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Machining troubles (i dont know how to be less ambigous)

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  • #16
    Personally, I'd drill the holes on the coordinates, even if I didn't have a DRO. As others have pointed out, a 4-hole circle is dead-simple.

    For those of you who don't have a bolt-circle function on their DROs (like me), Machinery's Handbook has tables of coordinates. Look in the Jig Borer chapter, it's near the front in my 22nd Edition. As long as you're paying attention, the bolt holes will line up perfectly every time. The tables go up to 28 holes.

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    • #17
      Dear Fasttrack

      When I was making my own replacement dials for my old Atlas lathe, I used the face plate as a pretty accurate indexing plate. you can lay out 90 degree lines using the existing axes for bolt holes, or you can divide up the circumference using a trip of paper taped to the edge. Didn't believe I or the lathe could do it, and it was so easy and so (for me) accurate I was amazed. Many bull gears are also pre drilled for indexing, my one is already divided into 60, with a special detente pin to lock in the setting. The bigger the circle you are using for this, the more accurate your spacing is going to be. If you'll excuse the terrible pun, there's no real need to re-invent the wheel :-) Good luck!
      Richard in Los Angeles

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      • #18
        Dear Fastrack
        Sorry, but with my 'brilliant' advice was only worth something assuming you had a lathe? Doesn't everybody? Only a mill?
        Richard in Los Angeles

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        • #19
          Bob has it,use the gear itself to index the holes.The one pictured counts as 36 teeth,36/4+9,every 9th space you have a hole.
          I just need one more tool,just one!

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          • #20
            I think the gear idea is the way i'll be going!

            "Personally, I'd drill the holes on the coordinates, even if I didn't have a DRO. As others have pointed out, a 4-hole circle is dead-simple."

            Thats exactly why i picked four holes instead of five or three. I figured, since it is four holes spaced 90* apart, and the y axis and x axis move perpindicular to each other, it would be super easy. Like i said, the first one went off fine with out a hitch. The second one - well it wasnt so hot. I think maybe i didn't have my spacing from the center the same for each hole. I can't figure out how i screwed up the 90* otherwise because it stayed in the vise the whole time.

            What i did was put a little divit in the center of the hub/spool to be drilled. I then used a v-block to hold it in the vise, used a transfer punch in my drill chuck (which has a surprising amount of run-out in it ... ) and then moved the carriage the radius i wanted to drill away from the center. After drilling this hole, i returned to the center and moved the carriage the opposite direction the same radius. Then, i returned to the center again and moved out, this time in the y direction, the radius i wanted to drill. Needless to say it took awhile with all the changing from bit to transfer punch.

            I think maybe that the run-out in the chuck had something to do with it. My spindle wasn't always centered on the work depending upon how my chuck was oriented. That would throw the distance from the center that my holes were. I think thats where my problem was.

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            • #21
              Originally posted by topct
              Fastrack,

              I would have used an existing transmission.

              I know it would not be as much fun, but accuratly duplicating the shaft centers on some plates to hold it together and figuring out some kind of clutch would still be quite an exersize.

              And you would not be wasting your time trying to reinvent the wheel.

              If i actually needed a mini-bike for some reason - i would have made a serious attempt at finding an exsisting tranny. I've got my truck to work on and a pretty fast go-kart to have fun on so this is just one of those "lets see if i can do it" projects.

              The clutch i'll be using is actually a centrifugal clutch salvaged from an old go-kart (and salvaged is the right word because it was all screwed up, but a bit of machining and creativity and i had something to mount on my lawnmower engine that will feed into the tranny. The release and engage time on a centrifugal clutch wont be as hot as a normal one so i'll have to put up with some soggy shifts as i take it out of gear and wait for the clutch to disengage to put it back in gear...)

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              • #22
                If your using the mill ,then setup a DTI and use it to positon the table instead of the dials.Far more accurate and it doesn't matter if you lash out the table or not before a move.
                I just need one more tool,just one!

                Comment


                • #23
                  Degree Wheel

                  Originally posted by RPM
                  When I was making my own replacement dials for my old Atlas lathe, I used the face plate as a pretty accurate indexing plate. you can lay out 90 degree lines using the existing axes for bolt holes, or you can divide up the circumference using a trip of paper taped to the edge. Didn't believe I or the lathe could do it, and it was so easy and so (for me) accurate I was amazed. Many bull gears are also pre drilled for indexing, my one is already divided into 60, with a special detente pin to lock in the setting. The bigger the circle you are using for this, the more accurate your spacing is going to be. If you'll excuse the terrible pun, there's no real need to re-invent the wheel :-) Good luck!
                  Richard in Los Angeles
                  I did kind of the same thing. Used my CAD program to draw a circle the size of a CD-Rom, and then used the divide(?) function to automatically make degree lines/marks all the around the circle every 5 deg or so, added some text numbers, printed it out and glued to the CD, and my very own degree wheel.
                  Retired - Journeyman Refrigeration Pipefitter - Master Electrician - Fine Line Automation CNC 4x4 Router

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                  • #24
                    Heh; uh what's a DTI? dial indicator...?

                    man i feel dumb lol

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                    • #25
                      Sounds like the part was not indicated properly before the pattern was drilled. Indicate each before drilling. If you were off center it can cause eccentric movement of the holes when you rotate.

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                      • #26
                        Originally posted by Fasttrack
                        Heh; uh what's a DTI? dial indicator...?

                        man i feel dumb lol
                        Yup,infact I keep a couple 2" throw indicators around just for that purpose.
                        I just need one more tool,just one!

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                        • #27
                          Dial Test Indicator?

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                          • #28
                            A DTI is a dial test indicator, but is not the right tool for the job. I was going to say a dial travel indicator was the correct instrument but a quick look in the MSC catalog lists them as dial indicators, available with up to 5 inches of travel. A caliper could also be used if you can set up a fixed stop to measure from.
                            North Central Arkansas

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                            • #29
                              "Sounds like the part was not indicated properly before the pattern was drilled. Indicate each before drilling. If you were off center it can cause eccentric movement of the holes when you rotate."


                              Rotated? I didn't rotate anything - left it clamped in the vise the whole time...



                              My dial indicator only measures .5" of travel but has a .0001 resolution. I was wondering about using a magnetic base and some kind of clamp on the table to make two fixed points to measure with a caliper. Not sure how accurate this would be though. Any thoughts?

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                              • #30
                                Originally posted by Fasttrack
                                "Sounds like the part was not indicated properly before the pattern was drilled. Indicate each before drilling. If you were off center it can cause eccentric movement of the holes when you rotate."


                                Rotated? I didn't rotate anything - left it clamped in the vise the whole time...



                                My dial indicator only measures .5" of travel but has a .0001 resolution. I was wondering about using a magnetic base and some kind of clamp on the table to make two fixed points to measure with a caliper. Not sure how accurate this would be though. Any thoughts?
                                ulav8r has it,make up a set of clamps for the mill table to hold your calipers.One clamp fixed to the table the other to the saddle.It will work like a primative DRO keeping track of table position by direct measurement.

                                Just make sure if the mill's travel is greater than the caliper's to remove the caliper before running the table down
                                I just need one more tool,just one!

                                Comment

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