Re: Machine Shop

On 2/23/2025 9:52 AM, AMuzi wrote:

On 2/22/2025 4:21 PM, Frank Krygowski wrote:

On 2/22/2025 4:06 PM, Jeff Liebermann wrote:

On Sat, 22 Feb 2025 19:58:29 GMT, cyclintom <cyclintom@yahoo.com>
wrote:
>

On Fri Nov 8 14:03:46 2024 Frank Krygowski  wrote:

It doesn't exist, Tom. You can't pop a dent out a bicycle frame tube by
riding the bike. Thinking you can is a sign of insanity.

>
If you have a slight dent in high performance steel. the tubing can revert to its natural shape under stress.

>
Tom.  The only steel that might do that is spring steel (1095, 1060,
1075, 1080, etc).  Bicycle frames are not made from spring steel.  If
they were made from spring steel, they would ride like the proverbial
wet noodle.
>
So, what's the SAE/AISI number for such a spring steel bicycle frame
and who is selling such bicycles?
<https://www.azom.com/article.aspx?ArticleID=6151>
Since you claim that you fixed the dent on YOUR bicycle, could I
trouble you for the maker and model number of this bicycle so I can
determine steel alloy that was used?  Some photos of the dent, before
and after, would also be nice.
>
Note that I'm not talking about shape memory metal alloys:
<https://en.wikipedia.org/wiki/Shape-memory_alloy>
>
I'm also not talking about hydroforming, which doesn't work at
removing dents in steel tubing without high pressure hydraulic
assistance.  It's commonly used for bending aluminum frames.  You
obviously don't have the necessary equipment in your garage workshop
because you claimed that the dent popped out after simply riding the
bicycle:
<https://www.bikeforums.net/bicycle-mechanics/919494-ding- removal.html>
>

Where the hell do you get off not knowing the properties of tempered steel and commenting on it?

>
Frank, he's all yours now.

Sorry, I'm going to disagree with you about spring steel. AFAIK there is _no_ steel that would spontaneously cure a dent in a bicycle tube from riding stresses. If the steel is dented, it's been stressed in that location beyond its yield point. There's no practical way for that to spontaneously reverse itself.
>
While Andrew knows much more than I about the applicable shop techniques, I think you might be able to partially remove a dent in a tube if, like a seat tube, you had access to an open end. Perhaps forcing in a series of mandrels of increasing diameter could gradually force the dent outward. (Something similar is done to repair dents in the tubing of brass instruments like trumpets.) But I doubt it would give a perfect result, and I think cosmetic repair (maybe Bondo?) would be needed to get it really pretty.
>
What Tom is describing is his usual mix of lying and fantasy and ignorance.
>

 Methods to form, or re form, steel are irrelevant here.
 The principle is that once you're beyond the elastic limit, the piece will have measurable deformation. That's a crystal slip, i.e., the structure of the material has changed.
 Regardless of human decisions after that (re form, cosmetically cover such as lead fill or bondo, replace the damaged piece, throw out the unit) the material has changed; it's not going to spontaneously pop back to pre-strain shape.

Yes, that was the main point of my first paragraph. My second paragraph was my speculation on how a dent might actually need removed, absent the type of magic Tom pretends to have witnessed.
--
- Frank Krygowski