My fail -Heat effect on Al hole size ?

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Jul 13, 2009
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I started to put this in the what's on your bench today, but feared I'd lose it there.

DSC_03152.jpg





I did some tidying up, some grass cutting, some pouting.



I had started a lathe project in the cold of this winter and left it in the lathe until I had the ambition to go back to it.

I was creating a new idler wheel for a grinder project

I had single point bored out an aluminium wheel to be, within .001" of my final dimension





I got back to it today and measuring / test fitting it find it's a sloppy hole by .001 ish
No press fit anymore

I kicked myself stupid for scrapping that relatively pricey hunk of Al



Then I got to thinking there was a delta of more than 60 * Celsius
Is that enough to make a 1.125 hole grow by .002 ?


I'm still ticked, but I believe that's probably enough to throw my fit out of target.



I'm thinking of gluing it in with a bearing retaining compound and seeing if I can still make it work.

IS there a chance of that working. or is this just a remake ?
 
Sam you just picked the wrong season to move off center on this one. Just wait another half orbit and find out for sure... :D
 
You might be able to sleeve it. Did you use steel calipers to measure the hole last winter? The thermal expansion for Al is about 2x that of stainless steel. If you kept the calipers in your pocket, but turned the hole at 20 below that could have an effect.
 
Telescoping gauges and a proper micrometer

I assume they were at the same temperature

I used the same mic to measure the bearing as the hole at the time,
 
I'm thinking your bearing is going to show quite a bit less expansion due to the space between the pieces. Your wheel is one solid piece. You could stick the bearing in the freezer and measure its OD compared to its OD at shop temperature and do the same with the ID of the wheel. This might give you some insight as to what happened. Let us know what you find out.
 
Aluminum thermal coefficient of expansion is .00001244 per inch per degree fahrenheit. 140F x .00001244 x 1.125 = .002
Use LocTite 290 for the repair. Its better than a press fit.
 
John Moran said:
Aluminum thermal coefficient of expansion is .00001244 per inch per degree fahrenheit. 140F x .00001244 x 1.125 = .002
Use LocTite 290 for the repair. Its better than a press fit.
Click to expand...

Good reply thanks

I was looking for some sort of calculation, but didn't have the right search terms.
 
You machinists get me..... one thousandth of an inch is a snug fit to the rest of us :) ......that's what super glue was made for, wasn't it?
 
Your could bore I out bigger and put a sleeve or bushing in it couldn't you? We do that sort of stuff all the time at the shop instea of scraping it out.

Jay
 
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