El Camexican
07-26-2014, 07:34 PM
One of the members here is fighting with some old bolts that may not have been turned for over thirty years. A lot can happen in that time that can make the bolts very difficult to remove, so here are a few tips I’ve picked up over the years. Hopefully some of the trade mechanics on here can add to this and maybe we can spare others some grief down the road.
First of all, to help you better grasp the complicated relationship between the threaded XY chromosome “male” bolt and its friend (and enemy) the XX chromosome “female nut” (AKA, threaded hole, insert, etc.) it helps to understand what goes on when these two very different creatures copulate and more so if we ever want to get them apart, as spraying them with cold water does not work as well as it does on dogs. It should also be pointed out that in spite of recent State legislation pertaining to marriage, bolts cannot be mated up with other bolts, but there is such a thing as double nutting and a lot of bolts seem to enjoy it (HINT HINT).
There are three critical prerequisites which must be met before the relationship between a bolt and a hole can be consummated. The first is diameter, the second is thread pitch and the third (which relates mainly to the thread pitch of the female of the species) is the finish of the male which is often increased by means of a coating such as hot dipped galvanizing, or powder-coat which increases the diameter and requires that the hole be increased fractionally to accept the enhanced male bolt. This is usually done by means of a special oversized tap. As it relates to three wheelers we don’t need to worry about this unless we are planning to use hot dip galvanized bolts, or have galvanized a part with a female hole in which case we would have to “chase” the tread with a tap to clean it out and ready it for the bolt (more on that later).
Of lesser importance (until they break) is the strength of the bolt which is measured in grades. For most of our applications Gr. 5 is fine, but 8 and 12 are options and may be standard on some types of hardware. You will want to avoid Gr. 2 hardware on your trike in critical strength areas, as calling Gr. 2 crap gives crap a bad name. There are also different grades of finish for threads which you can research if you are so inclined, http://en.wikipedia.org/wiki/Tap_and_ be patient and at some point this post is going to be about how to get the male and female hardware apart after a long term relationship.
Basically bolt threads are made one of three ways:
ROLLED: Most common for the bolts and studs found on our trikes, very cheap to produce
CUT ON A THREADING MACHINE: Commonly found on large structural bolts, made on a machine that resemble a pipe threading machine
CUT ON A LATHE: Produces precision threads like those found on brake fittings, or aluminum tubes
Either way involves tooling which wears out frequently and changes the resulting thread. This brings tolerances into the equation. A bolt made to the max. dia. tolerance and mated to a nut made to the min. dia. tolerance might go together a little hard, but in theory they should go together if both are within their respective tolerances. The tolerances (if anyone cares) are checked with an incredibly expensive tool called a thread gauge which for holes has a max and a min end. If both fit the part passes, but if either won’t work the part is junk. In the case of the male thread there are two different gauges required. In the event that a bolt has been made to the smallest passable O.D. and the threaded hole was made to the largest they might seem a little loose, going together but again, it should not be a problem. What is a problem is keeping them together when we need them to be and getting them apart whenever we want. If this wasn’t an issue we could just weld everything together and move on with life.
To keep the two together as best as possible we often use things like thread bonding, tensioning, or filling agents, like Loctite, lock washers, or nuts with serrated faces and if suitable, special nuts with nylon rings which some call “Nylock Nuts”. The problem with all of these is that they are harder to take apart when the day comes, some more so than others, but for the most part they do far more good than harm. What causes most of our problems is simply corrosion, or reactions between dissimilar metals that lead to corrosion caused by electrolysis.
Bolts, like humans can be monogamous if they so choose and can stay contently in the same female hole for years, but other less scrupulous bolts find themselves going in and out of different holes quite frequently. These “swinger” bolts often end up with tread damage which is often caused when they enter overused female threads which may have suffered damage from a prior and possibly undisclosed relationship with another bolt. While some might blame the hole for this problem the fact is that with the exception of a nut the female hole is usually stationary and somewhat at the mercy of the more aggressive roving bolt. Other than checking the condition of the bolt’s thread prior to insertion all one can really do is to try using lubricant which can help if they plan to keep doing the old “in an out” a lot, but in situations where maximum strength and security is needed it is always best to use two virgin sets of threads for the copulation of parts. However if one must reuse a female hole like that of an engine case and is doubtful of its purity it is always best to “chase” the hole with a tap. I prefer forming, or roll taps, especially for aluminum as they don’t cut any material away, they just kind of stuff it back where it belongs and straighten out the treads.
