Announcement

Collapse
No announcement yet.

Bolt circles with mill and DRO????

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Bolt circles with mill and DRO????

    Hey guys! I've just finished the last of the bolt circles for a project. Did them all on my lathe indexer.
    With a lathe you are limited to the swing size. With a mill you could do much bigger circles.
    Some of you have mentioned doing these with a DRO.
    I'm assuming you use bolt pattern formulas for the movement of the positions around the circle.
    Would you start in the center, go out to your first hole and continue around or do you do holes directly across from each other (on an even numbered pattern)and then position for the next one and go across to the opposite side again?
    I'm betting you could do some pretty large stuff on a mill with some imagination. Thanks!
    Russ
    I have tools I don't even know I own...

  • #2
    Drilling bolt holes with a DRO is great... I made a sprocket using a Bridgeport and a DRO, and a simple Sprocket program I wrote that just printed out a list of X,Y positions that I used to make this sprocket:



    Just make sure you move to your X,Y position, then lock the table in X/Y, drill, unlock and continue to your next hole.

    -Adrian

    Comment


    • #3
      this pipe flange was to big to use a dro

      I would have loved to not haul that heavy table with a 10" chuck onto the mill, then put that 25" x 1" plate circle on top of that. (as you can see I was too lazy to pull the vice)

      Comment


      • #4
        Nice stuff guys! Makes the price of a DRO look a little better when I see that.
        Ha, it also reminds me that I need to mount the chuck on my rotary table.
        I have tools I don't even know I own...

        Comment


        • #5
          Sorry to jump at you Tattoo, but here's a lesson for milling machine users to draw from.

          Look in Tattoo's photo how he's loading his Bridgeport table and saddle with all that weight off to one side. The overhung weight puts a big strain on the saddle dovetails. Dovetails don't like eccentric loading. The overhung weight trys to pry open the DT's producing unit loads far higher than a casual guess you estimate.

          That's why turret mills have the turret and ram - so you can center heavy table loads and move the head almost anyplace you need to in the work envelope. If in Tattoo's example you swing the turret over about 10" and extend it a bit you can put all that weight over the saddle. With the weight centered you can do all your machine work and drilling off to one side.

          I know Tattoo isn't moving the table or the saddle around much to drill and bore that hole circle but eccentric loading of a light duty machine is a bad habit to get into.

          I watched a BP worn to a rattling frazzle in less than 7 years thanks to eccentric loading from boring hydrant silver braze preps on a 10" 4 way fire main casting. The machine was practically dedicated to this job because of the swivel and knuckle of the head. They put a 15" K&T rotary table on the center of the table, then plunked that 200+ lb hydrant casting down on it for indexing the 4 nozzles. They dialed off center (almost to the end of the table travel) to get at the nozzle with the head tipped 45 degrees.

          On swingshift one weekend I took over the job, worked out the solid trig so the load was centered over the knee. Then I swiveled the turret to the right and tweaked the nod and tilt to produce the 45 degree boring axis along the table needed to bore the hydrant nozzle. Next time I saw the machine it was restored to the original way-off center set-up and the guy who "owned" the machine glared at me for daring to disturb his perfect set-up. What can you do?

          After a few years of this abuse you could snug the table clamp and jerk the table ends by hand to get VISIBLE rotation about the yaw axis as you listened to the oil slurp in the dovetails. How do I know all this? I'm the guy who did the machine work to rebuild it. After machining and scraping it took a 0.063 shim behind the table gib to restore it to adjustability.

          [This message has been edited by Forrest Addy (edited 04-25-2005).]

          Comment


          • #6
            Russ most of the better DRO's have bolt circle programs built in.You can start from one edge of a part or the center of the pattern.

            Shop down the street had an Accurite that would do any count up to 199 holes.Real nice if you need to make the odd indexing plate for the dividing head.

            Forrest,glad you brought that up,I agree several places I have seen the knee load on a b-port is supposed to be limited to 150lbs.

            A 6" mill vice takes up half of that so your left with 75lbs usable limit.Once and awhile if the load is centered doesn't hurt much.But if it's a day in day out job I was taught to use a bigger mill.
            I just need one more tool,just one!

            Comment


            • #7
              Answering your question.

              x coordinate = sin((#/n) x 360) x rBC

              y coordinate = Cos((#/n) x 360) x rBC

              # = the hole number you're working on

              n = total number of holes

              rBC = the bolt circle radius

              It's best to work out a spreadsheet in MS Works or equivalent and print a list of coordinates. If you're handier with a calculator then use the trig functions etc to make a list of hole coordinates. Hole circles evenly divisible by 4 require a list only for the first quadrant. By 2 requires the first semi-circle. By 1 requires a full circle's worth of numbers.

              Make the coordiante table at your liesure where you usually do your paperwork not at the machine where there's no surface to sketch and draw on.

              The next trick is to dial off the coordinates with out transposing a two digits, dialing off an x for one hole then the y for the next hole down, and similar blunders which my scrap bin has concealed at one time or another.

