Thread: Acorn headed bolts

you'll need a vernier and a thread gauge.

you work out the last half of the specification first.... the thread pitch, grab the thread gauge and place one of the "combs" onto the thread the one that fits neatly is the correct one, this is your thread pitch.

Metric is in mm. .25, .5, .75, 1, 1.25, 1.5, 1.75, 2, 2.5 and is the distance from thread tip to thread tip.

imperial is a bit more fun and is in TPI, 18,20,21,22,24,25,26,27,28,l30,32 and is the number of turns of Threads Per Inch. this doesnt tell you if its UNF or UNC yet.

next measure the major diameter (outside of the thread) and that gives you the first half of the measurement and this is why you measure the thread size first if you dont have an indicator on the head to give away metric V imperial. If a metric thread fits best, you have a metric fitting so set your vernier for metric and measure away. if its imperial set it to imperial and away you go. you need two measurements the width and the length.

if it was a .75 thread pitch and 8mm across what you have is an m8x.75 if its 25mm long you have a 25mm m8x.75

Thanks Dave. Started reading and thought ohmygawd, but makes sense after 1 reading. Cheers

Very succinct and well explained....Blknight aus

Cheers

Baggy

I'm guessing you don't have a vernier or thread gauge......

Given the type of head you are chasing you will more than likely have to go to a bolt shop.....just take a sample and that will do the rest.

Would j be right in assuming it should be metric being in a rangie?? If so just a ruler will sort out the thread size, you don't really need to know the pitch as this is generally standard for metric....if it imperial than it look like UNF (fine thread)

Originally Posted by weeds

you don't really need to know the pitch as this is generally standard for metric....

Is standard metric the same as metric coarse, metric fine or metric superfine?

Aaron

Originally Posted by Aaron IIA

Is standard metric the same as metric coarse, metric fine or metric superfine?

Aaron

The bolts look about M8, with all the bolts I purchase for work we never mention the pitch. Course I believe is the standard off the shelf.

Yes there applications that you may need to mention a particular thread size but my bet is on a rangie it will be a standard thread.

Could be wrong.....

You need a thread gauge... it's the only way

55?IMPERIAL 60?METRIC Thread Pitch Gauge Measure Braces Screw TSQUB3355 3360 | eBay

in theory all of my cars are metric.... I have a good range or metric fasteners from these cars.

It'll probably be M8 x 1.25, M7 x 1.0 or M5 x 0.8 ... ( Or if land rover feels like taking taking the **** out of owners/mechanics like Citroen they will change from M5 x .75 to M5 x 0.8 on a vehicle mid production run .... Just for the fun of it I'm guessing ?? ) Even my 1950 model cars are metric. Bloody land rover putting a smattering of A/F crap on a 1990's model range rovers is just to torment me and **** me off right ?? 'Cos none of my tools or fasteners will fit.

seeya,
shane L.

Originally Posted by DoubleChevron

You need a thread gauge... it's the only way ...

Pfah. If you can't gauge an external thread with a simple steel ruler you aren't even trying. Line up a thread peak with your chosen zero, count the number of threads until a peak lines up again with another mm marker, divide the mm by the number of threads counted and you've got it.