So here’s where it goes bad for the guy trying to work on a 30 year old trike. The manufacture of your machine took a mass produced bolt, possibly coated it with thread lock and spun it into a hole or nut until it had reached a tightness or “torque” specified by the engineer who designed the assembly. At that time the surface imperfections on the thread of the bolt and hole were forced to smear and squeeze to conform to each other. Had you wanted to separate the two say one or two years into the relationship it would likely been as easy as spinning a wrench, but over time something very bad called corrosion happened. Either because of moisture or electrolysis between dissimilar metals or a combination of both. The worse examples are seen when carbon steel bolts rust into aluminum cylinder heads near the exhaust port. Ever notice how when new these are often the first bolts to fall out of a motor, but after a year or so they are prone to stripping and breaking? That’s because when new they are usually coated with lubricant to facilitate assembly or removal, but once that lubricant burns off and the steel makes direct contact with the aluminum the destructive process of electrolysis between the two dissimilar metals begins. In the case of a sprocket bolt you usually have a steel bolt (often zinc plated) threaded into an aluminum hole, but in this case there is a known issue with the bolts coming loose, so there is usually some sort of retainer used along with thread locker and lock washers in this area, but this area is frequently exposed to moisture, so eventually some water will get in the threads and start the corrosion process.
If the key to separating the two sets of threads had to be defined in one word, it would be “movement”. Ok, so someone out there is saying “no kidding dumb azz” but, I’m actually referring to a much more subtle movement than just spinning the bolt out with a surge of brute force, as that is the best way to brake the bolt or strip the threads. I’m referring to minuet movement between the surfaces of the two threads which can be accomplished in a number of ways, some more suitable that others depending on the application.
1.Heat – Causes bolts and holes to grow, works particularly well if you can focus the heat on only one part as the dissimilar temperatures between the two are more likely to break the bond. Works well on metal brake fittings and exhaust bolts.
2.Vibration – A vertical (in relation to the bolt direction) blow from a hammer to the head of a bolt or stud will send a shock wave through the treads and possibly lessen the stress on the treads by slightly reliving the surface tension on them at the moment of impact. In the case of an impact driver it does this AND seats the tip at the same time to avoid rounding the head. Works great on studs.
3.Penetrating oil. I never use it (always in a rush) but if you can wait a few hours, or longer it can work very well. Works well on steel to steel threads where rust is the main issue.
Ok, so now that you’ve determined the method you are going to use, you need to make sure you have the right tools. If is a 12mm head, for God’’s sake don’t use a ½” wrench. If it’s a 6 sided head don’t use a 12 point socket, if it needs a 6mm hex key (AKA Allen wrench) don’t use a ¼” and if it needs a line wrench don’t even think about using that 8pc set you picked up at Harbor Freight for $5.99!!! Go buy a good one and pat yourself on the back for doing it later. Alignment is also important. You want as much force as possible exerted on the body of the bolt. Any misalignment with your wrench, or screw driver not only wastes force, but exerts it unevenly on the nut, or head of the bolt and can cause damage (that’s why I despise Philips head screws)
If I have any doubt as to the ease of which a bolt will come out I always try to tighten it a bit first. Why? Because all those surface imperfection on the surfaces of the bolt and hole threads I mentioned before are already lined up and ready to keep going in a clockwise direction. It is much easier to go another fraction of a turn in the last direction they were moving than it is to get all that corroded and smeared metal to separate and move backwards. If you’ve ever tried to loosen a bolt right after you torque it you’ll recall it required more force to loosen it than it did to torque it, so all I am really doing is taking a bolt that was torqued to say 18 pounds and adding a couple more pounds of pressure which doesn’t hurt anything, but it does brake up all the rust and/or thread locker that has found its way into the voids between the two threaded surfaces. Once that movement has been achieved I start carefully loosening the bolt, but (especially in the hole is aluminum, or magnesium) I am very careful not to just start cranking on the wrench. All that crud is still in-between the threads and it can easily strip the hole if forced. The best way I know of to deal with this is to treat the bolt like a tap and turn it back in a bit every time it feels too tight. By going back and forth you are breaking up the garbage into smaller parts that can more easily find a place to “get out of the way” and let the bolt spin out without damaging the hole.
