Bearing Interference fit problem on shaft in wheel - how to solve using only temperature differential if possible - already tried and failed.

[maple syrup]

Hello,
sorry about the wall of words, I don't think I can make it smaller, although not complicated to understand.

Background:
I have a bandsaw that needs bearing replacement. the guy I bought it from told me it was replaced only 5 years ago, but Both bearings are bad when I brought it home suspecting poor quality bearings or poor installation. They are 6003 bearings. I want to upgrade to seal bearings from shielded. I have tried a couple of trial and error methods to get this to work Without success.

parts
The wheel ( part 23) is made of aluminum alloy. Bearings ( part 19 and 27 A) are 6003. Parts 25 is a shaft ( not keyed, but friction fit) that is 17 mm in diameter ( unverified). As you can see from the picture, the shaft has a stop in the back for the bearing. I also don't have an inside micrometre to measure the Exact bearing diameter. The shaft is 17.05 mm I think, But this could be wrong, as my digital CalPERS are cheap.)

reassembly installation procedure, deduced:

1. install bearings in wheel. Achieved with a small toaster oven at 200°F, as wheels are made of aluminum. Maximum recommendation for bearings. shaft at room temperature.
2. part 25 must be slipped in through the back and not the front due to the bearing stop near the threads.

goal

I want to achieve an easy slip fit Using temperature differential for two reasons. The first has to do with Not able to swing a hammer anymore With a lot of force. The second, is that it seems to be a two-step process as the shaft if driven last with a hydraulicpress or mallet will be pushing on the inner race while the outer race is also under force, damaging the bearing. My hypothesis is this is what happens five years ago.

My current attempts and/or strategies.

1. ( failed Shaft/ success bearings in wheel, 310°F differential). the shaft and wheel are inserted in the oven together heated to 200°F. the shaft was cooled using dry ice is 109°F. I did not attempt to hammer it in, but tried placing. this may have been a mistake. two step process.
2. ( Not attempted, 560°F differential, unknown if possible). I can replace the two bearings with high temperature steel shielded bearings which are much worse in performance. more expensive bearings at $15 a piece. I can heat to 450°F and drop in a dry ice shaft. I don't like this as the tire will need replacing every time this is performed. this is very difficult to remove without destroying. I'm assuming the bearing can take the 500°F and not just the grease which might be wrong. Making this an expensive bearing placement, Done often). I can't find a seal bearing for 6003 high-temperature steel[ opinion: bad solution, But may B only option]
3. [not attempted, 360°F differential. bring the wheel my local nitrogen supplier in Toronto Canada. I called a guy and ask if I bring the one wheel. I told him it was 15.5 mm rather than 17 mm by mistake. He said this would fail and said don't bother coming.
4. [ not attempted, 510°F differential] I could go back to my same nitrogen supplier and bring my small toaster oven ha ha. Or my heat gun. He might say no. I don't know if this would work
5. different installation method not considered.

Please let me know how you think I should proceed. this is a real pain.
thanks

 

[RaisedByWolves]

" the shaft and wheel are inserted in the oven together heated to 200°F. the shaft was cooled using dry ice is 109°F."

Don't quite understand this sentence?


I would first heat the inner bearing and cool the shaft, then assemble.

Heat wheel and cool bearing and shaft, then assemble.

Heat outer bearing and cool wheel, bearing, shaft assembly then press outer bearing home.

Pressing the bearing gently should not damage the races, Im willing to bet the PO assembled this with a hammer which will damage the bearings.

 

[sdelivery]

Many will scoff but carefully work the shaft and bores for a 2 thumb press fit and if sceptical about a race turning than use bearing retaining compound .

 

[Asm109]

From a design perspective, I challenge the idea that both inner and outer races of the bearing need to be a press fit.
Generally bearing makers want the rotating ring to be press fit, stationary ring a slip fit. The shaft is stationary, it should slide into bearing bores by hand pressure.
You have succeeded in getting the bearing od into the wheel. I would get a good measurement (to 0.0001 inch) of the shaft od. Compare that to the bearing makers specs for id. If you need to remove less than .001 inch to get a slip fit, I would chuck the shaft in a lathe and use emery paper to bring the shaft down until the bearings just slip on.

 

[rabler]

I'd want to use a micrometer to check that shaft. You mentioned cheap calipers, but if the shaft really is .05 mm (almost 2 thou) oversized, I would worry that alone would damage the bearings no matter how they were mounted.

edited to add: Basically repeating @Asm109's thoughts

 

[jbobb1]

If you heat any bearing to 500F they will be toast. As Asm109 mentioned, the bearings should be slip fit on the shaft. I would be checking for burrs. This should not be a difficult assembly process.

