How tight and how loose?

Scoobydude · Apr 6, 2018

Ive tried searching in the internet for ideal tolerances for differant ordinary applications but no luck. I am no machinist, but my brother has access to a lathe and can make things if i give him a drawing so....
I am using that to my fullest

. is there a page or something where it would list ideal tolerances for spacing between material to be....
Pressure fitted
Loose fitting
Snug but able to get out
Etc...

Right now my question is for my axle plate fixture. It uses 3\4 all thread(bought a common universal fixture that uses 3\4 holes) but my axle slot size is .88, so i need a spacer to center the slot on the all thread, but what size do i make my spacer? Certainly not .75 id by .88od, how many thou under/over.

And all the other questions in my head have no frame of reference such as this pair of triple trees i wanted to swap a stem on, but i had no frame of referance for how many thou oversized the new stem should be to be preasure fitted to fit in the old hole etc........

Need first question answered and hopefully a website for any other possible project.

Scoobydude · Apr 6, 2018

for boring the hole in the spacer material(slightly less than .75id x 1.25 od) i have a harbor freight 3/4 bit, would the runout(correct word?) Of a crummy bit make the hole a couple thou over so that i dont have to pound it iver my allthread to get it to fit?

tnmgcarbide · Apr 7, 2018

the first question should include stuff ...like this is for motorcycle steering, or for a trashcan trolly..
or whatever, like we should all know what you are describing?

you should pretend that no-one knows anything , and tell us the hows and whys.
then we can be of help , before anyone makes assumptions. i don't know shit about motorcycles,
but i taught GD&T at a trade school....
ok?

azmachining · Apr 7, 2018

If your looking for fits "hole to shaft fits"you need the machinist hand book. Will I use mine and find the answer for you? Probably not, don't like you much, but you could ask what you need.

jrmach · Apr 7, 2018

Title sucks,,,thought I was checking out a thread about women

In b4 the lock

Jaxian · Apr 7, 2018

Machinery's Handbook has a whole section on fits, their names and the tolerances associated with them. Slip fits, loose fits, press fits, sliding fits etc. Get a copy go to that section and your answers are right there. Lots of them.

MushCreek · Apr 7, 2018

To begin with, all-thread is usually a very sloppy fit, and probably very inconsistent. It's hard to make something 'precise' made around something that isn't.

Scoobydude · Apr 7, 2018

Not sure why the one guy doesnt like me.....machinists handbook it is.

implmex · Apr 7, 2018

Hi Scoobydude:
Your question is one of "those kind of questions": It depends, it depends it depends.

What it depends on, is a huge body of knowledge about the application, the material properties, the forces that will operate on it, the consequences of failure etc etc etc.

So there is no universal standard you may apply, but there are standards for specific applications.

The best resource is a publication called "Machinery's Handbook": it's been around forever and is updated periodically to reflect the changing times.
In it you can look up all sorts of standards, from threads, to bearing fits to press fits to gear tolerances to pretty much whatever.

Get yourself a copy of it; even an older edition from Fleabay will be more than worth it.
Every self-respecting machinist has a copy; there used to even be custom drawers made in high end machinist's tool chests, just for the copy of Machinery's Handbook.
Be warned though, it's a big book written on thin paper in small type, so there's a mountain of information to go through.

Cheers

Marcus

Newman109 · Apr 7, 2018

jrmach said:
Title sucks,,,thought I was checking out a thread about women

In b4 the lock

I agree that's a bad title. Generally it's the new people who don't bother to read the rules on proper titles. There should be a two week training class with written exams followed by a strip search before new members are permitted to post with titles.

I mean, "How tight and how loose" is border-line salacious, don't you think?

tnmgcarbide · Apr 7, 2018

"When I buy my wife, at first she cook good, her vagine worked well, she strong on plow, but three years later when she was fifteen, she receive hair on her chest, her voice become deep, and her vagine hang like SLEEVE OF WIZARD.".

Borat

litlerob1 · Apr 7, 2018

"Fits for Nominal/Lay Machinists" Loose-well you can figure that one out, Slip-well you can figure that one out too, Light Press-It means, guess what? yes, light press, Press Fit-It means you need a Hammer, or a ball bearing, or both?????

R

sneed · Apr 7, 2018

azmachining said:
If your looking for fits "hole to shaft fits"you need the machinist hand book. Will I use mine and find the answer for you? Probably not, don't like you much, but you could ask what you need.

In the future you might try asking your questions in the “Home Shop Machinists” forum. They are generally more forgiving to those of us who are trying to find our way in the dark. The guys here are stone professionals and, even after 15 years of figuring machining stuff out, I still get a little paranoid about coming off as a total idiot here.

Hodge · Apr 7, 2018

It does sound like op is working on motorcycle steering head components based on terminology. I would recommend you have a competent machinist on board. A crappy 3/4 drill isn't suitable for drilling a tolerance fit .750 hole..... good luck

awander · Apr 7, 2018

So, drill a hole with your 3/4" drill, and see if the allthread fits through. It probably will.

As far as the stem press fit, a commonly-used rule of thumb for steel in steel is that you want the shaft about .001-002 oversize for each inch of shaft diameter. So for a 1 inch stem, make it about 1.002" in diameter. I'd feel better if it was welded in though.....

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How tight and how loose?

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Scoobydude

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tnmgcarbide

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azmachining

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jrmach

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Jaxian

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MushCreek

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Newman109

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litlerob1

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Hodge

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