Best bolt grade for Triumphs

[ichthos]

Hello,
Earlier I had asked about using stainless steel on some parts of my car. I received a lot of useful information. I One of the reoccuring suggestions was using grade 8 hardware on any areas that were subject to stress, like in the engine/drive train. I had a few questions about this, however. What grade was originally installed from the factory? What grade of bolts do vendors normally supply? If I use a grade 8 bolt, and it breaks, will it be more difficult to remove?

Thanks, Kevin

 

[DougF]

The factory used primarily grade 5(120,000 psi) on the cars. Grade 8(150,000 + psi) was used in high stress areas. This is also what is used on large trucks etc. It is overkill on body application.
Grade 8 is often coated in gold or blue to differentiate it from the other grades. If you get a fastener that has an oily coating on it, it is generally an import.
There were a lot of problems with poor quality fasteners coming from overseas in the 80's and 90's. I haven't seen where this is as much of a problem today. The biggest problem I've found with foreign is bunged up threads ie. needing a wrench to run the nut up the capscrew.
To identify the two grades, look at the head of the capscrew and count the lines bordering the edge. Add two the that number and that is the grade. Some fasteners will have three(grade 5), grade eight will have 6 or more. Some companies try to impress the consumer by decorating with markings. SAE does not recognize anything larger than a grade 8. Grade 2 has no marking and should not be used on your car. You will not find the slash markings on the original capsrews from the factory. Many people like to reuse the original fasteners for restoration, which isn't bad in non-torquing applications. But where torque settings are required, use new. Fastener threads stretch when torqued and each subsequent torque loses strength. The amount varies with quality.
Our cars use SAE or fine thread. Though a pain to work with on occasion, they make for a stronger connection than USS or coarse thread.
It depends on where and how the fastener broke regarding ease of removal after breakage. If there is a burr that is cutting into the mating surface, it can be harder. Chances are though, you will not break one.
Vendors will generally specify whether you are buying gr.5 or gr. 8. Generic fasteners with no id are often gr. 2.

 

[ichthos]

Thanks for the information. Does this system also apply to stainless steel? I looked at some of the stainless steel fasteners I used on non stress areas. There are no hash marks. They all have various letters and numbers, such as ABP...
Kevin

 

[trfourtune]

to my knowledge, this does not apply to stainless. it is best to find out from the manufacturer what the strength is. grade 5 is NOT the strongest common bolt (or cap screw-these can look the same,but are not).
you can get allen head "cap screws" to astm a574-04 specification which is 180,000 psi (there are a few manufacturers like sps that make to this standard but are stronger still.you will have to go to a fastener supplier.much less money than ARP for stuff like pan bolts etc.you should be looking for "forged and rolled threads"
rob

 

[trfourtune]

"Grade 8 is often coated in gold or blue to differentiate it from the other grades. If you get a fastener that has an oily coating on it, it is generally an import. "-doug

this is not necessarily true.grade 5 & 8 bolts will typically be black. you want to look for the astm code number for the qualification for the grade on the box . if they come out of a bin without proof of grade, don't buy them.
rob

 

[PeterK]

The raised letters on top of a bolt, I am told, refers to the bolt manufacturer company name.

I also recently ran across a hardened (~=grade8) metric bolt and found that a non-hardened metric bolt of the same size had a smaller hex head. I though this was interesting but don't really know if all are like this.

 

[Camping57]

OK guys, here is the skinny on fasteners from a guy who has been doing fastener engineering for the last 25+ years.

First off: Stainless Steel: The vast majority of the stainless steel parts that are available for consumer purchase are made from an alloy that is similar to 18-8. This is a work hardening grade of stainless. It generally ends up having a tensile strength of about 105,000 psi (grade 5 is 125ksi). It is truly corrosion resistant. This is the stuff that is used on most low load marine applications. That being said, I would not choose to use it on my TR. It is expensive for the strength that you get and that strength is only about 75% of grade 5. Inaddition, it suffers badly from galling when being tightened.
Someone earlier mentioned ARP for stainless. They make very high quality stuff but you pay an extremly high price for what you get (except on internal engine bolts and that is a whole different subject for another day). Also, there are a lot of high strength aerospace stainless alloys (A286, Custom 455, Inconel, etc) but they are made for very specific applications and I wouldn't want to start messing with them in the surplus market.

