Outside Diameter on constructed circle

[Buckeye]

Need some help on this one...

I am rewriting the program to qualify a gage used to check gears. The old gage had a large diameter ring that fit into the gear to locate it. the new one uses several pins around the diameter to locate it. I have measured the pins and constructed the circle, but I cannot figure out how to report the outside diameter. The constructed circle reports the diameter of the circle created through the centers of the circles.

Example.
Old gage had a large ring 158.15mm in diameter.
New gage has 4 pins in a circle, each 6.35mm in diameter. The constructed circle reports roughly 151.8mm. I need the diameter of the circle created from the outside of the pins (the smallest hole that would fit over the pins).

Any ideas?

[Matthew D. Hoedeman]

If the pins are al the same size, simply add it to the constructed circle's diameter, if the pins are 6.36mm in diameter, make a generic circle and add 6.35 to the diameter of the constructed circle.

[Don Ruggieri]

If you are using 3 pins, there is an option in the circle construction dialog to specify the method of construction as "Tangent 3 circles" which should give you the outer diameter.

[dwade]

The correct way would be to measure each pin, origin, then measure a point on the corresponding "outside" surface of each pin relative to the pin at X=0/Y=0 then construct your circle from that. This would pick any wear on the surface of the pins but if you want quick and dirty just measuring the pin diameters the code below works.

Duane

CIR1       =AUTO/CIRCLE,SHOWALLPARAMS = YES,SHOWHITS = NO
            THEO/75.9,0,0,0,0,1,6.35,0
            ACTL/75.9,0,0,0,0,1,6.35,0
            TARG/75.9,0,0,0,0,1
            THEO_THICKNESS = 0,RECT,OUT,CIRCULAR,LEAST_SQR,ONERROR = NO,$
            AUTO MOVE = NO,DISTANCE = 6,RMEAS = None,None,None,$
            READ POS = NO,FIND HOLE = NO,REMEASURE = NO,$
            NUMHITS = 4,INIT = 0,PERM = 0,SPACER = 0,PITCH = 0,$
            START ANG = 45,END ANG = 45,DEPTH = 0.25,$
            ANGLE VEC = 1,0,0
CIR2       =AUTO/CIRCLE,SHOWALLPARAMS = YES,SHOWHITS = NO
            THEO/0,75.9,0,0,0,1,6.35,0
            ACTL/0,75.9,0,0,0,1,6.35,0
            TARG/0,75.9,0,0,0,1
            THEO_THICKNESS = 0,RECT,OUT,CIRCULAR,LEAST_SQR,ONERROR = NO,$
            AUTO MOVE = NO,DISTANCE = 6,RMEAS = None,None,None,$
            READ POS = NO,FIND HOLE = NO,REMEASURE = NO,$
            NUMHITS = 4,INIT = 0,PERM = 0,SPACER = 0,PITCH = 0,$
            START ANG = 45,END ANG = 45,DEPTH = 0.25,$
            ANGLE VEC = 1,0,0
CIR3       =AUTO/CIRCLE,SHOWALLPARAMS = YES,SHOWHITS = NO
            THEO/-75.9,0,0,0,0,1,6.35,0
            ACTL/-75.9,0,0,0,0,1,6.35,0
            TARG/-75.9,0,0,0,0,1
            THEO_THICKNESS = 0,RECT,OUT,CIRCULAR,LEAST_SQR,ONERROR = NO,$
            AUTO MOVE = NO,DISTANCE = 6,RMEAS = None,None,None,$
            READ POS = NO,FIND HOLE = NO,REMEASURE = NO,$
            NUMHITS = 4,INIT = 0,PERM = 0,SPACER = 0,PITCH = 0,$
            START ANG = 45,END ANG = 45,DEPTH = 0.25,$
            ANGLE VEC = 1,0,0
CIR4       =AUTO/CIRCLE,SHOWALLPARAMS = YES,SHOWHITS = NO
            THEO/0,-75.9,0,0,0,1,6.35,0
            ACTL/0,-75.9,0,0,0,1,6.35,0
            TARG/0,-75.9,0,0,0,1
            THEO_THICKNESS = 0,RECT,OUT,CIRCULAR,LEAST_SQR,ONERROR = NO,$
            AUTO MOVE = NO,DISTANCE = 6,RMEAS = None,None,None,$
            READ POS = NO,FIND HOLE = NO,REMEASURE = NO,$
            NUMHITS = 4,INIT = 0,PERM = 0,SPACER = 0,PITCH = 0,$
            START ANG = 45,END ANG = 45,DEPTH = 0.25,$
            ANGLE VEC = 1,0,0
            ASSIGN/V1 = CIR1.X+(CIR1.DIAM/2)
            ASSIGN/V2 = CIR2.Y+(CIR2.DIAM/2)
            ASSIGN/V3 = CIR3.X-(CIR3.DIAM/2)
            ASSIGN/V4 = CIR4.Y-(CIR2.DIAM/2)
F1         =GENERIC/POINT,DEPENDENT,RECT,$
            NOM/XYZ,79.075,0,0,$
            MEAS/XYZ,V1,0,0,$
            NOM/IJK,0,0,1,$
            MEAS/IJK,0,0,1
F2         =GENERIC/POINT,DEPENDENT,RECT,$
            NOM/XYZ,0,79.075,0,$
            MEAS/XYZ,0,V2,0,$
            NOM/IJK,0,0,1,$
            MEAS/IJK,0,0,1
F3         =GENERIC/POINT,DEPENDENT,RECT,$
            NOM/XYZ,-79.075,0,0,$
            MEAS/XYZ,V3,0,0,$
            NOM/IJK,0,0,1,$
            MEAS/IJK,0,0,1
F4         =GENERIC/POINT,DEPENDENT,RECT,$
            NOM/XYZ,0,-79.075,0,$
            MEAS/XYZ,0,V4,0,$
            NOM/IJK,0,0,1,$
            MEAS/IJK,0,0,1
CIR5       =FEAT/CIRCLE,RECT,OUT,LEAST_SQR
            THEO/0,0,0,0,0,1,158.15
            ACTL/0,0,0,0,0,1,158.15
            CONSTR/CIRCLE,BF,F1,F2,F3,F4,,
            OUTLIER_REMOVAL/OFF,3
            FILTER/OFF,UPR=0

[Buckeye]

Can you do this with 4 circles?

