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Edwin Dirnbeck
06-24-2019, 11:48 AM
There seems to be an endless parade of new materials that are "stronger " than steel weight.In my world ,I use a lot of 3/8 and 1/2 inch screws. As a direct replacement,is anything stronger than steel? Edwin Dirnbeck

MikeL46
06-24-2019, 12:10 PM
Certainly there are stronger materials than steel. But, mostly they are not cost effective for home shop use.

And it depends on what your idea of strength is. Steel is more flexible than granite. Granite is heavier, harder to machine.
Carbonfiber can be almost anything the designers want it to be. Except cheaper than steel.
Titanium and aluminum alloys are stronger, lighter and machinable. Again, not cheap and difficult to weld.

Use the material that works for your application and be happy with it.

Mike

BCRider
06-24-2019, 12:40 PM
So you have exceeded the strength capabilities of Grade 8 bolts, nuts and studs? I find that a bit hard to believe.

Plus as discussed in other threads recently about threaded fasteners it's not always the fastener itself. The substrate also needs to be strong enough to avoid the threads being pulled out from a threaded part or the head directly pulling through the material being fastened. With this in mind do you really need stronger bolts?

projectnut
06-24-2019, 12:55 PM
There seems to be an endless parade of new materials that are "stronger " than steel weight.In my world ,I use a lot of 3/8 and 1/2 inch screws. As a direct replacement,is anything stronger than steel? Edwin Dirnbeck

As an example McMaster sells titanium bolts. A 3/8-16 x 1 has a tensile strength of 130,000 lbs. They are considerably stronger than the same size grade 2 or grade 5 steel bolts, but not as strong as grade 8 steel bolts.

There is however a considerable difference in cost. Grade 2 bolts sell for $11.06 for a pack of 100, grade 5's sell for $13.53 for a pack of 50, and the grade 8's sell for $8.15 for a pack of 25. The titanium bolts on the other hand are $6.95 each. While the titanium bolts exceed the strength of the grade 2's and 5's they are not cost effective for most applications.

MattiJ
06-24-2019, 01:36 PM
As an example McMaster sells titanium bolts. A 3/8-16 x 1 has a tensile strength of 130,000 lbs. They are considerably stronger than the same size grade 2 or grade 5 steel bolts, but not as strong as grade 8 steel bolts.

There is however a considerable difference in cost. Grade 2 bolts sell for $11.06 for a pack of 100, grade 5's sell for $13.53 for a pack of 50, and the grade 8's sell for $8.15 for a pack of 25. The titanium bolts on the other hand are $6.95 each. While the titanium bolts exceed the strength of the grade 2's and 5's they are not cost effective for most applications.
Aermet 100 and maraging 350 bolts are ”available” if you have enough thick wallet but they are not really replacement for steel as they are something like 100 to 1000x more expensive. But they have 300 to 350 ksi tensile strenght when needed..

J Tiers
06-24-2019, 02:36 PM
Most everything that is "stronger than steel" comes with an asterisk..... there are always special conditions that apply.

Perhaps it is only "stronger than steel" in the sense that the same weight of it has a higher ultimate tensile strength, or the like. If it has higher tensile strength, it may not be possible to use in the same was as steel, or it lacks compressive strength, etc, etc.

As a rule, you cannot make a bolt out of it that is the same size as the steel one, and have it be stronger than the steel one, which is the first sort of idea that comes to mind when something is said to be "stronger than steel".

"Direct replacement" would be mostly limited to the specialty aerospace stuff as per Mattij. And most of those are some form of steel.

old mart
06-24-2019, 02:57 PM
My firm used to machine pins out of ultra high tensile steel, 550000lbs/ square inch, not the average real world stuff, but part of the landing gear of Airbus planes. No titanium alloys could even sniff at it.

Doozer
06-24-2019, 03:01 PM
If you need stronger bolts than top grade Allen head cap screws,
the some engineering might need to be done. Sounds like something
in the design is not right.

