Thread: Followed Me Home II

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Good lord! We had a similar discussion a long time back and had folks adamant that it was unsafe to pick up an engine with a carburetor plate, 1/4" bolts and a cast aluminum intake. We need to be safe and practical, but we ain't building the space shuttle here.

100% Jack. What's the tensile strength of a 1/4" steel bolt, and what is the dynamic load on a hood restraint? I'd venture a guess that if we were designing for tensile strength I could be putting 4-40's in this service!! A 1/4-20 fills the f'n hole in the latch bracket, and that's the only reason for the choice of fastener size. Good Lord is right!!

So, I'm confused? Why does the bolt threads need to stick past the nut any at all?

They don't . . .

Originally Posted by 36 sedan

So, I'm confused? Why does the bolt threads need to stick past the nut any at all?

According to Jerry's rule of thumb all of the nuts sold are too short by about 50% or more. A 1/4-20 nut is not sufficient to use with a 1/4" bolt, and the same for all the other bolt sizes.

I thought it was the grading (ie., 5, 8 and so on) that determined the strength? I never gave it a thought that the nuts where engineered incorrectly, is this a common problem?
Perhaps someone has confused thread depth requirements (as in blocks and different materials) and applied it to the nuts?

Roger-I believe that you have read something into my posts that either you either misread or I wrote poorly----when I wrote rule of thumb that that there should be 1 1/2 times bolt diameter for depth of hole it applies to where you have the plate threaded-you said 3/16 plate, 1/4 in bolt------the thumb rule for a thread hole for your 1/4 bolt would be 3/8 inch--in mild steel plate that would really be overkill, however with your 3/16 plate it is questionable. and in the top of your frame which you posted as 1/8 (edited later) you are way below specs---not that your work on this is unacceptable(as it is a hood latch) but you are way off base on what should be used as a standard in some more critical areas. I couldn't find my Machinists Handbook but did find reference online and posted it--the info there does support the fact that with the bolt/nut ratings out there that the thickness of the SAE nuts are suffient for the diameter of the bolts they fit.


And I believe that no matter what you choose to do on your car with stuff you fab from scratch, it is the responsibility of others to post when the methods you or others choose ar inadequate for the public safety of others on our highways. I know that we have views of many things that don't alighn with the planets of internet universe, but I humbly believe that as a member on here with a long road that I've been down, I should pass on any info I have that can help others-------------- With that said I am going to check the ignore button on your threads, as it seems that somewhere we have come to an quagmire that you can't/won't accept any thing I say----------

Jerry, no disrespect intended, but every rule has its exception.

Not all fastening applications require the maximum strength of the bolt to achieve their purpose. Often the frames of our cars are tapped and used to secure things that require very little strength, often the bolt size is increased not for the strength of the bolt, but rather for the increased size allowing greater thread contact through the thin material which serves the purpose of the original fastening intent.

Case in point would be the hood latches, these latches require far less tensile strength than the 1/4” bolt delivers in the 3/16” plate or for that mater even 1/8” plate, especially with two bolts used on each. If there is a concern for their strength, a backing nut would serve the purpose.

I agree with you and commend you on safety and speaking up to protect others. However, sometimes it is better to nudge rather than trump to get a point across. You undoubtedly have a wealth of knowledge and ability and I enjoy learning from you. So please continue to bring your insights. All I’m saying is there is more than one way to skin the catfish.

Jerry, you may not read this, but as 36sedan says your rule of thumb may be right for tapped holes in plate or blind holes, but you're overlooking that the first step in that process is that the bolt is sized or selected for the tensile strength needed to withstand breaking. Step one, what size bolt is required; step two, calculate the depth of thread that's needed to restrain the bolt such that the bolt shears at or above the first exposed thread. That second calc deals with tensile stress area of the threads, the bolt major diameter, and the thread pitch.
In this application I picked 1/4" stainless bolts to fit the hole in the latch bracket, but more for appearance. There are two per latch, and that is very definitely over kill on strength for the application. Rather than consider the application and number of bolts per latch you simply jumped in criticizing the approach, preaching that what I had done is wrong. I agree that a couple of SS acorn nuts on the bottom of the back latch bolts is a nice finishing touch to cover the exposed threads, but I do not believe that nuts are needed on either place, for this application.
When you choose to pass on your wisdom it's probably best to focus on the specific task being discussed, or if a "general rule of thumb" is what you choose then explain the basis for that rule, and that it may or may not apply in this case. Just my humble opinion, and you can take it or leave it.

I think you really need 1/2 hardware on it... that 1/4 stuff is weak... LMFAO Bwahahahahaha.

I'm now sorry that I brought this subject up. After working in the aircraft industry I guess I tend to err on the side of caution. At the time inspectors demanded that between two to four threads were visible past the end of a nut, but we were dealing with vibration issues which hopefully you won't be. Everything, generally, was either a locking type nut or castle nut. The castle nuts were for safety wiring purposes and most often found around the engines and they were also used on any exterior lighting.
This could be where Jerry is coming from since he spent most of his time in aircraft and running diggers and floppers.

Originally Posted by NTFDAY

I'm now sorry that I brought this subject up. After working in the aircraft industry I guess I tend to err on the side of caution. At the time inspectors demanded that between two to four threads were visible past the end of a nut, but we were dealing with vibration issues which hopefully you won't be. Everything, generally, was either a locking type nut or castle nut. The castle nuts were for safety wiring purposes and most often found around the engines and they were also used on any exterior lighting.
This could be where Jerry is coming from since he spent most of his time in aircraft and running diggers and floppers.

Ken, there was absolutely nothing wrong with your comment. You saw something that raised a question in your mind, and you brought it to light as you should.

I spent four years in the Navy, trained in P & A schools as an Aviation Machinist's Mate for radial engines. I worked the aircraft line doing pre & post flight inspections, then worked the Powerplant Shop performing maintenance, and later doing QA/QC on the work done in our shop so I'm kind of aware of the aviation process, too. There are rules, and then there is application. One must consider the application in deciding how to apply the rules, and more to the point which rules actually apply, and which rules are not relevant to the situation which is what 36sedan said so well in his last post above. Jerry's general rule for tapped holes is a good, conservative rule for bolted joints pushing the tensile strength of the bolt, but it simply doesn't apply, IMO.

And now, unless someone wants to extend the discussion further, I'm done.

Once I thought I was wrong, but I was mistaken!!!!!

Hey, on a side note, you can probabaly use the rear tabs to bolt the front part of the frame to a rotisirie when you paint it, and use the 1/4" ss bolts.

The mounts do look nice and some acorn nuts would help keep the bolt threads from cutting your finger during a mit wash job. Been there.

Looking good Roger !