by K. C. Murphy and David Kasakitis
Note from editor: We have received several good submissions about ways to remove rusted fasteners and/or hardware. We've combined them here to have all the information in one place. If you do have a rusted bolt or other peice to remove, this page has some really good tips!
This article shows a couple different ways to unstick broken and frozen nuts and bolts.
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
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
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.
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.
Removing a stock lower shock bolt, the case where the steel sleeve of the shock eyelet has rust welded itself to the lower shock bolt, is a royal pain. You can remove the nut from the bolt, but you can’t pull the bolt out. The inner steel sleeve of the shock eyelet has become one with the bolt. If you torque on the bolt head, all that happens is that the rubber of the shock eyelet twists within the eyelet. This can happen with shocks left on the car since new (original shocks) and surprisingly (for me) with shocks that’s aren’t that old, say 4 or 5 years.
So what are you going to do? You tried pounding/driving the lower shock bolt out (3lb sledge hammer and blunt point chisel). You tried heating. You tried pressing it out with a big “C” clamp and socket. You soaked the assembly with a rust solvent and still the bolt won’t budge. Well here on Miata.net there are several choices including acetylene torch, using a Sawzall to cut it out, or using a cut-off tool (rotary air-powered tool) to cut it out. Lots of folks swear by using rust solvent/penetrating oil, but even after several days and many soakings, my bolt wouldn’t budge.
I used a rotary tool and believe me, it’s still a rough, ugly, dirty, tedious job. Let’s start with what I was working with…. The other three shocks were removed and replaced quickly. The 4th is where I got stuck; driver’s side. No amount of coaxing would free the bolt up. After two afternoons, in frustration I gave up, put my tools away and queried Miata.net. Of the advice I decided to go with the cut-off tool as I have a Sear air tank. So I purchased a cut off tool and here’s what I found …
First things first. I had removed the short sway bar link completely. The hub was broken away from the upper ball joint and was resting on the ground. I had removed the brake caliper and carrier too because I was replacing the rotors and doing a brake job along with replacing the shocks. The 17mm bolt at the top of the shock was loosened several turns and the two 14mm mounting nuts were unloosened too.
So I started by trying to cut the shock from the eyelet. However the upper A arm, the lower spring pad of the shock, and the bulk of the shock made it difficult for me to use my 3” diameter cut-off tool. I did manage to remove a fair amount of metal after a ½ hour or so, but I gave up in disgust and resorted to ‘old faithful’. Yes, that’s right my old trusty hacksaw with dead/spent blade. I spent another 10 or 15 minutes (with plenty of recovery breaks) to hacksaw through the weld point between the shock and eyelet. Surprisingly it wasn’t all that bad. The aftermarket (Autozone) shock was welded with a mild steel. If I had it to do over again, I think I would have just used a hacksaw but with a new blade. I know I have new hacksaw blades, but like most repairs you can’t find the tool(s) you know you have when you need them….
Once I sawed through the eyelet/shock junction it was easy to remove the shock from the car. My next strategy was to cut through the bolt in two locations. Seeing that I didn’t want to damage the mounting tabs on the lower A arm I decided to methodically attack the problem. I’m sure other folks might have simply cut the protruding bolt and head off the bolt, then wedged the mounting flanges outward to pry the bolt out. Or others might have simply decided to cut through the rubber into the sleeve and bolt. I just didn’t want to risk damage to the flange so I took quite a bit longer to systematically get to the bolt. Ergo this is WHAT I DID, not necessarily what you might want to do.
So to recap, the shock had been cut away from the eyelet. The brake caliper and carrier were removed. The hub was broken from the upper ball joint. I decided to remove the hub completely from the lower A arm. There are two 17mm bolts holding it in place. One is horizontal and is capped with a nut. The other sits near the bottom of the shock mounting point. Unfortunately sometimes the thickness of the shock eyelet prevents you from putting a socket on it and torqueing it loose. (note to make life easier when doing shock / suspension work only use 6 point sockets. You are way less likely to round a bolt or nut off).
I just used the cut off tool like an angle grinder and gently removed some material off the eyelet (perhaps a 16” of an inch). This gave me enough clearance to get my 6 point 17mm ½ drive socket on the bolt near the eyelet. Then I brought out “Gertrude”, my 2’ breaker bar, and took out the 17mm bolt. I removed the other 17mm bolt and then swung the hub completely out of the way.
Next I attacked the eyelet itself. The 1st part was fairly easy. On my shock the eyelet was formed by a band of steel that was bent into a circle then welded. My hacksawing had cut through most of the weld. I could see where the steel strap butted together. I took my 3 lb sledge and another chisel and pounded through the weld point. Next I rotated the eyelet ½ of a turn and cut through the eyelet with the cut off tool. To keep the eyelet from turning as it now moved freely, I just put a socket on my breaker bar and attached it to the shock bolt head. (I suppose you would use vice grips or something else).
I spent about 10-15 minutes gently cutting across the top of the eyelet and at about 90% through took my 3 lb sledge and chisel and broke the eyelet apart. It separated into 2 halves, an ‘upper shell’ and a ‘lower shell’.
Next I attacked the rubber surrounding the sleeve. It’s very tough stuff but my sledge and chisel was able to hammer it off. I suppose I spent about 10 minutes on that. This left me with just the shock bolt and frozen sleeve. My last operations were to cut the bolt in two places, both cuts were about 1/8” away from the lower A arm shock mounting flange. Each cut took about 10 minutes or so. Very slow going. I rotated the bolt after ever few minutes to cut all the way around the sleeve and bolt. Once the two cuts were done I removed the center piece (very hot!) and the threaded ‘stud’ portion of the bolt. The other part, the bolt head was still frozen with a 1/8” piece of sleeve. I just used my center punch and 3 lb hammer to knock it out and it took quite some pounding, testament that the sleeve was just about rust welded to the bolt.
All in all the cutting, sawing, grinding operation took me about 1 ½ hours. And yes I ordered a stock replacement bolt and nut from Mazda. I’m being charged $4.95 for the bolt and nut which have to be special ordered. Oh one more thing, I’m going back to the 3 shocks I just replaced and will be removing the bolts, applying anti-seize compound to them and will be re-installing them. I’ll be sure to use anti-seize on this last bolt too!!
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29 January, 2008