Need to shrink steel shaft

[mirage100]

I got a steel shaft that is 0.469 and a gear that is 0.465 . The shaft has has a half moon key that goes in it. I need to install the gear on the shaft. I can't use any heat because the shaft has a bearing and a seal already installed .So will dry ice shrink the shaft enough so I can install the gear. Thank you for any info

 

[PHPaul]

That and heating the gear may get you there.

 

[mirage100]

There is a bearing and a seal right next to the gear. Do you think the heat will do any damage to bearing and seal?

 

[RobertB]

You need to bore the gear out more. General rule of thumb is about .001" interference per inch of shaft diameter. Depending on what material your gear is made out of, even if you could manage to heat it enough to expand the bore .004" it would likely crack when it cooled.

 

[main_cogg]

I can't say for certain without doing the math, but from experience I would say that. 0015 to .002 is the maximum interference that you can get away with in that size range.If memory serves the dry ice will get the shaft down to 0F or so and you don't want to go much above 400F with the gear for fear of affecting its properties. That in theory gives a differential of 400 degrees, but as soon as you start the assembly that differential goes away very quickly. One thing you didn't mention was the thickness of the gear. The thinner it is the better chance you'll have to make it happen.

 

[Cadillac]

Usually a gear that is keyed to a shaft will not be a shrink fit onto shaft. Whats the application? Would think it would be a slip fit?

 

[mirage100]

the gear is 0.616 thick and 1.500 wide

 

[mirage100]

 

[mirage100]

I have been using dial calipers to measure. I will go use my 1 inch micrometer now and remeasure

 

[RobertB]

Have you tried pressing it on? If that is a factory gear on a factory keyed shaft it should be no more than a light press fit. If you were able to pull it off with a gear puller, you should be able to press it back on.