Checking Threads?

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  • Checking Threads?

    Newbie here. I can hear the laughing now. O.k., Ok. everyone calm done now. Boss brings in the part , about 12" diameter, it's a flat plate with close to 300 holes in it, with some other pretty simple features. However, the holes are already threaded, as they are 4-40 threaded holes. Do I have to create a cylinder for the holes? I don't even have a probe small enough to move around in these little holes. ( Well, my wife thinks different, but we won't go there.)LOL ( Actually John Holmes and I run neck and neck in size values (not).
    I have read some other posts on the forum how to check threaded holes, but this seems to be a bit tough. If the holes were only drilled ,it would be nice, but I am not for sure what to do here. A solid shank probe of some sort would probably do the trick. I don't have any on hand at work right now. Otherwise, I have to go to the Microhite and setup for a long inspection. By the way T.P. of the holes to -A-B-is .004.
    Thanks for your help in advance.
    I had to remind my boss that I have only been on the CMM for 17 hours total in learning experience with no formal training.
    I know: I should have figured this thing out by now.
    I don't feel tardy!sigpic
    B&S "One" V4.2
    Discovery D-12 V4.2

  • #2
    threads are not that big a deal
    TP of .004 is doable

    You will need a 1mm or 1.5mm ball.
    When you do "Autocircle" you will need to add one more value in.
    In the box called "properties" the bottom item is pitch.
    Put in the inch value of the 4-40 thread (.025).
    Make sure your depth is below that of the chamfer so the chamfer does not effect your readings.

    so what this does is follow the pitch while probing, kinda like running a screw into the hole

    it does not matter that the ball may hit between the crests or on the crest of the thread, it will be hitting the same way all around the hole, this will give you a fairly good location

    just don't apply MMC to the TP of the hole, this will not work properly on the threads form hole to hole, they will all give a different "minor" diameter depending on how it hits on or off of the crest

    HTH
    bob
    Last edited by bob mappes; 06-21-2007, 09:42 PM.
    Which one gets ridden today? MPH vs MPG..tough choice, both are FUN
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    • #3
      Another thing you could do is invest in a group of precision threaded studs.
      Although that would be kinds spendy and a bit of a pain as you would have to stop the program and move them to the next group of holes.
      Getting 300 studs is probably not practicle. (I wouldn't want to be the guy installing 300 studs in each part).
      Lately, it occurs to me
      What a long, strange trip it's been.

      2017 R1 (Offline programming)

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      • #4
        I don't think I want to deal with this at this moment, as I don't have the training to perform this inspection with the cmm. Our company is quoting this inspection for another shop down the street. Our company has quoted 100.00 for the first program. Uh............I think they are way out of the ball park. I wouldn't fire up the microhite to check this part for that price. Remember guys. I am just learning the cmm. I do not want to present an inspection report to the customer that is ill. I do appreciate all the help from everyone, but I need some basic training before I would attempt this on the cmm. I'm not afraid of learning, but the customer has deadlines too. I would rather be honest up front, than tell them I can do it in a pinch. Thanks again
        I don't feel tardy!sigpic
        B&S "One" V4.2
        Discovery D-12 V4.2

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        • #5
          Yes it is possible, and Bob's method is correct as is John's. The pitch # is the inches per thread. (1/40 = .025"). There is also a tool called paste with pattern, it will allow you to measure one feature, then repeat it in a set pattern. Definitely something to use on a part like this. But tricky if you have no training.
          Aren't bosses wonderful things?! Bet he wouldn't have a person who is entering college pre-med operate on him.
          When in doubt, post code. A second set of eyes might see something you missed.
          sigpic

