Press fit dimensions?

[clockworkcheval]

Sir, I'm impressed. It is quite possible that in my nick of the woods you would be considered as something more than your average hobby machinist.

 

[ajoeiam]

Sir, I'm impressed. It is quite possible that in my nick of the woods you would be considered as something more than your average hobby machinist.

Wasn't why I wrote what I did.

I have been too often awed by work done by what most would consider amateurs or tyros but they worked carefully methodically and created good, if not even sometimes, great, work.
Its the having to bang things out on the clock that often results in less than 'stellar' results.
One of my takeaways from my working life has been - - - - almost everyone has the time AND the money to do things right the second time.
One of my goals has been to do things 'right' - - - the first time.

I am far less impressed by those that say that the 'book' says it can't be done that way.
But then - - - I grew up where the mantra was 'its next year country' which meant - - - it'll go better next year.
Its quite a different attitude to the much more common thinking today - - - oh well - that's how it goes - - - kind of thinking.

So I'm an outlier - - - - ja - - - - I know this but there are others.
(I remember meeting an older gentleman who had taught himself how to use sand blasting to etch glass to create like painting. The examples I find from recognized artists in said field do not surpass what he produced and he was self taught with no training in the 'arts'. He did it for the love of creating or of beauty - - all without recourse to any assistance. Would that I were so gifted!)

 

[SmithDoor]

If you pressing ball bearing you do not want a heavy press fit or ball bearing will not turn.

But bronze bearing can great press if finishing bore.

Dave

Respectfully - - - - I would disagree!!

I have been able to achieve a shaft precision of 0.0000"+0.0005"- on a lathe with an total error range of some 0.023" in the same length.
In theory what you say is correct - - - - but then practice theory is all too often shown to be - - - - well less than correct.
Was this precision easy to achieve - - - - !@#$%^ NO!!! It was very very stressful and very not easy - - - but it WAS POSSIBLE.
This means that the possibility of a quality level is dictated from the 'office' - - - - if the office says you can't do it - - - you'll not even get the opportunity. If the office says you 'can' do it - - - - you've got to haul it out.

If you design using somewhat standard shafting (when shafts are called for) you can easily purchase this nice T & G (turned and ground and sometimes that includes stress relieved and, more rarely, even other features) and it will likely measure between 2 and 3 tenths under nominal and the rating is +0.0000"-0.0005" . It then behooves you to create the bore to your required dimension (hard press, press, interference, sliding and/or running) fit. So instead of requiring machining on 2 surfaces - - - bore and shaft - - - machine 1 - - - it makes life easier and things go faster.
Some would then argue that you can't machine a bearing - - - rightfully so - - - - now you machine the shaft - - - - and its funny that most bearing IDs are just so and give that recommended fit for the bearing on a standardized shaft. This is where that turned and ground shaft, due to its very slight undersize of nominal, is not quite as useful.

IMO hobby machining can be as good as any commercial - - - - if care is taken. Is it always as good - - - - I'd be willing to bet not.
But then I've had to fix enough commercially produced stuff that wasn't up to snuff either so the capability is not always reflected in the reality either.

 

[Steamchick]

We can (in theory) all determine machine capability... but in truth, the biggest variable is - as you say - People variability. If NASA have the money - it is possible. If it is your "humble" Hobby job, maybe not so possible. Industry is generally somewhere in the middle, though unfortunately often much poorer than the worst we can do in the home workshop. Because that's what the people make money doing!
K2

 

[Richard Hed]

We can (in theory) all determine machine capability... but in truth, the biggest variable is - as you say - People variability. If NASA have the money - it is possible. If it is your "humble" Hobby job, maybe not so possible. Industry is generally somewhere in the middle, though unfortunately often much poorer than the worst we can do in the home workshop. Because that's what the people make money doing!
K2

Speaking of NASA, there are still people out there who claim the moon landing never actually happened--seriously. There is good evidence for it too. Even the latest Chinese moon adventure claimed they never found any evidence of a landing nor any craft on the moon at the supposed sites. I don't know how difficult that would be to see from an orbiting craft, but still, it is a slap in the face for NASA. Also, the claim is that no living being could pass thru the Van Allen belt and live. I have done the calculations, and if one orbited in the VA belt, yes, you wouldn't live very long. However, if you passt thru it quickly, you would only get a slight toasting. Anyway, my point is that what ever NASA can do for 100B$, any amateur could do 100M$ and any competent ordinary company could do easily for 1B$

 

[dnalot]

Anyway, my point is that what ever NASA can do for 100B$, any amateur could do 100M$ and any competent ordinary company could do easily for 1B$

I can do it for $15 but I'm busy

Mark T

 

[nautilus29]

An interesting debate going on. Although I can achieve the same precision at home as I can at work (to a certain extent) I find it much easier at work. Many hobbyists are using used equipment from schools or long closed job shops which sets you up at a disadvantage right off the bat. That's not me saying it's impossible, but it just makes it harder. We also have more specialized tooling at work, but the biggest factor is the inspection equipment that I get to utilize at work. Although I can use the same practices at home to achieve ultra precision parts, I can't check them on the laxor mic that I have at work so how do I k ow if they are the same quality? I can't run them on the form gage we have, or the cmm.