Just arrived - 12" contact wheel from China, only $78 shipped!* - and some high-quality 6202-8 dual-sealed bearings.
Having a heck of a time figuring out how to press them in right (I know all kinds of ways to do it wrong, and damage them.) So far I've used some WD-40 and put the bearings in the freezer to shrink them, and tried to carefully press them in both manually and using a wood block to try to apply even pressure - no love.
I've read about heating the wheel itself, too, but I also read a good point from an old hand: it doesn't matter if you heat just the hole area -- you have to heat the entire wheel to get it to expand so that the hole expands**, and I'm nervous about heating it near the rubber. It's an aluminum wheel. I did a quick calc using the coefficient of expansion of aluminum and got that heating it from room temp to 80°C (about 175°F) would get me about 0.015mm -> 6 ten-thou's (and that'd be diameter so divide by 2, I believe...?). I'm probably way off, but doesn't sound worth trying.
I don't have a Really Big Shop Press. I do have lots of clamps, and lots of other tools. If possible, I'd rather find that there's an old trick to this so that I don't have to build a one-time jig with, say, my 10-ton bottle jack or tapping some threads in some bars... Any ideas?
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*yeah, China, I know - but it looks exactly like the Ameribrade wheel, down to the grind-hole from the dynamic balancing - and Ameribrade says theirs are foreign-sourced, so you connect the dots.... With shipping and bearings, the Ameribrade's $139; I bought high-quality bearings but even with factory bearings mine would've been $83.90, so I'm happy with the 40% ($55) discount. And I received it - from Hong Kong - 5 days from placing the order.
** this is a classic case of the old riddle: if you heat a piece of material with a hole in the middle, will the hole expand or shrink? There're some really clever thought-experiments that show that the answer is that the hole will in fact get larger. The easiest is to imagine that the cutout piece - the circle from the hole - is still in place. When you heat the whole (hole?) thing up, obviously that disc will expand. Ergo, the hole must, too. But, as I mentioned, that means the entire outer piece all the way to the edges must as well. Otherwise the hole and thus the piece in it would be constrained and there's no room for expansion. Which is my problem, as mentioned above.
Having a heck of a time figuring out how to press them in right (I know all kinds of ways to do it wrong, and damage them.) So far I've used some WD-40 and put the bearings in the freezer to shrink them, and tried to carefully press them in both manually and using a wood block to try to apply even pressure - no love.
I've read about heating the wheel itself, too, but I also read a good point from an old hand: it doesn't matter if you heat just the hole area -- you have to heat the entire wheel to get it to expand so that the hole expands**, and I'm nervous about heating it near the rubber. It's an aluminum wheel. I did a quick calc using the coefficient of expansion of aluminum and got that heating it from room temp to 80°C (about 175°F) would get me about 0.015mm -> 6 ten-thou's (and that'd be diameter so divide by 2, I believe...?). I'm probably way off, but doesn't sound worth trying.
I don't have a Really Big Shop Press. I do have lots of clamps, and lots of other tools. If possible, I'd rather find that there's an old trick to this so that I don't have to build a one-time jig with, say, my 10-ton bottle jack or tapping some threads in some bars... Any ideas?
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*yeah, China, I know - but it looks exactly like the Ameribrade wheel, down to the grind-hole from the dynamic balancing - and Ameribrade says theirs are foreign-sourced, so you connect the dots.... With shipping and bearings, the Ameribrade's $139; I bought high-quality bearings but even with factory bearings mine would've been $83.90, so I'm happy with the 40% ($55) discount. And I received it - from Hong Kong - 5 days from placing the order.
** this is a classic case of the old riddle: if you heat a piece of material with a hole in the middle, will the hole expand or shrink? There're some really clever thought-experiments that show that the answer is that the hole will in fact get larger. The easiest is to imagine that the cutout piece - the circle from the hole - is still in place. When you heat the whole (hole?) thing up, obviously that disc will expand. Ergo, the hole must, too. But, as I mentioned, that means the entire outer piece all the way to the edges must as well. Otherwise the hole and thus the piece in it would be constrained and there's no room for expansion. Which is my problem, as mentioned above.
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). OTOH, 6202-8 bearings (which I ordered and pressed in) have the same OD and width, so they'd fit the metric bore - but an ID of 1/2" - so I can use a $2 hardware-store bolt as the spindle.