Bolt size

[stranger12]

Hi All,

Just a slight clarification. When buying bolts or nuts, most places refer to the size by M so M8 , M10.

I understand the M is the diameter of the bolt or nut and not the socket size , right ? so for instance M8 could have a socket or spanner size of 14mm or bigger ?

I am asking as I am trying to get those tools which can be used to put stripped threads right , forgot its name but will try to find it .

Thanks
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R6 Red

[Islander]

M8 indicates that the thread diameter is 8mm. The spanner size is measured across the flats of the bolt head or nut and will obviously be larger than the thread size.

Thread repair kits used to repair/replace stripped threads are called helicoil kits although if the thread isn't too badly damaged a tap of the appropriate size might clean it up.

[stranger12]

thanks,

this is what i meant

https://www.ebay.co.uk/itm/NEW-40PC-PRO-TOOL-CUTTING-SCREW-THREAD-TAP-AND-DIE-SET-/140571926513?pt=UK_Hand_Tools_Equipment&hash=item20babd5ff1

it is apparently also called tap and die
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[lihp]

Chances are if you have damaged the thread, then a tap and die set isn't likely to help, unless you have enough material to drill out to the next bolt size, you are however likely to then need drill bits that you won't get in normal sets for the correct bolt size.

You would likely be better with something like this https://www.ebay.co.uk/itm/TOOLSHACK-M-8-00-x-1-25-Coarse-pitch-V-Coil-thread-repair-kit-/111250055284?pt=LH_DefaultDomain_3&hash=item19e7052074

I use the V-Coil ones primarily because I had to try one when HeliCoil didn't make them in a size I needed (M7) but was very impressed with the quality of them and they worked perfect.

Just search ebay for VCoil bolt size x thread pitch, so say VCoil m8 x 1.00

They come with the correct size drill bit, and the correct size tap, but again you need to have enough material to drill it out.
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[stranger12]

well when getting the bolt out as the bolt was under pressure and I was stupied enough to ignore it , and continue putting pressure on it to undo, the bolt cam out but saw 1/2 threads out of the 20 or so on the bolt so means damaged internal thread.

What is the difference between tap and die and the one you posted ?
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R6 Red

[lihp]

the tap and dies are designed to cut new threads into freshly drilled holes, what I posted is a thread repair kit.

If your bolt is m8 x 1.00 you buy the m8 x 1.00 kit, you drill the hole out with the drill bit in the kit, use the tap that comes with the kit and then use the included tool to screw the insert into the new hole.

The inside of that insert is the same thread size as the original, meaning you don't need to use larger bolts. They are also generally stronger than the original thread in aluminium too.

By 1/2 do you mean 1 or 2 threads, or half the threads? If just 1 or 2 threads, I would test the bolt and see if you can get the correct torque, if half the threads have stripped then it's unlikely you will get the correct torque.

As I said, the regular tap and die set you posted will only cut new threads, meaning that without an insert, you can't get that bolt back to the same size as you have no material to cut a thread into, meaning that you are going to have to go the next bolt size up so m10 from m8 or you need to use an insert to repair it to the same size.
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[DrDonnyBrago]

[stranger12]

Thanks for the explanation

I meant 1 to 2 and i managed to tighten it up to 100 nm which is recommanded by the haynes , why is it not possible to get the right torque? Would the stripped thread give you a wrong torque ?
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R6 Red

[lihp]

If you can achieve the correct torque then I would just leave it, with all due respect, trying something like this with your inexperience is worthwhile if the thread is destroyed, but if you can get it to 100NM which is the correct spec then I wouldn't mess with it, as you can easily make it worse.

If you lose too many threads you can get to the point where the bolt will just rip threads out rather than holding the tension, however the fact you can get to the correct torque suggests that there is adequate strength in the remaining threads, and I would recommend that you leave it be rather than drilling and tapping something that still works fine.
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[DrDonnyBrago]

100 Nm is a lot of torque, so presumably a rather large bolt which wouldn't make fixing the threads any easier.

[stranger12]

so in a way does it mean when I apply 100nm on a nut, I am applying around 1 ton of pressure on it ?

or 50 nm is 500kg or 200 is 2 ton ?

if so that is a lot of force.

I know it is newton per meter or kg per cm , so what is the rule of the cm or meter in there?


I also know you can have a 24mm nut which should be torqued to 100nm and the same size on my bmw is suggested to be torqued to 250 , isn't the size what determines the torque applied to it ?
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R6 Red

[dydey90]

I think 100nm is around 100kg of force?

This table may help with bolt sizes as per the OP.
https://www.boltdepot.com/fastener-information/bolts/metric-bolt-head-size.aspx
From my experience, you should be looking at the DIN column. Although the ISO one should be the standard, I have never encountered an M12 bolt with less than a 19mm head.
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[stranger12]

I used this

https://www.convertunits.com/from/N-m/to/kg-cm

it says 100 nm is 1 ton or 1000kg but that is per cm so not sure hence why i asked
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R6 Red

[Vincent]

Torque(t) = Force(f) x Radius(r)

Force being the amount of force being applied to the end of a spanner, for example, and radius being the length of the spanner.

https://i77.photobucket.com/albums/j71/Drewskovitch/Jap%2070s%20bike%20toys/torque_zpsbbef49c0.png
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[stranger12]

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