With respect, this is not for the ham fisted but a commonly employed technique among techs.
For fasteners such as the drain plug which are not seized in the threads as a drain plug will not be due to the oil film, a chisel and hammer will work well and quickly.
Use a sharp chisel, placed at 90 degrees to the axis of the fastener's threaded portion. This is to say that the chisel would be in the same orientation as would an open end wrench used on the fastener.
Use a small hammer (for shock rather and movement) and notch a deep groove into the face of one flat about 3/4 of the way to the corner.
Now use a dull chisel (keep one in your box for this purpose) in the notch and orient the chisel so that the tip of the chisel is pointed along the curve of an imaginary circle formed around the centre of the fastener. This is to say, "a circle as would be drawn by a compass with the tip placed on the centre of the fastener's head and drawing a circle around the head at the radius of the notch.
Tap the chisel in order to rotate the fastener.
The idea is to use the sharp chisel to make a driving notch in the fastener. The dull chisel is used to drive against the notch rather than to continue cutting as would occur if the sharp chisel were used. A cheap chisel is ideal because it will be soft and stay nice and round.
The hammer blows will attempt to rotate the fastener. Works very well, fast and easy to do. Much easier and quicker than drilling and there's no risk of breaking a screw extractor, etc.
Cautions: One should be constrained in how much impact is employed and generally I prefer to use an 8 oz. or lighter hammer.
Obviously cutting into the engine case by misaligning the edge of the chisel is not a good thing. Given six flats, a convenient orientation and more than one attempt are possible.
Blake's mention of a Dremel cut groove to accept a screwdriver, is a very useful technique for small screws such as handle bar lever mounts.
If you don't have a Dremel, I highly recommend one for the utility. The easiest method of cutting a screwdriver groove is to use a cut-off wheel in a mandrel. These are abrasive disks which are used to cut as would be done by a rotary saw blade.
If the cut-off wheel cannot be employed due to space constraints, a cutting burr or rotary file can suit the bill. Talk to your dentist and ask them to save discarded dental burrs. They will autoclave (sp?) them to sterilize and give you a bunch. The dentist discards the burrs if there is a small nick in the burr because people seem to object to the chattering and vibration..... (who knows why? VBG)
These burrs are tiny and are super for removing nasty items. The fact that they are free is a real bonus.
From time to time, someone will drill a broken fastener out of line. Whether this is due to the drilling being not axial to the fastener or due to the drilling being off the centre line, a big problem has occurred.
When drilling a broken fastener (stud, capscrew, dowel, or the like but never a broken bolt), it is crucial that the hole be drilled exactly at the centre of the fastener and that the hole pass through the centre length-wise (axially) to the fastener.
If the hole is not centred and not parallel the torque applied will no act directly to rotate the fastener and more torque will be required which increases the risk of breaking the extractor. In addition the extractor will have a bending stress applied, increasing the risk.
In addition, it is impossible to re-drill a hole onto the centre of the fastener once an off-centre hole or out of line hole has been drilled. Die grinding or milling will be the only options to increase the hole size at this point.
When beginning drilling to utilize a (broken) screw extractor, it is always best practice to drill so that the option of drilling the fastener out completely remains.
If the fastener is so tight that an extractor cannot rotate the broken piece, the extractor will need to be recovered (without breaking the extractor) and the fastener will need to be drilled out.
Drilling is usually done in stages to remove the broken fastener to the root of the screw threads.
An important bit of physics is that a broken fastener is best drilled completely from end to end before any attempt to remove is undertaken. Drilling completely from end to end will cause the fastener to reduce in diameter (shrink) slightly.
Although tiny, this reduction in size can be very useful in reducing the force required to move the fastener.
If the fastener is to be drilled out, it is best to attempt the drilling to remove the fastener to the start of the threads. This will avoid removal of the threads in the parent part.
Removal of the threaded portion of two parts has an inherent risk because the material may tend to shift and pile up so as to jam the drill. This may be even more the case when drilling a higher tension material such as steel, inside a lower tension material such as aluminium.
It is also nice to retain the option to chase and re-use the original threads.
Once the broken fastener has been drilled from end to end a useful option can be considered. If the broken fastener is drilled to leave a cylindrical (tube) of material which is still thick enough to accept a screw extractor, the broken fastener can be shrunk by heat to reduce it in diameter. A reduction in diameter will usually free the broken piece from the parent (surrounding) material's threads.
Judgment is required in this operation because a balance between the thinnest possible cylinder of broken fastener will shrink the most effectively, however sufficient thickness of material to accept the extractor must be retained.
As stated earlier, a broken fastener should be drilled completely from end to end to reduce the diameter. This will also allow a broken extractor to be drive out from the other end if necessary assuming access is possible.
