Half a croissant, on a plate, with a sign in front of it saying '50c'
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Stubborn Bolt Extractor

(A pipe wrench)^3
  [vote for,

To understand how this works, you must be familiar with how a standard pipe wrench works. A pipe wrench applies more pressure when more torque is given, assuming you have it adjusted correctly. One side of the wrench face pivots to allow compression of both faces onto the pipe/bolt/nut. This in turn allows the wrench to have a grip even if there is no flat faces to turn, i.e. a pipe.

The problem with a pipe wrench in everyday use is the teeth that grip the surface also create ridges and in extremes can round off the flat surfaces of the fastener. Without these ridges a pipe wrench is rendered near useless due to lack of initial grip.

Imagine an assembly of three sets of pipe wrench faces all in the proper position to grip all 6 sides of the fastener. The S.B.E.(stubborn bolt extractor)* is this type of assembly. It is simply a socket/pipe wrench combination. The S.B.E. slides over the bolt in the same way a socket does. The faces are flat to avoid marring the surface of the fastener. The S.B.E. consists of 6 faces, all are hinged on the right side(this can be reversed for tightening), and the left side is connected via thick rods to a disk. This disk is then connected to a thick rod that has a standard 3/8" drive. Once torque is applied, the disk rotates and in turn the six rods are pulled in the direction of applied torque, and the hinged faces are pulled onto the fastener with force. This allows for the same mechanical workings of a pipe wrench. Once the torque has tensioned the rods, the S.B.E. twists the fastener off without slipping.

Since the S.B.E. is operated via a 3/8" drive, ratchets, air ratchets, and torque wrenches can be used. Of course, the S.B.E. can come in different sizes allowing for larger or smaller drive sizes to be used.

*S.B.E. is not to be confused with strong bad email.

destructionism, Aug 05 2004

A Semi-Similar Tool http://www.irwin.co...rrentType=BM1000002
...this thing works wonders... [bpilot, Oct 05 2004, last modified Oct 17 2004]

Recommended by Bob Vila http://www.sears.co...cal=TOOL&Tool_Id=45
Main benefit is that the spiral flute design has no moving parts to fail (other than your arm). [jurist, Oct 05 2004, last modified Oct 17 2004]

Self Adjusting Socket http://woodworker.c...exe?PARTNUM=947-562
Claims to handle even rusted, broken and odd-shaped fasteners without marring. [jurist, Oct 05 2004, last modified Oct 17 2004]

flank drive socket http://www.allprodu...re7/dess/460mm.html
[scubadooper, Oct 05 2004, last modified Oct 17 2004]

RoboGrip® http://www.robogrip.com/products01.html
Also quite useful, according to my guy. [bristolz, Oct 05 2004, last modified Oct 17 2004]


       Why are you using a pipe wrench (Stilson?) to undo a hex nut or bolt? Use a spanner or socket - it's what they are designed for.
suctionpad, Aug 05 2004

       So are you suggesting an adjustable socket with greater pressure applied to the faces of the nut proportional to the torque applied to the socket?   

       Can you post a diagram, it'll be easier to understand how you want it to work. What's the geometry of the 'faces' of each of the pipe wrenches?
scubadooper, Aug 05 2004

       [suctionpad] No, I don't use a pipe wrench on hex fasteners unless I have to. Spanners and sockets can round off the corners if you get too physical with a fastener that's stubborn. A nut or bolt that is tough to get off can be used again, most of the time all it needs is a little cleaning afterward. This is especially handy if the fastener is hard to find or expensive.   

       [scubadooper] Yes. An adjustable socket that uses the pipe wrench concept.   

       Although I took three years of drafting, I have no place to put any kind of drawing on the internet. So, instead, I'll attemp to describe it.   

