shaft and hole can't fit
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Re: shaft and hole can't fit
Re: shaft and hole can't fit -- shijian	Post Reply	Top of thread	Forum

Posted by: kelly_bramble ® Administrator, Administrator 07/31/2005, 14:04:19 Author Profile Mail author Edit

Your specification doesn't seem complete. I think you are saying that; the hole is: 8 +0.1 / -0.05, 130 deep the shaft is: 8 +0 / -.1, 50 long The MMC of the hole is 7.95, and the MMC of the shaft is 8, so by design, you could have an interferance of 0.05. Depending of the tolerancing standard you use, the envelope principle could apply or not. The Envelope principle states that the specified MMC of a feature of size, is a boundary that can not be violated due to the cumulative effects of size and form (warp) of the feature of size. For the hole, this means that the hole surface inner boundary should not encroach into a inner diameter area 7.95. With this you should be able verify the Envelope principle with a gage pin very slightly smaller than 7.95. My best guess, is that the hole was actually drilled non-straight. Modified by kelly_bramble at Sun, Jul 31, 2005, 14:09:40

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Re: shaft and hole can't fit
Re: shaft and hole can't fit -- shijian	Post Reply	Top of thread	Forum

Posted by: Gary Kemp ® 07/31/2005, 10:25:03 Author Profile Mail author Edit

First I would ream the hole to make sure the diameter was constant. If the problem persisted, I would check the hole and shaft for straightness. Depending on how the hole was manufactured, it could be curved. I would make shorter and shorter shafts and try them until one goes through. From that you will be able to establish to what degree the hole is not straight. You may have to change your manufacturing method or lossen the fit.

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Re: shaft and hole can't fit
Re: Re: shaft and hole can't fit -- Gary Kemp	Post Reply	Top of thread	Forum

Posted by: randykimball ® 07/31/2005, 12:10:57 Author Profile Mail author Edit

Often this is because although the shaft and the hole check to be the correct sizes with measuring equipment they are not actually round. A micrometer will measure a shaft that is somewhat triangle shaped as round. Most often when this happens though it is the hole that is not round. Sometimes it is necessary to hone the hole or push a correct sized ball bearing through the hole. -randykimball- 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.

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Re: shaft and hole can't fit
Re: Re: shaft and hole can't fit -- randykimball	Post Reply	Top of thread	Forum

Posted by: gary kemp ® 08/04/2005, 18:56:12 Author Profile Mail author Edit

I agree with mr. Kimball except I believe that long skinny holes always will have the additional angularity issues because of long skinny drills tendenacy to walk a little.

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