If access is not possible, a broken extractor can sometimes be driven into an open cavity beyond the bottom of the broken fastener. At this point you are really trying to save what was a SNAFU and has become a TARFU. (Don't ask! VBG)
Try an extractor on the broken fastener. If it still won't move you have two options:
1) Stop and try something else.
2) Continue applying more torque until the extractor breaks.
I prefer option #1 but have been asked to intervene after option #2 may times. (VBG)
If the fastener won't move, remove the extractor and decide on whether to drill the broken material out to the root of the treads or to attempt to shrink by heating.
Heating has the risk that the broken material may be hardened an more difficult to drill.
Heating can shrink the broken material making it easy to turn out. A decision needs to be made.
If you have a die grinder and a bunch of free dental burrs, even a hard, asymmetrical material can be removed with time, patience and swearing. I have done so many times to remove broken taps, drill bits and extractors.
Sorry that this is dis-jointed but put that down to my unwillingness to edit material for which I am not being paid to write. (VBG)
Let's consider a hypothetical, bad situation in which someone has drilled a broken fastener in an engine case. The fastener was seized an attempt to drill has been made. The drilling was out of line with the axis of the fastener and off centre. As a bonus the drill was broken before the hole penetrated the length of the fastener. Nice!
This situation could be worse. How? Someone else did it and you are being paid to save the situation.
Step one is to assess the situation. What are your options/what are the risks?
Removal of the broken drill is likely the first task since further drilling is ill advised on the broken bit. How to remove?
If the hole had completely penetrated the fastener, simply using a pin punch from the other end can be a simple solution. Can you drill from the other end?
If so, drill only to the point where the other drill is encountered but not beyond. Once your drill encounters the broken drill section, the drills may interlock and break you drill. A pin punch can often penetrate the remaining thin section of the broken fastener and drive the broken drill section out of the hole.
Now you can step back and enjoy the praise of the unskilled. If judicious use of a pin punch is not successful, use of a Dremel (or other die grinder) and a small burr to remove material to allow the pin punch to penetrate will make you look even more amazing to the non-skilled. It is often difficult to resist the temptation to add this step even if not required (VBG).
If the other end of the fastener can not be accessed for drilling, the broken drill will have to be extracted from the original end.
There are many options which can be considered.
-can you tack a welding rod to the end?
-is it best to heat the broken drill to yellow heat, then hit it with a shot of oxygen to burn the broken drill away in a quick blast of O2?
- is it best to use a tiny hammer and high quality pin punches to shatter the drill into tine pieces which can be removed, piece by piece?
-is it best to use a tiny burr to remove material around the drill until the drill can be grasped and rotated out by pliers?
-is it best to use a "hard metal drill" to drill the broken drill section?
All of the above have benefits and risks but I'm getting tired of writing and want to go for a ride.
If the broken fastener has been drilled out of line of off centre and no one has broken a drill or extractor in the hole, use your Dremel and burrs to grind the hole back to centre.
Big caution:
If the broken fastener piece has been drilled off the axis of the hole and it is drilled out beyond the edge of the broken fastener such that the hole enters the parent material, STOP!!!!
If a rotation of the broken fastener occurs, the broken section will turn and lock any tool in place such that it will be extremely difficult to extract!!!!
THIS IS A WORST CASE SCENARIO!
This kind of broken fastener will need to be removed with extreme care using a technique such as die grinding the broken section until it is small enough in diameter to be pulled from the hole.
If you are lucky enough that the broken section is not loose enough to rotate, Use a Dremel and small burr to cut the four slots from the centre hole out through the threads in the parent material so that the broken section is able to be removed in four sections. It will be necessary for the slots to be wide enough to allow the threads on the first section to disengage. The first broken segment can be driven into the centre so that it disengages from the threads and is loose in the hole. A magnet will usually extract the broken segment at this point.
Subsequent sections will be easier to remove.
The slots into the parent threads are usually not a problem to reuse of the hole. I usually prefer to use a stud in the hole in future to increase the thread engagement.
Heating the cylinder of broken material is often the best option if the hole can be drilled completely thought the broken section.
Quick heating of the broken "tube" of material to yellow heat will cause extreme expansion stress in the broken material. The Parent material surrounding will prevent the broken "tube" from expanding and since the heated "tube" has so much stress and is so hot, the material will be plastic enough to flow length-wise.
When the material is allowed to cool, the "tube" will shrink to a much smaller diameter because material has flowed to increase the length. The smaller tube will usually turn out readily.
Common practice is to through-drill and the place a nut against the end. The nut is inside welded to the broken "tube" allowed to cool and the resulting heat of welding has shrunk the tube. The nut is used to turn out.
Sorry if this is not as complete as wanted but I' going riding.
Norm
> I am a hamfisted fool. I rounded the edges on my low profile drain plug
> and now I can't get it off. Any ideas?Thanks, Dave
> ________________________________________________
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