--Doozer

darryl
06-24-2019, 03:58 PM
Stronger than steel- there are a lot of materials that are 'stronger than steel' in terms of tensile strength. But for a fastener with threads it has to be a homogeneous material with strength in all directions. That would mean an alloy of some kind and not a composite where the binder is weaker than the fibers. I can just see the carbon fiber bolt with the threads stripped off- but the shank still being stronger than the steel equivalent. And in this case, if you were able to make the carbon fiber bolt without any binder, what would you have- a diamond? I'd like to see how a diamond bolt would work-

Mark Rand
06-24-2019, 05:05 PM
Certainly there are stronger materials than steel. But, mostly they are not cost effective for home shop use.

And it depends on what your idea of strength is. Steel is more flexible than granite. Granite is heavier, harder to machine.
Carbonfiber can be almost anything the designers want it to be. Except cheaper than steel.
Titanium and aluminum alloys are stronger, lighter and machinable. Again, not cheap and difficult to weld.

Use the material that works for your application and be happy with it.

Mike

Just a small niggle:- steel is almost three times the density of granite. I find this useful when using my granite straight edges.

Fasttrack
06-24-2019, 06:25 PM
If you need stronger bolts than top grade Allen head cap screws,
the some engineering might need to be done. Sounds like something
in the design is not right.

--Doozer

I assumed he was asking for educational purposes, not because he actually needed a stronger screw. I think we are all aware of marketing claims that say a particular material is "x times stronger than steel!". Of course, there are always caveats. Perhaps is stronger per pound or stronger in tension but also more brittle or etc.

Kevlar is one such material. Interestingly, Kevlar was introduced in the climbing market because it was so strong and light. However, climbers quickly discovered some detractors: it has very poor fatigue performance and it is difficult to tie a good knot. They still sell technical cords and sling based on aramid fibers but, in many cases, nylon or steel cable is better, even though the initial tensile strength of both of those materials is lower. They have much better fatigue properties and, in the case of steel, better resistance to abrasion.

Edwin Dirnbeck
06-24-2019, 06:59 PM
Certainly there are stronger materials than steel. But, mostly they are not cost effective for home shop use.

And it depends on what your idea of strength is. Steel is more flexible than granite. Granite is heavier, harder to machine.
Carbonfiber can be almost anything the designers want it to be. Except cheaper than steel.
Titanium and aluminum alloys are stronger, lighter and machinable. Again, not cheap and difficult to weld.

Use the material that works for your application and be happy with it.

Mike
My question is about DIRECT REPLACMENT FOR 3/8 AND 1/2 INCH BOLTS. This obviously means involves tensile strength.Granite 20,000 psi isn't even close.Carbonfiber bolts seem to be about 60,000 psi .The best aluminum and titanium is about 2/3 the strength of the best steel. Once again ,I am talking about a size for size direct replacement. As for as using the best material and being happy ,that isn't an option and why I am on this forum. Edwin Dirnbeck

Edwin Dirnbeck
06-24-2019, 07:01 PM
So you have exceeded the strength capabilities of Grade 8 bolts, nuts and studs? I find that a bit hard to believe.

Plus as discussed in other threads recently about threaded fasteners it's not always the fastener itself. The substrate also needs to be strong enough to avoid the threads being pulled out from a threaded part or the head directly pulling through the material being fastened. With this in mind do you really need stronger bolts?
YES I DO.Edwin Dirnbeck

Edwin Dirnbeck
06-24-2019, 07:15 PM
As an example McMaster sells titanium bolts. A 3/8-16 x 1 has a tensile strength of 130,000 lbs. They are considerably stronger than the same size grade 2 or grade 5 steel bolts, but not as strong as grade 8 steel bolts.

