Is a finer pitch stronger than a courser thread as far as holding more torque and not easily stripping??? Base metal would be aluminum.
-
Required reading for all forum users!!!
Welcome!
Register to access the full functionality of the GSResources forum. Until you register and activate your account you will not have full forum access, nor will you be able to post or reply to messages.A note to new registrants...
All new forum registrations must be activated via email before you have full access to the forum.A Special Note about Email accounts!
DO NOT SIGN UP USING hotmail, outlook, gmx, sbcglobal, att, bellsouth or email.com. They delete our forum signup emails.A note to old forum members...
I receive numerous requests from people who can no longer log in because their accounts were deleted. As mentioned in the forum FAQ, user accounts are deleted if you haven't logged in for the past 6 months. If you can't log in, then create a new forum account. If you don't get an error message, then check your email account for an activation message. If you get a message stating that the email address is already in use, then your account still exists so follow the instructions in the forum FAQ for resetting your password.Have you forgotten your password or have a new email address? Then read the forum FAQ for details on how to reset it.
Any email requests for "can't log in anymore" problems or "lost my password" problems will be deleted. Read the forum FAQ and follow the instructions there - that's what we have one for...
-
Returning Visitors
If you are a returning visitor who never received your confirmation email, then odds are your email provider is blockinig emails from our server. The only thing that can be done to get around this is you will have to try creating another forum account using an email address from another domain.
If you are a returning visitor to the forum and can't log in using your old forum name and password but used to be able to then chances are your account is deleted. Purges of the databases are done regularly. You will have to create a new forum account and you should be all set.
-
In order to help others find info on a particular bike, be sure to put the year, make or model of bike that you are asking a question about, in the Topic Title. This will allow people to pass by posts they have no interest in.
Thread pitch strength??
- Thread starter chuck hahn
- Start date
G
Guest
Guest
Yes, a finer thread pitch means more metal to metal contact area. A finer pitch is often used when it is not practical to up a size in diameter.
Take things to an extreme and imagine a nut and bolt with a very coarse thread with only one turn available. This would easily strip out.
I've noticed that in many automotive applications there are many times when a fine pitch is used instead of a 'standard' pitch. e.g. wheel spindles and nuts.
Take things to an extreme and imagine a nut and bolt with a very coarse thread with only one turn available. This would easily strip out.
I've noticed that in many automotive applications there are many times when a fine pitch is used instead of a 'standard' pitch. e.g. wheel spindles and nuts.
I think they are less likely to back out from vibration or whatever, because the smaller thread pitch puts it at more of a perpendicular angle to the bolt. I don't think fine threads are any stronger for ultimate strength to failure. Picture the total amount of aluminum that would have to be pulled out for a coarse thread to fail, it's a lot more metal than pulling a fine thread out. Also the coarse thread will take a lot more abuse than a fine thread, as far as sand or rust on the threads, loosening and tightening many times, cross threading, over torque, under torque and rattling around, any of these things and fine threads will get damaged easier.
We need a real live mechanical engineer who designs this crap to post the truth.
We need a real live mechanical engineer who designs this crap to post the truth.
Dogma
Forum Sage
BSME checking in...
TL;DR: Fine threads are for stronger screws, not stronger female threads. You can't make aluminum stronger by putting a stronger screw in it.
A screw is a wedge wrapped around a cylinder, so finer threads are a sharper wedge. That means less torque to deliver the same tension, so if you apply the same torque, it strips easier. With regards to stripping threads, the tension you can hold for the same length of engagement is not significantly different. This is easier to see in inch fastener designations: 1" of thread engagement of 1/4-20 threads divides that 1" into 20 threads. 1" of thread engagement for 1/4-28 divides the 1" into 28 threads. That's the same ?0.25 x 1" cylinder of material carrying the load in the female thread (The male thread root diameter is larger and stronger in the fine thread). Now, that's a little bit of an oversimplification, since the stress distributions are a little different and I think the fine thread does carry a few % more tension before stripping. I'm not sure because it's close enough to never think about. As Tom pointed out, fine threads are easier to mess up. Engineers usually design everything with coarse threads, except the #10-32 inch size (easier tap breakage on the #10-24 for some reason).
Fine thread fasteners do have a larger root diameter (larger cross-section), so the screw itself is stronger and less likely to break, or strip the male threads. So in some circumstances where higher tension is required in a stronger fastener, but a larger nominal size is not desired, fine threads are used. Of course, the female threads need to be in a sufficiently strong material.
So, fine threads in aluminum are not a good idea. That would just be easier to strip out by over-torquing. Go up a nominal size, or go deeper, or add more fasteners, or use a torque wrench, or add a Helicoil. Adding thread inserts like a Helicoil not only repairs threads in aluminum, but reinforces them. The insert's threads are more durable, and where they engage the aluminum they are larger than what used to be there. So a M6 hole becomes almost M8 where it engages the aluminum. Helicoil probably has design reference materials that would give values for the increase in pull-out strength.
TL;DR: Fine threads are for stronger screws, not stronger female threads. You can't make aluminum stronger by putting a stronger screw in it.
A screw is a wedge wrapped around a cylinder, so finer threads are a sharper wedge. That means less torque to deliver the same tension, so if you apply the same torque, it strips easier. With regards to stripping threads, the tension you can hold for the same length of engagement is not significantly different. This is easier to see in inch fastener designations: 1" of thread engagement of 1/4-20 threads divides that 1" into 20 threads. 1" of thread engagement for 1/4-28 divides the 1" into 28 threads. That's the same ?0.25 x 1" cylinder of material carrying the load in the female thread (The male thread root diameter is larger and stronger in the fine thread). Now, that's a little bit of an oversimplification, since the stress distributions are a little different and I think the fine thread does carry a few % more tension before stripping. I'm not sure because it's close enough to never think about. As Tom pointed out, fine threads are easier to mess up. Engineers usually design everything with coarse threads, except the #10-32 inch size (easier tap breakage on the #10-24 for some reason).
Fine thread fasteners do have a larger root diameter (larger cross-section), so the screw itself is stronger and less likely to break, or strip the male threads. So in some circumstances where higher tension is required in a stronger fastener, but a larger nominal size is not desired, fine threads are used. Of course, the female threads need to be in a sufficiently strong material.
So, fine threads in aluminum are not a good idea. That would just be easier to strip out by over-torquing. Go up a nominal size, or go deeper, or add more fasteners, or use a torque wrench, or add a Helicoil. Adding thread inserts like a Helicoil not only repairs threads in aluminum, but reinforces them. The insert's threads are more durable, and where they engage the aluminum they are larger than what used to be there. So a M6 hole becomes almost M8 where it engages the aluminum. Helicoil probably has design reference materials that would give values for the increase in pull-out strength.
Last edited:
