erileykc

More of a metal working question I'd imagine but I installed a rear rack many years ago using carbon steel fasteners thinking I'd swap them for stainless in a timely fashion Needless to say I forgot all about them and they rusted in the threads of my aluminum Jamis Coda. One drilled out very easily essentially disintegrating without even using the easy out. On the other I've gone thru five drill bits and only managed to get a single 1/16" off center hole in the broken off flush threaded section of the screw. Really trying to not damage the thread in the frame so what are best practices for drilling out a machine screw ( now just a threaded stud ) from an aluminum bike frame?

Edit: My image loading skills were deficient

redshift1

"Ezy-Outs" ( I think that's the original tool spelling ) aren't easy to use. Especially for small diameter threaded fasteners. I avoid them completely nowadays.

I found that trying to drill a central hole in the broken off fastener using an ordinary right hand twist drill of let's say around 1/16 inch diameter, involved lots of drill bit flexing and often breakage. Then assuming you get your hole, you next have the challenge of judging when to stop exerting force before the Ezy-Out snaps...

I have less drama using more modern extraction tools, with shorter and stiffer drill and extraction tools. I use tools of this style now ( in link ). Both drill and extractor are on opposite ends of the same tool. And the drilling is done by left handed drills, which alone sometimes winds out the broken fastener.

Alden Grabit Select Series 7 piece Broken-Bolt Extractor Set - 7017P - Penn Tool Co., Inc

The other thing I would say, is do not buy cheap tools in this instance ! If they break inside the hole, you have new problems.

I assume you are centre punching the broken off fastener before drilling.

Edit : Also apply heat to the aluminium before using the screw extractor.

spclark 

What size are the carbon steel machine screws?

Rather than relying on EzOuts, you may want to look into using properly-sized left-hand drill bits. They're available in metric sizes too if necessary.

With judicious use of Kroil (or some other available penetrant) ahead of time, you may find that a lefty bit itself provides enough torque during drilling that the screw loosens & backs out on its own.

Whatever penetrant you choose, leave it to soak in for at least twelve hours after application. Twenty-four is even better.

Be careful not to attempt using too large a bit however as you'll thin the screw's wall thickness when drilling, making further extraction efforts difficult as the thinned wall tends to stretch from the torque on an EzOut-type extractor. Try to choose a bit roughly 50 - 60% the core diameter of the fastener to be removed.

grumpus

You could try welding a washer to the screw, then a nut to the washer. This applies heat to the threads to loosen the rust scale, and gives you something to grab and turn; the weld won't stick to the aluminium frame. Or nitric acid will dissolve steel and not damage aluminium.

FBinNY 

"Best practiice", which is expensive unless you have a friend with a machine shop is removal by EDM. This is how I used to remove broken taps (usually micro-adjust) for frame builders.

Here, I'd start by patient soaking with a proven "rusted screw" remover product like Kroil" or similar. Then use a series of drills to enlarge the hole so you can use a larger EZ out. Since this is a through hole, I'd file or Dremel flush, to make removal by pushing forward possible, hoping the drill does that before going through. In any case, since you started a hole off center, proceed with caution because any drill used to enlarge it will follow the hole, causing a high likelihood of breaking through on one side and cutting into the frame.

Lastly, depending on the size of the eye and amount of surrounding metal, consider that you may have more breathing room, and can use a thread insert if the finished job rather than saving the original threads, which in any case, may already be compromised by rust.

BTinNYC 

Left hand drill bits is my go-to for smaller bolts. Freed this stuck SOB leaving the caliper threads intact.

ericoseveins

IDK if this is necessarily helpful but I live in NW DC and have a manual mini mill and center drill bits. If there's a way to easily fixture the frame in the mill vise you could drill a precise hole, after milling out the off angle hole a bit. A drill press might be better. I also have a SMAW/GTAW welder and am intrigued by the one suggestion of welding a nut to the sheared bolt. The powder coat around the boss would almost certainly fry but it might be just a few millimeters under the edges of the nut. You're welcome to come over and give any of that a shot!

2_i 

You should normally only use carbide drill bits for such a task.

FBinNY 

Why?

Quality. HSS is more than adequate to the task. Besides, it would be hard to get adequate speed for carbide to offer a benefit.

Carbide MIGHT make sense if this were a heat treated CrMo cap screw, but we know bit isn't since the OP already drilled it.

