In a code like 16ER16UN, the 16 is the insert size, E means external (I means internal), R means right hand, and what follows gives the pitch and the thread standard. Some makers also add a profile group such as A, AG or G with the thread angle, for example A60, which decides how many pitches one insert can cut.
Reading 16ER and 16IR
| Part |
Meaning |
| 16 |
Insert size. This is a laydown threading insert with a 3/8 inch (9.525 mm) inscribed circle |
| E or I |
E is an external thread, I is an internal thread |
| R |
Right hand. L is left hand |
| Pitch and standard |
The pitch (mm or threads per inch) followed by the standard, such as ISO, UN or W for Whitworth |
The E or I matters in practice: an insert marked E is made for an external holder and an I insert for an internal one, so check it against the holder.
Two inserts read from their product pages
Both pages say the inserts are suitable for steel, stainless steel and cast iron. The suffix after the thread standard is the maker's own and is not part of the pitch and standard reading above.
Full profile and partial profile
A full profile insert cuts the whole thread form, including the crest, but suits one profile and pitch only. A partial profile insert (also called non-topping) cuts the groove without machining the crest, so one insert can cut a range of pitches and the crest needs a separate turning operation.
|
Full profile |
Partial profile |
| Pitches per insert |
One profile and pitch |
A range of pitches |
| Crest |
Cut by the insert |
Finished by extra turning |
| Stock needed |
A larger stock of inserts |
A smaller stock |
Letters such as A, AG and G name profile groups. Each group covers a limited range of pitches, and the radius at the crest matches the smallest pitch in the group. The number after the letters, such as 60, is the thread angle. Check the maker's catalogue for the pitch range of each group before choosing one.
Which holder takes a 16ER insert?
The Threading Holder SER M16 is listed for a size 16 external threading insert (16ER). It comes in 25x25 and 20x20 shank sizes and is right hand. A 16IR insert is internal, so it needs a different holder and is not covered by this page.
What to check before you order
- Size 16, and E or I to suit external or internal threading.
- Hand: R or L.
- The pitch and the standard (ISO metric, UN or W) of the thread you need to cut.
- Whether you want full profile for one pitch or partial profile for several.
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