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Calculating bolt hole circles?

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  • Calculating bolt hole circles?

    Is there a quick and easy way or a website to find the x-y dimensions from 0 center of a bolt hole pattern? Thanks.

  • #2
    Check your "Machinery's Handbook"


    • #3
      Here ya go, just, just put your info in and hit calculate.....

      Last edited by metalmole; 12-31-2012, 08:52 PM.


      • #4
        Or here:

        Marv Klotz Web Page

        It's a few down from the top called "BOLTCIRC.ZIP"



        • #5
          May as well toss my hat into the ring:


          • #6
            Maybe a bit facetious? A Newall DP900 along with almost any other DRO will do it with a few key strokes, You did ask for quick and easy. Machinery's Handbook is my second choice only because I'm too computer stupid to figure out how to get Marv's programs to work for me.



            • #7
              i have a dro that does the calculation for me, works great ... some times i forget and put in numbers IE for 6 holes for 360degrees which actully results in 5 holes ,(0 degrees and 360 is the same hole
              ive scored a circle in to the part and sectioned it for 1/4 the of the circle , protractor score the holes i want then with vernier score a grid from a square fixed edge , done well id think the holes would be with in a few thou's


              • #8
                Here's the one I use:


                • #9
                  x = r*cos(angle)
                  y = r*sin(angle)

                  r = radius of bolt circle
                  angle = angle of hole with respect to the x-axis
                  "The truth is incontrovertible, malice may attack it, ignorance may deride it, but in the end; there it is." Winston Churchill


                  • #10
                    I just wrote a macro for my CAD program that draws them. These drawings took less than a minute each to make. It took me longer to convert them to black on white and JPEG file format for display.

                    The top shows a 4" bolt hole circle with seven 1/2" diameter holes and the first hole at 270 degrees. I just input the numbers with keyboard or mouse and then click on the center of the circle. A few seconds later it is done. I can use any diameters, any number of bolt holes, and any angle to the first hole. The cross hairs allow dimensions to be snapped to the hole centers: it would take more time to add all the dimensions than it took to draw the bolt hole circle but if I did, it would be spot on to better than tenths.

                    The bottom half shows some fun I have when I input ridiculous parameters. Hole diameter greater than the circle diameter and severely overlapping holes.

                    Here is another fun drawing with wild parameters. These two have 100 overlapping circles.

                    CAD is fun.
                    Paul A.
                    SE Texas

                    Make it fit.
                    You can't win and there is a penalty for trying!


                    • #11
                      My DRO does it in less than a minute too. And displays each of the coordinates as well.
                      Doesn't have the "Spirograph" function though.


                      • #12
                        I have a "Machinists calculator" phone app that does bolt circles.....


                        • #13
                          "Machinists' Journeyman" app for iphone works well.
                          John Burchett
                          in Byng OK


                          • #14
                            Do a search for Bolt Circle Calculations and you'll find an online app that works great.

                            My DRO doesn't have the B.C. function, and the Machinery's Handbook method is tedious, albeit workable. FYI: it's under "Jig Borer".


                            • #15
                              Thanks for the replies and links, they will work well. Happy New Years to all.