The minimum thread engagement length is crucial for achieving optimum joint strength with a thread forming fastener. It depends on the strength of the nut material and the diameter and thread pitch of the screw or bolt. A common guideline is around 1 to 1.5 times the bolt diameter for wheels. The minimum thread engagement length is multiplied by a ratio of the shear areas and ultimate tensile strengths of the respective materials.
The minimum thread engagement for steel and cast iron or brass threads is approximately 1.0 to 1.5 times the base diameter of the screw or bolt. For cast iron or brass threads, the minimum thread engagement distance is 1.5 to 2.0 times the base diameter of the screw or bolt. The tool’s efficiency enhances both design and construction processes.
The first thread takes a third of the load, the first three threads take three-quarters of the load, and the first six threads take nearly the whole load. The percentage of total load carried by engaged full threads is roughly: 1st = 34%, 2nd = 57%, 3rd = 73%, 4th = 84%, 5th = 93%, 6th = 100%.
The minimum recommended thread engagement for a component with a tapped hole is approximately 1 times the nominal diameter in steel and 2 times the nominal diameter in aluminum. In many cases, (tapped hole in softer materials, special alloys, etc.), these values are not sufficient and the required thread engagement length is determined by multiplying the minimum thread engagement available by the ratio of minimum full threads available to full threads required.
📹 How Many Threads Does Nut Need To Be Strong?
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How much thread engagement is required?
1. How many threads do I need? At least three threads. Look at a nut. For best thread engagement, use 1.5 times the screw diameter. For a 1/4-inch screw, you need 0.375 of thread depth. For a 1/4-20 screw, you have (.375 x 20) = 7.5 threads.
How many threads can you put in your face?
How many threads are used in a PDO lift? Our team takes great care to customize each thread lift to meet the patient’s needs. Your provider will discuss your concerns, assess your skin laxity, and determine how many PDO threads you need to achieve your desired outcome during your initial evaluation for thread lifting. On average, patients need 2–4 threads on each side of the face for a mid-face thread lift. You may need more threads for the lower face and/or neck. How long does a thread lift last? A thread lift can last for 1–3 years, so it’s a great long-lasting alternative to cosmetic injectables. Get a PDO thread lift in San Francisco, CA. If you’re starting to notice drooping jowls or a saggy neck but don’t want surgery, a thread lift might be a good option. Call Bay Area Cosmetic Dermatology to schedule your private consultation for a personalized San Francisco thread lift today.
Is it better to have more or less threads?
Which is better: Cores or threads? The answer depends on the application. For multithreaded apps, more threads usually perform better. However, for non-multithreaded apps, more cores may be better. It’s good to have a balance of cores and threads. A CPU with a few powerful cores and a few lightweight threads will perform better than a CPU with many weak cores and many heavy threads. If you need help choosing the right CPU for your website or application, please contact us. A member of our Enterprise Hosting team will be happy to speak with you. What else should I think about when choosing a CPU? When choosing a CPU, consider the number of cores, clock speed, cache size, and supported instruction set. The number of cores affects multitasking performance, while the clock speed affects single-threaded performance. The cache size is important for storing frequently accessed data, and the supported instruction set is important for compatibility with certain applications.
What is the minimum nut engagement?
How does thread engagement affect bolt/joint strength? More thread engagement makes a joint stronger. Tensile strength is the force needed to pull something until it breaks. If a bolt is longer than needed, it’s wasted. If there’s not enough bolt length engaged in a nut member, the bolt has a higher probability of stripping out before it reaches its full tensile strength. You need at least one-and-a-half times the bolt diameter engaged in the nut member to achieve optimum joint strength with a thread-forming fastener. The nut material affects this. Steel is about 1-1.5, while softer materials need more thread engagement to achieve optimum joint strength.
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How many threads should be engaged for a nut?
ASME B1.1 says the last thread of an externally threaded fastener is about three threads from the end. A stud or bolt is joined with the nut when it extends three or more threads beyond the end. ASME B31.1 (Power Piping) says all bolts must be fully engaged so that the nut or threaded attachment is visible. ASME B31.3 (Process Piping) says bolts should go all the way through their nuts. If the nut is not fully engaged, it is not considered secure. This standard requires you to check that there is no more than one open nut thread at the end of each nut. The references show that thread protrusion and engagement criteria differ by system application. Inspecting your system for thread protrusion and engagement can be challenging. These systems are often hard to access. You may only be able to see them from a nearby platform. You can’t tell if a flange is properly engaged unless you can see the studs coming through all the nuts. Stud bolt protrusion lets you see if the bolts are properly engaged without looking inside each nut. Experienced pipe fitters see the value of this method and use it.