For good old graded bolts: Doug had it right about most of the bolts being grade 5 with higher load ones being grade 8. His info on the hash marks is also right on (add 2 to the number of lines to get the grade). There are other head markings that are required by law on certain parts and they usually indicate the manufacturer or the material spec (it may be two or three letters, a symbol or combination of the above). When I am replacing bolts on my car I tend to change them out with grade 5 bolts if they are general purpose parts (holding the horn on, mounting the water pump or the differential cover), but if they are important structural bolts (shock mounts, suspension parts) I change to grade 8. Critical ones I keep the same (drive shaft, main bearing) and replace with like parts.

As far as making any kind of generalization about finishes or plating and fasteners, it is really a tough area. Most of the original bolts were phosphate coated (a sort of black finish) which ws very popular with the factories at that time. You are going to find that most aftermarket bolts are zinc plated. It tends (but not a rule by any means) to be that the grade 8 bolts have a yellow chromate over the zinc and the grade 5 bolts and a clear chromate over the silver zinc. I have not seen any metric fasteners on a TR so lets not worry about them today because that is a whole 'nother set of problems.
As far as using higher strength parts (180,000 psi and up). These are the socket head cap screw parts the were emntioned above. There are a couple problems with those parts. The first is that the head area that bears on surface was designed for use in hardened steel tool and die work and if you use them on soft steel at loads up their full rating you will embed the heads into the surface. The second problem is a really scarey one. As bolts become stronger (and harder) they become suseptable to something called hydrogen assisted cracking. This can be caused by rust on the parts or from galvanic corrosion. Anyhow, the net result is "Sudden, Unexpected, Catastrophic Failure"! Don't use Socket head screws in exterior applications; it isn't worth the risk.
Quality: This is an interesting subject. Ten years ago there were serious problems with the quality of bolts you could buy in many locations. This situation has improved quite a bit. There are a number of places that I will not buy parts at: Any Big Box store ( I've seen their purchasing policies up close; shudder), all the big auto parts chains (Pep Boys, Advance Auto...their bolts are junk). So where would I buy parts? I would go to a farm supply store (farmers livelyhoods depend on good hardware and the quality is usually pretty decent and the prices are right). A step up from that is to go on line to mcMaster Carr, they have good quality and you can buy small quantities, but the prices are a little steep. The other place to look is your local industrial fastener distributor (Fastenal, etc). They make their living selling thousands of parts at a time, but in a lot of cases the guys working the counter sales are car guys and they will be interested in helping you out if you explain what you are doing. Give them time to work on your request for 12 1/4 -28 X 1 3/8 hex bolts, they have to take care of their industrial customers first.

Too Long a posting!
One last word of advice. Buy a tube of Locktite and use it on everything! Lockwashers don't work!

Dick

 

[aeronca65t]

Two common markings on better quality bolt heads (inches):

 

[Camping57]

Thanks Aero. One (OK two) pictures are worth my thousand words. I have never understood the logic behind the add two to the number of dashes code for grade, but I guess it is just there to make the subject more obtuse.

Dick

 

[Alan_Myers]

Hi,

As noted, McMasters Carr online is a good source of hardware.

Also check near your local airport for a parts vendor, who will often have aircraft maintenance hardware. Aviation quality fasteners (AN) are good to use for some highly stressed applications (drive shaft nuts & bolts, for example, where all-metal/self-locking nuts, grade 8 or better, and bolt shank length are all very important).

Another online source is www.boltdepot.com They have some good, general reference info there, too. An advantage they have over McMaster-Carr is that Bolt Depot offers small quantities at reasonable prices. Many places don't. (What the heck am I gonna do with 100 Grade 8 SAE 5/16 x 2" bolts?)

