Need to shrink steel shaft

broke the gear pressing it off. Took a chip out of it around the keyway
 
Cooling the shaft in dry ice will shrink the diameter to .4685". Heating the gear to 200ºC will increase the diameter to .466" so you still have an interference. Shrink fitting parts require the parts are a slip fit at assembly. Otherwise heat transfer will normalize the parts and the attempt will fail.

So in a word, the answer is no.

The easiest solution would be to modify the gear as machining the shaft will require recutting the Woodruff keyway. For .004", you may have that much clearance in the key seat though. I see that the shaft has been brazed. More than likely, it wasn't heat treated afterwards. You might be able to reduce the shaft diameter enough for a fit. As Cadillac said, it shouldn't be a press fit. A heavy slip fit at most.
 
+1 x3 to the responses above. .004" is too much of a 'press-fit'
 
The way I got the gear off the broken shaft was heat and a air hammer. Might have to go liquid nitrogen. When I worked at a plastic plant I rebuilt molds . The way we would get the 3 inch pins back in the molds was liquid nitrogen. then to get the back out was a big press.
 
Liquid nitrogen will give you .4678" on the shaft.. I wouldn't heat the gear to more than 300ºC which will give you .4666", still an interference fit. And you really want a slip fit, especially at those temperatures. Also, there is a possibility of damaging the repair due to the different thermal expansion coefficients of brass and steel. 19 microns microinches/in.-ºC for brass and 12 microns microinches/ inch-ºC for steel.
Edit: I typed microns rather than microinches in the original post. The post has been changed to correct that error.
 
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.004 is WAY too much interference for that dia shaft/gear. There are four ways to approach this.
1. Heat the gear and cool the shaft and try tapping it on.
2. Heat the gear and cool the shaft and get a bigger hammer.
3. Heat the gear and cool the shaft and beat the living s**t out of it until you ruin both the gear and shaft and then buy a new assembly.
4. The correct way.......... open the hole or reduce the shaft so the gear is a nice slip fit allowing you to line up the key as you assemble.......Bob
 
I will go with four. But how and the hell did the factory get this on the first time?
 
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I'm respectfully guessing your measurements are off a bit. A .004 interference fit on a .469 shaft is huge. Even with heating the gear and a hydraulic press it's quite a feat considering a shrink fit has to be accomplished rapidly, correctly, and the key requires exact line up the first and only try...........Bob
 
bhigdog said:
I'm respectfully guessing your measurements are off a bit. A .004 interference fit on a .469 shaft is huge. Even with heating the gear and a hydraulic press it's quite a feat considering a shrink fit has to be accomplished rapidly, correctly, and the key requires exact line up the first and only try...........Bob
Click to expand...

WellI I got out the micrometers and bore gauges and checked it out . it was worse than .004. I will be more than happy to send it to you and you can Measure it and then install it. This thing is CRAZY I know
 
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