Say you had a cylinder with a diameter of exactly 100mm and a circular sleeve with an internal diameter of exactly 100mm, would the cylinder fit inside the sleeve? It's been bugging me (for absolutely no reason other than somehow I started thinking about it), and a bit of my brain thinks that the cylinder must be slightly, even microscopically, smaller than the sleeve to be able to fit inside.
no
google "engineering fits and tolerances"
we used to use a handy pocket book for working out the desired shaft and hole fits, ie sliding, interference, transitional
same for bearing fits etc etc
types of fit
Preferred Fits and Tolerances Charts (ISO)
Yes in theory, but in real life impossible to achieve exactly 100
Both cylinders will deform slightly so yes. But if they are the same dimensions then it will take an amount of force depending on the material properties.
If you had a magic material that couldn't deform at all then no. If it was exactly 100mm (and you had a way of determining that to the nearest atom) then you would still have atoms from both cylinders attempting to occupy the same space (ie, the space at 100mm on both cylinders).
Good to see the response was exactly as expected
"No"
"Yes"
"Yes but no"
🙂
Which is why there's a difference between 'in theory' and 'in practice'.
Slow work day?
even if perfectly engineered round, and the inner shaft exactly one molecule smaller you would then encounter
Molecular adhesion (van der Waals forces)
essentially the inner and outer would be come one piece... but you wouldn't be able to get the inner in to become one piece anyway
In theory? No.
In practice? No.
In theoretical practice and you freeze the inner one first, yes.
we used to use a handy pocket book for working out the desired shaft and hole fits, ie sliding, interference, transitional
Aah Zeus Tables. Still have a copy tucked in my everyday tool bag. Not that I use them everyday mind.
In theoretical practice and you freeze the inner one first, yes.
It would be more common to heat the outer one with an induction heater.
yup the Zeus book
bible of fits, threads, conversion tables... i cant remember what else was in there now
No, that's called an "interference fit." In cases like cylinder bore sleeves in car engines (where you have an aluminium cylinder block and a steel or cast iron inner sleeve), they are designed for an interference fit. By cooling the inner sleeve and heating the cylinder block, you can create enough clearance to fit the sleeve into the block. Then, when the temperatures equalize, the sleeve expands and the block shrinks so the sleeve is locked tightly in place.
No, we need much more info, material types, co-efficients of thermal expansion, what temperature the reference dimensions were measured at. The original question doesn't have enough info to answer, or at least variables are not discussed or eliminated.
even if perfectly engineered round, and the inner shaft exactly one molecule smaller you would then encounter
Molecular adhesion (van der Waals forces)
essentially the inner and outer would be come one piece... but you wouldn't be able to get the inner in to become one piece anyway
Yep, My Slip Gauge set, whilst only grade 1 are a thing of wonder with their molecular adhesion properties
Can be handily summarised as "If you have a big enough hammer".
A hammer would deform the cylinder and prevent the fit from fitting as intended.
Or, no, in short...
I seem to recall being told at an RAF Squadron disbanding piss-up that the wing on the Panavia Tornado was held on by almost this exact principle. The wing held into the fuselage by a big fat cylinder of metal through holes in the wing/fuselage. The cylinder was super-cooled with liquid nitrogen to allow it to shrink just enough to slip between the two and then when it warmed back up everything was held tight.
A hammer would deform the cylinder and prevent the fit from fitting as intended.
Or, no, in short...
Tell that to every headset I installed before I was rich enough to afford a headset press...
Or is this a proxy thread like the allotment/Israel one and someone's boasting about their girth?
OP you might be interested in looking at videos about the Metmo cube which is manufactured tolerances of 0.1 mm using Wire Electro Discharge Machining.
https://www.metmo.co.uk/products/mk3-steel-metmo-cube
https://www.youtube.com/shorts/jUm3ucl0qCs
This thing has very close tolerances but the pins are definitely narrower than the slots in the cube.
Which is why there's a difference between 'in theory' and 'in practice'.
The 2 parts will not be perfected circular, and wont be perfectly cylindrical / at 90 degrees egres. So the slight ovality or general not perfectly round-ness mean they will bind on each other, even if you think they are both 100mm.
On top if they were absolutely perfect, some sof the surfaces will cold weld together when in contact.
You can force the 2 together as both are elastic and will deform.
Mechanical engineer here, as pointed out an interference fit, although not enough of an interference fit to be reliable.
even if perfectly engineered round, and the inner shaft exactly one molecule smaller you would then encounter
Molecular adhesion (van der Waals forces)
essentially the inner and outer would be come one piece... but you wouldn't be able to get the inner in to become one piece anyway
Yep, My Slip Gauge set, whilst only grade 1 are a thing of wonder with their molecular adhesion properties
Ringing