What is the optimal number of threads?
Running a background process in multiple threads is faster than running it in a single thread. You have to find the right number of threads for each process. One thread for every 100 MHz of CPU is a good rule of thumb. If you have four 450 MHz processors, start with 18 threads: (450 4) / 100 = 18. This is a rough guide because each process is different. Your hardware also affects the optimal number of threads. Use these guidelines to find the best number of threads for each background process.
Run the background process with the number of threads from the rule of thumb. Monitor the usage of your application server, database server, and network traffic during this process.
Is 1000 threads too much?
There are limits, but no hard limits. How many can you use? It depends. If your threads are all doing network calls, you can probably have 100-1000 before it becomes a problem.
Is it bad to have too many threads?
2.3 Too many threads slow down performance. Having too many threads can have two negative effects. When too many threads are used, each thread does not get enough work to be productive. Second, too many threads compete for limited hardware resources, which is costly.
It’s important to know the difference between hardware and software threads. Software threads are created by programs. Hardware threads are physical resources. A chip may have one or more hardware threads per core. Limiting the number of runnable threads to the number of hardware threads is a good idea. If cache contention is an issue, we might also want to limit it to the number of outer-level caches. Don’t hard-code our software to a particular number of threads because target platforms have different numbers of hardware threads. Let our software adjust to the hardware.
How many threads per inch do I need?
US thread size is measured in threads per inch (TPI). Screws are classified as coarse or fine based on TPI. TPI is only used on US screws because metric screws have a different thread pitch and are not interchangeable.
Table below shows screw sizes and relevant UNC and UNF versions. Some are common, others are not (like #5-44). Note: In addition to UNC and UNF, there is a less common UNEF thread that is not listed here because it is not widely used.
What happens if you don’t have enough thread engagement?
If a bolt is longer than needed, it wastes material. If there’s not enough bolt length in a nut member, the bolt has a higher chance of stripping out before it can reach its full strength. What is the right thread engagement for a strong connection with a tapped hole?
Design rules say the screw must break before the threads strip.
Can you have too much thread engagement?
Longer engagement times can be bad. If threads bind during assembly, the screw or bolt can’t be properly stressed. This makes the joint weak and may cause it to fail early.
📹 Thread Anatomy- (In less than 5 min!)
A 3D animated video showing the anatomy of threads. Machining threads is difficult enough so its time to start with the basics.
Thread stripping is always expected on the bolt before the nut. As suggested it is because the shear plane is at a larger diameter. This means there is more area for the shear force to act over. The formula for thread stripping is roughly: Thread profile width (half pitch) * Diameter at shear plane of thread (this is bigger for nut than for bolt) * Pi * Number of threads of engagement.
Another Mechanical Engineer here! From the Strength of Materials class in the first year we were taught that the first three threads (in tension) take 98+% of the load. Since you are testing in compression the results are different. BTW ASMET and BSMET, retired after 40+ years in Forensic Failure Analysis …
Hi, Great article as always. You should (as you mentioned) test with a “pull” configuration. by testing pull strength, you would be able to check at which point adding threads is pointless because threads are strong enough to break the bolt itself.Here, you really tested the material strength and the differences you saw, were probably caused by different alloys from which bolts and nuts are made. Cant wait for pull test wideo.
The cupping deformation is interesting, since when it deforms like I think that the interior diameter should get wider at the bottom and the nut might “let go” of the lower thread. The bolts you made with only a few threads should be testing exactly that, since it’s the same number of threads but without the nut easily deforming, but the results of that test were definitely strange. I’m sure at some point a manufacturer somewhere did all sorts of tests like this to characterize the standardized threads.
Here’s my guess before perusal the article: 7 (based on existing tests I’ve heard about). It seems that 4 threads was surprisingly strong already. However, it seems you measured compression when real world bolt usage will see stretching forces only. Logically compression forces make the bolt thicker so it should make the connection stronger. Of course, building a test setup that can those huge stretch bolts is much harder.