There is however a considerable difference in cost. Grade 2 bolts sell for $11.06 for a pack of 100, grade 5's sell for $13.53 for a pack of 50, and the grade 8's sell for $8.15 for a pack of 25. The titanium bolts on the other hand are $6.95 each. While the titanium bolts exceed the strength of the grade 2's and 5's they are not cost effective for most applications.
Yes, this confirms my post.Most people would say titanium is stronger than steel.Simply put,by weight it is but not by volume.Edwin Dirnbeck

Illinoyance
06-24-2019, 07:19 PM
It is impossible to help with your problem without knowing more about the application or the mode of failure of your fasteners.. The practical fasteners for almost all purposes is limited to steel bolts, grades 2 though 8 and socket cap screws. There are super alloys available from which studs and nuts could be made but cost would likely be prohibitive. With high strength materials the yield point becomes closer to the ultimate strength so these high strength fasteners will have less reserve strength than more common fasteners.

epicfail48
06-24-2019, 07:26 PM
Seems to me that a more succinct, and polite, way of asking this question wouldve been "is there any commercially available bolt with a higher tensile strength than a grade 8 steel one". You cant get ticked off at people for responding for a very broad question to the best of their abilities, even if that wasnt the exact answer to your question. The answer to "is there anthing stronger than steel" is "it depends on the application". Rubber is more resilient, diamond is harder, but i wouldnt make a bolt out of either of those things. Carbon fiber has a higher tensile strength, but again, not what you want a bolt to be made out of.

Now that thats out of the way, if you need something with a higher tensile strength than steel for a bolt, youd probably want to look for tungsten. Yeild strength up near 300,000 psi according to McMaster

Edwin Dirnbeck
06-24-2019, 07:27 PM
I maintain and repair dies and molds. These are often built with over stressed screws that break repeatedly . As with most repair work,I don't have the option to change the design. I must work with what I have. Edwin Dirnbeck

Mcgyver
06-24-2019, 07:40 PM
Pick up truck military grade steel. No, wait, that's Aluminum

Arcane
06-24-2019, 07:49 PM
I maintain and repair dies and molds. These are often built with over stressed screws that break repeatedly . As with most repair work,I don't have the option to change the design. I must work with what I have. Edwin Dirnbeck

So what happens if you make the bolts stronger? Would it move the failure point to the die or mold itself and how do you fix that if you don't have the option to change the design? Maybe the bolt is designed to be the failure point so the die or mold isn't.

darryl
06-24-2019, 08:04 PM
Makes me wonder what the failure mode is- perhaps the bolts are being loaded more on one side of the head than the other, and perhaps a copper washer would help with this. Maybe the transition from the shank to the head is too sharp, maybe the bolts you're using are not properly heat treated. I would tend to think that grade 8 bolts shouldn't have these last two problems though. Could be a bad batch you're using?

Edwin Dirnbeck
06-24-2019, 09:11 PM
So what happens if you make the bolts stronger? Would it move the failure point to the die or mold itself and how do you fix that if you don't have the option to change the design? Maybe the bolt is designed to be the failure point so the die or mold isn't.
This is not about a specific die or mold. I have been doing this type of work for many many years.This is quite common. Not just in dies and molds.As for as the designer doing this on purpose,well I have been repairing things for to long to give the designers that much credit. Edwin Dirnbeck

Paul Alciatore
06-24-2019, 10:05 PM
Steel is not one material. There are literally thousands of steel alloys. Tens of thousands, probably hundreds of thousands. And then there are the methods of manufacture and heat treatments. Steel can be from dead soft (common nails) to alloys with well over 150,000 PSI tensile strength with various degrees of hardness.

You have a specific problem: the screws in the dies and molds that you work with are breaking. What grade of screws/bolts are you using? And, just what is the failure mode? Materials (steels) will have different properties, different strengths, when subject to different kinds of stress. Tensile strength, compressive strength, resistance to tortion, repetitive or static stress, WHAT IS THE FAILURE MODE????????? Before you can even begin to select a better screw, you must know what you have and WHY it is failing.




I maintain and repair dies and molds. These are often built with over stressed screws that break repeatedly . As with most repair work,I don't have the option to change the design. I must work with what I have. Edwin Dirnbeck

Paul Alciatore
06-24-2019, 10:07 PM
Yes, think about that too. I would be willing to bet that the screws are a lot cheaper and easier to replace than many of the other parts of these dies and molds. You could easily make your job a lot harder.




So what happens if you make the bolts stronger? Would it move the failure point to the die or mold itself and how do you fix that if you don't have the option to change the design? Maybe the bolt is designed to be the failure point so the die or mold isn't.

