Installing a ball bearing

I'm making a set of wheels to roll a Harbor Freight electric hoist on an overhead rail of 3" C channels. The wheels are nearly a copy of the
ones on the HF 1 ton Trolley which I turned down to fit into the channel. http://www.harborfreight.com/1-ton-push-trolley-97392.html
I need two trolleys to suspend a log from both ends when I move it in or out of the storage shed, to avoid having to climb dangerously on the pile to operate one manual lever hoist in the center.
Both the originals and mine use 6203 ball bearings, 40mm OD x 17mm ID x 12mm thick. On the HF trolley they are a fairly light press fit on the OD and slide loosely on the axle pin.
For something that won't be used much is there a problem if a bearing fits loosely in the 40mm bore? This isn't the same as an old bearing seizing and spinning millions of times in an electric motor. A shoulder and a snap ring on the axle will keep the bearing nearly bottomed in its recess, if friction doesn't. The taper on the wheels and in the channel will force the wheel and bearing against the axle shoulder under load.
My 1" - 2" inside bore mike resolves to only 0.001" and don't want to beat up on the bearings by trying to pound them out by the inner race if a trial fit is too tight.
tia -jsw
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Not TOO much of a problem, so long as you have a 'keeper' to prevent it's migrating out of its cavity. That, and so long as the speed is kept low, it won't damage the bearing to 'roll' on its outer periphery.
But (cough!) why would you be pounding on the INNER race to remove a bearing? The access hole at the bottom of the cavity (through which the shaft will penetrate) can be only a few-thou smaller than the outer race, and it will be retained on that end just fine. Then you'd be able to use a proper outer race-sized drift to remove it, were the fit too snug.
Lloyd
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Lloyd E. Sponenburgh wrote:

Or he can make the bearing a slip fit and use some bearing retaining loctite to keep the outer race stationary .
--
Snag



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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote in message

The reason is because I'm copying the existing wheels closely in hopefully better metal instead of re-engineering a heavily loaded design I don't fully understand. The HF wheels have an 18mm center hole that catches a snap ring on the 17mm axle. Presumably the solid metal from 18mm out to 40mm stiffens the wheel rim against distortion.
I could drill three holes for push-out pins and use one wheel to hold and guide them while pressing the bearing out of another.
-jsw
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On Fri, 29 May 2015 06:01:20 -0400, "Jim Wilkins"

If the concern is that you don't trust your mics, remember that you have the bearing that's going in the bored hole. Treat the mic as a comparator and the bearing as your standard. Ideally you want a line to line fit to at most a couple tenths interference. You can interpolate the graduations closely enough for that. I'd be more concerned about the machine used for boring than the mics.
On the other hand, if you just want to be sure the bearing goes in OK the first time you can always heat the wheels if the fit after boring is too tight. Assuming the wheels are steel, a 300F temp rise will open the bore .003. If you can get within .001, you should be good. You do need to plan and work carefully when it's time to drop the bearing into the hot wheel - the last thing you want is to get the bearing cocked and jammed in the bore. It doesn't take long for the bearing to warm up and expand.
--
Ned Simmons

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wrote:

I practiced measuring the setting ring. This Enco 508-00150730 inside mike doesn't have a good enough feel to repeat to better than half a thousandth.
The machine is my 1965 South Bend 10L, with a 3/4" boring bar that I cut and ground a 5/16" square HHS bit for. It's more rigid than any other boring bar I've used so this is my first go at boring a smooth hole to a more precise diameter than Oilite requires.
On outside diameters that I can measure to 0.0001" the lathe can shave a few tenths with a freshly honed bit.
-jsw
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So, turn a "setting standard" that IS the couple of tenths smaller than the bearing, and use that to feel out your hole as you enlarge it a half-thou at a time (after boring to a nominal under-sized dimension).
Lloyd
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote in message

My question really resolves to what that feel should be, if I can't measure the ID to 0.0001" to match the interference fit from a table. Your previous response suggests that a drop-in fit would be fine as long as the axle shoulder and snap ring keep the wheel and bearing together. Subsequent machining on the other side will be much easier if I can remove the bearing and chuck within its recess rather than by the rim.
Maybe while doing it I'll learn how to bore and measure accurately enough for a future job where the bearing can't be allowed to slip.
-jsw
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On Fri, 29 May 2015 09:12:36 -0400, "Jim Wilkins"

I missed the fact that you're using an inside mic. I have a couple of that style, but rarely use them. For this sort of thing I'm more comfortable with a telescoping gauge and outside mic, thus my suggestion to use the bearing as a standard. It seems to me the telescoping gauge gives a better feel than the inside mics and makes a direct comparison between the bearing and bore easier.
--
Ned Simmons

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wrote:

Thanks. I've had trouble with telescoping gauges previously, probably because I didn't have a rigid enough boring bar to get a smooth finish. I just measured the inside mike's setting ring with one and hit 1.0000" on the first try.
-jsw
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wrote:

I've had the 3/4" boring bar for a long time, but was stuck on how to cut a 5/16" lathe bit for it to length at the correct angle until I tried the 7" angle grinder with a cutoff disk. -jsw
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wrote:

No, this is: Final velocity = (exhaust velocity) * ln ((mass at liftoff) / (mass at burnout ) )
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wrote:

That was a learning experience!
Thanks to those who helped, especially Ned for this advice on measuring and Gunner for a simpler way to extract the bearings than I had planned on.
Three of the bearings press into the wheels with heavy thumb pressure, the fourth is loose by less than 0.001".
-jsw
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On Fri, 29 May 2015 09:12:36 -0400, "Jim Wilkins"

Essentially, you do not want the bearing outer race to rotate in the hole and you do not want the shaft to rotate in the bearing inner race. You also do not want to have too much of a "press fit" on either diameter as it is very possible to cause the bearing outer race or inner race to contract or swell sufficiently to cause it to "bind" to at least some extent.
If I were doing it I would aim for a hole diameter of the bearing O.D. to perhaps 0.001 larger and a shaft diameter of from bearing inner diameter to 0.0005 smaller. If there is concern about either the outer race rotating in the hole of the shaft rotating in the bearing inner race than just assemble it with some of that bearing mounting goo.
It is not "rocket science".
--
Cheers,

John B.
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On Thu, 28 May 2015 18:59:40 -0500, "Lloyd E. Sponenburgh"

Obviously, there are no keepers or access holes. Chiwanese Tech, y'know? ;)
--
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that within me there lay an invincible summer.
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??? He's MAKING THE WHEELS HIMSELF! Such features don't just 'come' like gravy in the pan. One MAKES them.
Lloyd
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote in message

I suspect that the HF trolley is a "value-engineered" copy of a well-designed US original, perhaps this one: http://www.chdist.com/product/cm-series-633-universal-trolleys-2000-lb-capacity-328080.aspx?var 253
-jsw
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On Fri, 29 May 2015 10:02:11 -0400, "Jim Wilkins"

Dere's snap rings in dem puppies.
--
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On Fri, 29 May 2015 08:10:30 -0500, "Lloyd E. Sponenburgh"

But if he's following the old pattern exactly...
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On Thu, 28 May 2015 19:50:25 -0400, "Jim Wilkins"

Excellent idea.

Because you won't have any side loading (to speak of) acting on them, it shouldn't be a problem. The taper should keep things together just fine.
--
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that within me there lay an invincible summer.
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