       The SBE has a housing much similar to a socket, but larger than a standard socket for the same size fastener. The "wrench faces" are more or less like triangles with the inside point cut to make the "contact face". The left point is attached to the rods going to the drive, and the right point has a large pin. The housing has six grooves running from the center out to the edge for the pin on the wrench face to slide in and out for adjustment. Keeping the pin from moving outward and cancelling the pressure is a presized ring to put over the pins. These rings are presized for most all sized fasteners. Once the torque is applied, the "face" pivots on the fastener outward but is stopped by the ring and all force is directed onto the fastener. This is how the SBE grips with a flat face on the fastener no matter what size it is. The driving or pulling rods opposite the pins are attached to a plate with a drive on the top. As the plate rotates, it pulls the rods counter-clockwise and in turn pulls on the wrench faces. Since the wrench faces have no other object to exert this force on, they put pressure on the fastener.   

       Hope that confuses you...err, clears things up.   

       Just as a note, my ideas are usually excruciatingly complex, but I usually don't mean for them to be.
destructionism, Aug 05 2004

       I don't see why you need more pressure, if you can get a socket onto the nut, that's the best way. There are already sockets designed for rounded nuts (can't find a link at the moment) that work sort of like your description. Rather than a hexagonal plan view they have a rounded star shape that means they connect to the surface of the nut's faces rather than the points, which means that as you apply torque that torque is effectively greater pressure on the nuts faces.
scubadooper, Aug 05 2004

       Just building another mousetrap, I guess.
destructionism, Aug 05 2004

       I used a mouse trap for the first time ever the other day. Very impressed with the design, effectively a bent tube with a square cross-section and a trap door that falls when the mouse over balances the trap.   

       Your trouble is that the existing socket is cheap to produce as it's a single piece of metal with no moving parts.
scubadooper, Aug 05 2004

       I agree with the approach of applying pressure to the sides of the stuck nut. My experience with sockets on frozen fasteners on older cars is less than satisfactory, although I have not seen [scuba]'s star-shaped ones. There is a wrench similar to a nut splitter (it grabs a hex nut like a vise) that I've heard is great, but I can't find a link. See link for a tool that a friend has that is very effective, I think because of the pressure applied. I've used it on totally rounded nuts with success, as long as they're not rusted solid.
bpilot, Aug 06 2004

       I've put together and taken apart lots of things, and never have I witnessed a situation where the proper fitting socket was used and resulted in the flats being sheared off the head. In every case of failure due to over-torquing, either the socket itself failed, or the bolt failed in torque shear at the shaft.
Freefall, Aug 06 2004

       [Freefall], how do you find a /proper fitting socket/ when the hex corners have already been rounded over and the thing's been sitting outdoors for five or six decades. This is a tool to use when the standard tool is not right for the job.
bpilot, Aug 07 2004

       I'm sure I've seen something like this already, but can't find any reference to it. As I recall, the device I saw still had rounded surfaces in contact with the faces of the nut, and I remember thinking at the time that would simply result in shearing off the corners to a greater degree. So (+) for suggesting flat faces.   

       I've found one of the best ways to shift stubborn fasteners is to apply a tightening torque until the joint cracks. It is then easier to undo. Doesn't work every time, though.
egbert, Aug 07 2004

       A flank-drive socket (to which [egbert] refers) is a better choice so long as it's exactly the correct size, and the head of the bolt or nut is not already damaged. This is because it never actually contacts the corners of the hex, so cannot round them off. If it's slightly too large (due to the nut having been damaged), it will tend to round off the edges more than a flat-drive socket.
angel, Aug 07 2004

       [freefall] Nuts are a totally different story. The smaller nuts (less than 1/2") have a tendency to round off quite easily. I have had plenty of bolts shear, and some nuts will heat up to the point that they'll melt to the bolt threads, and in every successive rotation, they ruin threads.
destructionism, Aug 07 2004

       Grips like offset driven nails each toeing into the nut face.   

       I like it.
dpsyplc, Aug 07 2004

       Thanks to angel for providing the correct erminology, this is what I was talking about (see link)
scubadooper, Aug 07 2004

       Ah yeah [Bris] they're great!
scubadooper, Aug 07 2004


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