J Tiers
06-25-2019, 01:17 AM
I maintain and repair dies and molds. These are often built with over stressed screws that break repeatedly . As with most repair work,I don't have the option to change the design. I must work with what I have. Edwin Dirnbeck

Dies and molds..... These are usually loaded in cycles.... a part is formed or molded, meaning a high stress, and then the pressure is off again and there is no load, and it repeats, thousands of times, perhaps.

What seems to be wanted here is NOT actually something stronger than steel, the issue is fatigue. If the part were really not strong enough, it would break or yield in one of the first few cycles. Of course, if the steel of the fastener were stronger, then the fatigue issue would be less,because the stress as a percentage of the yield stress would be less.

But, the probably superior approach as a practical matter would be regular maintenance, meaning the replacement of the screws after "X" amount of use, anticipating the breakage and simply replacing the screw before it breaks.

Using one of the very strong alloys, if it is even possible to do so effectively, would only be a better choice if there is a known stress on the screw, so that the fatigue performance can be predicted. The difference between the existing material and the "super alloy" as far as probable life could then be estimated and the use of the "super alloy" vs a replacement schedule evaluated.

There is also the point that making custom screws of the "super alloy" may not actually realize the strength, because you would be cutting threads, vs the rolled threads probably existing on the regular commercial screws. That might be case-by-case depending on how the screws are loaded. It might turn out that the "super alloy" did not actually lower the cost, because it is so expensive, if the strength of the alloy is not realized in a cut screw.

It would SEEM that if you start with using 180 K psi screws, and change to screws that really were over 300 K psi, that the fatigue life should be considerably more than doubled. I do not know if that would really happen with cut screws of the "super alloy".

MattiJ
06-25-2019, 03:18 AM
My question is about DIRECT REPLACMENT FOR 3/8 AND 1/2 INCH BOLTS. This obviously means involves tensile strength.Granite 20,000 psi isn't even close.Carbonfiber bolts seem to be about 60,000 psi .The best aluminum and titanium is about 2/3 the strength of the best steel. Once again ,I am talking about a size for size direct replacement. As for as using the best material and being happy ,that isn't an option and why I am on this forum. Edwin Dirnbeck

Direct, "COTS" =commercial off the shelf replacements replacements are hard to come by.

Superalloy bolts are more in the NASA, Boieng & motorsport category.
Poggipolini in italy for example specializes to these but I'm pretty sure your budget is screwed :rolleyes: if you special order 1/2" Aermet 100 fasteners from there.
http://www.poggipolini.it/fasteners-catalog.pdf

old mart
06-25-2019, 07:18 AM
Critical stressed bolts in the aircraft industry usually have a radius between the head and the shank which increases their fatigue resistance. They must be fitted with a thick washer which has a chamfer inside one end to provide clearance for the radius.
12.9 equivalent or better commercial bolts should be ok for most situations if the component design is any good.
Titanium studs were used in the gearboxes of Westland Lynx helicopters, but there were problems with them stretching. They were replaced with steel at the cost of a couple of pounds weight.

wdtom44
06-25-2019, 07:27 AM
Old mart, would these be L-9 series? L-9 is stronger than grade 8 but is costly and needs washers under the head I believe. McMaster carries some I believe, or maybe MSC.

tlfamm
06-25-2019, 07:34 AM
...
But, the probably superior approach as a practical matter would be regular maintenance, meaning the replacement of the screws after "X" amount of use, anticipating the breakage and simply replacing the screw before it breaks.
...


Seems like an eminently sensible suggestion - and what possible objection could there be, other than the 'chore' of maintaining a history of die usage?

cameron
06-25-2019, 07:55 AM
Is it possible that the users of these dies and molds are habitually over-torqueing the fasteners when assembling?

Edwin Dirnbeck
06-25-2019, 09:18 AM
Most everything that is "stronger than steel" comes with an asterisk..... there are always special conditions that apply.

Perhaps it is only "stronger than steel" in the sense that the same weight of it has a higher ultimate tensile strength, or the like. If it has higher tensile strength, it may not be possible to use in the same was as steel, or it lacks compressive strength, etc, etc.

As a rule, you cannot make a bolt out of it that is the same size as the steel one, and have it be stronger than the steel one, which is the first sort of idea that comes to mind when something is said to be "stronger than steel".