That’s all I have time for, hopefully it helps someone and like I said at the beginning, there are likely some professional wrenches out there that can add to this please do.
First of all, to help you better grasp the complicated relationship between the threaded XY chromosome “male” bolt and its friend (and enemy) the XX chromosome “female nut” (AKA, threaded hole, insert, etc.) it helps to understand what goes on when these two very different creatures copulate and more so if we ever want to get them apart, as spraying them with cold water does not work as well as it does on dogs. It should also be pointed out that in spite of recent State legislation pertaining to marriage, bolts cannot be mated up with other bolts, but there is such a thing as double nutting and a lot of bolts seem to enjoy it (HINT HINT).
There are three critical prerequisites which must be met before the relationship between a bolt and a hole can be consummated. The first is diameter, the second is thread pitch and the third (which relates mainly to the thread pitch of the female of the species) is the finish of the male which is often increased by means of a coating such as hot dipped galvanizing, or powder-coat which increases the diameter and requires that the hole be increased fractionally to accept the enhanced male bolt. This is usually done by means of a special oversized tap. As it relates to three wheelers we don’t need to worry about this unless we are planning to use hot dip galvanized bolts, or have galvanized a part with a female hole in which case we would have to “chase” the tread with a tap to clean it out and ready it for the bolt (more on that later).
Of lesser importance (until they break) is the strength of the bolt which is measured in grades. For most of our applications Gr. 5 is fine, but 8 and 12 are options and may be standard on some types of hardware. You will want to avoid Gr. 2 hardware on your trike in critical strength areas, as calling Gr. 2 crap gives crap a bad name. There are also different grades of finish for threads which you can research if you are so inclined, http://en.wikipedia.org/wiki/Tap_and_ be patient and at some point this post is going to be about how to get the male and female hardware apart after a long term relationship.
Basically bolt threads are made one of three ways:
ROLLED: Most common for the bolts and studs found on our trikes, very cheap to produce
CUT ON A THREADING MACHINE: Commonly found on large structural bolts, made on a machine that resemble a pipe threading machine
CUT ON A LATHE: Produces precision threads like those found on brake fittings, or aluminum tubes
Either way involves tooling which wears out frequently and changes the resulting thread. This brings tolerances into the equation. A bolt made to the max. dia. tolerance and mated to a nut made to the min. dia. tolerance might go together a little hard, but in theory they should go together if both are within their respective tolerances. The tolerances (if anyone cares) are checked with an incredibly expensive tool called a thread gauge which for holes has a max and a min end. If both fit the part passes, but if either won’t work the part is junk. In the case of the male thread there are two different gauges required. In the event that a bolt has been made to the smallest passable O.D. and the threaded hole was made to the largest they might seem a little loose, going together but again, it should not be a problem. What is a problem is keeping them together when we need them to be and getting them apart whenever we want. If this wasn’t an issue we could just weld everything together and move on with life.
To keep the two together as best as possible we often use things like thread bonding, tensioning, or filling agents, like Loctite, lock washers, or nuts with serrated faces and if suitable, special nuts with nylon rings which some call “Nylock Nuts”. The problem with all of these is that they are harder to take apart when the day comes, some more so than others, but for the most part they do far more good than harm. What causes most of our problems is simply corrosion, or reactions between dissimilar metals that lead to corrosion caused by electrolysis.
Bolts, like humans can be monogamous if they so choose and can stay contently in the same female hole for years, but other less scrupulous bolts find themselves going in and out of different holes quite frequently. These “swinger” bolts often end up with tread damage which is often caused when they enter overused female threads which may have suffered damage from a prior and possibly undisclosed relationship with another bolt. While some might blame the hole for this problem the fact is that with the exception of a nut the female hole is usually stationary and somewhat at the mercy of the more aggressive roving bolt. Other than checking the condition of the bolt’s thread prior to insertion all one can really do is to try using lubricant which can help if they plan to keep doing the old “in an out” a lot, but in situations where maximum strength and security is needed it is always best to use two virgin sets of threads for the copulation of parts. However if one must reuse a female hole like that of an engine case and is doubtful of its purity it is always best to “chase” the hole with a tap. I prefer forming, or roll taps, especially for aluminum as they don’t cut any material away, they just kind of stuff it back where it belongs and straighten out the treads.
