opinions on different grades of hardware

[Chris4747]

I have been using hardened bolts and nuts for about every aplication on my rail biuld .Im cuoriuse about opinions on the different grades of hardware for the different aplications ( brakes,Trany mounts ,moter to tranny ,acsesories,ect....)I do have a firm belief in anti-seize and know of the torch issues while using anti-sieze but my main curiosity lies with the different grades of hardware and the opinions of the efectiveness of said hardware.

[Dale M.]

I always use (minimal) grade 5 bolts ( three bars on bolt heads) and nuts..... These are 120,000 psi medium carbon steel.....A metric bolt grade of 8.8 is same 120,000 psi medium carbon steel as SAE bolts....

IF you are using "socket head cap screws" ( Allen head) these are 160,000 psi ...

IF you are using thread lubes and anti-seize yes you need to decrease torque values by proper percentage (anywhere from 35 to 55 %) for type of lube/anti-sieze compounds you use....

I have never had true bolt failure unless I used to small a fastener for application or got dumb and improperly torqued bolt ( over tighten with air tools)... Always check torque setting on air tools as you tighten things.... Proper way is to use air tools to speed assembly but torque value setting on tool should be less than bolt requirement, and you should always (final) hand tighten to proper torque spec...

Dale

[Ol'fogasaurus]

That is a good question... a very good question. To be short, nothing less than a grade 5 (unless it is light weight electrical component) and you (like most of us) are probably using more fastener than you need. For example: you don't need a grade 8 bolt for holding two pieces of 22 gauge sheet metal together; silly, maybe to the extreme but I have seen things almost that bad done w/o people realizing it. It is not always the grade that makes the difference; it is often the use the fastener was designed for.

Unless you have access to a very, very good fastener/hardware store you usually can only get fasteners in ¼” length increments while in reality they are available in 1/16 lengths and some are in 1/32” lengths. It is the same with diameters, 1/16th and 1/32nds are available. Most stores cannot afford the room needed to store and maintain this plus the inventory tax and theft problems. Even in Aerospace we often had to go through several suppliers to get what we wanted as it is just not possible for one place to have everything. My sister’s father-in-law had a specialty fastener store and he stocked the hard to get/find stuff; the two-story building took the best of a whole city block.

Shank: Box and most fastener stores keep fasteners in total lengths not in shank lengths which is the most important thing you want buy. Fully threaded bolts have their uses, short shanks are usually for single shear or short grips and longer shanks are more commonly used for double sheer, long grips or other reasons. The shank needs to be sized for the grip with the “grip” being defined as the total stack of materials you are trying to hold together. The threaded part should be as close to the top of the material stack as you can reasonably get. This is so you get full use of shank and remember, when you cinch up on the nut the bolt is going to stretch which could make your choice of shank off. You can use washers under the head or under the nut to adjust the length of the bolt but if you need more than three washers in a stack then go to a spacer. This is because the washers don’t like to align up straight or can move (for many reasons) and the stack then is not giving you all the load of the bolt head or nut back onto the parts being held together.

Threads: You never want the threads to be in sheer or under load as they are the weakest part of the fastener along with the meeting of the shank and the fasteners’ head… the radius is usually very tight here. Also, pay attention to the torque readings for the size bolt you are using; exceeding the torque gets you into the territory of weakening the bolt due to over stretching the bolt (you reef on a bolt then all of a sudden it gets soft on you… Aw $#it, you have over stretched the bolt). One of the reasons for not going into you save bolt collection unless you know the history of the bolt… assuming the bolt is going to be used in a critical application. Also, you want a minimum of 2 ½ to 3 threads showing; this is to ensure you have the use of all full threads. When bolts are made the top of the shank is tapered (I posted a bit on the making of bolts in the Off-road forum) so when the treads are rolled or cut, this area does not contain full sized threads. Some places, some racing rules, will call for a minimum of 2 ½ diameters of thread showing; this is for safety applications.