"Direct replacement" would be mostly limited to the specialty aerospace stuff as per Mattij. And most of those are some form of steel.

Thanks, I guess that I knew the answer already. I get tired of the hot air blowhards breathlessly proclaiming that a spider web is 100 times stronger than steel. I am still waiting for the first spider bolt or Bucky ball bolt.Meanwhile,I will keep using SPS and UNBRAKO socket head (alan head)cap screws. Edwin Dirnbeck

old mart
06-25-2019, 09:31 AM
I am only familiar with metric fasteners with strength designations of 8.8, 10.9 and 12.9, to name the commonest ones that are stronger than mild steel. The USA and Japan have their own equivalents. There are plenty of charts, this site could be useful:

https://www.fastenerdata.co.uk/fastener-grades#inchb

A.K. Boomer
06-25-2019, 09:39 AM
Makes me wonder what the failure mode is- perhaps the bolts are being loaded more on one side of the head than the other, and perhaps a copper washer would help with this. Maybe the transition from the shank to the head is too sharp, maybe the bolts you're using are not properly heat treated. I would tend to think that grade 8 bolts shouldn't have these last two problems though. Could be a bad batch you're using?

For sure, sometimes repetitive shear stresses can get to them or expansion rates of the die in comparison, some high quality bolts will just keep on breaking unless intentional elasticity is built into the system - like a much longer bolt with a huge spacer placed in-be-tween... or a more forgiving clamping opening (hole in the work piece) with a spring washer...

nickel-city-fab
06-25-2019, 01:59 PM
If you need something direct off the shelf, I've always recommended ARP fasteners. They are quite familiar with your failure modes, albeit in a different application (connecting rod/crank bolts for racing and HD diesels)... https://arp-bolts.com/

They have fastener kits up so some insane strength levels, but not cheap. Scroll down to their "Fastener Tech" section for some interesting stuff...

JRouche
06-25-2019, 02:07 PM
There seems to be an endless parade of new materials that are "stronger " than steel weight.In my world ,I use a lot of 3/8 and 1/2 inch screws. As a direct replacement,is anything stronger than steel? Edwin Dirnbeck

Quick answer, no. Most if not all the options presented here are still steel. JR

Paul Alciatore
06-25-2019, 10:07 PM
J, This may well be a fatigue problem, but I don't know and neither do you. Since he has not done a proper analysis of a single failure or even posted a photo of a single failed screw/bolt, that would be just a guess. It really would be nice to see one of these failed screws/bolts AND of the location where it failed.

But, lets assume for the minute that it may be a fatigue problem. If that is so, would a "stronger" bolt be the answer. If fatigue is the problem, then perhaps a weaker BUT MORE COMPLIANT material may last longer. Glass can be quite strong, but if a fatigue crack starts, it can run across a distance of many feet in a split second. Replacing that sheet of glass with a flexible plastic that is a lot weaker may prevent that failure. IF IT MUST FLEX IN THE APPLICATION, THEN YOU NEED A FLEXIBLE MATERIAL.

I said it above and I will say it again, he really needs to nail down the actual failure mechanism. Only then he can find a better material and that better material may not be technically stronger.

And even if it is a problem that can be solved with a stronger screw/bolt, he has not said what kind of screws/bolts he is using now. Hardware store grade 3? Grade 5? Grade 8? Something better? All he has really said is that they are steel. There are bolts out there that exceed 200,000 PSI tensile strength. They are harder to find and cost a pretty penny, but they exist. Has he tried any of them? We don't know. Frankly, from the tone of his posts, I have to wonder if even he knows what is presently being used.

Another good question would be to ask about the temperatures, both high and low, they are subjected to and the times and cycle times of those temperatures. Perhaps he is starting out with a grade 8 bolt but, after a month of use it becomes a grade 1.




Dies and molds..... These are usually loaded in cycles.... a part is formed or molded, meaning a high stress, and then the pressure is off again and there is no load, and it repeats, thousands of times, perhaps.