So here’s where it goes bad for the guy trying to work on a 30 year old trike. The manufacture of your machine took a mass produced bolt, possibly coated it with thread lock and spun it into a hole or nut until it had reached a tightness or “torque” specified by the engineer who designed the assembly. At that time the surface imperfections on the thread of the bolt and hole were forced to smear and squeeze to conform to each other. Had you wanted to separate the two say one or two years into the relationship it would likely been as easy as spinning a wrench, but over time something very bad called corrosion happened. Either because of moisture or electrolysis between dissimilar metals or a combination of both. The worse examples are seen when carbon steel bolts rust into aluminum cylinder heads near the exhaust port. Ever notice how when new these are often the first bolts to fall out of a motor, but after a year or so they are prone to stripping and breaking? That’s because when new they are usually coated with lubricant to facilitate assembly or removal, but once that lubricant burns off and the steel makes direct contact with the aluminum the destructive process of electrolysis between the two dissimilar metals begins. In the case of a sprocket bolt you usually have a steel bolt (often zinc plated) threaded into an aluminum hole, but in this case there is a known issue with the bolts coming loose, so there is usually some sort of retainer used along with thread locker and lock washers in this area, but this area is frequently exposed to moisture, so eventually some water will get in the threads and start the corrosion process.
If the key to separating the two sets of threads had to be defined in one word, it would be “movement”. Ok, so someone out there is saying “no kidding dumb azz” but, I’m actually referring to a much more subtle movement than just spinning the bolt out with a surge of brute force, as that is the best way to brake the bolt or strip the threads. I’m referring to minuet movement between the surfaces of the two threads which can be accomplished in a number of ways, some more suitable that others depending on the application.
1.Heat – Causes bolts and holes to grow, works particularly well if you can focus the heat on only one part as the dissimilar temperatures between the two are more likely to break the bond. Works well on metal brake fittings and exhaust bolts.
2.Vibration – A vertical (in relation to the bolt direction) blow from a hammer to the head of a bolt or stud will send a shock wave through the treads and possibly lessen the stress on the treads by slightly reliving the surface tension on them at the moment of impact. In the case of an impact driver it does this AND seats the tip at the same time to avoid rounding the head. Works great on studs.
3.Penetrating oil. I never use it (always in a rush) but if you can wait a few hours, or longer it can work very well. Works well on steel to steel threads where rust is the main issue.
Ok, so now that you’ve determined the method you are going to use, you need to make sure you have the right tools. If is a 12mm head, for God’’s sake don’t use a ½” wrench. If it’s a 6 sided head don’t use a 12 point socket, if it needs a 6mm hex key (AKA Allen wrench) don’t use a ¼” and if it needs a line wrench don’t even think about using that 8pc set you picked up at Harbor Freight for $5.99!!! Go buy a good one and pat yourself on the back for doing it later. Alignment is also important. You want as much force as possible exerted on the body of the bolt. Any misalignment with your wrench, or screw driver not only wastes force, but exerts it unevenly on the nut, or head of the bolt and can cause damage (that’s why I despise Philips head screws)
If I have any doubt as to the ease of which a bolt will come out I always try to tighten it a bit first. Why? Because all those surface imperfection on the surfaces of the bolt and hole threads I mentioned before are already lined up and ready to keep going in a clockwise direction. It is much easier to go another fraction of a turn in the last direction they were moving than it is to get all that corroded and smeared metal to separate and move backwards. If you’ve ever tried to loosen a bolt right after you torque it you’ll recall it required more force to loosen it than it did to torque it, so all I am really doing is taking a bolt that was torqued to say 18 pounds and adding a couple more pounds of pressure which doesn’t hurt anything, but it does brake up all the rust and/or thread locker that has found its way into the voids between the two threaded surfaces. Once that movement has been achieved I start carefully loosening the bolt, but (especially in the hole is aluminum, or magnesium) I am very careful not to just start cranking on the wrench. All that crud is still in-between the threads and it can easily strip the hole if forced. The best way I know of to deal with this is to treat the bolt like a tap and turn it back in a bit every time it feels too tight. By going back and forth you are breaking up the garbage into smaller parts that can more easily find a place to “get out of the way” and let the bolt spin out without damaging the hole.
That’s all I have time for, hopefully it helps someone and like I said at the beginning, there are likely some professional wrenches out there that can add to this please do.