2_i 

With a carbide bit, you do not need to analyze what is before you, and your chances of the hole ending up where you want it are much higher.

grumpus

It's a standard auto mechanic technique, possibly less effective on the 5 mm threads a bike mechanic has to remove. If you don't get good fusion pretty much as soon as you strike an arc you're just getting it hot, so be sure you're aiming at a good clean bit of bolt, and with adequate current. Welding a washer first helps with smaller bolts, because you're not obstructed by a nut so you can see your arc, and work on some sort of bead, rather than just point and hope.

veganbikes

Just FYI the Jamis Coda is a steel bike and has been a steel bike I think throughout history. The Allegro is the aluminum hybrid they make similar to the Coda.

grumpus

In that case it's probably fairly easy to weld up a ragged hole and drill and tap a new one. Worst case scenario, if surgical removal fails and oversizing to 6 mm is not appropriate.

ericoseveins

Apparently the Coda comes in both Reynolds 520 and aluminum. Kind of bizarre marketing.

spclark 

I'd use a carbide end mill if I could set up the part to be drilled in proper support on a drill press, yes. Controlled feed along one axis rather than trying to attempt coring a busted steel screw with an expensive carbide bit held in a battery-operated hand drill.

5mm's a small target for welding on a spud, particularly if the broken screw's been drilled into already. If it's stuck in an aluminum threaded fitting, way easy to overheat & melt the aluminum threads, maybe more. Only positive aspect is that aluminum conducts heat so fast a careful attempt just might work.

zandoval 

Its just a shame how these things can humble us...

spclark 

True enough, but meeting a good challenge head-on is a worthwhile endeavor if you have the experience to make a good show of it.

OP hadn't posted a pic with his opening post.

I just looked again, there's a pic now & I see two holes, one off-center in busted fastener w/ t'other splitting the thread @ ~ 11 o'clock. That second hole into the threads may complicate things a bit.

erileykc

The magnet test says this is true, thanks. Not sure why I thought it was aluminum.

3alarmer 

.
...not sure if anyone has mentioned it yet, but a good point on a center punch, used to mark your start point for drilling with an indent, is usually enough to keep the drill bit from wandering around as you start. If you're careful.


With what you've got there now, I'd be tempted to just drill one of those holes all the way through. The enlarge it a little to the size you need, and rethread it. I presume you're just going to mount another rack.

veganbikes

I have never seen an aluminum Coda, I know they did/do a threaded version at one point with Tourney but I have yet to see an aluminum Jamis Coda. They use aluminum parts on it but having worked at a Jamis dealer for 9 years I never saw one and any of the older versions (pre me working there) that have come in have all been steel. The Allegro is the aluminum model and I don't think that has ever changed. There might be some sellers that are mislabeling it but the Coda as far as I know has been steel and is still steel and hopefully will never not be steel (unless they go Titanium which would be fine as well)

It happens our intern swore his aluminum Specialized was steel because it is a DH bike and DH bikes are heavy and people have this assumption that steel must be the heaviest when it is not always the case. The Coda has generally been a great bike!

Crankycrank

That top hole that was partially drilled into the threads may actually help some penetrating fluid penetrate further and faster. I would go ahead and carefully finish drilling out the other hole and as mentioned, use some good PF such as Kroil Oil, PB Blaster or if you have some automatic transmission fluid and acetone laying around, mix them 50/50 for one of the best penetrants available. Drip it into the hole and on the end of the broken bolt, let sit for at least 24 hours and without using gorilla strength and an easy out bit keep trying to extract the bolt once or twice a day for at least a week before giving up.

Mr. 66

I think you screwed the pooch with the off center holes.

Do you have any needle end pliers, maybe the tip ends of some wire cutters may have enough to grab in the two holes.

grumpus

First reply, before he'd posted the photo.
I'd assumed we were talking about bosses on the dropout - seat stays puts a different complexion on it, and the ultimate solution is to unbraze the eyelet and fit a new one, pretty easy if it's actually silver soldered, rather than risking damage to the stay. But before going there I'd attack it with a small carbide burr in a dremel, which would have been a good idea in the first place to create a dimple that a drill could follow.

grumpus

They can be great in blind holes, not sure why you'd prefer one over a right handed drill when there's access from the back.

Iride01 

EDIT..... My dementia had me thinking this is what you meant so I FIFY. Geeze I need to learn to read better and fully. Or maybe I need Prevagen!

This surprisingly works on very tiny screws. I've done it and seen it done many times. But for tiny screws with the head broken off, you need a very good quality punch with a tiny but sharply squared off edge or point for pushing that screw.

I don't think there will be enough material left. And the broken bolt will fall out leaving nothing to thread on that side.