What seems to be wanted here is NOT actually something stronger than steel, the issue is fatigue. If the part were really not strong enough, it would break or yield in one of the first few cycles. Of course, if the steel of the fastener were stronger, then the fatigue issue would be less,because the stress as a percentage of the yield stress would be less.

But, the probably superior approach as a practical matter would be regular maintenance, meaning the replacement of the screws after "X" amount of use, anticipating the breakage and simply replacing the screw before it breaks.

Using one of the very strong alloys, if it is even possible to do so effectively, would only be a better choice if there is a known stress on the screw, so that the fatigue performance can be predicted. The difference between the existing material and the "super alloy" as far as probable life could then be estimated and the use of the "super alloy" vs a replacement schedule evaluated.

There is also the point that making custom screws of the "super alloy" may not actually realize the strength, because you would be cutting threads, vs the rolled threads probably existing on the regular commercial screws. That might be case-by-case depending on how the screws are loaded. It might turn out that the "super alloy" did not actually lower the cost, because it is so expensive, if the strength of the alloy is not realized in a cut screw.

It would SEEM that if you start with using 180 K psi screws, and change to screws that really were over 300 K psi, that the fatigue life should be considerably more than doubled. I do not know if that would really happen with cut screws of the "super alloy".

wyop
06-25-2019, 11:24 PM
There seems to be an endless parade of new materials that are "stronger " than steel weight.In my world ,I use a lot of 3/8 and 1/2 inch screws. As a direct replacement,is anything stronger than steel? Edwin Dirnbeck

I believe so:

https://www.extreme-bolt.com/mp35n-bolts.html

NB: The last time I helped someone order some bolts from them, the price was... up there.

J Tiers
06-25-2019, 11:59 PM
J, This may well be a fatigue problem, but I don't know and neither do you. Since he has not done a proper analysis of a single failure or even posted a photo of a single failed screw/bolt, that would be just a guess. It really would be nice to see one of these failed screws/bolts AND of the location where it failed.

But, lets assume for the minute that it may be a fatigue problem. If that is so, would a "stronger" bolt be the answer. If fatigue is the problem, then perhaps a weaker BUT MORE COMPLIANT material may last longer........

The fatigue seems reasonable, because the screws (stated to be Unbrako or SPS Allen head.... "I will keep using SPS and UNBRAKO socket head (alan head)cap screws.") clearly last some time, but then fail. If they were truly overstressed into yield, they should break in a relatively few cycles. The assumption here is that they do last a reasonable time, but they break before the tool is no longer needed, since Mr Dirnbeck is asked to fix them. However, "technically" we do not "know" that.

A "stronger" bolt would very likely reduce the problem, and potentially eliminate it, since the fatigue life appears in general to be longer at a lower stress relative to the yield point. The stress being constant due to the design and the forces/pressures involved, the stronger material should last longer as the stress is less vs the strength.

A general fatigue limit for steel is half the ultimate tensile strength, although that has a limit well below the strength of very high strength steels, and the idea may not apply to those alloys. The limit is a point below which fatigue does not occur. I do not know how the fatigue life is affected by highe strength material in terms of number of cycles at a given stress. I THINK it is improved, but the mechanical guys here can confirm or deny that. we also may not have a reversing stress cycle, but rather a pulsating stress with a mean value.... another factor I am not familiar with.

The more compliant part could be an answer, depending on what you mean by "weaker but more compliant"..... One made of lead would be an obvious issue, and presumably one made of 1018 would also be an issue. Someone suggested a longer screw, which might allow some movement without breaking. But in general, dies and molds are not places one wants movement, they are supposed to be a fixed shape.

The real answer is to redesign the dies, but that best of all worlds solution is not usually practical or allowable, the redesign could be as simple as adding screws. However the shape, size etc of die parts may not allow it, and the potential necessity for heat treating and so forth may kill that. Likewise, molds often have heaters and cooling passages, which can knock out the chance for modifications by blocking any addition of holes for screws.

And I get the impression hat these are wanted back pronto.... the usual situation. Simple replacement of the screws before they break is likely to be the cheapest solution overall, and would take care of the problem.

loose nut
06-28-2019, 03:28 PM
You all forgot the obvious answer....Superman