Extracting broken screws

[99tahoe]

have another one that I am working on has a busted fuel tank screw any suggestions on how to remove it I don't have a drill press

[sweepleader]

You don't need a drill press but you do need to be careful. Of course you want to start with a center punch mark as close to the middle as you can get it. You can move the mark a little if your first try is not on center. Put the tip of the punch in the mark and angle the punch so when you strike it with the hammer it moves toward the center. When you get it where you want it, straighten up the punch and strike it once more. Start slow and angle the drill toward the center if it walks off to one side. Catch it before it goes too far, any amount that you can see it off center means you need to correct by tipping the drill a little. You can start with a smaller drill, they are often easier to center up. The drill bit needs to be sharp. Be careful when you get near the end of the screw, it is easy to break the drill bit as it punches through into the space below the screw. You should be able to get an easy-out into the screw and back it out. If it won't come out, you can drill the hole bigger and dig whats left of the screw out with a small chisel or pointy tool. You may have to put in a helicoil to repair the hole. They are not tough or expensive and make a very good repair. Be sure to stay in the screw with the drill and do not drill sideways into the mag. That will make if tough to get the repair back on center with the original hole.

[jerseyhighlander]

Many years back I discovered left handed drill bits and since don't use anything else for drilling out broken bolts & screws. 9 times out of 10, using the left hand drill, and with lots of application of penetrating oil, moderate heat and jolting the bolt/screw with a punch, the drill will snag the metal and turn the broken piece out of the threads. No further repair needed except just cleaning the threads with a tap & some corrosion inhibitor.

McMaster-Carr carries them. The smaller sizes I buy several of the same size because they will break like any other.

[sweepleader]

Jersey makes a very good point, I have left hand drills myself.

Another method, IF the screw is big enough and IF you are skillful enough, a handle or nut can be welded to the broken part. The heat will help loosen the screw and it can be backed out of the hole. TIG welding a blob to the screw and then building it to a T shape will often allow pliers to be used to extract the broken part.

[jerseyhighlander]

Dec 23, 2017 11:45:59 GMT -5 sweepleader said:

Jersey makes a very good point, I have left hand drills myself.

Another method, IF the screw is big enough and IF you are skillful enough, a handle or nut can be welded to the broken part. The heat will help loosen the screw and it can be backed out of the hole. TIG welding a blob to the screw and then building it to a T shape will often allow pliers to be used to extract the broken part.

I did consider putting that down as well but my first thought was the screws being small diameter and surrounded my the lower melting point Magnesium case. And if they're broken below flush with the surrounding case, it's probably not possible for the case to survive without damage. Not a technique for the lower end TIG welders or the novice skill level. I know I would be very hesitant to try it myself in this instance and with my current machine. (Ha, Current Machine... Pun discovered )

It's a great technique for when a bolt is broken off in a cast iron engine block or piece of heavy machinery. Lots of good U-tube videos out there that show it.

[sweepleader]

Current machine, good one. I think that if you (I) were being anal about that pun, you (I) would have to say it is a voltage machine and it sort of loses some of the pazazz. :{)

[jerseyhighlander]

Dec 23, 2017 14:02:27 GMT -5 sweepleader said:

Current machine, good one. I think that if you (I) were being anal about that pun, you (I) would have to say it is a voltage machine and it sort of loses some of the pazazz. :{)

Well, the welding or virtually any other electrical process, doesn't happen without both voltage & amperage. the amperage, being the major player in my book, at least the one that determines the capacity of the machine in most respects & being referred to also as current, if it makes my joke work, I'm sticking with that one.

[sweepleader]

[99tahoe]

well drilled it out and re tapped it, gasket made up and ready to start putting it back toghter thanks

[sweepleader]

Here is an idea of what can be done "welding" broken bolts out. This is about 30-35 years worth collected into one spot.

This is most of my collection
Welded collection by Dan MacDonald, on Flickr


This is the small stuff, down to about #8 I think.  The washer is welded to a 1/8" pin, just above it and to the right is the tip of a small Torx driver.
Small by Dan MacDonald, on Flickr


This a a group of medium stuff, the largest is 7/16, several 3/8, there is a broken tap in the center, next to it and at the top are broken brake bleeder screws.
Medium by Dan MacDonald, on Flickr


Bigger stuff, left is a pipe plug, middle is a crankshaft bolt from a Honda with a pipe nipple welded to it (stick welding rod down the center of the nipple to keep from messing up the crank).  Far right is a socket head welded to a Homelite crank bearing retaining screw.  Across the bottom are some large ones with nuts welded on.
Big by Dan MacDonald, on Flickr


Transmission oil pan drain plug from a Chev with a chunk of trailer hitch hardware attached.  Used a hammer on the lever to get this one loose. This one had to be done upside down.
Trans by Dan MacDonald, on Flickr


This is that Homelite crank bearing retainer screw again.
XL-500 by Dan MacDonald, on Flickr


In the middle is a disc brake caliper retainer pin, in the lower right corner is another brake bleeder screw.
Brake by Dan MacDonald, on Flickr

I have drilled a lot of them too, and installed a lot of Helicoils and other inserts, all good fun.

[Deleted]

WOW Dan, That is unbelievable number of saved successes.

[onlyhomelites]

How many of those are exhaust manifold flange bolts from a small block Chevy?

[sweepleader]

I don't remember the number but I am sure there are some. They often responded to heat and a drill by screwing all the way out through the back side. Chev had some tall brass nuts that would hold the flange in place but not make enough torque to break the studs. The nut would strip off, you could then easily chase the threads and install new nuts.

No Chrysler manifold to head bolts though, they came from the factory predrilled for easy-outs. Of course that made them easier to break.

Some of the time it takes 3-4 tries with the involved heat cycles to get enough torque to pull a stuck screw from steel. Of course sometimes the screw gets welded in place. :{( Its much easier in aluminum, no way to weld it in place.

The Honda crank bolt above was done by running a new stick welding rod down the pipe nipple. They have a tip on them that will start an arc by touching, no need to drag the rod. I had a helper handling the ground so I could put the nipple and rod in place without arcing. When I was ready, he grounded the welder and I slid the rod in, pulling it back enough to weld to the stud and then the nipple. Had to work through the wheel well and inner fender panel. Honda had quoted a new crank to the customer, he was pretty happy with our bill. I think I charged him 2 hours plus a new bolt, not much compared to pulling the crank.

Just so everyone knows, I am not a welder. I have the gear and look pretty good but I have known some welders and I am not one.

[dieseltech]

I've got a collection of welded broken bolts/studs that I've gotten out over the years also. I now teach at a tech college we have a Bolt Buster that is a magnetic resonance heater. Works great on seized nuts. Heats the nut up red hot without getting the bolt red hot also.