Something not yet discussed is correct fitting of nuts & bolts in higher stress automotive applications. The idea is to use proper shank (body) or unthreaded area length, so that no threads end up located within the holes. The reason is that during normal running vibrations will cause threads within the holes to act like a milling machine, eventually enlarging the hole and loosening the fastener. If you look at many original fasteners on TRs, you will find that Triumph paid a good deal of attention to this in most applications, especially throughout the drivetrain and suspension. One place they didn't is the lower/front generator mount at the front engine plate, and that's very commonly badly worn oversize.

Another fitting procedure that's important is to see that there are adequate threads so that 5-7 full turns are within any nut. Too few makes for a weak joint.

Airframe or AN bolts are sold by the length of the shank and usually available in 1/8" or 1/16" increments, allowing far more accurate fitting than typical Grade 8 or Grade 5, where shank length is pretty uniform but in large increments (say 1/2" or so).

One or two washers can be used to adjust shank length slightly. If necessary, extra thread length can be trimmed off. I often use a Dremel tool with a reinforced cutting wheel for this. It works well. Try not to overheat a bolt when cutting the length, though. That might remove its hardening. In most cases, it's not a good idea to use a die to cut more threads to a shanked bolt... For one thing, Grade 8 is pretty hard for this and will quickly dull dies. For another, cutting more threads can weaken the bolt.

There are also low-profile nuts and bolts, and reduced size heads, for tight applications.

In terms of locking - I agree that using Locktite is a good practice. There are several types available. Medium strength works well for many applications. High strength often needs to be heated to release, so take that into consideration. Some locations simply make it difficult or impossible to heat the fastener with a torch even momentarily to loosen high-strength Locktite. In other locations, it's ideal.

Split ring locking washers can be used, but should be replaced after one or two uses. Split rings do not work well in combination with flat washers. All the other locking methods listed below work well in combination with flat washers.

Speaking of which, in restoration projects, I like to add extra flat washers in a lot of locations, to help spread the tightening load out a bit on the old parts, just in case there is some fatigue.

For locking, Nylock nuts work well, but should only be used once. Most widely available Nylock nuts are at best Grade 5. Grade 8 is available, but harder to find and a whole lot more expensive.

All-metal self-locking nuts are better and can be reused a few times. These are often referred to as "aircraft nuts".

Castellated nuts with cotter pins and stainless steel safety wire are about the most secure arrangements, overall. But, Grade 8 can be a bugger to drill for safety wire!

A side note regarding stainless steel fasteners, some screws I bought from a local hardware store recently are really bad. They are phillips head and strip super easily with a power driver, snap off easily and I notice the shards are sticking like crazy to the magnetic screwdriver tip (stainless is usually largely non-magnetic, or so I thot!). Still, the are simply wood screws being used to hold a trim/seal around a garage door, so will do the job. Just watch out for the quality from many hardware stores. If it's "only" 2X or 3X the price of regular steel stcrews, I'd suspect the quality of any S/S screws might be substandard.

/ubbthreads/images/graemlins/cheers.gif

 

[trfourtune]

one more,
cat/catterpillar bolts are supposed to be really good.they have their own made (because no-one else made them good enough for them). watch out for cheap copies though. you have to go to an authorized cat dealer.
rob
ps-i worked for a major dealer in vancouver when i was in technical college.

 

[ichthos]

Thanks again for all the information everyone. I especially appreciated the detailed explanations. I'm glad I asked this question early on before I replaced more of my hardware. Sometimes I get frustrated with having taken almost a year to get this car up an running, but I have gained a wealth of information in the process. As soon as the weather lets up I get to take her out for the first test drive (can't afford a top yet)!
Kevin

 

[AngliaGT]

I just picked up a set of grade 8 bolts to replace the
head bolts on my Cortina.
Went to the local Caterpiller dealer (they moved about 15 miles South of here).Had them in stock,& the price was fair ($1.16 each).
They also have excellent replacement batteries (twice as many plates as most other car batteries - same price).

- Doug

 

[Alan_Myers]

[ QUOTE ]
Sometimes I get frustrated with having taken almost a year to get this car up an running...

