How to inspect this feature? Arc on part with center off some distance
Close
Login to Your Account
Page 1 of 2 12 LastLast
Results 1 to 20 of 40
  1. #1
    Join Date
    Jun 2015
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    407
    Post Thanks / Like
    Likes (Given)
    84
    Likes (Received)
    98

    Default How to inspect this feature? Arc on part with center off some distance

    Can anyone tell me a good method for checking this feature? Is an optical comparator the best equipment to use shy of a CMM? What I've done before is turn a custom pin and use with with the height gauge to get the location, but that doesn't do very well for radius as finding a .005" discrepancy seems very iffy.

    ex.jpg
    (drawn in metric)

    Anyone know a good book on inspection techniques? I've looked in my area for classes but can't find any.

    Thanks

  2. #2
    Join Date
    Sep 2015
    Country
    UNITED STATES
    State/Province
    Ohio
    Posts
    1,091
    Post Thanks / Like
    Likes (Given)
    658
    Likes (Received)
    1060

    Default

    That's pretty big feature for a comparator. You're not going to be able to use an overlay.
    You might have some luck by picking up 3 points on the radius and drawing it up on the computer.
    Fit your radius to the points and see where the center comes out.

  3. #3
    Join Date
    Jan 2014
    Location
    Temecula, Ca
    Posts
    2,811
    Post Thanks / Like
    Likes (Given)
    1264
    Likes (Received)
    3648

    Default

    can you probe it on a machine? If not, you could put it on a mill, zero at the (theo) center of the arc, then pick up a couple points on the arc with an edge finder.

  4. Likes CosmosK liked this post
  5. #4
    Join Date
    Jun 2015
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    407
    Post Thanks / Like
    Likes (Given)
    84
    Likes (Received)
    98

    Default

    I have a Haimer 3D taster, but unless I'm missing something, I can only accurately pick up flat faces in X or Y (or z).

    So, an overlay on a comparator would be for the diameter? I'd like to get one at some point. I imagine I could get three points with the comparator then throw it in CAD to find the measured center.

    This is just an example. I see stuff like this from time to time doing job shop work and I'm trying to improve.

    Thanks

  6. #5
    Join Date
    Jun 2008
    Location
    Roanoke, VA
    Posts
    666
    Post Thanks / Like
    Likes (Given)
    192
    Likes (Received)
    252

    Default

    You can pick up angles or arcs with the 3D Taster, you just have to account for the offset made by the probe diameter. If you were using cad and your mill as a cmm you would pick up 3 locations on the arc and draw a circle that is the probe diameter at each point. Construct an arc tangent to each probe tip circle and you'll have the radius and center location.

  7. Likes CosmosK liked this post
  8. #6
    Join Date
    Sep 2015
    Country
    UNITED STATES
    State/Province
    Ohio
    Posts
    1,091
    Post Thanks / Like
    Likes (Given)
    658
    Likes (Received)
    1060

    Default

    I’ve made my own overlays before. You could make one to check the radius but you won’t be able to check to the center because even at 10X the center of the radius overlay won’t fit on the screen. Some comparators have an edge finder attachment where you sweep across the shadow of the radius and it picks up the points and calculates the radius and center but I haven’t found them to be that accurate.

  9. Likes CosmosK liked this post
  10. #7
    Join Date
    May 2007
    Country
    UNITED STATES
    State/Province
    Massachusetts
    Posts
    842
    Post Thanks / Like
    Likes (Given)
    13
    Likes (Received)
    73

    Default

    I had one inspector that would have dialed to the virtual center point, then measured from there to points on the radius. Comparator. If they didn't have a GeoCheck, they'd trig out the hypotenuse.

  11. #8
    Join Date
    Sep 2009
    Location
    barcelona, spain
    Posts
    2,381
    Post Thanks / Like
    Likes (Given)
    530
    Likes (Received)
    1431

    Default

    0.005" == 0.1 mm.
    Any di swung at the right point should easily qualify 0.1 mm, much better usually.

    Optionally, laser cut templates, even plastic, of under and net and oversize might qualify the part.

    If the part is big, printing optical reference cards, and a good digital camera, could easily prove edge size/geometry.
    Internal round ridge geometry is another thing.

