM
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While paint isn't the issue here you can look into "Paintless dent repair" . https://www.automoblog.net/2020/04/1...s-dent-repair/
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Old 10-11-20, 09:03 PM
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This is what I had done on a pretty nice frame. Looks great! Cost about $50.

https://varcocycles.com/2020/07/02/d...n-old-serotta/
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Old 10-12-20, 04:38 AM
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I've successfully fixed a badly dented head tube. That said, head tubes are open at both ends plus there was a fair amount of paint loss. Based on personal experience..... embrace it as a page in the bike's story and "fuhgetaboutit".
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Old 10-12-20, 05:09 AM
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I would fill the dent with some JB Weld, put a Chiquita Banana sticker over it, and then find something else to worry about. Actually, with a dent that small, you won't even need any JB Weld.
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Old 10-12-20, 06:40 AM
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Originally Posted by ddeand View Post
This is what I had done on a pretty nice frame. Looks great! Cost about $50.

https://varcocycles.com/2020/07/02/d...n-old-serotta/
On an important frame to me this is what I have had done twice by our local frame builder and is routine for a good bicycle paint shop. New paint on both have thousands of miles and are perfect. I also have a MTB frame needing help and will have this done as it is the only technique that is recommended for powder coating.
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Old 10-12-20, 07:22 AM
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This is why they make stickers.
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Old 10-13-20, 10:33 AM
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Originally Posted by Iride01 View Post
You got the basics, but how do you get the expander plug up in there, much less pull it out without damaging anything else. Some of which has been mentioned by others, like the the brazed parts of the tube ends where it's lugged.

Also, this dent isn't something just ready to pop out. The metal was re-shaped and will have to be re-shaped if you swage it with your plug. And typically that requires going a little more in the other direction which has you bulging the tube all the way.

Also, inside diameters on tubes used for bikes isn't always the same through the length of the tube. I think the ends are narrower diameter than the middles. Don't know where this changes or if it is unique to double butted tubes or what.
Exactly!

Originally Posted by dedhed View Post
While paint isn't the issue here you can look into "Paintless dent repair" . https://www.automoblog.net/2020/04/1...s-dent-repair/
Perhaps an option if they have the right tool and do not deform the opposite side of the tube.
Originally Posted by ddeand View Post
This is what I had done on a pretty nice frame. Looks great! Cost about $50.

https://varcocycles.com/2020/07/02/d...n-old-serotta/
This type of repair still leaves a dent that has to be filled as well as new matching spot repair or repaint...to me it seems excessive, BTETO.

Originally Posted by Koyote View Post
This is why they make stickers.
The best option in my estimation or no sticker (not calling attention to the area)....repairing it will likely cause one to notice it more.

JMHO, Best, Ben
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Old 10-14-20, 06:42 AM
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Steel? Leave it alone, consider it a mark of a well used bike.
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Old 10-14-20, 06:48 AM
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Ben,

I agree with your spot repair comment but not on frames worth a respray, example below. With the "https://varcocycles.com/2020/07/02/dent-repair-on-an-old-serotta/" like repairs I had done on two similar sized dents the tubing blocks removed the high spots caused with the dent pushing out material around the dent. The brazing then completely filled the dent and excess was removed by filing until perfectly round. These were custom frames, a Reynolds 753 and Prestige Ultralight from local framebuilders and I get a great price on Imron paint from our painter. This procedure also allows powder coating which is as much as I would invest in the dented MTB I have, but I may not as the yellow color I like looks better with a clear coat which nearly doubles the cost and then the decal issues.
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Old 10-14-20, 09:33 AM
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Originally Posted by easyupbug View Post
Ben,

I agree with your spot repair comment but not on frames worth a respray, example below. With the "https://varcocycles.com/2020/07/02/dent-repair-on-an-old-serotta/" like repairs I had done on two similar sized dents the tubing blocks removed the high spots caused with the dent pushing out material around the dent. The brazing then completely filled the dent and excess was removed by filing until perfectly round. These were custom frames, a Reynolds 753 and Prestige Ultralight from local framebuilders and I get a great price on Imron paint from our painter. This procedure also allows powder coating which is as much as I would invest in the dented MTB I have, but I may not as the yellow color I like looks better with a clear coat which nearly doubles the cost and then the decal issues.
I am not against restoration...My comment about respray had more to do with how much the OP is willing and able to spend on a bicycle, too often I read recommendations that in my estimation would be cost-prohibitive....everyone has a budget and an idea of the direction with which they want to proceed. The dent is not something that I would be worried about.
Personally, I am in the camp of those that prefer original unrestored...that being said, I do not own a rare bike in need of attention.
Hight spots can be tapped out by using a pick or jewelers hammer and the brazing if powder coating is the preferred finish...plastic filler can be used if a more traditional finish is in the works, precluding the need for blocks.
BTW, very nice looking resto!
Best, Ben

Last edited by xiaoman1; 10-14-20 at 12:15 PM.
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Old 10-14-20, 07:58 PM
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I've heard of dents like this one repaired by filling them with tin solder. Never tried it myself tough.
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Old 10-15-20, 06:57 AM
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I've successfully used LAB METAL on frames to be powdercoated. JB Weld on painted frames. I wouldn't refinish a frame just because of a dent that small, but each to his/her own. Get your finest model detailing brush and a jar of yellow paint. Clean the dent out real good and paint a microscopic smiley face in it. That way, it adds a little surprise to anyone who actually looks at it and notices what you've done with it. Class. Not classy, but a display of class and style.
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Old 10-15-20, 08:58 AM
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Use a filler and paint over it. I wouldn't risk damaging a frame that is perfectly rideable just to fix a small dent.
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