Tolerance. For press fit

[joebiplane]

I am making a test bar for my lathe that uses a I inch x 18" shaft that I wish to install two discs on that are about 3" in diameter and about an inch wide these parts are all aluminium
How much interference should I create between the hole in the disks and the shaft.
If I read machinrys book correctly I think the number is .008. Does this seem right?
My shaft is, presently 1.125 and the hole in my disks is. 1.004. I can turn the shaft down or bore the holes larger( turning the shaft down is the easiest for me). what is the proper interference ??
Thanks
Joe

 

[Grumpy Gator]

Are you going to freeze the shaft and heat the Al disk? .008 is a lot for a dry fit at room temp. My rule of thumb is a .001 per inch. for a press fit. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
**********Just Saying***********Gator***************************************

 

[6530]

Are you going to freeze the shaft and heat the Al disk? .008 is a lot for a dry fit at room temp. My rule of thumb is a .001 per inch. for a press fit. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
**********Just Saying***********Gator***************************************

.001 per inch diameter or length?

 

[xalky]

.001 per inch diameter or length?

Diameter. You can go even a bit tighter on smaller diameters, like up to .003 for a really tight fit. For larger diameters the.001 per inch over about 3" is about right. It all depends on how tight you need it to be, really. For the tighter fits you need a press.

 

[zmotorsports]

Like already mentioned, .008" is a LOT of difference and will require a LOT of force to install. When I did my test bar I used .0015" and it still required several hundred pounds of force on the press to install.

Mike.

 

[6530]

Diameter. You can go even a bit tighter on smaller diameters, like up to .003 for a really tight fit. For larger diameters the.001 per inch over about 3" is about right. It all depends on how tight you need it to be, really. For the tighter fits you need a press.

OK, thanks. Just to make sure I understand, for a press fit shaft of 1" diameter the hole should be 1.001". Likewise, for a shaft of 0.5" the hole should be 1.0005?

I'm new to metalworking so I need a lot of dumb clarifications like this.

 

[Grumpy Gator]

Sorry I should have been more concise in my explanation. In my defence there is a football game on.Thanks for the back up Marcel. ​*******G********

- - - Updated - - -

1.000" shaft will press fit into a 0.999" hole. To make it easier freeze the shaft and heat the Al disk. This will be easier on the parts.The press part needs to be larger than the hole.
*********G*********P.S. chamfer the leading edge of the shaft.

 

[6530]

- - - Updated - - -[/SIZE][/COLOR]

1.000" shaft will press fit into a 0.999" hole. To make it easier freeze the shaft and heat the Al disk. This will be easier on the parts.The press part needs to be larger than the hole.
*********G*********

Doh. That's what I meant to type. The shaft has to be larger than the hole.

What about the 0.5" shaft? A .0495" hole?

 

[Grumpy Gator]

Like Xalky said for a real tight fit up to 0.003" under 1.000".So for a 0.500" shaft into 0.497" hole. Once again freeze the shaft and heat the Al.
******G*******

 

[6530]

Like Xalky said for a real tight fit up to 0.003" under 1.000".So for a 0.500" shaft into 0.497" hole. Once again freeze the shaft and heat the Al.
******G*******

Got it, thanks.