We've just had some steel shafts made up for a machine at work, they were supposed to be 50mm, a quick try of the 50mm bearing indicated something wasn't right.
Without digital verniers the manual type indicated something like 50.25mm (definitely not 2inch =50.8mm)
I tried some emery tape and made sure there weren't any burrs with a file.
Several questions. What is the accepted tolerance for bearing fitting ?
When you buy shaft, 50mm what do you get, 50 mm that a bearing should fit straight onto, or 50 mm that requires machining to a bearing tolerance ?
you generally need to machine the shaft- it's rarely spot on or perfectly round.
what does the inside of the bearing measure?
ps- a manual vernier is just as accurate, if not more, than a digital one
Definitely 50mm bearings.^^
We also had some 60 mm shafts made up, when they were delivered I checked the bearing fit and same issue, I reckon they were also about .25 mm oversize.
The work know all said they'll be right, after two half days on the emery he finally gave up.(that's 2 half days I spent chuckling to myself under my breath)
Sounds like your shafts have been turned leaving 0.25mm material on for cylindrical grinding......If you normally fit 50mm bearings by hand, shafts would be 50.00 - 49.985mm. PS . be careful using emery on a lathe, .....A mate lost a few digits doing the same thing .
unsure exactly what youre doing, but when fitting bearings to shafts on industrial electric motors, we heat the bearings up with a magnetic induction heater, then slip them onto shaft hot, cools down to a tight fit, again unsure if your doing anything similar, good luck
Select to expand quoteMilsy said..
unsure exactly what youre doing, but when fitting bearings to shafts on industrial electric motors, we heat the bearings up with a magnetic induction heater, then slip them onto shaft hot, cools down to a tight fit, again unsure if your doing anything similar, good luck
bearings are locking collar type and from my previous experience should slide on without to much troubleSelect to expand quoteMacRab said..
Sounds like your shafts have been turned leaving 0.25mm material on for cylindrical grinding......If you normally fit 50mm bearings by hand, shafts would be 50.00 - 49.985mm. PS . be careful using emery on a lathe, .....A mate lost a few digits doing the same thing .
exactly what I was thinking.
Select to expand quoteMark _australia said..
I would think solved by specifying a shaft to fit "this" and give them a bearing
yes Mark, now he's got the bearings
he shouldn't need the bearings
the order should specify the purpose and the tolerance
this isn't frikken china
Select to expand quotetheDoctor said..
he shouldn't need the bearings
the order should specify the purpose and the tolerance
this isn't frikken china
Correct ......The reason we have ISO limit / fits tolerances is so part "A" made in Australia fits part "B" from Sweden.
It's not rocket science, I can understand a tolerance in bearing manufacture, be it magnetic induction, press fit or the type of bearing that we are using, but 50mm onto 50+ doesn't work and would have thought our machinist would have known better.
you have to remember that you're dealing with a fitter. they're generally incapable of tying their own shoelaces unless they have a drawing to refer to
Select to expand quotestamp said..
you have to remember that you're dealing with a fitter. they're generally incapable of tying their own shoelaces unless they have a drawing to refer to
I think we are talking about Fitting and MACHINING.
Besides which even a half trained Fitter can out plumb a plumber, out carpent a carpenter, fit up a power point better than a sparky and never pays a plasterer who leaves splat all over the floor.
If the Fitter and Machinist is also a Marine Engineer, he is the most intelligent man you will ever meet and has power of veto over the so called Master of the ship.
If he also has a Master's Certificate, he is known as God and you pray to him to keep you safe at sea.
So there, stick that in your pipe and smoke it.
Select to expand quotestamp said..
you have to remember that you're dealing with a fitter. they're generally incapable of tying their own shoelaces unless they have a drawing to refer to
never give a drawing to a fitter
1st they would know what to do with it
2nd they'd lose it
3rd if they didn't lose and actually looked at it..... they'd just draw dicks all over it
Select to expand quotetheDoctor said..stamp said..
you have to remember that you're dealing with a fitter. they're generally incapable of tying their own shoelaces unless they have a drawing to refer to
never give a drawing to a fitter
1st they would know what to do with it
2nd they'd lose it
3rd if they didn't lose and actually looked at it..... they'd just draw dicks all over it
Reasons being that fitters do not need a drawing to get the job done correctly and to a better standard than the draughting room wallas could concieve.
Basic training for a properly trained fitter is drawing board skills.
The problem is there that many guys around who think they are fitters, get called fitters and paid as fitters, who have not a clue how to measure something accurately with a pair of hand calipers and steel rule (to within .005"), to "feel" a difference of .002" with a pair of hand calipers, how to file a piece of metal to + or - .002" of required size or even able to file a flat surface.
Then we could talk about using a 2 lb hammer and cold chisel and hack saws. Why bother?? You obviously know all about it Doc.
Select to expand quotetheDoctor said..stamp said..
you have to remember that you're dealing with a fitter. they're generally incapable of tying their own shoelaces unless they have a drawing to refer to
never give a drawing to a fitter
1st they would know what to do with it
2nd they'd lose it
3rd if they didn't lose and actually looked at it..... they'd just draw dicks all over it
...even this is beyond most fitters unless there is a 'dick drawing' program already entered into an n.c. machine for them
dont you need to "freeze" the shaft, usually with a carbon dioxide fire extinguisher, to reduce the size, then fit the bearing?
when it warms back up the shaft expands into the bearing and it willl be locked in place.
Stop sledging us Fitters!
