Finding bolt head size

[mjoekingz28]

I got the bolt thread size, male and female, chart on the list....but how do you tell what size the bolt is without narrowing it down by playing Cliffhanger from Price is Right.

I guess a measuring tape could work, but my measurements arent accurate. I compared my rulers to tapes and it is difficult to tell where exactly they start and they do seem to be off by a 1/16 or so. Like when I was trying to measure my bicycle chain, they say, like, for every ten links should be a foot I believe and a quarter of an inch means the chain is toast.

 

[ilovevocs]

Lots of ways to do this. Simplest is with a thread checker or similar.

 

[brownbagg]

i just look at it

 

[Katodog]

After over 30 years of maintenance and machinery work I'm able to look at most common hardware and know what size wrench I need. For thread count, shank size, etc. the two best things to always have is a caliper and a bolt gauge.

 

[454ragtop]

If you're trying to measure the shank of a bolt without a caliper, just use an open end wrench.

 

[OutsideMachinist]

Measure the bolt head or nut. Measure the diameter of the threads. Use a ''scale'' - a 6'' steel ruler. Don't use a wooden ruler or a tape measure.

 

[laser3kw]

^^^edit^^^ beat me to it! I was ********* slower than454!
use an open end wrench as go - nogo gauge.
example: a 3/8" open end wrench should fit over the threaded portion of a 3/8" bolt. Or use your adjustable wrench in the same fashion. Screw the jaw down till it just slides over the shank of the bolt, then measure that gap with your ruler.

 

[OutsideMachinist]

use an open end wrench as go - nogo gauge.
example: a 3/8" open end wrench should fit over the threaded portion of a 3/8" bolt. Or use your cresten wrench in the same fashion. Screw the jaw down till it just slides over the shank of the bolt, then measure that gap with your ruler.

Just measure the thread diameter. Look up a chart/print one out buy it whatever. Look if its course or fine threads. Failing that, for sae hardware for instance, measure 1'' of the bolt and count the threads. The thread checkers/gaugers are nice too but don't help if you have to remove it still.

 

[SAATR]

Developing an eye for it takes time, but I always found just finding the wrench that fits works best. For the bicycle chain, a machinist's rule would work well.

Sent from my XT1585 using Tapatalk

 

[BD1]

Wrench size is 1 1/2 X bolt diameter. 1 1/2 X 3/8" diameter = 9/16" wrench.

 

[readhead]

Sure about that? 1/4" x 1.5=3/8. Should be 7/16. By the way the nut is the same height as the diameter. That should help to figure out length needed.

 

[BD1]

Sure about that? 1/4" x 1.5=3/8. Should be 7/16. By the way the nut is the same height as the diameter. That should help to figure out length needed.

Yes, 1/4'' bolts can have either a 3/8'' or a 7/16'' head. If you check a bolt chart they state that. I had to check that out, don't use any 1/4'' stuff.
https://www.boltdepot.com/fastener-information/bolts/us-bolt-head-size.aspx

 

[mjoekingz28]

. Look if its course or fine .

It is 'coArse'

 

[mjoekingz28]

Developing an eye for it takes time, but I always found just finding the wrench that fits works best. For the bicycle chain, a machinist's rule would work well.

Sent from my XT1585 using Tapatalk

Yes, indeed! Finding the proper wrench is my go to....but I kind of worry if I miss a size. Like say, I ink my wrench (SAE) goes like this. While it begins with 32nd size, after 11/32 it goes 3/8, 7/16, 1/2, 9/16. It leaves out 13/32, 15/32, 17/32......like that and I just wonder if I could round off a fastener . Also, I feel there could be a time when you need to 'know' what size socket/wrench you need, so you dont have to carry the toolbox with you.

I guess I was worrying about Armageddon more or less, but I think the professionals and some others may have a method that is commonplace......

 

[JamieK]

 

[csp]

I got the bolt thread size, male and female, chart on the list....but how do you tell what size the bolt is without narrowing it down by playing Cliffhanger from Price is Right.

Your thread topic and the sentence above aren't the same thing.

Are you asking about the bolt size or the bolt head size?

 

[ilovevocs]

It is 'coArse'

This really advanced thread. Great contribution.

 

[mjoekingz28]

csp, I meant I know which tool I need for threads: a thread identifier, which shows size and pitch/ for both male and female. So, yes, the sizecatcher JamieK posted appears to be perfect.


ilovevocs,

I am picking up your sarcasm, but think of this.... OutsideMachinist apparently did not make a typo. He may now know from here on the differences between course and coarse, which could possibly cause disambiguation at some point in time.

 

[brownbagg]

if its bolt head, I just look at it and pick up a wrench, nothing more is needed

 

[Tig Master]

if its bolt head, I just look at it and pick up a wrench, nothing more is needed

Yup x 2 ^^^^^^^^^!!!!!!!!!!!! wtf.

T

 

[OutsideMachinist]

csp, I meant I know which tool I need for threads: a thread identifier, which shows size and pitch/ for both male and female. So, yes, the sizecatcher JamieK posted appears to be perfect.


ilovevocs,

I am picking up your sarcasm, but think of this.... OutsideMachinist apparently did not make a typo. He may now know from here on the differences between course and coarse, which could possibly cause disambiguation at some point in time.

Yes it was a mistake. I do know the difference. I also know how to measure a bolt, stud, diameter of whatever object without a gimmicky performax tool. In any case, thanks for the correction.

 

[joecon]

If you know what you are working on you can narrow down the sizes if
it is cars and trucks you can get it down two 4 sizes. Old old cars 3/8,7/16
1/2,9/16.Moderan American cars 10,13,15,18.Japanese cars 10,12,14,17.
If you want to know if it is fractional or metric look at the head if it has
lines it is fractional if it has a number it is metric.

 

[mikegt4]

Spend $3, actually get a couple of them. Keep one in your "Pick n Pull" tool bag.
They even measure bolt length (up to 6")

http://www.harborfreight.com/6-inch-utility-caliper-7914.html