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Tech Article: Broken Bolt Removal
2001/8/20 12:00
From Mount Airy
Posts: 453
Level : 19; EXP : 73
HP : 0 / 468
MP : 151 / 24408
FROM: Winter 2012 VBOOST

A broken bolt or screw is the bane of all gar rage mechanics and motorcycle owners, not to mention anyone else trying to fix a piece of machinery. The job can't proceed until the broken fastener is removed and, of course, you didn't allow for all that extra time, did you? What to do now? What alternatives are there to get the broken bolt out?

There are, in fact, many different ways to get broken bolts and screws out. Which method you use will depend upon the circumstances and also your available tools. A t a minimum, however, we recommend every hobbyist own a small Easy-Out kit, set of lefthand drill bits, propane torch, electric drill (3/8ths chuck and variable speed), and Vise-Grip pliers.

We'll talk about all these momentarily, but first a word about penetrating oils. These are light oils that (supposedly) work their way down between rusted threads and help to release the bolt. While it's true that - given sufficient time - these oils do help, you will find that using them seldom gives instant gratification. They generally take a lot of time to soak in and are useful in situations where you can leave the seized part for days or even weeks. You should have a good selection of lubricants and cutting oils and penetrating oils, but don't assume you're going to get anywhere with them when you're pressed for time.

Okay, let's look at some of the more routine steps in removing a broken bolt. In all cases the best rule of thumb is to start with the simplest procedures and work your way up from there, as each approach fails to get results.

First, let's assume part of its shaft is protruding from the metal surface. In such cases it's always best to try to remove it by clamping the Vise Grips (very tight!) onto the shaft and attempting to turn it out. In our years of experience we've found that in about half the attempts the bolt or screw comes out, so it's well worth trying.

If however there is not enough of the broken bolt to grab with the Vise Grips, try the “pin-punch” and hammer method. It’s simple, just remember the axiom “righty tighty - lefty loosely” place the pin punch against the broken bolt shaft and start tapping with a hammer so the each hammer tap applies counter clockwise force.

If the broken bolt doesn’t start to rotate out it's time to get the propane (or MAPP) torch and heat the shaft and surrounding metal to a dull red color. This will, in most cases, break the molecular bond between the bolt threads and those in the material and allow you to turn the bolt out using the Vise Grips. Heat also expands the metal a little, and all this helps. Heating too much, however, causes the fastener to soften and it might break off again, so don't overdo it. Do I need to mention that this method shouldn't be used in situations where heat will harm or destroy the finished surface, or anywhere there is gasoline present!

Didn't work or the bolt broke off again? Now it's time to get out the drill, but first you need to grind or file the bolt's shaft perfectly flat. Once you do you can use a drill bit or center punch to locate the center of the shaft, then to create a starter- hole for the drill bit. Choose a bit that's smaller than the diameter of the bolt shaft and start drilling. If you have an extractor kit, choose a left handed drill and it’s corresponding easyout that are smaller than the diameter of the broken bolt you want to remove.

In this case it's going to work better if you have a left-hand drill set, because once you've drilled far enough into the bolt the drill will bind up and probably unscrew the remaining shaft. If the drill goes all the way through the bolt shaft you can drill again, using a slightly larger bit. Eventually you will be left with thin remnants of the bolt's threads which you can remove with a dental pick or run a threading tap into the hole to clean it out.

If you don't have left-hand drill bits you should have an Easy-Out set. These are little hardened bits with twisted flutes arranged in a lefthand pattern. The top of each bit is squared to allow turning with a wrench. The bits are tapered, so the several sizes in the kit will fit a large range of bolt sizes. The procedure is to drill into the broken shaft a short way, hammer the appropriate Easy-Out bit into the hole until it wedges and then turn it out with an adjustable wrench.

If all these methods fail to remove the broken bolt (yes, I've had this happen plenty of times over the years!) then the only choice is to drill it out completely, which means drilling away the mating threads where the bolt was fastened. In this case you will have to tap new, larger threads into the hole and find a larger bolt to use in that location.

Can't use a larger bolt because of specific fit or appearance reasons? Well, in such cases you can obtain a Helicoil kit. A Helicoil is a ready-made threaded adapter that will screw into the larger hole you tapped. The adapter has its own internal threads of the original size, so the proper fastener can be used. Helicoil kits are available wherever you find Easy-Out kits, (good hardware stores, auto parts stores, tool stores and online, etc.)

