I've worked with a few people who didn't know the difference between a coarse thread and a fine thread, often with disasterous results.
YES. I stop into different farm stores that sell hardware this way, some dont differentiate between stainless in the mix per pound.
Coarse thread car nuts wear greasy jeans steel toe boots and work shirts and buy oil by the case. Fine thread car nuts wear slacks, loafers and Lacoste shirts and buy wax by the case.
I once read Lil' John Buttera said, more or less, having a model train set in the basement was as good a requirement as any to use 'engineer' or 'engineering' in the name of your company. I post this without any desire to cast aspersions on those who are real engineers. In making a speech, opening with a joke warms up the audience, it is said. What I came here to say is that those who wish to be wise about fasteners should add at least a couple of Carroll Smith's books to their libraries, for reference. It is also good to close with a joke. If any of you even get one of those robots with artificial intelligence and it gets a virus, you might think about giving it Robitussin.
Put a different grade and thread pitch in each place you are going to attach the battery box and see which one loosens up first. I seem to always be at battle with engineers... I am a contractor and it always my fault Sent from my XT1585 using The H.A.M.B. mobile app
The general rule of thumb according to the puritans is that you cannot beat your with with a rod any thicker than your thumb. LOL The basics is that a part that will be assembled and disassembled on a regular basis uses course threads and a part that is seldom disassembled uses fine threads. Now this does not take into account loads and thread distortion and etc. But this is the general rule regarding the choice of course v fine threads.
If you want a connection that will never come loose, thread a coarse thead bolt into a fine thread nut..........better n locktite
Agree... but the answer is not that simple. The lower grade bolts have lower yield and tensile strengths, as shown in Mike's table above. Put a force on them, and the lower grade bolts deform earlier and normally snap earlier. However, the energy (not force) that is needed to bust the lower grade bolts is often substantially higher. This is related to the the area under a stress/elongation curve. Lower grade bolts typically have a lot more area in that graph than higher grade bolts. The low grade bolts plastically deform, soaking up a large amount of energy. So yes - if you put a force on a higher grade bolt for a short period of time, often the higher grade bolt will last longer. Put a lower force on the bolts for a longer time, and the lower grade bolts perform better. Dammit... I woz not suphosed to Enjinur any maw Cheers, Harv
If you are getting into issues of fastener longevity, you have the incorrect fastener specification, and/or an improperly engineered component, and/or the incorrect number of fasteners.
I've always heard fine thread has more tensile and shear strength then coarse, coarse are easier to start, harder to strip, nick and gall. As far a grade 5 vs 8, Mack truck used only grade 5 hardware up until Volvo got involved in the engineering of them.
I agree. I pulled the front end off of my 51 woodie all the way back to the firewall and every bolt (except the chassis which I havent gotten to yet ) has been a fine thread. I was really surprised.
...if I thought that I was addressing a house full of like minded individuals then I would have used 'different' terminology but Engineers are a small minority on this board... Feel free to offer the 'right' term...... .
Less so longevity, and more the type of force. If it is something that pushes and can keep pushing (unlimited energy behind it), then the high grade bolts do better. If it is something that can push then run out of ooomph (impact or intermittent force), then the low grade bolts do better - they stretch (plastically deform) to absorb the ooomph energy. Cheers, Harv
When you find an unlimited source of energy, do let us know. Until then, if the force being applied to the assembly exceeds the design specification of the fasteners, then it has been engineered poorly. Attempting to make up for bad design by finessing fastener grade is just plain sad.
When it come to suspension I use a factory bolt. All my suspensions have factory hardware. Sometimes hard but doable. I have even made trips to the boneyard to just locate bolts. As a professional, all damaged or non reusable bolts gets a factory bolt. I was installing a bolt in cage once. The cage came with grade 5. Grabbed bolts from our grade 8 bin. Was told to check the rule book. Rules specified grade 5. As far as thread count, it depend on a few things. Thickness of material is one. I use fine threads when adding threads for fuel or brake lines to a chassis. But you will see the factory use screw threads for stuff like this. Just general stuff, like body panels, I use grade 5 standard thread stuff. But I’m also the crazy person that will reuse every dang bolt I can. My friends look at me crazy as I soak old bolts in rust removers or sandblast em. I pay attention to what the factory used. If they used a fine thread bolt and lock nut, then I try to duplicate that. If it’s corse and a lock washer, then I duplicate that.
Squirrel is right (again) that the aviation industry (including the USAF) use fine threads almost exclusively. The exception seems to be the reciprocating engines.
What Jim said.....sure seams to be a lot of that in early pre war and after the war (surplus) that was fine thread - was just demo-ing a 1960 Chevy and still a lot of fine and not some much coarse stuff.
I was going to post something similar. Now, I didn't stay in a Holliday Inn last night but, I notice when taking apart anything suspension related, it's almost always fine thread.
Ahhhhhhhh... Nothing like sitting around the fireplace after a nice Thanksgiving dinner with friends and having an engaging (2.5 X dia.) discussion on the pros and cons of coarse vs fine thread fasteners and the like. Better 'n football. Of coarse, I hope you all had a fine Thanksgiving.
Fine thread bolts have a larger minor diameter, something around 25 thou on a 3/8s bolt, so there is that. But being the same major diameter, the threads aren't as deep as coarse, of course..
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