CNC BSPP threading

To BSPP or not to BSPT

British Standard Pipe Parallel and British Standard Pipe Tapered.

ISO inch unit based standard with 55 deg thread flank angle. How an inch based thread ended up as an ISO standard I do not know...

The sizes concerned for the Aurora are:

1/4 - 19 (dash 04)
3/8 - 19 (dash 06)
1/2 - 14 (dash 08)
1"   - 11 (dash 16)

possibly also:
1/8 - 28 






For externally threaded parts, the major diameter is nominal size plus 1/4", thus 1/4 - 19 is 1/2" diameter (and 19 tpi).

Full discussion of how to identify threads and for the "dash" naming convention are here and here.

Discussion of carbide inserts for cutting BSPP threads

BSPP and BSPT threads are 55 degrees, not 60.

A good visual reference guide to threading standards.

A good discussion on Practical Machinist of how to cut BSPT and BSP - which is the same as Whitworth. 

Inserts:

If you select the Whitworth or BSP profile Carmex inserts, they will cut the full profile. Only the "partial profile" inserts leave the crests as-is.

So, Carmex "11 IR 11 W" or "16 IR 11 W" [for BSP, BSF, BSP, BSP] or "11 IR 11 BSPT" or "16 IR 11 BSPT" [for BSPT] or the equivalent Vardex or other competing inserts should do what you want.

Supplier (at $31USD each!) - (possibly not the best grade of carbide/coating for non-ferrous metal).
https://www.grainger.com/product/CARMEX-Threading-Insert-4PRZ6

Notes - a full profile insert is specific to the pitch and will cut radiused roots and crests. A partial insert will cut a range of pitches but leave flat roots and crests.

Carmex inserts seem to have the same naming convention as the Iscar, so the 11 IR 11 W example translates to:

11- insert size 11 (which is 1/4" inscribed circle)
I - Internal
R - Right hand
11 - 11 tpi
W - whitworth

Also, there seems to be some debate as to whether the radius roots and crests are necessary ("only important to amateurs"). My guess is that a sharp root will decrease the strength of the part, but that is highly unlikely to be an issue at the low working pressure in this application.


Possible inserts:

Explanation of ISCAR threading insert codes.
Good explanation of threading concepts, geometry and terminology.

Partial profile inserts (i.e. one size for a range of thread pitches with non radiused crests and roots)

ISCAR - External 55° partial profile, laydown threading inserts.
16ER A 55 IC908 - part number 5902222 
TPI min 16 - TPI max 48 - which would exclude the 1/2 inch

16ER AG 55
External 55° partial profile, laydown threading inserts.
TPI min 8 - TPI max 48

any of these carbide grades would do:

IC 508 grade
IC 228 TiN PVD
IC 908

Full profile inserts:

11ER 19 W   for cutting 1/4 - 19 and 3/8 - 19
11ER 14 W   for cutting 1/2 - 14

holder for all of these(?)


SER 1616 H16

Presuming that one holder can accommodate different sizes of insert (the 11,16 and 22 refer to the length of one side of the triangular inserts which inscribe a circle of 1/4", 3/8" and 1/2" diameter respectively).

References for CNC threading 

excellent explanation of code for CNC threading inch parts - however, while the code is specific to the HAAS or whatever he is using, the concepts are the same for the canned cycles in Mach3.

https://m.youtube.com/watch?v=e03pTbEBuGg

And now in Metric...

https://m.youtube.com/watch?v=e03pTbEBuGg


NYCNC guy's guide to thread milling with HSMworks and a Tormach

https://www.youtube.com/watch?v=a43S2y7Ccy8


HSMworks importing form tools
https://forums.autodesk.com/t5/support/hsm-2017-form-tool-does-not-show-on-import/td-p/6311059


G76 canned cycle explained
http://www.helmancnc.com/mach3-turn-g76-threading-canned-cycle/