Request for advice regarding dowel press fit (with drawing for illustration) Question
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Posted by: john2003 ®

07/21/2006, 15:06:11

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Hi everyone,

I have a small cantilevered mounted bearing housing that rotates about it's longitudinal axis. The bearing housing is loaded perpendicular to it's rotation axis, as is usually the case.

I am using a standard hardened steel dowel pin as the bearing shaft. The dowel pin is just pressed into a steel support, and then the bearing housing is installed onto the dowel pin / shaft. The steel support can slide up or down on two dowel pins and can be adjusted and locked as needed. This allows for adjustment of the vertical location of the bearing housing.

The bearing housing shaft is pressed in-between two other dowel pins that the steel support slides on, which have a very close tolerance slide fit. I think I should probably use a light press on the bearing shaft, so that the press of the bearing shaft does not affect the hole size of the slide fit dowel holes located on each side of the bearing shaft.

The bearing housing is oscillated manually by hand and the device is always used at room temperature. There are no vibrations present since the device moves so slow, but there are reversing loads on the bearing housing, and cyclic loading with variable loads.

I was hoping to use a light press fit for the dowel of 0.0001" minimum to 0.0012" maximum.

I have a picture of the housing arrangement at the following link. It is "housing # 2" i.e., the one shown on the left, that I am using...

https://www.ice9.zoomshare.com/

1. Can anyone please give me a recommendation for a minimum amount of press fit that I can probably get away with for the bearing shaft ? Is 0.0001" minimum to 0.0012" maximum probably OK ?

2. Due to the way the housing is loaded, I think for the most part the load would not tend to pull the dowel / shaft out of the support and would actually make it bind in the support ? However, there still may be some tendency for the housing load to pull the dowel out of the support. Is there a way to calculate or get a close estimate how much axial force will be applied to the 3/8" OD shaft due to the housing load ?

3. Can anyone please tell me the method or formula for calculating how much axial force it takes to pull the dowel out of the hole, based on the amount of interference of the press fit ? The dowel and support are both steel.

4. Do I need to be concerned with changes in the minimum interference of the press fit, just due to normal changes in ambient air temperature ? The device is always used a room temperature.

Thanks for your help.

Sincerely,
John








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Re: Request for advice regarding dowel press fit (with drawing for illustration)
Re: Request for advice regarding dowel press fit (with drawing for illustration) -- john2003 Post Reply Top of thread Forum
Posted by: randykimball ®
Barney
07/21/2006, 23:39:24

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After reviewing your questions a couple of things come to mind:

Are you going to be rotating this hub at high speed?

How heavy is the load?

I'd be more concerned about the balance of the spinning load, if it is spinning. Vibration will not be your friend. I'd consider a shrink fit. The thing with a shrink fit is you do not damage the surface of the dowel nor the bore in the fit process. Pressing a dowel into a hole will often tear or shear out material, weakening the grip. Plus with a shrink (warmed support and frozen shaft) you may have an opportunity to add a bonding agent such as a loc-tite product to additionally sheize the bond. I'd not be afraid to skuff the finish on the hardened pin and consider that in the tolerances of the fits.






The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

Modified by randykimball at Fri, Jul 21, 2006, 23:41:55


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Re: Request for advice regarding dowel press fit (with drawing for illustration)
Re: Request for advice regarding dowel press fit (with drawing for illustration) -- john2003 Post Reply Top of thread Forum
Posted by: stewart ®

07/21/2006, 20:48:33

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Hello John

If I'm understanding correctly. I'd use a heavy PF on the axle and drill and ream the slide pin holes after the axle has been pressed in.

Stewart








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