 

[Beckerkumm]

I agree that something is wrong in that one or the other of the fits should be slip and even the press fit doesn't need to be real tight and need that kind of heat to accomplish it. The bearings revolve slowly and the wheel is under tension so the bearing is unlikely to turn on either the shaft or the wheel bore.

While sealed bearings are fine in this application, they are not an upgrade. Usually it is the other way around.

Dave

 

[maple syrup]

" the shaft and wheel are inserted in the oven together heated to 200°F. the shaft was cooled using dry ice is 109°F."

Don't quite understand this sentence?


I would first heat the inner bearing and cool the shaft, then assemble.

Heat wheel and cool bearing and shaft, then assemble.

Heat outer bearing and cool wheel, bearing, shaft assembly then press outer bearing home.

Pressing the bearing gently should not damage the races, Im willing to bet the PO assembled this with a hammer which will damage the bearings.

The shaft and wheel inserted in the oven together is step two. The bearings are placed in in step one. They are then clamped down.

I'm with you on the first two steps. And this was my original thought, But when we get to the third step you mentioned
" heat the outer bearing and cool we'll, shaft and assembly and press better bearing home"..

.. issue with this is if I Heat the outer bearing and cool the wheel the second bearing would expand . I don't see how I could press that together. This is the conundrum how I ended up here.I'm trying to avoid pressing as much is possible due to the injury. Pressing the bearings from what I see requires more than a gentle tapping.

Many will scoff but carefully work the shaft and bores for a 2 thumb press fit and if sceptical about a race turning than use bearing retaining compound .

what you mean by " two thumb press fit". Do you mean very light pressure? I don't really understand how bearing retaining compound could work here

From a design perspective, I challenge the idea that both inner and outer races of the bearing need to be a press fit.
Generally bearing makers want the rotating ring to be press fit, stationary ring a slip fit. The shaft is stationary, it should slide into bearing bores by hand pressure.
You have succeeded in getting the bearing od into the wheel. I would get a good measurement (to 0.0001 inch) of the shaft od. Compare that to the bearing makers specs for id. If you need to remove less than .001 inch to get a slip fit, I would chuck the shaft in a lathe and use emery paper to bring the shaft down until the bearings just slip on.

Interesting about bringing the shaft down by sanding. I'm very cautious about reducing the diameter. Wouldn't it need oil For slip fit? I thought that was frowned upon? I don't have an inside micrometer.

I like this though as I guess that means I have to make a telephone call on Monday. I'm still looking at my options of what to do.

I'd want to use a micrometer to check that shaft. You mentioned cheap calipers, but if the shaft really is .05 mm (almost 2 thou) oversized, I would worry that alone would damage the bearings no matter how they were mounted.

edited to add: Basically repeating @Asm109's thoughts

I guess I really need to know the exact dimension of both. Measuring 17.05 mm, I wonder how accurate that is as I don't have a standard to measure against.

If you heat any bearing to 500F they will be toast. As Asm109 mentioned, the bearings should be slip fit on the shaft. I would be checking for burrs. This should not be a difficult assembly process.

Does that go for even high temperature bearings? Isn't that why they're rated to these temperatures?I have checked for burrs and didn't find any

I agree that something is wrong in that one or the other of the fits should be slip and even the press fit doesn't need to be real tight and need that kind of heat to accomplish it. The bearings revolve slowly and the wheel is under tension so the bearing is unlikely to turn on either the shaft or the wheel bore.

While sealed bearings are fine in this application, they are not an upgrade. Usually it is the other way around.

Dave

The bandsaw is a wood bandsaw not a metal one, so I'm trying to reduce the dust getting in. How much of a difference in size should it be if it should be a slip on the shaft?

 

[jbobb1]

Does that go for even high temperature bearings? I have checked for burrs and didn't find any

No, but that type of bearing is for an entirely different application, not for a bandsaw.

 

[Deleted member 69715]

If you decide that the inner race just has to be a press fit (I don't really agree with this) take the shaft and freeze it. By putting a container in another pan and surrounding it with dry ice. Put the shaft into the inner can and pour acetone over it. It'll get cold enough; believe me. After waiting for the temp of the shaft to get down, remove it and quickly clamp it in a vise or something. Do NOT touch that shaft with bare skin! While all this is happening get the bearing up to 200-220 degrees F. Bearing should slide on.
I have seen an old tool and die guy do this. He claimed it got the frozen part to below 300.