[cmmguy]

4 pins suck for locating a feature, as does three, 2 are correct.

The other problem is that if the pins are not of equal size and the locations are not perfectly correct, the contact points are not tangent to the calculated circle.

So....
If diameters and locations are resonable correct, and you dont want to write code(assignments, generic features, etc...) then:

Measure all four pins.
Construct circle from their centers.
Construct lines from all four pin diameters to the constructed circle.
Construct point by intersection of each line and corresponding pin diameter.(you want the outer point)
Construct circle from the four intersection points.

[Buckeye]

I agree that 4 pins suck, but that is the way the gage was made.

In any case, the intersecting lines looks like the easiest, however, I just realized the drawing is missing some of the key dimensions, so I will have to table it until Engineering gets the rest of the dimensions.

[philwell]

Need some help on this one...

I am rewriting the program to qualify a gage used to check gears. The old gage had a large diameter ring that fit into the gear to locate it. the new one uses several pins around the diameter to locate it. I have measured the pins and constructed the circle, but I cannot figure out how to report the outside diameter. The constructed circle reports the diameter of the circle created through the centers of the circles.

Example.
Old gage had a large ring 158.15mm in diameter.
New gage has 4 pins in a circle, each 6.35mm in diameter. The constructed circle reports roughly 151.8mm. I need the diameter of the circle created from the outside of the pins (the smallest hole that would fit over the pins).

Any ideas?

I would hate to base my rep. as and QA professional on the gage that you describe. Even if the gage is for internal use only I ask who ever dictating that you use such a gage sign off on the dimensions’ from it use.

[JEFMAN]

If you have three or more pins, you can create a circle(CE7) with centers of pins, create an alignment (REF2) on this circle, and then execute a loop like this (6 circles in the example) :

CE7 =FEAT/CIRCLE,CARTESIAN,OUT,LEAST_SQR,NO
THEO/<509.9244,-1.9255,-5>,<0,0,1>,169.9675
ACTL/<509.9244,-1.9255,-5>,<0,0,1>,169.9675
CONSTR/CIRCLE,BF,CE1,CE2,CE3,CE4,CE5,CE6,,
OUTLIER_REMOVAL/OFF,3
FILTER/OFF,UPR=0
REF2 =ALIGNMENT/START,RECALL:REF1,LIST=YES
ALIGNMENT/TRANS,XAXIS,CE7
ALIGNMENT/TRANS,YAXIS,CE7
ALIGNMENT/END
ASSIGN/I = 1
VAR10 =LOOP/START, ID = YES, NUMBER = 6, START = 1, SKIP = ,
OFFSET: XAXIS = 0, YAXIS = 0, ZAXIS = 0, ANGLE = 0
ASSIGN/CEI = "CE"+I
ASSIGN/VAR_X = CEI.X+CEI.R*COS(DEG2RAD(CEI.PA))
ASSIGN/VAR_Y = CEI.Y+CEI.R*SIN(DEG2RAD(CEI.PA))
ASSIGN/VAR_Z = CEI.Z
POINT_I =GENERIC/POINT,DEPENDENT,CARTESIAN,$
NOM/XYZ,<VAR_X,VAR_Y,VAR_Z>,$
MEAS/XYZ,<VAR_X,VAR_Y,VAR_Z>,$
NOM/IJK,<0,0,1>,$
MEAS/IJK,<0,0,1>
ASSIGN/I = I+1
LOOP/END
CE8 =FEAT/CIRCLE,CARTESIAN,OUT,MIN_CIRCSC,NO
THEO/<0,0,-5>,<0,0,1>,179
ACTL/<-0.0019,0.0006,-5.>,<0,0,1>,178.9383
CONSTR/CIRCLE,BF,POINT_I[1..6],,
OUTLIER_REMOVAL/OFF,3
FILTER/OFF,UPR=0

If each pin as a small circularity, the diameter and the center of CE8 are good. You can also replace "plus" by "minus" in assignment if you search an internal circle. You have to use options inscribed circle or circumscribed circle in those different cases.
No more idea for this time...

[Buckeye]

Thanks to all.

dwade - I use the outside points for the manual alignment as a quick way of starting the program. It is not accurate enough for certification of the gage, but is a great "quick and dirty" way of capturing the rough alignment.

cmmguy - The intersection points works well for a relative neophyte like me. I had some trouble until I figured out the line direction piece of the pierce point property (say that 5 times fast!!)

philwell - I agree entirely. I can only check what was given. I believe I have them talked into replacing the 4 pins with a solid ring, like some of the others.

JEFMAN - I am not familiar with the more advanced stuff, but it appears you are replicating the measuremt of each of the pins. The min_circumscribed circle appears to still use the pin centers, not the outside of them.

In any case, the program is working exactly as I needed it to. Thanks again, all.

[JEFMAN]

If you look at the difference between CE7 diameter (constructed on centers of pins) and CE8 diameter (constructed with calculated external points), you will see that min_circumscribed circle is outside of pins. It's also outside of the 6 pins, and tangent with only 3 of them...