If the central shaft is far enough out of the way, use a pair of calipers to measure the distance between two adjacent pin holes. Use the inside jaws then the outside jaws and average the readings to get center to center, or use the inside jaws and measure the dia of one hole (less accurate because it's hard get the dia of a small hole accurately). If the shaft is in the way and you have roll pins that fit tightly just put them in and measure from the side, again measure inside and outside and average. Once you know the center to center distance of the holes and the fact that they form a pentagon you can calculate the x and y coordinates of all five holes and the coordinates of the central hole, and then use your dro to go to each x,y position and drill. Easiest way is to draw it in a cad program, or dust off your trig skills and remember that each internal angle of a pentagon is 108 degrees. I don't have a cad program here at home but the Redskins are finding another way to lose to the Cowboys so I'll work on the trig a little :-(. Oops, just checked and the Redskins scored a td to tie with 14 sec left so this may take a little longer :-). Anyway, I'm going to call the distance between adjacent holes that you measure S, locate the first hole at (x,y)=(0,0), and the second hole at (S,0). The third hole going counterclockwise will be at (S+S*cos(72), S*sin(72)). The fourth hole lands at (S/2, S*sin(72)+S*cos(72)), and the fifth hole is at (-S*cos(72), S*sin(72)). cos(72)=0.3090 and sin(72)=0.9511, and for illustration purposes if you measure 30 mm for S the holes will be at (0,0), (30,0), (39.27,28.53), (15,37.80), (-9.27,28.53). I'll leave the central hole as an exercise for the reader :-). Hope I got all that right, got to go watch the rest of the game.
----- Regards, Carl Ijames "Chris Wilson" wrote in message news:19oacb1kmugp9$. snipped-for-privacy@40tude.net...
I have a Bridgeport milling machine with a DRO that is basically wasted on me, to be honest. I have been asked by a good friend to help him out, and am now well out of my depth. He has an automotive dampweer (shock absorber) that I need to dismantle. The cap of the main tube is an externally threaded insert with five equi distant holes atop it for a pin spanner on a PCD a little less than 50 mm which is roughly the OD of the insert. In other words the holes are very near the OD of the female plug. The thing is tight in the tube, tapping with a punch won't shift it, nor will two roll pins in adjacent hooles, with a leverage bar. I need to make a proper tool out of say a .25 inch plate with a central hole to go around the shaft of the damper, and five equi distant pins to engege the holes in the cap. How, given the shaft of the damper is in the way, do I get the PCD of the holes, plus, how in idiot's terms, do I use the DRO on the Bridgeport, to a drill central hole in a piece of .25 plate (easy) to go around the shaft of the dmper, and then use its readout to set the drill chuck to drill the 3 mm holes arond this central hole to allow me to insert pins in the bar to engage the 5 holes in the cap to allow the best purchase to undo this thing? Thanks. link to crude drawing of the problem below:
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