    Likewise, turning milling or laser a gage part in thin sheet steel might prove part size/form to 0.1 mm.

  12. #9
    Join Date
    May 2008
    Location
    San Diego
    Posts
    346
    Post Thanks / Like
    Likes (Given)
    2
    Likes (Received)
    65

    Default

    A rotary table on a vertical mill with a DRO is good for this. Even better with an XY slide on top.rotab.jpg

  13. #10
    Join Date
    May 2010
    Country
    DENMARK
    Posts
    3,252
    Post Thanks / Like
    Likes (Given)
    4016
    Likes (Received)
    12702

    Default

    Quote Originally Posted by CosmosK View Post
    Can anyone tell me a good method for checking this feature? Is an optical comparator the best equipment to use shy of a CMM? What I've done before is turn a custom pin and use with with the height gauge to get the location, but that doesn't do very well for radius as finding a .005" discrepancy seems very iffy.

    ex.jpg
    (drawn in metric)

    Thanks
    How many and what are the tolerances? What's the material and thickness?

  14. #11
    Join Date
    Jun 2015
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    407
    Post Thanks / Like
    Likes (Given)
    84
    Likes (Received)
    98

    Default

    Quote Originally Posted by Gordon B. Clarke View Post
    How many and what are the tolerances? What's the material and thickness?
    This is just an example. I see stuff like this from time to time doing job shop work.

    Quantities are usually low.

    Seems like next time I will chuck up a dial indicator, set the radius off a know edge (side of vise), go to theo center and sweep.

    Thanks all for the input

  15. Likes Derek Smalls liked this post
  16. #12
    Join Date
    May 2010
    Country
    DENMARK
    Posts
    3,252
    Post Thanks / Like
    Likes (Given)
    4016
    Likes (Received)
    12702

    Default

    Quote Originally Posted by CosmosK View Post
    This is just an example. I see stuff like this from time to time doing job shop work.

    Quantities are usually low.

    Seems like next time I will chuck up a dial indicator, set the radius off a know edge (side of vise), go to theo center and sweep.

    Thanks all for the input
    And what will you be measuring if you do that? You have 3 dimensions on your drawing.

    There's an easy way to measure all three so think harder.

  17. #13
    Join Date
    May 2010
    Country
    DENMARK
    Posts
    3,252
    Post Thanks / Like
    Likes (Given)
    4016
    Likes (Received)
    12702

    Default

    Quote Originally Posted by CosmosK View Post
    Can anyone tell me a good method for checking this feature? Is an optical comparator the best equipment to use shy of a CMM? What I've done before is turn a custom pin and use with with the height gauge to get the location, but that doesn't do very well for radius as finding a .005" discrepancy seems very iffy.

    ex.jpg
    (drawn in metric)
    This post annoys me. Before measuring tell me how this would be made.

    Add to that the fact that the dimensions are without tolerances makes measuring senseless.

  18. #14
    Join Date
    Jan 2007
    Location
    Flushing/Flint, Michigan
    Posts
    7,705
    Post Thanks / Like
    Likes (Given)
    384
    Likes (Received)
    6423

    Default

    Gordon,
    The op says within .005 (inches here I will guess from the ").
    Let's assume milled profile and at 5 you'd want .001 or .0025 worst case on rad size and center location for a check.
    How would you do it?
    Not much of an arc there to do a three point pickup on either rad size or projected center.
    Best fit 10 point means a special box or a lot of CAD work.
    Just for giggles assume the OP has other parts with differing rad sizes and positions so special fit rolls or masters are impractical.
    Bob

  19. Likes Paolo_MD liked this post
  20. #15
    Join Date
    May 2010
    Country
    DENMARK
    Posts
    3,252
    Post Thanks / Like
    Likes (Given)
    4016
    Likes (Received)
    12702

    Default

    Quote Originally Posted by CarbideBob View Post
    Gordon,
    The op says within .005 (inches here I will guess from the ").
    Let's assume milled profile and at 5 you'd want .001 or .0025 worst case on rad size and center location for a check.
    How would you do it?
    Not much of an arc there to do a three point pickup on either rad size or projected center.
    Best fit 10 point means a special box or a lot of CAD work.
    Just for giggles assume the OP has other parts with differing rad sizes and positions so special fit rolls or masters are impractical.
    Bob
    I think I'm repeating myself but I wouldn't "do it" with the information given by the OP.