One of your best articles ever. This is a serious technical issue that you would think has been settled since threaded fasteners we’re invented but reading the comments I keep seeing “rule of thumb”. You’re just sciencing the shit out of this! Somebody had to do it and I’m glad it was you. I hope other YouTubers follow in your footsteps on this topic. What I did not expect was the sudden failures of the multi thread nuts. I expected the single thread nut to do that, not to bend. Finding out you were wrong is the best part of doing science!
Really interesting results. I would have liked to see a graph of force as compared to number of threads and more numbers of thread tested. I would have expected a continuous linear progression with increase in the number of threads, since each thread takes some amount of force to shear, and I would expect that to stack.
This is a topic I’ve actually wondered about in the past deciding if my jeep wheel studs were long enough for my wheel nuts to get maximum engagement. What I found in research was that the nut should have as much thread engagement as the bolt shaft is wide, minimum. In both your nuts and bolts here, the surface was machined into, decreasing the case hardening of the nut or bolt. The only way I can think of the avoid that is to only screw an uncut nut onto an unmachined bolt as many threads as you want to test. Good article, thanks.
I’m an engineer and I’ve actually studied this. You are testing the nuts with the bolts in compression. Normally nuts are used to put bolts in tension, and in that application the distribution of load in the threads will change, usually the first 3 or so threads are taking most of the load. There is a real old book by D. G. Sopwith called “The Distribution of Load in Screw Threads” that goes into this quite a bit. This is counting on a full size nut so the nut itself doesn’t deform the way your thin nuts are deforming.
Mechanical Engineer here. If you are really interested look up the Handbook of Bolted Joints by Bickford. When designing joints you have to do much more than look at the shearing of the threads. The industry usually dictates how joints are designed. Steel Construction, Piping, Aerospace, etc all have different standards.
I find this incredibly intriguing to watch even if I’m not entirely sure that the results are actually useful for from the perspective of understanding the strength of a fastener (I could be convinced either way). All the bolt “rating tests” I’ve seen have been under tension, and in every scenario, the bolt itself snaps and the threads do not fail. Seeing the threads themselves fail seems to be a scenario an engineer would not be accounting for, since that is not the designed mode of failure. Super fun articles nonetheless, I’d love to see more!
I’d be interested to see what happens with interrupted threads with the same size nut. Like how is it any different with two 45˚ opposed sections of thread removed from the bolt shaft vs three equally spaced 30˚ sections vs a single 90˚ section removed, and how much weaker is the bolt with two 90˚ opposed sections of thread removed vs three equally spaced 60˚ sections and finally 180˚ threaded and 180˚ smooth. I have a gut feeling that evenly spaced interruptions to the thread will be stronger than a single large one of the same size but I don’t know why.
Hello HPC. Greetings and hoping all your windows are properly sealed. Nearly winter, and Finland does not do winter halfway. Meant to be a cold, snowy one this time. So, the rule of thumb in mech engineering is the threads engaged should be at least 1.5 x the bolt diameter. Cylinder head bolts show this works. On aluminum engines you have to use low torque to avoid warping around cylinder studs, while coping with huge heat and pressure variations. High load stress situations need a minimum of 1.5 x bolt diameter of bolt protruding beyond the nut, the theory being it’s easier for the bolt to tolerate the load by spreading the load away from the nut. Given enough space. No space, increase bolt diameter. We used this simple solution for decades on heavy railroad applications. Few failures, even at -50 c or lower with vibration present. Looseness or shock loads, at lows temps all bets are off, it’s going to break pretty quick. Keepeace. ( traditional Finnish toast)
This was very interesting I’ve been an A&P mechanic for 47 years and our NAS manual on average requires two threads showing at a minimum after torquing a structural bolt. I’ve never seen an experiment like this, actually seeing when the nut failed. In most applications you’re looking at shear and tensile strength of the bolt and your tech data dictates the nut. I believe that the nut usually catches four threads and two showing after torque requirements. That would be six threads over all and I’ve never seen a structural bolt fail under normal operating conditions.
It would be cool to have the original 7 thread nut result as well for a standard test group. Even smaller nuts and bolts testing their rating and what the effects of damage (or half nuts) has on its rating. Like. Some people can’t get a bolt to fit or it has a couple of stripped threads. Under what circumstances will it go? What is your bolts SAE rating?
Great article! But why not have a tension load in the bolt instead of compression? That would answer question how man threads you need to reach same strength as the bolt. Generally you are comparing shear vs tension. In some cases you want the bolt to fail before the nut. You adjust the nut width accordingly. 👍
The number of threads takes into account the shear and surface pressure conditions. The threaded connection is not meant to be one-time, to prove something, it is necessary to check at what load can still be unscrewed. What class was the bolt in, and what was the nut? What was the size and thread pitch?
