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:

http://www.chriswilson.tv/cap.jpg

On 11/20/2011 12:29 PM, Chris Wilson wrote:
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:

http://www.chriswilson.tv/cap.jpg


http://www.engineersedge.com/manufac...olt-circle.htm

cheers
T.Alan

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
...

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:

http://www.chriswilson.tv/cap.jpg

"Chris Wilson" wrote in message
...
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. ...

Make five pointed pins that fit the holes snugly, place the wrench blank
over them and tap around it to center-punch the hole locations. Or make one
pointed pin and mark, drill and insert the wrench pins sequentially.

If you don't have a lathe the mill can serve for short pieces of stock that
fit a collet. Hold the lathe bit in the vise.

jsw