[Miata] Loosening rusty and broken bolts

[K.C. Murphy]

Hi Miatateers --

This is a pretty good post from the Volvo list I'm on -- I thought I
would share it (with the OP's blessing, of course.)

Murph


-----Original Message-----
From: Peter 
Of course. Thanks for the courtesy of asking.
-----Original Message-----
From: K.C. Murphy 
Peter,
Since this seems to be your work... may I repost it on Miata.net?
Good stuff! Thanks!

------
   Chuck Lesweather picked up on a posting of mine in alt.autos.volvo
under "240 -- removing brake lines?". There are a couple of other tips
involving rusty bolts or studs that weren't relevant to that  particular
question but might be worth passing on, since Volvos are   among the few
vehicles that last long enough for rust to be a serious problem:
  
  1. When studs break off below the surface they're hard to drill
accurately without running the risk of going off into the block. This is
especially true if the stud is hard steel and the block is alloy.

  If you have this problem, take the broken stud, or a piece of a
similarly-sized bolt, and chuck it into a drill press. Now put your
drill bit vertically into a small vice, or clamp it into a pair of
multigrips, and center it under the bolt. Carefully lower the drill
press and drill a hole centrally up through the stud. 

Thread the stud into the block over the broken stud and use it as a
drilling guide. 	For smaller studs, you may be able to use a
piece of copper or steel pipe jammed into the block.
  
  2. If the stud breaks off at the surface, the easiest way to start a
drill centrally is with a Dremel and a small ball-headed carbide
grinder. Come in at about a 45-degree angle and make a dimple in the
center of the stud. Work slowly, and if the dimple is off-center, adjust
it. It's easier to do than to describe. This is also a good way of
starting a centered hole in the end of a stud chucked into your drill
press, only in this case you do it with the drill running.

if the stud is set at right-angles to the block - usually the case -
there's a simple guide that lets you drill absolutely square. Get a
small piece of stainless steel sheet - like a camping mirror - and drill
a hole in it. Place it flat on the block over the stud to be  drilled.
If your drill is square, it and its reflection will appear as a dead
straight line. The slightest angle will be immediately apparent.
  
  3. If you're using a stud extractor and it slips uselessly around in
its hole, don't despair just yet. The fact that it slips means that
you've made a tapered hole. Find a piece of round bar stock, the harder
the better, and chuck it into a reversible drill. With a flat file,
roughly taper the end of the steel to match the taper of the hole. You
don't need to be too finicky about this, just make sure that the stock
doesn't bottom in the hole. Now, with your drill running in reverse,
push the stock into the stud. It'll very quickly heat up the stud,
expanding it. It may even weld itself into the stud and spin it out. If
it doesn't, switch off the drill, unchuck the stud and take a
coffee-break. When you come back, the stud will have cooled onto the bar
stock and away from the block. The expansion and contraction will also
have started to break up the oxide binding stud and block together.
Squirt some penetrating oil between the stud and the block. Grip the bar
stock with a pair of multigrips and rock it gently backwards and
forwards. If it still doesn't want to move, tap the end with a small
hammer, then try rocking again. If the bar stock and stud separate, use
the drill and go through the process again. Go gently - this will work
given time and patience. (At least in this shade-tree mechanic's
experience, it hasn't failed yet.)
  
  4. The combination of tapping and torquing can be used another way. If
you have a bolt rusted into place, take a heavy-duty impact screwdriver
and the largest straight bit you have. (You're going to  end up
sacrificing this bit, or at least keeping it for jobs like  this, so be
sure you're not emotionally attached to it.) Set the  impact driver into
reverse. Put the bit squarely onto the bolt head  and pound the driver
with a heavy hammer. The bit will drive into the bolt head just enough
to transfer some of the torque to the bolt. When you get tired of
pounding, grip the bolt head any way you can - wrench, socket,
multigrips, whatever - and rock it backwards and forwards without
putting too much stress on it. If it doesn't move at all, go back to
pounding.  

  With all of these methods, you're trying to break up the iron rust
with small impacts rather than trying to shear it with one mighty
twist. Rust is something like glass - amazing shear, compression and
tension strength, but relatively easy to crack.
  
  Pete (fP)

No virus found in this outgoing message.
Checked by AVG Free Edition. 
Version: 7.5.476 / Virus Database: 269.9.14/883 - Release Date: 7/1/2007
12:19 PM