Hole and shaft diameter for bearings

A

Alberto-sp

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Hello.

I´m making a belt sander. I have made a hollow aluminum roller, put bearings in each side and a steel shaft. The problem, it is too tight, because I mathe the holes in the aluminum a little bit smaller and the shaft a little bit bigger, so I had to use a press (made whit a car jack) to aseembly and now the roller is hard to turn.

So what is the relation between the aluminium hole and the OD of the bearing? The bearing OD is 1.125"

And the same whit the relation between the shaft OD and the OD of the bearing hole. The bearing hole OD is 0,5".

Thank you

best regards
 
benmychree said:
Most all press fits should be about .001 per inch of diameter, most close running fits should be about the same allowance, in example, the bushing should be at least .0005" larger than the shaft.
Click to expand...


Thank for your answer.

So, the shaft has to be slighly small than the hole in the bearing?
 
Alberto-sp said:
Thank for your answer.

So, the shaft has to be slighly small than the hole in the bearing?
Click to expand...

The bearing has one stationary race and one rotating race (relative to the loading). You want the fit on the rotating race to be tight and the fit on the stationary race to be moveable.

A tight fit will be something like 0.001” (0.025mm) interference, but scaled somewhat for diameter. The moveable fit should be a line fit (same size for both parts) or maybe up to a little clearance around 0.0005” (0.013mm).

In your case, the load on the bearing ID is fixed and the load on the OD is moving. So you want the shaft no bigger than the bearing ID and you want the bore in your aluminum wheel about 0.02mm smaller than the bearing OD. Alternatively you can use retaining compound to secure the bearing in an aluminum wheel that has a bore matching the bearing OD.
 
benmychree said:
Most all press fits should be about .001 per inch of diameter, most close running fits should be about the same allowance, in example, the bushing should be at least .0005" larger than the shaft.
Click to expand...
Hi, I just can't remember, but it was .001 up to a certain diameter which I think was 5 inches then it was ??????? larger. CRS is terrible.
 
Thank you, I have used this tolerances and the fix is perfect!! That was for the crowned pulley.

I´m making a belt sander, and for the pulley that is attached to the motor shaft I´m using to 4" OD heavy cast iron wheels. I think the iron is not evenly distributed and at 3000 rpm vibrates a lot.

I tried with a wooden wheel and there are no vibrations. I´m thinking on wood or aluminum.

It is OK to do it with pine wood or it is dangerous a 4" wood pulley at 3000 rpm?

I can do it with aluminum but it would be easier with pine wood
 
Alberto-sp said:
Hello.

I´m making a belt sander. I have made a hollow aluminum roller, put bearings in each side and a steel shaft. The problem, it is too tight, because I mathe the holes in the aluminum a little bit smaller and the shaft a little bit bigger, so I had to use a press (made whit a car jack) to aseembly and now the roller is hard to turn.

So what is the relation between the aluminium hole and the OD of the bearing? The bearing OD is 1.125"

And the same whit the relation between the shaft OD and the OD of the bearing hole. The bearing hole OD is 0,5".

Thank you

best regards
Click to expand...
I have to think when you pressed the bearing into the roller you pressed it using the inner race which would result in the bearing binding. You must press a bearing on its outer race to avoid that problem, even if it means making a race setting tool. I personally wouldn't use pine wood for a roller. Go with the alum. roller.
 
no no, in that pulley I havent used beaings. Here it's a picture.


pull.jpeg
 
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