Partial Arc help

[Devaney]

I have an arc thats giving me a lot of trouble. Please help me!

I am using CAD with an iterative alignement but not CAD=Part. The mojority of the part is completed and dimensioned accurately. The 7.25 Rad that mates with the bobmb surface is also datum -E- and is required for the TP callouts in several areas.

I tried this method that Mike N. posted (thank you Mike) on 06-06-2006.

To measure a partial arc/radius:

1. create a "measured" circle
2. edit (F9) the circle and add additional hits and edit the "best fit math type" to "FIXED Radius", edit the NOMINAL DIAMETER, check box to "regenerate hits", when prompted "equal spacing" answer YES
3. ctrl E the feature to execute it and re-capture the measured hit points
4. dimension the "location only" of the fixed radius circle/arc
5. edit dimension tol's to print
6. create an alignment and set origin on fixed radius circle
7. (if using CAD skip this step) F10/Parameters>Probing> enable polar compensation for the active workplane
8. with joystick measure more individual/separate points on arc radius (if using CAD use "vector point" skipping step #7)
9. dimension individual points using the "PR" polar radius function
10. F10/Parameters>Probing> turn off or disable polar compensation

I changed workplanes and completed number 1. I completed numbers 2 and 3. I did number 4 and 5 but was not sure if it applied to the part I am working on. I don't if I satisfied the requirement. I think number 6 went well, I just inserted alignment and translated x,y, and zto new feature. I didn't do seven because I'm using the CAD. I did 8 and 9, I am assuming tha PR is the sam as PRAD in the location dimension dialogue box. And 10, what does this do for me at the end of all of this. I don't get it.

Sorry for the long post. The part is on the plate and I'd be happy to try anything. See the attached screen shot of the print area I'm working with
http://C:\Documents and Settings\pde...op\support.jpg
Thanks everyone

[Devaney]

How do I get a jpg attached

[Wes Cisco]

First row in the message box, just the right of the font selection area & the smilely face, there is a paperclip. Click it to manage attachments. HTH

[Mike N.]

[QUOTE]To measure a partial arc/radius:

1. create a "measured" circle
2. edit (F9) the circle and add additional hits and edit the "best fit math type" to "FIXED Radius", edit the NOMINAL DIAMETER, check box to "regenerate hits", when prompted "equal spacing" answer YES
3. ctrl E the feature to execute it and re-capture the measured hit points
4. dimension the "location only" of the fixed radius circle/arc
5. edit dimension tol's to print
6. create an alignment and set origin on fixed radius circle
7. (if using CAD skip this step) F10/Parameters>Probing> enable polar compensation for the active workplane
8. with joystick measure more individual/separate points on arc radius (if using CAD use "vector point" skipping step #7)
9. dimension individual points using the "PR" polar radius function
10. F10/Parameters>Probing> turn off or disable polar compensation

I changed workplanes and completed number 1. I completed numbers 2 and 3. I did number 4 and 5 but was not sure if it applied to the part I am working on. I don't if I satisfied the requirement. I think number 6 went well, I just inserted alignment and translated x,y, and zto new feature. I didn't do seven because I'm using the CAD. I did 8 and 9, I am assuming tha PR is the sam as PRAD in the location dimension dialogue box. And 10, what does this do for me at the end of all of this. I don't get it.
[QUOTE]

Well......
4 will give you the l o c a t i o n of the feature and 5 is simply a reminder to tolerance the feature location if you didn't do it in the dimension window already. 6 is simply an alignment to the xy,yz or zx of the feature in question ( I hope you did it right too ) 7 turns on polar (if you use CAD it assumes you clicked on the CAD model to obtain your proper vectors and nominals for the points) 9 was a typo and should have been Prad (you got me)
and 10 well..... it turns off polar if you turned it on in step 7

this is a lengthy process but it will give you an accurate location first then an accurate radius value(s).

[phil george]

Mike,

I just happen to be reading this post after I'd just decided check a .420 radius with radius gages and key it in because there wasn't much arc to pick up with the cmm. Then I tried this method using .840 for the diameter of the fixed radius circle and it worked great, my polar points were all within a tenth or two of .420. So then out of curiosity I measured the same circle and put in 2 inches for the diameter of the fixed radius circle, measured it, set it to zero, took some polar points and they were all within a tenth or two of 1.000. Have you experimented with this method at all? I'd like to know if it's just me and I'm doing something wrong because it would be great if this worked.

...forgot to mention, the .450 radius gage fits pretty well. Seems like you're telling it that these points make up a cirlce of this diameter so it constructs it, then when you do the polar points they're going to be pretty much whatever you make them when you input the diameter. Not sure how this effects the location part, though.