Most bolts are designed for either shear, tension or a combination of the two applications. This means that most box or even some specialty stores cannot carry what is available. Application/use/grade is also controlled by not only the design; e.g., the radius under the head of the bolt, but the material also. You can tell to a certain extent what the application is but you will often be wrong so don’t assume… you will most likely be wrong! Some bolts, like head bolts/studs, are single use applications; they are usually installed by measuring the stretch. Measuring the stretch is the best way to torque a bolt but it is also the slowest way.

Self- locking nuts and bolts have a minimum number of cycles (a cycle is on and off once) before their holding power starts to diminish. Tapered ovaling of the nut or bolt is often one of the ways it is done but not the only way. For what it is worth, high heat or repeated heat applications can cause a ovaled nut to take on the round shape and diminish the locking ability the nut originally had. Mechanical locking mechanisms such as the Nylocs (reg) also wear but should not be used around high heat. I tried to see how hot it took before the nylon failed and I was surprised how hot it took but don’t go there. Use the proper locking fastener for the proper application.

Locking washers: In this case split washers do have a life expectancy and it is shorter than you think. Star and wavy washers are considered light duty so use appropriately.

Also, if you never thought about it, when a nut or bolt are cinched up only one surface of the threads of the nut and the opposite threads of the bolts are under load. Think of that when you are choosing how tight to reef on something.

Some quick thoughts and by no means is this anyway close to all there is to know.

Lee

[Chris4747]

I always use (minimal) grade 5 bolts ( three bars on bolt heads) and nuts..... These are 120,000 psi medium carbon steel.....A metric bolt grade of 8.8 is same 120,000 psi medium carbon steel as SAE bolts....

IF you are using "socket head cap screws" ( Allen head) these are 160,000 psi ...

IF you are using thread lubes and anti-seize yes you need to decrease torque values by proper percentage (anywhere from 35 to 55 %) for type of lube/anti-sieze compounds you use....

I have never had true bolt failure unless I used to small a fastener for application or got dumb and improperly torqued bolt ( over tighten with air tools)... Always check torque setting on air tools as you tighten things.... Proper way is to use air tools to speed assembly but torque value setting on tool should be less than bolt requirement, and you should always (final) hand tighten to proper torque spec...

Dale

one thing that i have learned over the years is I dont use air tools unless its something unimportant .i like hand tools a lot better (this is creepy but) its a little more personal when im working on something like my new rail.

[Chris4747]

Lee I still use the navy standard of 3 threads showing past the nut,and i agree with every thing that you mentioned .I was wondering how many people go to the hardware store and just grab anything with the rite thread patturn .its something that a lot of people wont think about .

[Ol'fogasaurus]

Lee I still use the navy standard of 3 threads showing past the nut,and i agree with every thing that you mentioned .I was wondering how many people go to the hardware store and just grab anything with the rite thread patturn .its something that a lot of people wont think about .

Hand tools give you more control over things. When I was young and was starting to collect tools when asked what I wanted it was sockets and socket wrenches; the neighbor, across the cemetery we lived by told my father to get hand tools, I would end up using them more... which I finally figured out. I seldom use them but I do use the ratcheting hand wrenches though; you still have the feel that a hand wrench gives. I have a minimum of 2 of each of "combination" hand wrenches, one for the head and one for the nut.

I don't think most people really know enough about fasteners to know the difference which is a shame.

Lee

[Chris4747]

your probably rite Lee ,Like the ratchet wrenches .snug it with the ratchet and flip it over for the final tightening with the open end.I broke some teeth off the geers on acouple of them when i first started using them ,I dont guess there made to stand on LOL.

[Ol'fogasaurus]

I seldom use an open end wrench., I prefer to use a box end but there are occasions when one has no choice: when a torque wrench needs to be used when an open wrench is the only option then you have to have a set if crows feet.

Way too many wrenches you can buy (Craftsman, which I have, for example) are way too loose fitting to be of much good and they hit towards the ends of the flats which is one of the reasons you round the heads of the bolts. It seems to be that the double ended open end wrenches are getting hard to find, the same for double ended box end wrenches. I am starting to see some off-set box end wrenches again but they are expensive. Another wrench I have one of is open end at one end and a socket on a pivot at the other end. It is surprising on how often that little jewel can come in handy.

