Bolt Thread question

TJ1978

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So I venture to ACE to get crank shaft pulley bolts. 3/8-24 1”.... Ace doesn’t really state whether or not it 24—16– or whatever but I’m sure more experienced people “just know”.

So, whatever it says 3/8 corse thread . I thought they were fine thread on the crank pulley to harmonic balancer... Low and behold the bolts I got don’t work that are corse thread.

I knew what I bought probably wouldn’t work but... who doesn’t need more random bolt sizes in their bolt coffee can?

what other ways is a bolt labeled for “fine” thread?

so I had to order from amazon crank pulley bolt kit for spectre.

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ktmoutfront

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That chart lays it out as clean as possible. 7/16"x20 is fine thread. The 20 is threads per inch.

I believe it is that size. Of course, I do not remember. Old age sucks.
 

TJ1978

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Bent77

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Sometimes fine threads are called SAE. Or they used to be...
 

ktmoutfront

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SAE is used for both thread pitches on inch bolts now. Like internal combustion engines being called motors.
 

Magikal

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Generally, the bolt size is a quarter inch smaller then the size wrench it takes.
 

Blue85

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Hardware stores (interesting name for them, isn't it?) have limited interest is stocking automotive fasteners, but sometimes you get lucky with the little bins. You can always pull out your tape measure and count threads.
 

Bent77

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1/4-20 uses 7/16
 

JoshHefnerX

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I've got a place by me that is a fantastic place for hardware. If they don't have it, you don't need it. Marks Nut and Bolt. You ever get over in this area, it's worth a stop.
 

diesel4me

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Sometimes fine threads are called SAE. Or they used to be...
"NF" for "National Fine"was also commonly used..

Also they do sell thread pitch gauges,we always kept on on the bolt rack at the parts stores ,hanging on a chain...and a thread chart,that told what pitch a particular sized bolt could be had in..
Metrics suck,they had four different pitch threads and usually the store only had 1.00 or 1.50 pitch,and you needed 1.25 !..

They also make "heavy hex" bolts and nuts with hex sizes larger than the usual,like a 1/2" bolt normally has a 3/4" hex,but some with 13/16" are available in "heavy hex"...things like leaf spring u-bolt nuts often are "oversized hex" too..
 

diesel4me

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Hard to say...supposedly fine threads are stronger,having more surface area than course,and can apply more crush force--but in my experience they strip out easier and stripped threads dont hold things together too good most of the time..
 

swettysblazer

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I was always told that the maximum strength of the bolt is when it is engaged at least 1x it's diameter. No difference in thread.
 

JoshHefnerX

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Yeah, and not to throw a wrench into the works but is the class 1a/2a/3a stronger, and and are the bolts and nuts interchangeable between them? :D
 

AJs72K5

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Do we need to call Muddin Manny?
 

Magikal

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I'm usually happy if i even have a bolt that fits. I live in the sticks and it's an hour drive to a hardware store, local ACE that never has what you need anyways. My experience is that fine usually holds better but the number of threads engaged makes the real difference. I am fond of barrel nuts for my leaf springs as i can really torque on them and not strip em out.
 
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