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          • #6
            Originally posted by John Kingston View Post
            Yes it is possible, and Bob's method is correct as is John's. The pitch # is the inches per thread. (1/40 = .025"). There is also a tool called paste with pattern, it will allow you to measure one feature, then repeat it in a set pattern. Definitely something to use on a part like this. But tricky if you have no training.
            Aren't bosses wonderful things?! Bet he wouldn't have a person who is entering college pre-med operate on him.
            Ditto on all the above... Try to learn paste with pattern its a great tool to use and saves allot of time like BIG JOHN KINGSTON SAID (watch him he's from Cleveland)
            sigpicRegards,
            Donald Henger
            B&S Micro Excel Pfx
            3.5mr2 & 3.7mr3
            PHH10MQ, TP20 & TP2
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            • #7
              Originally posted by 1CMM4ME View Post
              Newbie here. I can hear the laughing now. O.k., Ok. everyone calm done now. Boss brings in the part , about 12" diameter, it's a flat plate with close to 300 holes in it, with some other pretty simple features. However, the holes are already threaded, as they are 4-40 threaded holes. Do I have to create a cylinder for the holes? I don't even have a probe small enough to move around in these little holes. ( Well, my wife thinks different, but we won't go there.)LOL ( Actually John Holmes and I run neck and neck in size values (not).
              I have read some other posts on the forum how to check threaded holes, but this seems to be a bit tough. If the holes were only drilled ,it would be nice, but I am not for sure what to do here. A solid shank probe of some sort would probably do the trick. I don't have any on hand at work right now. Otherwise, I have to go to the Microhite and setup for a long inspection. By the way T.P. of the holes to -A-B-is .004.
              Thanks for your help in advance.
              I had to remind my boss that I have only been on the CMM for 17 hours total in learning experience with no formal training.
              I know: I should have figured this thing out by now.
              Did you get the info I sent you?
              Kevin

              Comment


              • #8
                Any recommendations on what size ball to use to check threads? We are checking 5/8 18UNF 2B threads in a shaft. We are chasing the threads and this seems to be working OK, but I want to ensure we have the best mechanical interaction.
                sigpic"Common sense in an uncommon degree is what the world calls widsom." -Samuel Taylor Coleridge

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                • #9
                  Originally posted by Buckeye View Post
                  Any recommendations on what size ball to use to check threads? We are checking 5/8 18UNF 2B threads in a shaft. We are chasing the threads and this seems to be working OK, but I want to ensure we have the best mechanical interaction.

                  Unless it is going to cause problems with checking other features, I would use a 4 or 5 mm ball to check this thread. The universal rule of thumb is to use the largest diameter ruby possible on the shortest, stiffest shank possible to reduce potential for errors. HTH (Hope This Helps)
                  sigpic"Hated by Many, Loved by Few" _ A.B. - Stone brewery

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                  • #10
                    Originally posted by Wes Cisco View Post
                    Unless it is going to cause problems with checking other features, I would use a 4 or 5 mm ball to check this thread. The universal rule of thumb is to use the largest diameter ruby possible on the shortest, stiffest shank possible to reduce potential for errors. HTH (Hope This Helps)
                    Really? I get better results with a smaller probe (assuming that shanking isn't an issue). I'd still use a 4mm ball for that thread because of the possibility of shanking.

                    For threads, you must use a probe with diameter large enough that it will not fall between the thread crests and hit on the shank. Unless of course you are willing to adjust the program for each part to ensure that this isn't happening.

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                    • #11
                      why wouldn't a cylinder work for 4-40 thd.?

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                      • #12
                        Originally posted by MIKEY View Post
                        why wouldn't a cylinder work for 4-40 thd.?
                        I don't believe anyone said it wouldn't.

                        You could do an autocylinder, but you'd need to use the pitch function and you'd need to ensure that the rows fall on the same part of the thread (distance between rows needs to be a multiple of the pitch).

                        Or did you mean a cylinder probe. That too would work but you'd need to ensure that the probe is 'square' to the part or you'll get funny results. Since he doesn't have one on hand AND because of the 'square' issue, it is easier to use the pitch function.

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                        • #13
                          Thanks all. I typically use a 2mm ball due to some of the other constraints and I do not have a probe changer. In this case, I will look at the program and see if a larger ball will work.

                          As for the cylinder probe, I have a fairly long buildup necessitated by a deep throw in between counterweights on a crankshaft, and as mentioned by GOODLUCK, am concerned about square with that much buildup.
                          sigpic"Common sense in an uncommon degree is what the world calls widsom." -Samuel Taylor Coleridge

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                          • #14
                            No, I meant autocyl with pitch. I thought with a cyl. you get more acurate #'s.

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                            • #15
                              Originally posted by MIKEY View Post
                              No, I meant autocyl with pitch. I thought with a cyl. you get more acurate #'s.
                              It depends on what you want. Technically if the callout is |TP|Ø .004|A|B|C| you would want to measure as a cylinder since the TP callout controls perpendicularity as well as location.

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