              Comment


              • #8
                Forrest,

                Or the mathematically challenged can download BOLTCIRC from my page and use it
                to produce a printable file that looks like:

                ---------------------------
                Boltcircle specification:
                Radius of bolt circle = 1.0000
                Bolt hole diameter = 0.5000
                Spacing between hole edges = 0.6756
                Angular offset of first hole = 0.0000 deg
                X offset of bolt circle center = 0.0000
                Y offset of bolt circle center = 0.0000

                HOLE ANGLE X-COORD Y-COORD

                1 0.0000 1.0000 0.0000
                2 72.0000 0.3090 0.9511
                3 144.0000 -0.8090 0.5878
                4 216.0000 -0.8090 -0.5878
                5 288.0000 0.3090 -0.9511
                ---------------------------

                Regards, Marv

                Home Shop Freeware - Tools for People Who Build Things
                http://www.geocities.com/mklotz.geo
                Regards, Marv

                Home Shop Freeware - Tools for People Who Build Things
                http://www.myvirtualnetwork.com/mklotz

                Location: LA, CA, USA

                Comment


                • #9
                  <font face="Verdana, Arial" size="2">Originally posted by Forrest Addy:
                  Answering your question.

                  x coordinate = sin((#/n) x 360) x rBC

                  y coordinate = Cos((#/n) x 360) x rBC

                  # = the hole number you're working on

                  n = total number of holes

                  rBC = the bolt circle radius

                  It's best to work out a spreadsheet in MS Works or equivalent and print a list of coordinates. If you're handier with a calculator then use the trig functions etc to make a list of hole coordinates. Hole circles evenly divisible by 4 require a list only for the first quadrant. By 2 requires the first semi-circle. By 1 requires a full circle's worth of numbers.

                  Make the coordiante table at your liesure where you usually do your paperwork not at the machine where there's no surface to sketch and draw on.

                  The next trick is to dial off the coordinates with out transposing a two digits, dialing off an x for one hole then the y for the next hole down, and similar blunders which my scrap bin has concealed at one time or another.
                  </font>

                  Actually, your equations are completely wrong...

                  Here is the correct equation:

                  PI = 3.1415926

                  thetaDelta = ((PI * 2) / numberOfHoles)

                  X position = Cos(n * thetaDelta) * radius
                  Y position = Sin(n * thetaDelta) * radius

                  Where n equals 0 to numberOfHoles-1 and radius is diameter of your hole pattern divided by 2.

                  For additional information, and an example, you can see my sprocket/bolt hole program here:

                  http://bbssystem.com/viewtopic.php?t=148

                  -Adrian

                  Comment


                  • #10
                    Forrest Addy you are 100% right. I did have a dead man and screw jack under the table before the picture (I was tearing it down)

                    that machine is bigger than it looks (10x50 table), it get all kinds of stuff that makes that look like nothing , big cat parts, 1" keys in rock crusher shafts, motor blocks, big machine walking beams,saw mill head shafts.(things im sure you have done too)

                    It is our "beater" mill, every shop needs one. we need to drag it over to the welding side of the shop and let it be the welders drill press.

                    Comment


                    • #11
                      Russ,

                      As Weird mentioned, see if your DRO has the bolthole program. My Accurite does. All you do is center the part, input the hole radius & number of holes, and follow the DRO to zero-zero.

                      I usually start the first hole at three o'clock (directly right of dead center by an amount equal to the radius of the circle). There are other options in the program.

                      Takes a lot longer to dial in the center than it does to program the pattern.

                      ------------------
                      Barry Milton
                      Barry Milton

                      Comment


                      • #12
                        <font face="Verdana, Arial" size="2">Originally posted by 3 Phase Lightbulb:

                        Actually, your equations are completely wrong...

                        Here is the correct equation:

                        PI = 3.1415926

                        thetaDelta = ((PI * 2) / numberOfHoles)

                        X position = Cos(n * thetaDelta) * radius
                        Y position = Sin(n * thetaDelta) * radius

                        Where n equals 0 to numberOfHoles-1 and radius is diameter of your hole pattern divided by 2.

                        For additional information, and an example, you can see my sprocket/bolt hole program here:

                        http://bbssystem.com/viewtopic.php?t=148

                        -Adrian
                        </font>
                        Forrest's equations are sound. You converted the angle to radians with the 2pi, then back again by muliplying by the radius. That's appropriate because your C program uses the math.h library, whose trig functions take radian arguments.

                        Forrest used degrees (#/n * 360 = degrees of the angle), which is much more appropriate for folks using pocket calculators and/or spreadsheets.



                        [This message has been edited by rfrey (edited 04-25-2005).]

                        Comment


                        • #13
                          That REALLY makes me appreciate the bolthole program.
                          Barry Milton

                          Comment


                          • #14
                            <font face="Verdana, Arial" size="2">Originally posted by wierdscience:
                            Russ most of the better DRO's have bolt circle programs built in.</font>
                            weird...That's why I asked the question. I'm starting to figure out the milling machine package I want and was not even aware that there where programs built into the DRO's. I guess yer sayin to let a few more moths out of the ol' wallet huh? (quite a few more actually...lol!)

                            Barry, I think I likey the bolt hole program now also!
                            Thanks for ALL the info guys! I'm starting to see a DRO as a must, MUST have now!
                            Russ

                            I have tools I don't even know I own...

                            Comment


                            • #15
                              Machinery's handbook has bolt circle tables which you might find helpful. Personally, I'd either calculate them, or work them out on Mastercam.

                              Comment

                              Working...
                              X