Repair dent in aluminum MacBook laptop?

On Wed, 03 Jun 2015 22:19:07 -0700, mike wrote as underneath :

Why didnt you just take out the screw/bracket so you can see? You will need a metal anvil then planish by hand, you wont get it perfect but close, depending on your skillset. C+

You might want to anneal that corner before you try to take the dent out. I find that often when aluminum is formed that there is some work hardening and it is useful to soften the aluminum. It is easy to do, just paint the area with a marker - permanent or white board - and then heat the area with a torch until the marker goes away. Don't get excited and decide that if a little heat is good more might be better, it isn't, but it isn't rocket science either.

Then I would either press or pound the dent out. Some kind of dolly and planishing hammer might be a good scheme but a smooth ball peen will probably work.

There is a standard way to fix such problems in hollowware (such as silver bowls and pitchers) and to make hollowware called "chasing".

Basically, one hammers a blunt tool into the sheet metal, which is resting on a bed of pitch. No special tooling is used.

In your case, the frame corner would be pushed by hand into warm pitch, which would then be allowed to cool. Then, working from the inside of the frame, the corner would be pushed out by hammering a rounded hardwood dowel into the corner, stretching it back roughly into place.

I learned this in a course on making jewelry. The textbook was "Metalwork for Craftsmen" by Emil Kronquist, Dover 1972.

Joe Gwinn

Interesting - i'd never heard of using a marker as a heat indicator. Any idea what temperature that "vanishing point" would indicate?

I've always used these:

I don't know the temperature for markers, but this is a variation on the method used in aluminum bodywork for most of a century.

If you have to work out a dent, you strip the paint, like you would with steel bodywork, and then you take your O/A torch and light it with no oxygen. You then play the sooty flame over the aluminum, giving it a thin coat of soot.

You then turn on the oxygen and heat the aluminum until the soot just burns off. This is something typically done with a rosebud torch.

It's not very accurate, but it's good enough to anneal the aluminum sifficiently to work it with a hammer and dolly -- or a slapper and dolly, more typically with aluminum.

I just recently made a similar repair to my iPad. I dropped it and the corner deformed to the point that the glass broke. Anyway, I took everything apart to replace the glass and used a small tool I made from a small flat blade screwdriver to pound the corner back out. I rounded the end of the screwdriver blade, which was about 3/16" wide, such that the end is now a section of a thin disc. The radius of this disc section is slightly less than the radius of the corner. I then braced the aluminum case with some resilient material and made several taps on the handle end of the screwdriver while the tool was engaged with the work. I thought, before opening it up, that the iPad case was drawn or stamped aluminum but it is actually machined, there are cutter marks visible in many places and even some chatter marks. You want the aluminum to move every time you hit the screwdriver, too light a hit will start to harden the metal and it may crack. I used a small ball pein hammer that Starret sells which has a magnifying lens in the hammer head, it was the perfect weight. But any small hammer will do. The trick is to always move the metal with each hit and to complete the job with as few hits as possible. Eric

snipped-for-privacy@whidbey.com fired this volley in news: snipped-for-privacy@4ax.com:

There is a mantra for repairing old MacBooks that reads a bit like the classic recipe for cooking Tofu:

1) Throw the Tofu in the garbage 2) Buy some meat.

Much the same treatment works well for MacBooks.

Lloyd

It's an APPLE. carve out a negative of the case, with the repaired corner, out of some strong material. Put half an oz or so of C4 in the case, clamp the negative mold tightly anround the case and detonate. That should push the dent out - and since APPLE equipment is so extra-ordinarily robust, it shouldn't do any harm to the computer --- (tongue firmly planted in cheek)

Supposedly around 800F, which isn't too far below the (alloy-dependent) melting point. Aluminum melts without glowing red, so don't heat it much past that vanishing point or you'll reach another one.

I'd practice on a piece of 6061 sheet first, especially if you don't have hands-on experience forming metals that work-harden and crack.

-jsw

Chances are that the case was drawn/stamped in a single op , if so work-hardening shouldn't be a problem .

Macbooks built since 2008 are made of extruded blocks of "aircraft-quality" aluminum. In the consumer world, at least among quality manufacturers, that generally means any heat-treatable grade. I'm told it's 6061, but my source wouldn't be able to tell that from beverage-can aluminum.

The extruded billet is machined. I don't know how they finish it, but it's alleged to be "hard-anodized." That sounds funny, because hard anodizing (which is no harder than regular anodizing, only thicker) generally is dull and gray. Macbooks look pretty bright.

Anyway, they're apparently not stamped, but rather 3D milled. That shouldn't influence knocking out a dent, but if the aluminum is any heat-treatable grade, and hard, it could crack if you don't anodize it first.

Frankly, doing that, if one isn't comfortable with heat treating, could be problematic.

One last point: If the OP decides to go for it, and finds a way to anneal that corner, make sure he finishes knocking out the dent within a day or so. 6061, if that's what it is, starts to age-harden pretty quickly.

From the picture it's stamped, not extruded and machined.

Eh, I didn't look at the picture. Let's see...yeah, that looks like it's stamped. Apparently they machined them for a while after 2008, then went to back-extrusion (not actually "stamping," but more like soda cans and brass firearm cartridges are made). I don't know when that happened.

Anyway, stamped or back-extruded, or even machined, the final properties are going to be roughly the same. Age-hardening will overwhelm any work-hardening effects.

Ed Huntress fired this volley in news: snipped-for-privacy@4ax.com:

Very likely will crack even if you DO anodize it.

I'd be more prone to tell him to anneal it.

Lloyd

Aack! I meant anneal, not anodize. Great, now I'm really screwing him up, I'm sure.

These seemingly simple little things can really get messy. If it's

6061, no matter what he does, he's going to have a range of different hardnesses across the dent a week or two after he knocks it out. That shouldn't matter at all in this job, but it will make a big difference if he anneals it and then lets it sit for a week before he pokes the dent out.

Here's something for those with a general shop interest, although it doesn't apply to the OP's question. With 6000 or 2000 Series aluminums, you can anneal them, and they will never harden. But raise the temperature a bit to the "solution" stage, and they'll naturally age harden. 6061 will harden to T3, just sitting there. I think that

2024 is in the same range. And if you anneal with a torch, you're very likely to hit the solution temperature in some part of the job.

Where hardness changes, you have a weak spot. Again, that should mean nothing in this case, but it could matter on another project. Heat treat aluminum with care. It doesn't behave at all like steel.

6061 is correct. Milled from a single billet because it allows for mounting points and standoffs to be machined without adding material. Plus they are heat treated to make them stronger and stiffer.

Type 3 anodized, with a decorative second treatment.

Anneal yes BUT it will probably still fracture.

Hoookay. So, maybe they've gone back and forth on the production method.

Aha. I see that a Type 3 coating on 6061 is 0.003" thick and "dark gray," which is what I've seen. They must apply a coating that looks brighter.

Yeah, I meant anneal. Brain glitch.

Thanks for the clarifications.

No idea, but you can also "smoke" the area with an acetylene torch with a very rich flame... or even a candle :-)

I suggested the markers because (1) it works and (2) you might not have an acetylene torch :-)

Yes and no. But I've found a lot of aluminum "things" bend better after "annealing" :-)