Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations cowski on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
Mechanical Drawing Notes 3
- Thread starter turner91
- Start date
It depends upon the type of fit you need. Take a look at and you should find everything you need to know.
Dan
Dan's Blog
Dan
Dan's Blog
What kind of bearing, what tolerance on the bearing dia, what are the material(s), do the bearing manufacturers (if an off the shelf bearing) not give this information?
Posting guidelines faq731-376 (probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484
What is Engineering anyway: faq1088-1484
- Thread starter
- #4
- Thread starter
- #5
- Thread starter
- #7
Do you know what the 'P7' is all about - standard limits & fits?
What drawing standards are you working to/where are you located?
What drawing standards are you working to/where are you located?
Posting guidelines faq731-376 (probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484
What is Engineering anyway: faq1088-1484
- Thread starter
- #9
I honestly have no idea what P7 means at all. I have never worked with bearings before and have never had to use different fits before. I am a first year engineering intern and we haven't covered anything about it yet. I am working for a very small government contractor and am designing a machine for them.
Unfortunately I don,t know an English version, but maybe this explains a little
When you identify the bearing either by "Part Number" or "Find Number" add a "Flag Note #" and then over by the Header Block or Part Number Listing create a Flag Notes List and describe in text the spec or specific instructions to press fit the bearing.
Rerig
Rerig
Do a search for limits and fits charts. You will find your P7 fit in a chart with the standard tolerance to be added and/or subtracted from your nominal dimensions. Put the dimensions and tolerances on your drawing(s). If you want you can put a note at the bottom that calls out that P7.
Dan
Dan's Blog
Dan
Dan's Blog
turner91, you may never "covered anything about it" in your classes. They only go so far.
A learned skill that will be valuable in your career is to identify who might know the things you need to know don't but, and ask them your questions. Nobody expects you to know everything.
As an example, the applications engineers at SKF. Most manufacturers of engineered equipment have them, and that's what they are there for.
Of course you did start here, so that's good
Regards,
Mike
A learned skill that will be valuable in your career is to identify who might know the things you need to know don't but, and ask them your questions. Nobody expects you to know everything.
As an example, the applications engineers at SKF. Most manufacturers of engineered equipment have them, and that's what they are there for.
Of course you did start here, so that's good
Regards,
Mike
-
1
- #14
(sigh) ![[deadhorse]](/data/assets/smilies/deadhorse.gif "[deadhorse] [deadhorse]")
TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering
TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering
-
1
- #15
The loading direction, and what is rotating will determine if the fits with bearing OD and ID should be some level of interference, or could be a "slip fit." Often only one needs to be interference, which is good (maybe even a lifesaver) for assembly
P7 is a bore tolerance. (Bores use capital letters, shaft tolerances are lower case letters , p, k, n, r , etc). On a 100 mm bearing It would result in a theoretical interference fit with the bearing outer race of 14 to 54 microns ( ~ 0.0005 inch to roughly 0.002 inch ) . Those are diametral fits, not radial.
Beyond the size there are equally important tolerances for shoulder runout, bore and journal coaxiality (relative runout is sometimes recommended as easier to gage), roundness and cylindricity, etc.
The info is online and in most catalogs, but I'd talk to an application engineer until you are real comfortable with all the design steps. It takes a while.
These days machine more machine shops are familiar with the ISO fit designators. I think it is smart to include a copy of the appropriate hunk of the ISO fit table right on the drawing. It sure beats having a whiny pillow fight about mysterious or imaginary tables when parts are the wrong size.
P7 is a bore tolerance. (Bores use capital letters, shaft tolerances are lower case letters , p, k, n, r , etc). On a 100 mm bearing It would result in a theoretical interference fit with the bearing outer race of 14 to 54 microns ( ~ 0.0005 inch to roughly 0.002 inch ) . Those are diametral fits, not radial.
Beyond the size there are equally important tolerances for shoulder runout, bore and journal coaxiality (relative runout is sometimes recommended as easier to gage), roundness and cylindricity, etc.
The info is online and in most catalogs, but I'd talk to an application engineer until you are real comfortable with all the design steps. It takes a while.
These days machine more machine shops are familiar with the ISO fit designators. I think it is smart to include a copy of the appropriate hunk of the ISO fit table right on the drawing. It sure beats having a whiny pillow fight about mysterious or imaginary tables when parts are the wrong size.
-
1
- #16
turner91,
Who is going to press fit the bearing, you, or the fabricator?
This affects how your drawing is presented.
A dig for SKF here. If you need info like the tolerances on the OD of your bearing, buy your bearings from people who publish this information. Better yet, buy your bearings from people who publish handbooks telling you how to analyze your bearings and design and tolerance the mounts. SKF might cost more, but if they support your engineering, you will get your job done right, the first time.
JHG
Who is going to press fit the bearing, you, or the fabricator?
This affects how your drawing is presented.
A dig for SKF here. If you need info like the tolerances on the OD of your bearing, buy your bearings from people who publish this information. Better yet, buy your bearings from people who publish handbooks telling you how to analyze your bearings and design and tolerance the mounts. SKF might cost more, but if they support your engineering, you will get your job done right, the first time.
- Thread starter
- #18
- Status
Similar threads
- Locked
- Question
- Locked
- Question
- Locked
- Question
- Locked
- Question