Dog bone wrenches were old when I was a kid and the old timers told me to stay away from them for that reason alone... they're gimmick things. Maybe the only reason I would get one would be for an off-road tool bag to keep the number of tools down. I am not sure about the new design of box end and sockets with the spline looking insides. Unless they are good fitting they won't work well on anything any better than the older tools. They still try to push gimmicks on us don't they but then the fastener designers are having a field day too.

Lee

[fusername]

6 point box wrench is a must, esp in the smaller sizes when you are always rounding stuff out, but then you still need a 12 point for those hard to reach places.

as for hardware, grade 3 doesnt exist. don't buy it, it is NEVER worth the cost saving.

[ProctorSilex]

Chris, what do you mean by your belief in anti-seize? I was interested in that subject years ago because so many fasteners on my cars were seized or hard to turn (late model cars at that!). I read that lubricants can greatly increase the amount of torque applied to a fastener with less effort. In effect, a lubricated fastener should be tighter than a dry fastener. Torque specifications are typically based on dry conditions, making it hard to adjust for lubricated. I could not find good info on how anti-seize affected torque and whether it negatively affected unintended loosening, therefore, I only use anti-seize on spark plugs. Everything else is as dry and clean as I can get it with a locking mechanism such as a lock washer or thread locker and I just pray that the fasteners don't seize up.

[Ol'fogasaurus]

I think it is ARP that is now advertising a torqueing lube that allows you to get to the proper torque reading on the first set of pulls (doesn't eliminate step torqueing such as on torqueing heads on). There are also a lot of new self-help chemicals on the market which run from freeing up rusted fasteners, breaking loose long sitting engines w/o damage to cleaning rusted diapers. What a time in history we are living in!

Lee

[fusername]

remember that "torque" is an inderect reading of what the bolt is doing. clamping power (measured in pounds or similar) is the goal of tightneing most any bolt. shoulder bolts are the special case that I will ignore right now. when you measure torque you are using some super rough estimates of how that translates to clamping power. HOWEVER those stupid equations have error ranges of 20-90% error, so they are bad at best, and usually experiemental values are used instead of what the equation says. the rough equation tree is this:

ideal equation
Torque (ft*lbs)*thread pitch (Teeth per inch)*correction factor (some number that is always the same and probably made up) = clamping force (lbs)
Torque (ft*lbs)*thread pitch (Teeth per inch) = clamping force (lbs)

but of course we have tons of friction so you have to use a new equation
(torque-friction)*pitch*correction factor - Friction = clamping force

if you add lubricant, the friction goes DOWN so clamping force goes UP. same if you use finer/coarser threads, or a clean bolt, or a misaligned hole, you get to add in or remove friction in very hard to measure ways. Measuring clamping force by bolt stretch is much more direct. As you konw, you tighten the bolt unitll there is no slop left. Then you measure how long it is (not always simple!) and then tighten it . if you measure how long it is now, you know how much it has streched (everything stretches when you tightne it, it only depends what scale you measure on, ie feet for rubber bands, inchs for limit straps, .002 inches for bolts) and can use the equation

bolt stretch (inches) * bolt strength (psi)* bolt size (square inches)-friction = clamping force (lbs)

notice friction is still there, but it is only in the one stretching direction, and the distance moved is so tiny it is a much smaller value , and a much more repeatable value than in the torque equation where you have friction on the bolt in the hole, friction on the nut against the clamping surface, friction on the nut threads to the bolt threads etc.

I have no idea why I just wrote this post.

[Ol'fogasaurus]

I think what you are trying to say is that all things being equal... they aren't... which is true. There are too many variables which, unless you get the fasteners from a known reputable source that are designed for what you are using them for and get the fastening specs with the fastener(s) the (general) posted specs for a fastener are not what they (may) seem to be... or vice-versa. Howz that?

Lee

[ProctorSilex]

I have no idea why I just wrote this post.

To demonstrate how complex is the mysterious world of fasteners! Thanks

[rubbachicken]

what is the reason for metric bolts being 3 or 4 X's the cost of SAE bolts
it can't be because no one uses them, most cars now are metric.
i'm from the UK originally, there, metric and SAE fasteners were the same price, although i think it's a little more difficult now to find SAE fasteners.