[/ QUOTE ]

Just a year?!

Heck, the license plate on my TR4 expired in 1986! /ubbthreads/images/graemlins/crazy.gif

Must admit, it spent most of the intervening years in storage. I got it shipped here from Colorado in 1999 and have been working on it a little at a time since, with the most serious efforts being made the past couple years. /ubbthreads/images/graemlins/hammer.gif

Maybe I should try to get Chip Foose and the Overhaulin' gang to do one of their 7-day turn-arounds on it!

/ubbthreads/images/graemlins/cheers.gif

 

[Leavitt]

Something to watch is that fasteners are a complete system. A lot of stores carry grade 5 and 8 bolts, but only grade 2 nuts. Nuts also have indicating dots on them showing the grade. In structural applications, this hold true for the washers as well.

 

[trfourtune]

/ubbthreads/images/graemlins/iagree.gif
also use HARDENED flat washers with quality hardware. if you go to the trouble of puting in gr.5 or gr.8 bolts & nuts you need to use compatible flat washers under them. NOT cheap washers.you cannot get an accurate torque(i use a torque wrench on everything). the heads will just bite into the soft washer.even if you don't use a torque wrench this is important.
rob

 

[Leavitt]

I agree with trfourtune entirely since torque is obtained by actually stretching the bolt. If any element yields, the correct torque cannot be obtained or maintained. For very large fasteners such as turbine bolts (6" plus diameter) they measure the torque by using dial indicators to determine the actual bolt stretch.

 

[ichthos]

Yeah only a year (I'm not actually finished yet), but it took 17 years for me to get my Bugeye rebuilt. I am finally finishing the paint this summer for the Bugeye. What a learning curve that was. Maybe I better say 18 years on the Bugeye. The Bugeye is for my wife - she is not happy at my progress. My current dilema is that she has no idea that the Triumph will be moving shortly. I don't think she will take it well watching me driving the TR6 with her car dismantled. I at least I learned my lesson - I am going to have fun this car and get it running correctly before doing any cosmetics.
Kevin

 

[DougF]

Wow! Eighteen years, that's about seven inches of car per year

 

[Camping57]

Good points on the nuts and washers. One thing about nuts is that it is safe to match a nut of one grade lower (say grade 5) with a botl of one grade higher (say grade 8). Don't ask me why...I don't know why they did that. By the way; that only works with inch parts (it has to do with the thickness of the nuts in the standards), on metrics it will create all sorts of problems.
Fortune is absolutely right about using good quality washers. One of the bigest problems that I see is embedment of parts into the bearing surface. Make sure to put a washer under the rotating part (nut or bolt, it doesn't matter). Hardened washers are cheap if you buy them in bulk (make a run down to that industrial distributor in town and buy a couple hundred each in 1/4, 5/16 and 3/8 sizes and you'll be pretty much set. The odds and ends can come from the farm supply store...farmers use a lot of hard washers on their equipment.
Cat does make good quality bolts. Buy them direct from a Cat dealer though..there is an outfit that is making fakes somewhere in Asia and selling them through flea markets.

Important note on critical engine bolts (rods, mains and head bolts). Read the factory manual about how to install the parts and then follow that exactly as to the amount and type of lubrication and the procedure to use (sequence and torque values). If you use aftermarket bolts follow their instructions to the letter. Don't think that because it says to use some oil on the bolts you will make things better if you use anti-sieze..it will just cause you to increase the clamp load on the bolts and maybe crush the gasket of yield the bolts. There have been a lot of hours of testing and work that go into creating those instructions and it isn't likely that you can do better at home. For really critical parts assembled by guys with money and time the way to find out how tight the bolts are is to measure the stretch. To do this you use a milling machine to cut a center mark on each end and then a ball end mic to measure the before and after length. The change in length has previously been plotted out on a load / deflection chart using a tensile testing machine. It's a lot of work and not something that is neeeded on anything but full out pro race or jet engines (pulling to the side of the road isn't much of an option at 35,000 feet).

Dick