Thread strength is ultimately dictated by shear force as long as the base material is strong enough for deformation to be negligible. You get less incremental strength from excess extra threads since bolt stretch puts most of the load on the leading threads. There is no point in having more threads what the bolt will yield at.
What about different types of threads? Instead of a typical 60*, what about square thread? Or that wedge one what’s perpendicular on one side and more angled on the other? Or something like NATO/GOST respirator threads that are rounded over? Bolt diameter and thread pitch being equal, what holds the best and how exactly does each fail? As for why thin nut held so good in this test, i suppose it is because as they cupped, they grabbed the bolt tighter, where a full nut on reduced bolt simply sheared the threads.
I am thinking that the bolt may have had it’s heat treatment compromised during the lathe work. I didn’t see any cutting oil or anything used. Also I think that the bolts structural interiority was compromised with the loss of the other threads. That is my theory as to why the modified nuts held up better than the modified bolts.
The answer, according to basically every bolt manufacturer on the planet is 7. 7 threads, regardless of fastener diameter or thread profile or thread pitch will essentially guarantee a failure would be the entire fastener and not the threads. This isn’t a mystery they did all these exact tests thousands of times in the 1940s
It makes sense why it was weaker in the bolt than in the nut; within the nut, the threads are attached to a larger surface, it’s anchored in a way, with a rough triangular shape to the anchor. For the metal to shear and snap and break the threads, it has to heat up, which expands it, right? The amount of mass surrounding the nut thread prevents there expansion. On the bolt, it has nothing to restrict the expansion of the metal.
It was always my understanding as a mechanical engineer, that you need at least three full turns on the thread to get the full tensile strength to the metal’s yield point. Traditionally it was not a good idea to design fasterners to be torqued past the yield point. This is why in classic American cars, you can reuse the head bolts and other fasteners when rebuilding or repairing an engine. During subsequent years, when the “geniuses” took over automotive design and regulation, we deliberately designed the head bolts to be torqued PAST the yield point, meaning that they have to be replaced and cannot be safely reused when doing any work that requires removal of the head. When I first found this out my reaction was “What the F?”
So the general rule in design is with steel the used thread needs to equal to the diameter of the bolt for maximum strength and that more is a waste. With weaker alloys that has to be adjusted. As for you bolts with the threads cut off; by cutting the threads you have destroyed the support they get from the roll forming process and you introduce stress risers radically reducing their strength. So nothing surprising there.
I believe that because the nut was cupping the top thread or threads were being pushed tighter to the bolt making it harder for the bolt to pass. I think if the die you’re using was just big enough for the bolt to pass and the pressure was only being applied very close to the inside of the nut your results would mirror each other much closer.
probably more to do with the manufacturing method, alot of bolts have cold formed threads that are rolled in, where as the nut is probably tapped/turned or someother machining op. the cold formed stuff probably doesn’t have as good of a chemical bond as the nut which is one homogeneous material. just guessing tho
I think you took too much off the bolt when you removed threads. if there was more left it mightve held up better. Although it looks like there’s still quite a bit left when you think about how threads aren’t perfect fits. There has to be a gap so they can spin and not bind. So you could leave a little bit of the threads and still see some results.
This test has limited value. Repeated, it can give a good idea of the sheer strength of the threads. However, bolts/nuts are almost never loaded in compression, but in tension, where the tensile strength of the bolt/nut is a factor. This might be one factor you would use in computing a maximum safe tension load for a given nut/bolt combination, taking the lower of this yield strength and the bolt’s tension yield strength, the stretch of the bolt, then multiplying by a fraction to give a safety margin and converting that tension into a torque load value. And, of course, many bolts will be used in a sheering load, which will be more directly related to the diameter of the bolt than to the tension load on the bolt/nut. I’ve deliberately ignored the material used, but clearly that will affect the calculations and measurements above.
So 50 tons with four threads. Pretty impressive. You should see if you can get your hand on some Grade 8 or Grade 12 bolts (much stronger than metric junk) and see if it makes a difference. Actually another test that would be interesting is pre-stressing the threads. You’re using what… 1-1/2″ bolts, right? So torque the nut down to 300ft/lbs or so and then run it through the press and see if it requires more or less force to strip the threads out of it. I’d guess it’s less force required.