    Even as a theoretical question, which it is, I'd want to know more than just being given 3 dimensions.

    I can certainly understand why you write "assuming" and "just for giggles" but I'm not going to assume or do anything for giggles. A drawing in metric and then a dimension (0.005") in inches.

    I asked the OP questions but got no answers. I can understand why I haven't gotten an answer. It's all theoretical and as theoretical task I could give many options. I suggest he asks his teacher at school if he's in doubt.

    What's drawn is something that going to be placed on or fit something so what is it that's important?

    The distance from the edge for the arc radius?
    The arc diameter?
    Me? I'd want more dimensions than just those 3 plus tolerances.

    IRL things like:
    Quantity, material and material thickness, how it was made, etc., etc, would be known.
    What is available to measure?

  21. #16
    Join Date
    Jan 2019
    Country
    UNITED STATES
    State/Province
    Tennessee
    Posts
    456
    Post Thanks / Like
    Likes (Given)
    139
    Likes (Received)
    120

    Default

    If it was a structural part, I would use d1 to check square, d2 to check radius, S1, S2, S2, S4 I hope are self explanatory. you could add a vertical (perpendicular to s3) layout to assist d2 location easy enough.rr.jpg

  22. Likes CosmosK liked this post
  23. #17
    Join Date
    Dec 2018
    Country
    UNITED STATES
    State/Province
    Arizona
    Posts
    19
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    13

    Default

    Easy to do with either a comparator or CMM with just the dims on the drawing, other than tolerance which was stated in the op. Material thickness and all that other stuff is irrelevant. Origin on lower left corner of the part (in this example). Move to theoretical center point of arc and re-zero. Measure straight line distance to multiple points at both ends and the center of the arc. I would do at least 5 points. If those measurements are within your arc radius callout and tolerance, you're good to go. If the numbers vary significantly from one end of the arc to the other, then the position (not size necessarily) of the arc itself is off. I have to measure quite a few parts like this at my day job on a regular basis.

    Sent from my SM-N960U using Tapatalk

  24. Likes Paolo_MD, CosmosK liked this post
  25. #18
    Join Date
    Jan 2019
    Country
    UNITED STATES
    State/Province
    Tennessee
    Posts
    456
    Post Thanks / Like
    Likes (Given)
    139
    Likes (Received)
    120

    Default

    Gordon, I agree missing dimensions, like height and width. Forget tolerances or units, that is irrelevant on how to measure "this shape".

  26. #19
    Join Date
    May 2010
    Country
    DENMARK
    Posts
    3,252
    Post Thanks / Like
    Likes (Given)
    4016
    Likes (Received)
    12702

    Default

    Quote Originally Posted by memphisjed View Post
    Gordon, I agree missing dimensions, like height and width. Forget tolerances or units, that is irrelevant on how to measure "this shape".
    What you regard as "irrelevant" isn't irrelevant to me. It's the difference between theoretical and practical. Theoretically and practically there are many ways of measuring the part.

    This thread is yet again one of those where somebody wants help but is too lazy (or worse) to give enough information to give a sensible answer.

    I'm still far from certain what the "shape" is he's wanting to measure. Given tolerances for all 3 dimensions can alter "the shape".

  27. #20
    Join Date
    Jan 2019
    Country
    UNITED STATES
    State/Province
    Tennessee
    Posts
    456
    Post Thanks / Like
    Likes (Given)
    139
    Likes (Received)
    120

    Default

    I am trying to see how thickness maters. Assuming that all cuts are perpendicular to shape, and part is flat... but that is something that should be checked before going thru effort of shape checking.
    I now am curious on how you change measuring thin (say paper thick) vs thick (1")? can we say 3" long x 2" tall? How that would differ from 3' x 2' or even 30' x 20'. +- 2 ticks on dial calibers or tape measure.

  28. Likes camscan liked this post

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •