47 Replies Latest reply on May 6, 2017 12:35 AM by Christian Chu Branched to a new discussion.

    Job ad Question

    Maha Nadarasa

      A job ad required an answer for this question.

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        • Re: Question
          John Stoltzfus

          If I answer and you get the job, what do I get, a yearly or monthly commission ?

            • Re: Question
              Maha Nadarasa

              I am not interested in this job. Only thing is curiosity about this question. 

                • Re: Question
                  John Stoltzfus

                  lol - The only thing that I memorized was a "Rule Of Thumb" - .0015" for every 1" in diameter is considered a slide fit, however there are material differences and surface finishes that come into play as well..

                  • Re: Question
                    Andy Sanders

                    Basically, you are trying to find how how "tight" a fit you want between 2 mating parts.

                    "Shaft Basis" means the shaft is your nominal dimension.

                    Look up the fit tables for a free running type fit and you can calculate the tolerance for the shaft and then what the corresponding hole and tolerance should be for the mating part.

                     

                    When I first started out tolerancing and what should be done was a mystery to me.  These types of tables are great way to achieve the fit you need without all the guesswork.

                      • Re: Question
                        Jim Steinmeyer

                        Would this be a Machinery's Handbook table? That valuable resource wes never mentioned when I was in school. Wish I had known about it back then.

                          • Re: Question
                            Andy Sanders

                            Yep.

                            I've found that "imperial" based tables like in the MH give you good guides as to what the fit combos mean and will do for you.

                            If you look up an ISO tolerance chart, you get a ton of fit classes but not a real good explanation of what fit means what.  Just a bunch of F8/f8 so on and so on.

                            There are a few good tables I've found for the ISO charts that give some good combination assistance.

                             

                            In my MH 23rd edition, you'll find it all under "Fits" in the index.

                    • Re: Question
                      Andy Sanders

                      I know how to do that but I have to admit I'd rely on looking up the tables.  Don't have that stuff memorized!

                        • Re: Question
                          Maha Nadarasa

                          If one can look at the table and answer this question, it is not a challenging question.

                            • Re: Question
                              J. Mather

                              Maha Nadarasa wrote:

                               

                              If one can look at the table and answer this question, it is not an challenging question.

                              Good!

                              It is not supposed to be a challenging question.

                              You are supposed to look it up in a table.

                              The challenge is - "Has you instructor taught you how to use the table?"

                              Has your instructor taught you realistic tolerances for the machining processes to be used in manufacturing the parts?

                               

                              Watch out - beginners forget to move the decimal places in that table and return ridiculous answers that make no logical sense if they took the time to model at min/max they specify.

                               

                              What is the title/author of the textbook you are using?

                              Do you own a Machinery's Handbook (or whatever is appropriate for the standards in your country)?

                               

                              (And actually, this stuff in built into SolidWorks now.)

                              • Re: Question
                                Derek Parks

                                I beg to differ. By asking a question like this the company knows you know how to find the answer.

                            • Re: Question
                              Christian Chu

                              see below image where 8mm in the range of .24 to .40"

                               

                              EDIT: by the way, can you change the title to "Tolerance Fit"

                               

                              • Re: Question
                                Dan Pihlaja

                                ISO shaft/hole preferred fits

                                 

                                https://mdmetric.com/Ch6.8wGO.pdf

                                 

                                 

                                ANSI Fits calculator and charts:

                                 

                                Preferred Tolerances & Fits Chart ANSI B4.1 Calculator RC - LT Fits | GD&T Tolerances - Engineers Edge

                                 

                                 

                                 

                                Unfortunately, they don't mention material, nor do they mention the standard by which they base themselves.   I know that the standards are similar, but they are not exact.

                                • Re: Question
                                  Vladimir Urazhdin

                                  How this question relates to SolidWorks?

                                    • Re: Question
                                      Maha Nadarasa

                                      Here is the file.

                                        • Re: Question
                                          Vladimir Urazhdin

                                          Forum is designed to clarify the issues related to SOLIDWORKS.

                                            • Re: Question
                                              Jim Steinmeyer

                                              To echo Paul  , If all we were to consider here was SolidWorks we could, and should, shortly be replaced by an AI program. There is a lot of judgement and external ability that is involved with being a good designer which relates to our ability to properly use SW.

                                                    I have to applaud Maha Nadarasa for his desire to have all kinds of questions answered. Sometimes I think he needs to vet the youtube videos he looks at better, but he apparently is at a place where he has the opportunity to increase his knowledge and he is doing that rather than focusing on Call of Duty.

                                                • Re: Question
                                                  Vladimir Urazhdin

                                                  This is the question I have myself: what is the reason to ask people very simple questions if the answer is just one click away in Google and/or in any engineering textbook?

                                                    • Re: Question
                                                      Jim Steinmeyer

                                                      I must admit that is a good question. And I see where you are going. Not totally incorrect. Sometimes we need to dig for the answers for a while first before asking.

                                                           Of course some people look at asking a question on a forum to being on the same level as using Google with the exception that you may have built up a respect for the knowledge of some of the people on a forum where any old Joe can post something that shows up on Google (or make a youtube video ). And I often find myself asking for someone to point me towards a standard or textbook so I can read up on a topic when I don't know what textbook to look to. That is why I suggested the Machinery's Handbook as a good source for this information.

                                                      • Re: Question
                                                        S. Casale

                                                        You know, I like the forums because I can receive answers. Sometimes I receive the exact correct one, sometimes not. Sometimes I receive insight in how to accomplish something in a way that I may not have thought of, or should have been doing in the first place. Sometimes I receive answer that are absurd.

                                                         

                                                        However, whether the answers are incorrect, almost there, close, close-enough, or correct in a way, exactly correct. I can honestly write that I've received a better insight on how to do something on the forums a lot of the time.

                                              • Re: Question
                                                Paul Risley

                                                This is a standard style question of which I ask candidates for internship here. It is not that they have to memorize a table. It is can you open your machinery handbook, then find and apply the appropriate fits to 2 mated parts.

                                                 

                                                This is related to solidworks in the fact that drawing a picture on your screen is not good enough. What you draw has to be made by someone and there are other parts that will need to work with it.

                                                 

                                                It is a basic question regarding the understanding of mechanics and how to apply them at a project level.

                                                 

                                                If we have a machine with 15 operation stations and I have a designer working on 1 station I don't want him coming over and asking me every 15 minutes on how to apply fits between a shaft and a hole. I want them to be able to take the criteria for the job (shaft diameters, load applied, length of motion etc...) & calculate what the fits are and where and how to apply them.

                                                 

                                                Just like I expect someone coming in as an intern to be able to detail a shaft with the input of what the fitment is to apply tolerancing to the print to get the part made correctly.(Which is in essence what this question was) You were given the basics(what type of fit and nominal size).

                                                  • Re: Job ad Question
                                                    Nick Hallworth

                                                    I'd agree that this is a really good interview question, and shows that the design engineer has a grounding in what information he/she needs to have to hand in order to design the different types of fits.

                                                     

                                                    On a similar theme I have been asked previously to describe/explain what particular geometric tolerancing symbols mean and how they should be applied.

                                                  • Re: Question
                                                    Paul Risley

                                                    Jim Steinmeyer that is what my earlier post was referring to. We require new designers and interns to utilize the machinery handbook. If a question arises about a design or drawing I don't want to hear let me find the google answer I found earlier. Just show me which page in the handbook you used to derive the information.

                                                     

                                                    As for the original question, if it was a take home application then google would be the answer most people would utilize I am sure. Our questions during the interview process revolve around in person and written problems that are answered in our office to see that the candidate has the aptitude to utilize the handbook. (We do not require memorization)  Just can you use the handbook to find the answers you need to do the job. 

                                                      • Re: Question
                                                        Christian Chu
                                                        We require new designers and interns to utilize the machinery handbook. If a question arises about a design or drawing I don't want to hear let me find the google answer I found earlier. Just show me which page in the handbook you used to derive the information.

                                                        Not sure what page?

                                                      • Re: Question
                                                        J. Mather

                                                        So -

                                                        there has been a long discussion on the topic.

                                                         

                                                        Now, could you do the job.

                                                        Create a simple block with hole sized and toleranced as specified in your original post?

                                                        Create a simple cylinder sized and toleranced as specified in your original post?

                                                        Attach the assembly and *.slddrw detail drawing here.

                                                        Answer question on min/max clearance between the parts.

                                                          • Re: Question
                                                            Jim Steinmeyer

                                                            Spoken like a true teacher. "Let's see the application of the knowledge."

                                                            • Re: Question
                                                              Maha Nadarasa

                                                              Thank you very much for volunteering help.

                                                               

                                                              I haven’t been told to buy any book yet in the class. Any how I am more comfortable with online resources only. I buy e-books only. Because it is very versatile. You can zoom-in, zoom-out, can jump into a chapter and search option also there.   

                                                               

                                                              In this question hole diameter is given (8mm) & talking about hole tolerance & clearance, therefore I assumed that hole is with nominal diameter (8.000 ± 0.040) according chart given by Dan Pihlaja. Shaft diameter is not given in the question. Therefore I decided to calculate it.

                                                               

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                                                            • Re: Question
                                                              Dave Bear

                                                              My only gripe here (if any) would be that the post was only headed "Question" and could have been more descriptive perhaps, but that's just me, nothing major. Maha loves sucking in information and that's a good thing, probably could have gone a few different tutorial routes but each to their own.

                                                               

                                                              Dave.

                                                              • Re: Job ad Question
                                                                Doug Seibel

                                                                Per the Machinery's Handbook, a "Free Running Fit" is also referred to as a "Class RC 7" fit.

                                                                 

                                                                Clearance between parts of .0016" - .0039"

                                                                 

                                                                Hole tolerance of +.0014" / -0.000

                                                                 

                                                                Shaft tolerance of -.0016" / -.0025"

                                                                 

                                                                 

                                                                The question is a challenging question in that it tests whether or not a person has the knowledge or motivation to get the answer.  There are many that have the knowledge...they are worth considering when hiring.  There are many that may not have the knowledge, but they do have the motivation/resourcefulness to find the answer...they are worth considering when hiring.  There are those that lack both the knowledge and the motivation...they are not worth hiring.  One "unchallenging" question cuts straight to one of the most important issues..."is this applicant even worth considering".

                                                                • Re: Job ad Question
                                                                  Timothy Taby

                                                                  I like the idea of asking something technical on a application like this.  Right off the bat you know if the person is worth even talking to or has no clue what they are doing when it come to basic engineering information.

                                                                   

                                                                  I have it as the third tab on my book (under fits)

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