That's the email I got upon entering the shop today. I was using a 1 x 10 styli for a part with 3-48 & 6-32 threaded holes. Just trying to get a decent location within tolerance of +/- .005. Now, the customer (we are the sub-contractor) is "coming in today with a cylindrical probe which will take more accurate hits on thread holes". I checked some of the postings in the forum and it looks like there's a lot involved and the results are sketchy.
We generally use a cylindrical stylus for inspecting threaded holes. The tip is a .5mm X 15.25 carbide cylinder stylus (Renishaw P/N A-5003-1210). This is because we generally have hundreds of holes to check.
This is not the most accurate way to check threaded hole locations because you are picking up the minor diameter of the thread and if the hole is crooked you can still shank out inside the hole (See Ninjas Graphic above). I would never just use a ruby ball inside a threaded hole because the ball will fall in between the threads on one side of the hole while it may hit the "peak" of the thread on the other side of the hole. Therefore, the measure would definitely be incorrect. Also, bear in mind that we are inspecting precision machined parts. Where there is less chance of the hole being significantly crooked.
There are inserts you can buy that you screw into each hole leaving a cylindrical protrusion. Then you can use a ruby ball stylus to pick up the location of each cylinder. See MSC P/N 84344027 as an example. It's called a true position tapped hole gage. This (IMO) is the best way to pick up threaded holes if you only have a few of them to measure.
We generally use a cylindrical stylus for inspecting threaded holes. The tip is a .5mm X 15.25 carbide cylinder stylus (Renishaw P/N A-5003-1210). This is because we generally have hundreds of holes to check.
This is not the most accurate way to check threaded hole locations because you are picking up the minor diameter of the thread and if the hole is crooked you can still shank out inside the hole (See Ninjas Graphic above). I would never just use a ruby ball inside a threaded hole because the ball will fall in between the threads on one side of the hole while it may hit the "peak" of the thread on the other side of the hole. Therefore, the measure would definitely be incorrect. Also, bear in mind that we are inspecting precision machined parts. Where there is less chance of the hole being significantly crooked.
There are inserts you can buy that you screw into each hole leaving a cylindrical protrusion. Then you can use a ruby ball stylus to pick up the location of each cylinder. See MSC P/N 84344027 as an example. It's called a true position tapped hole gage. This (IMO) is the best way to pick up threaded holes if you only have a few of them to measure.
