extracting a broke off screw from aluminim pannel.

[Alan0354]

Hi, I made a mistake assembling a chassis I bought, I used a too long a screw to screw into a thick aluminum front panel with blind holes ( screw not coming out from the other side). I broke it when I tried to tighten and bottomed out. It's a small screw like 4-40 or even slightly smaller. Is there any way to extract the broken piece out. It is flush with the surface.

I know for bigger screws, they have tools that drill into the middle and screw in something to extract it out. But this is a small screw!!! Any suggestion? The only resort I can think of is drill through and use a black screw and nut so it is not as noticeable.

Thanks

[Dave H]

I did that once. I attempted to drill it out but failed because the screw is harder than the panel and the drill was wandering all over the place. I ended up drilling and tapping a new hole next to the original. Wrap some masking tape around the drill bit as a depth guage so you don't go right through and next time don't tighten it like a gorilla OK?

[Chuck H]

Dave covered it. IMHE you (as I have done) will almost surely do more dirt than good trying to recreate your original plan by attempting to extract that screw. Make a new retrofit plan.

Maybe a hole right next to the embedded screw (as in, the embedded screw IS part of the hole wall) might allow for the new screw head to cover the blemish.

[J M Fahey]

4-40 is still drillable and you can pull it out with a bolt extractor.

It's harder than aluminum, of course, but its surface is hard (it's usually cemented) , the core not so much.

Were you using it as a self tapping screw?
Did it have a self tapping head?

With fine thread screws you need a thread cutting tip, unless aluminum is thin.

Like tip style #23 here, and none other:



And a guide hole is needed anyway to have someplace to push shavings, otherwise it clogs quickly and stalls.

And remember to lubricate it, at least with some soap or candle.

[Jazz P Bass]

Just a thought, but have tried a heat gun.
The screw & the chassis will have a different coefficient of expansion.
Use a small sewing needle to try & get the screw to turn.

[R.G.]

Getting broken steel screws out of aluminum is a classical problem in machining. Often the problem is how to get out a hardened steel tap that has broken off in aluminum. No drilling that one - it's as hard as the drill unless you're using carbide.

There are a couple of solutions. One is chemical. Aluminum forms an insoluble layer of aluminum nitride stuff in response to nitric acid. Steel just corrodes away. Machine shops and motor repair places will sometimes build a parafine/wax dam around the screw hole and pour in nitric acid - verrrry carefully. It eats the steel, leaves the aluminum. It's a bit like magic.

The other common way is to use an Electro-Discharge Machine (EDM) to eat away the tap or screw. EDM is also like magic. An insulating/washing solution covers the area being worked and a charged electrode is lowered toward the target. When it nearly touches the target, a spark leaps between the two, eating off a tiny bit of the electrode and target. The machine sets this up so the spark erosion happens in a continuous stream of arcs and slowly eats the target away.

Many auto machine shops have EDMs or know where to get it done.

[Alan0354]

Thanks guys, I was going to drill it out and replace with a screw that goes through, I guess that's out as the screw is harder than aluminum and the drill will walk. That will really destroy the panel. I think I am either leave it or maybe tapping a new hole.

Thanks

[Chuck H]

Thanks guys, I was going to drill it out and replace with a screw that goes through, I guess that's out as the screw is harder than aluminum and the drill will walk. That will really destroy the panel. I think I am either leave it or maybe tapping a new hole.

Thanks

If a hole all the way through is alright you may be able to remove it from the back by Dremel-ing around the old screw from the back (unseen?) until you can get a bite on it with needle nose pliers.

That's only if you don't have or can't get any nitric acid or an EDM

I thought Jazz's idea was worth a try too. But since you forced the screw into an untapped hole it's likely too gnarly to get it to spin with just friction and no bite.

If it's not too tight maybe you could solder something to grab onto it and get it to turn. The aluminum won't solder but the screw will. The possible catastrophe is that you melt solder down around the threads and make it even tighter. I might at least try a dot of super glue on a stick pressed onto the screw until it sets. Then see if you can turn it out. Same downside though since super glue is basically Loctite.

[g1]

I was also thinking about going from the back, like Chuck mentioned. If it is possible it will save from "defacing".
Also, if you can get some support behind it, you can use a punch to put a dimple or score mark in the center of the screw so your bit will not walk.
Just recently I had a screw broke flush like yours in an aluminum (or magnesium?) bike engine side cover. The screw ended up being much softer than I thought, and I had no problem drilling it.

[Chuck H]

I was also thinking about going from the back, like Chuck mentioned. If it is possible it will save from "defacing".
Also, if you can get some support behind it, you can use a punch to put a dimple or score mark in the center of the screw so your bit will not walk.
Just recently I had a screw broke flush like yours in an aluminum (or magnesium?) bike engine side cover. The screw ended up being much softer than I thought, and I had no problem drilling it.

To add... If anyone chooses to attempt this, DO punch a dimple as mentioned and don't even f@#k with "some drill bit you have around" unless you REALLY know how to sharpen a drill bit. Otherwise just buy a new, sharp one.

[R.G.]

Upon further thought:
If you have any reasonable amount behind the panel to get a grip on:
1. carefully, with magnifiers, file two opposing flats on the bit of screw available
2. soak the snot out of it with penetrating oil
3. see if you can grasp it with vise grips on the flat to gently unscrew/move it; once it moves at all, you've probably won.

[Alan0354]

Thanks guys, I don't think it's worth the effort. It was tight when I broke the screw after I cranked very hard. I can even see a slight bump on the other side of the panel!!! I even thought about using the thin cutting disc on the Dremel to cut a slot into the broken stem and turn it using a small screw driver. But I think I just leave it. This is a front panel that has screws on 4 sides. I just broke one of the 12 screws. When I put the whole thing together, it's really not important.

What I hate is the chassis did not come with instruction. Some of the tapped hole are tight to screw in, so I did not think much to crank it. Also, after I broke the screw, I separated all the screws, there are 4 shorter screws in a pile of screws that otherwise look exactly the same as the others. They all came in the same package and unless you look for it, you can't tell the difference. The kicker is there is no instruction to warn people.

Thanks

[okcrum]

Is the screw actually steel? Lots of 4-40 I have seen is nickel-plated brass. I've walked those out with a small reverse drill (drill rotates counterclockwise to cut) a few times. Another approach is to drill out the 4-40 and any matching holes and retap for 6-32 so they all still match.