Take the shaft back to the manufacturer It should of been made out of precision 50mm ground round bar as requested.. Size on size is enough of an interference fit depending on application.If the desired bearing journal is oversize and you dont require the whole shaft 50mm put it in the and use emery to suite. Think they have mixed up off the shelf bright mild steel with precision ground.
.25 is on a on a 50mm shaft is a heavy really heavy interference fit and i wouldn't recommend it !
Not sure on the tolerance but type the bearing number into google
Select to expand quotechoco said..
a hammer 50mm pipe and some heat will get the bearings on
not a chance if it's 1/4 mm oversize on a 50mm shaft. i'm a boilermaker and even i think that's rough...
Select to expand quotecisco said..
If the Fitter and Machinist is also a Marine Engineer, he is the most intelligent man you will ever meet and has power of veto over the so called Master of the ship.
What is this power of veto you refer to? You can turn off the a/c?
You do know that the definition of Marine Engineer is "the unfortunate period between sail and automation"Select to expand quote
If he also has a Master's Certificate, he is known as God and you pray to him to keep you safe at sea.
Well at least there's hope for you as you seem to understand the concept that it is a Master who keeps you safe at sea.
Select to expand quotelongwinded said..cisco said..
If the Fitter and Machinist is also a Marine Engineer, he is the most intelligent man you will ever meet and has power of veto over the so called Master of the ship.
What is this power of veto you refer to? You can turn off the a/c?
It goes quite a bit further than that as you well know.
1. Maybe your work should buy a copy of 'the machinists handbook', it has all you will need to know about tolerances plus a wealth of other info.
Failing that, get the recommended tolerance from the bearing supplier (expect it will be remarkably close to MacRab's post).
2. If you give the shaft to a fitter to machine, tell him you need a "bee's d*ck" off the diameter, because if you don't he will probably just skim off a "**** hair" and the bearing will still be too tight! 
3. I used to be a fitter (before i is un enjuneer), so I am allowed to post this video (but should mention there is some swearing)
Australia is the only country that treats fitters like second class citizens .
In Germany & Canada fitters earn more than doctors & rightly so can the doctor make an artificial heart , A heart lung machine etc
What do the sledges of fitters do . Nothing constructive I'm sure
Cisco is totally correct a well trained fitter can do anything with precision & skill & even do it using hand tools .
A frigging desk jockey never built anything except a pile of red tape to piss capable people off
I agree, fitting is a good trade, especially tool making, or just anything precise, but also they can fabricate steel, weld, finish, etc, when i did my apprenticeship, we didnt really talk in metric in regards to tolerance, we talked more in thous, 1/1000 of an inch tolerance when machine, i cant remember how to convert from metric to imperial, but 0.25mm is a lot when talking precision, yes, a bees dick is an acceptable measurement as well
, really the drawing should indicate the acceptable tolerance, usually .025mm, ten thou i think
Select to expand quoteactiomax said..
Australia is the only country that treats fitters like second class citizens .
In Germany & Canada fitters earn more than doctors & rightly so can the doctor make an artificial heart , A heart lung machine etc
What do the sledges of fitters do . Nothing constructive I'm sure
Cisco is totally correct a well trained fitter can do anything with precision & skill & even do it using hand tools .
A frigging desk jockey never built anything except a pile of red tape to piss capable people off
it's exactly this sort of attitude that gives fitters a bad reputation. it's just a trade like any other, yet you think you're somehow a cut above the rest and deserve more respect than boilies or diesel fitters or plumbers or sparkies... pretty much anyone you come into contact with. even doctors apparently ffs.
a fitter can't do 'anything with precision and skill'. i've seen hundreds of examples of fitters' 'fabrication' and 'welding' that wouldn't reach a 2nd year apprentice boily's level. anyone with common sense can learn the basics of other trades.
get over yourself. yes you do great machining and precision toolmaking, but it's your trade.
you're a failure at your job if you can't do it competently- it doesn't make you special when you can.
and i just called an old mate of mine. he's a canadian toolmaker who emigrated in the 90s. he was paid slightly more in canada, but is probably still laughing now after i asked whether his wages approached those of a doctor.
Select to expand quoteMilsy said..
I agree, fitting is a good trade, especially tool making, or just anything precise, but also they can fabricate steel, weld, finish, etc, when i did my apprenticeship, we didnt really talk in metric in regards to tolerance, we talked more in thous, 1/1000 of an inch tolerance when machine, i cant remember how to convert from metric to imperial, but 0.25mm is a lot when talking precision, yes, a bees dick is an acceptable measurement as well, really the drawing should indicate the acceptable tolerance, usually .025mm, ten thou i think
.025 is 1 thou
did u make the shaft for pirrad? 
easy way to remember is 40 thou to the mm - near enough.
I wanna know the conversion between a hair, bee's dick, and a p00fteenth
ha, if i'd made the shaft, it would have been big, black, angry with an affro,,,,no, if i made the shaft, it would be out more than .25mm, i like my tolerances in cm, ha, thank you mark, favour returned,,,, a bees dick is basically just about ten times your dick
, ha, enjoy big boy (yeah, i took it there)
As I said a well trained fitter &Machinist & I know plenty of people who claim to be fitters but in reality are not & a fitter working on the oil wells in Alaska do earn more than some doctors just like people who drive big trucks in mines do . Not every doctor is a neurosurgeon just like fitters there are bad doctors also But unlike doctors fitters don't have the option if they stuff it up a bit it might heal alright anyway.
