DRoam
Mechanical
- May 11, 2015
- 6
We are designing a couple of parts which will thread into each other. The OD of the internal part is 8.75 inches. From I've seen, standard UN threads only go up to 4 inches maximum.
We need a thread with a nominal size of 8.75 inches, and a relatively fine pitch, say 16 threads per inch or more (I'm not really sure what's a reasonable value for such a large diameter).
My question is twofold:
1. What method would the machinist use to cut such custom threads?
2. How do I call out custom threads in a way that communicates everything the machinist would need to know to cut them?
This topic was discussed some in another thread (thread404-226452) but the resolution was that the OP's desired thread designation turned out to be a standard size. User KENAT gave some valuable information in the thread and in a related FAQ he created (How Do I Specify Unified Thread Form Custom Threads?), but I'm not quite sure how to apply it to my situation. I've seen some slightly contradictory information which indicates I should not have to call out the pitch diameter or even the major/minor-diameter tolerances, but rather those should be dictated by the UN standard.
Any information and expertise would be very appreciated. Thanks!
We need a thread with a nominal size of 8.75 inches, and a relatively fine pitch, say 16 threads per inch or more (I'm not really sure what's a reasonable value for such a large diameter).
My question is twofold:
1. What method would the machinist use to cut such custom threads?
2. How do I call out custom threads in a way that communicates everything the machinist would need to know to cut them?
This topic was discussed some in another thread (thread404-226452) but the resolution was that the OP's desired thread designation turned out to be a standard size. User KENAT gave some valuable information in the thread and in a related FAQ he created (How Do I Specify Unified Thread Form Custom Threads?), but I'm not quite sure how to apply it to my situation. I've seen some slightly contradictory information which indicates I should not have to call out the pitch diameter or even the major/minor-diameter tolerances, but rather those should be dictated by the UN standard.
Any information and expertise would be very appreciated. Thanks!