Mechanical Design, Manufacturing and Engineering Forum
DFM DFA Training and Trainers | Engineering and Design Data | Product Services Directory | Advertise
Engineering Forum | Engineering Specifications Forum |
Engineering and Drafting Store | ASME Y14.5M - 1994 GD&T Training
POSTING POLICY / RULES | Archive#1 | Archive #2 | Archive #3 | Calculators

Forum Moderators: Administrator

shaft and hole can't fit Question
Post Reply   Forum
Posted by: shijian ®

06/15/2005, 05:22:08

Author Profile Mail author Edit
basic size:8mm
hole: upper deviation 0.1 lower deviation:+0.05 length:130
shaft:upper deviation 0 lower deviation:-0.1 length:50

two side diameter of hole are 8.05
three part diameter(head, middle, tail) of shaft are 7.99

but shaft can't slide along hole and stuff at middle.

what wrong? is cylindricity too big? is it possible that cylindricity is 0.01 for length 130mm.







Post Reply | Recommend | Alert View All   | Next |

Replies to this message


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

Post Reply | Recommend | Alert Where am I? Original Top of thread
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.






Post Reply | Recommend | Alert Where am I? Original Top of thread | |
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 ®
Barney
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.


Post Reply | Recommend | Alert Where am I? Original Top of thread | |
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.






Post Reply | Recommend | Alert Where am I? Original Top of thread

Powered by Engineers Edge

© Copyright 2000 - 2024, by Engineers Edge, LLC All rights reserved.  Disclaimer