greenimi
Mechanical
- Nov 30, 2011
- 2,407
A cylinder has three inside diameters,
ID#1 on one end ½-20UNF thread (called datum feature A)
ID#2 middle section ø.375 and
the other end ID#3 again ½-20UNF thread (called datum feature B)
Datum feature A is ID#1 thread
Datum feature B is ID#3 thread
The middle section width/length is dimensioned with ± and is called datum feature C
Other features on this part (such as holes perpendicular to axis of the cylinder) are positioned to A(M) –B(M) primary and C (RFS) secondary.
The two inside mating parts (one on each end of the cylinder) threaded on ½ -20 thread will create a sealing surface/contact with datum feature C (and that’s why datum feature C is called RFS). In other words, take the mating part and threaded all the way in until touches one side on datum feature C to create a contact surface. The same thing on the other side (just to describe a little bit the functionality)
Is this compound datum (used for threads !!) a good option? I would say it is legal option, but it is a functional one?
ID#1 on one end ½-20UNF thread (called datum feature A)
ID#2 middle section ø.375 and
the other end ID#3 again ½-20UNF thread (called datum feature B)
Datum feature A is ID#1 thread
Datum feature B is ID#3 thread
The middle section width/length is dimensioned with ± and is called datum feature C
Other features on this part (such as holes perpendicular to axis of the cylinder) are positioned to A(M) –B(M) primary and C (RFS) secondary.
The two inside mating parts (one on each end of the cylinder) threaded on ½ -20 thread will create a sealing surface/contact with datum feature C (and that’s why datum feature C is called RFS). In other words, take the mating part and threaded all the way in until touches one side on datum feature C to create a contact surface. The same thing on the other side (just to describe a little bit the functionality)
Is this compound datum (used for threads !!) a good option? I would say it is legal option, but it is a functional one?