If the broken bolt is below the surface making it impossible to use vise grips or a pin punch. Your only choice is to attempt to drill out the broken stud. For this you will need to find a Drill Guide, A, that fits the pre existing hole. Drill out the broken stud, A left handed drill is best, then use the corresponding easyout, B, to turn the broken stud out of the casting.

If you are trying to remove a stripped out allenhead cap screw or bolt, which is a very common occurrence! You know what I’m talking about… the bolt/screw is not broken but the head has been stripped out by the Allen key! Worst of all you can’t get a pair of vise grips on the head or it’s a counter sunk cap screw. Well don’t fret, there are many new extractors designed for just this problem. As long as you can get to the bolt, straight on, with a drill you can use one of these tools. By the way they also work on the inevitable mucked up Phillips head screws.

Now some of you might be asking; What about rounded off Hex head bolts? Well there are a variety of special socket adaptors designed to get you out a this jam also. All you need to do is select the right size and then tap it down, around the rounded off bolt head, and then you can turn the bolt out with an adjustable wrench or a socket wrench There is also a nifty type pliers specifically designed to be used to remove a rounded off bolt or a stripped Allen head bolt and they work amazing well.

No matter how you extract a broken or rounded bolt, mucked up Allen head or Phillips head I highly suggest running the appropriate size tap into the treaded hole. This will insure that the new bolt you are going to install will not get stuck by a burr or corrosion left in the threads. After you “chase” the threads be sure to blow out the hole with a blast of compressed air.

When it comes to the Aluminum engine block and all of the aluminum covers on the VMAX it is important to remember that the metal IS NOT STEEL or cast Iron. Aluminum is a lot softer and lighter… It demands a “finer” more delicate touch while trying to remove a broken bolt.

I have also, when I worked in a machine shop and had access to industrial tools, used a Mig welder to remove a rather large broken, hardened, dowel pin. In this case I was able to weld a hardened 4”x1/2” bolt right onto the end of the dowel pin and then I was able to attach a puller to the bolt. A couple of hits with a hammer, to shock the pin, and then I applied the hydraulic pressure of the puller and the dowel pin came right out. This technique works well on broken bolts also, as long as there is enough of the broken stud sticking out to weld a “puller” bolt to. You can then just turn the welded pair right out. This technique also works well by welding a washer (1) to the broken stud and then, in turn, welding a nut to the washer.(2) You can than just turn the broken stud/washer/nut out (3).

I mentioned Helicoil's earlier. It is important to know that Helicoil's are “Harder” than the casting you are putting them in. When using them in Aluminum it is very important to follow ALL of the directions and procedures included in the Helicoil kit.

I have touched on only a sampling of tools and techniques that can be used to remove a broken stud or bolt and mucked up screws. Be sure to take your time and evaluate your options when confronted with this problem. Decide if you can remove the offending broken hardware in place, without disassembling the entire project. Decide which tool or tools you are going to use and then layout a game plan. Start with the easiest removal method and if that fails move on to the next.

Here are some other specialty tools for removing broken bolts/studs and rounded off Hex Heads and mucked up Slotted/Philips and Allen heads:

In the very extreme case where every other method has failed you can pull the part, with the broken bolt/stud, and take it to a machine shop and pay to have the broken stud removed with an EDM machine (Electric Discharge Machine), or more commonly know as a Metal Disintegrator.

One scenario that I have not covered here is the often and stubborn situation where no matter what you do, short of breaking the bolt, you just can’t remove a nut. Not to worry, because just as with broken bolts and studs, there are many special tools just for removing a pesky nut from a bolt, especially when you want to save the bolt! These tools are called “Nut Splitters” and they come in various sizes and configurations. They all work pretty much the same way… you place the splitter around the offending nut and then using a wrench you turn the screw of the splitter. As you do so the knife end of the splitter cuts (splits) the nut and makes removal a snap! There are even Hydraulic splitters that utilize a small hydraulic hand pump so you can let the tool do almost all of the work!

In conclusion, Remember that any broken bolt can be extracted or drilled out. The threaded holes can be repaired and new hardware installed. It is important to use the same grade of bolt and torque settings that the manual calls for. Take your time so you don’t damage the casting/engine block or the mating parts. Most of all don’t get discouraged when you break a bolt or muck up a screw… it happens to all of us, even Master Mechanics!

Steve Jasse

Posted on: 2013/11/5 11:59
Be safe out there and enjoy the ride....

Mike Moore
VMOA Webmaster

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