Hob Positoning

[Nickfromwales]

On 14/09/2026 at 15:54, Alan Ambrose said:

He he he, no reason not to have some big Mitutoyo verniers on-site so you can ‘measure’ mm to 2 dp / 10 microns 🤣.

And a second, more accurate one to check that one has remained “within acceptable tolerance”. 🫣🤣  

[-rick-]

45 minutes ago, Nickfromwales said:

And a second, more accurate one to check that one has remained “within acceptable tolerance”. 🫣🤣  

 

It's when the laser interferometer comes out you really have to worry. Microns? Pah! we want nanometers here!

 

Remember seeing someone proudly show off 4 or 5ft Mitutoyo calipers he got from somewhere 'Not sure I know what I'll use them for but I couldn't pass up them for the price - they are worth 5 figures!'

[SteamyTea]

18 hours ago, -rick- said:

nanometers

They are for pansies.

Apply the below and you will still be 'out' a bit.

 

ΔxΔp≥ℏ/2ΔxΔp≥ℏ/2

 

where Δx is the uncertainty in position, Δp is the uncertainty in momentum, and ℏ is the reduced Planck's constant.

[saveasteading]

Loved the crossed h which was new to me,   so looked it up.

I thought this was all a terribly clever joke but see it's a real thing . The explanation is beyond me but I assume can be summarised as  the thickness  of a shortened length of scaffold board.

[SteamyTea]

36 minutes ago, saveasteading said:

explanation is beyond me

Really easy.

Imagine you are taking a picture of spinning turbine. At a slow shutter speed, you get blurring of the blades. From the arc a blurred blade covers, and it's length, you can work out the angular speed, radians per second.

Increase the shutter speed and you get less of a blurred arc, but a better idea of where the blade actually is. But if you keep reducing the shutter speed, you get to a point where you get a clear picture of the blade, but no idea how fast it is rotating.

You also get 1/∞ which is a nonsense fraction, to a Plank Length is substituted, 1.8 x 10^-35m, this is considered the smallest length that can still show information, and where quantum affects start to dominate.

But to make matters worse, because the turbine is spinning, and the camera isn't, relativistic effects start to happen, changing the length of the turbine blade's arc, this is known as Lorentz–FitzGerald contraction.

At this point, Newtonian Physics and traditional modern mathematics breaks down and witchcraft takes over.

 

As for where to place a hob, the answer is quite simple, but can't be bothered to explain it.

[saveasteading]

I started to understand it then got lost.

I must be as hbar as 2 reduced plancks.

[Spinny]

Have you guys finished taking the piss yet ?

 

(and good luck getting your turbine tip speed close enough to the speed of light for relativistic length contraction to be in any way relevant to it)