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Carbide insert 11 IR A55 MTA Horn
€5.18 tax inc.
Net price: €4.21
Description
11 IR A55 internal inch threading insert
Technical data for the partial-profile insert for threads from 48 to 16 threads per inch
| Technical data | |
|---|---|
| Designation | 11 IR A55 MTA |
| Type | internal threading insert, right-hand |
| Profile | partial (incomplete), 55° angle |
| Threads per inch | 48–16 |
| Pitch range | 0.53–1.59 mm |
| Corner radius | 0.05 mm |
| Insert size | 11: edge 11 mm, IC 6.35 mm |
| Cutting edges | 3 |
| Tool holders | right-hand internal SIR holders, size 11, for bores from Ø12 mm, alternatively left-hand external SEL 11 holders |
| Grade | MTA: submicron carbide, PVD TiAlN |
Thread angle55°
Pitch range0.53–1.59 mm
Threads per inch48–16
Tool holdersSIR 11
11 IR A55 internal inch threading insert turns internal threads with a 55° thread angle and 48 to 16 threads per inch. A single insert cuts G pipe threads G 3/8 and Whitworth BSF threads within this range in bores from Ø12 mm. It works in size 11 right-hand SIR boring bars and, alternatively, in left-hand SEL 11 external holders. It has three corners: when an edge wears out, index the insert to the next corner.
How the 11 IR A55 insert cuts threads – rotation, feed, and passes
Feed equal to the pitch and several progressively shallower passes
Schematic illustration: an insert in a right-hand SIR boring bar inside the workpiece bore. The insert is highlighted in gold.
One spindle revolution – one thread pitch
The workpiece rotates while the boring bar with the insert moves along the bore axis. For each spindle revolution, it advances by exactly one pitch, e.g. 1.337 mm for a G 3/8 thread. In a typical setup, the right-hand insert feeds toward the chuck and cuts a right-hand thread.
The A55 insert does not touch the thread crests. They retain the bore diameter machined before threading, so this dimension determines the finished thread.
Schematic of the passes for a G 3/8 thread (1.337 mm pitch). Lines 1–6 show successive cutting edge positions.
Successive passes deepen the profile
A threading insert does not cut the thread in a single pass. It cuts deeper with each pass, while the thickness of material removed decreases from the first pass to the last. The final pass removes approx. 0.05–0.08 mm; a thinner layer causes the material to be compressed rather than cut.
Use flank infeed at an angle slightly less than 27.5°, which is half the thread angle. The insert then cuts mainly on one flank, and the chip flows to one side. The narrow A55 tip cuts deeper than the Whitworth thread root: for G 3/8, approximately 1.01 mm instead of 0.86 mm. Stop the infeed when a thread plug gauge or screw fits into the thread.
Cutting speed, spindle speed and number of passes
MTA grade is a submicron carbide with a PVD TiAlN coating. It machines steels, stainless steels and cast irons. The speeds in the table apply to thread turning with this insert.
| Workpiece material | Cutting speed vc [m/min] |
|---|---|
| P Unalloyed steel, cast steel, free-cutting steel | 120–180 |
| P Low-alloy steel and cast steel (up to 5% alloying elements) | 80–130 |
| P High-alloy and tool steel | 60–80 |
| M Stainless steel and stainless cast steel | 90–130 |
| K Gray cast iron | 120–130 |
| K Ductile and malleable cast iron | 100–130 |
Select the number of passes to suit the pitch. Start in the middle of the range and add passes for harder materials.
| Threads per inch | 48 | 28 | 19 | 16 |
|---|---|---|---|---|
| Pitch P [mm] (equivalent) | 0.53 | 0.91 | 1.34 | 1.59 |
| Number of passes | 3–6 | 4–8 | 6–10 | 5–11 |
For 28 and 19 threads per inch, the number of passes is interpolated from the manufacturer's table.
Spindle speed and feed for G 3/8
Pitch P is measured along the axis between corresponding points on adjacent thread turns.
For each spindle revolution, the insert advances by one pitch: fn = P = 1.337 mm/rev.
Example: G 3/8 in a bore in low-alloy steel, vc = 100 m/min
n = 1000 × vc / (π × d) = 1000 × 100 / (π × 16.662) ≈ 1910 rpm
vf = n × P = 1910 × 1.337
2553 mm/min
feed rate
d – thread diameter (16.662 mm), n – spindle speed, vc – cutting speed from the middle of the range in the table, vf – feed rate.
Universal 55° profile – from 48 to 16 threads per inch
One profile angle, many pipe and Whitworth threads
28 threads per inch
19 threads per inch – G 3/8
16 threads per inch – BSF 9/16"
Three threads shown at the same scale. The same insert tip cuts each groove: angle 55°, radius 0.05 mm.
The universal 55° insert has a tip radius of 0.05 mm. It fits into both a thread groove with 28 threads per inch and one with 16 threads per inch. The threads per inch are determined by the lathe feed, and the depth by the infeed over successive passes. This allows one insert to cut any 55° thread within this range.
G pipe threads according to ISO 228-1 and Whitworth threads have a 55° thread angle. The insert can therefore cut G threads in size G 3/8 and BSF 9/16" threads in holes from Ø12 mm. For short production runs, this replaces several full-profile inserts, each suitable for a single threads-per-inch value.
| Threads per inch | 19 |
|---|---|
| G pipe thread | G 3/8 |
A55 versus a full-profile insert – how they differ
Thread crest, pitch range and root radius
This insert
Partial profile 11 IR A55
The insert machines the flanks and root of the groove over a range of 48 to 16 threads per inch. It does not touch the crests: they retain the previously turned diameter.
Choose for: short runs and various pitches.
Comparison
Full profile, e.g. 11 IR 19 W
The insert cuts the flanks and the rounded root and crests of a thread with 19 threads per inch. The radii are formed in the same cycle as the flanks, ensuring a repeatable profile in production runs.
Choose for: production runs of threads with a single pitch.
| Feature | 11 IR A55 | W full profile |
|---|---|---|
| Pitch range | from 48 to 16 threads per inch | one number of threads per inch, e.g., 19 |
| Thread crest | previously bored hole diameter | turned together with the flanks |
| Hole preparation | diameter to the thread specification | diameter with a small machining allowance |
| Corner radius | 0.05 mm | matches the Whitworth profile for the specified pitch |
| Groove depth for G 3/8 | approx. 1.01 mm, deeper than the Whitworth profile | 0.86 mm, matching the Whitworth profile |
| Inserts for 48–16 threads per inch | 1 | one for each pitch |
A full-profile insert finishes the thread, including its crests, making the profile easier to maintain in production runs. A55 leaves the crests at the prepared hole diameter. Its narrow corner also produces a sharper thread root than the Whitworth profile.
Hole and thread root with the A55 insert
Before threading, bore the hole to the dimension required for the thread, e.g. G 3/8: bore 14.950–15.395 mm. A corner with a 0.05 mm radius produces a sharper root than the Whitworth profile, which rounds the root with a radius of 0.137 times the pitch (0.18 mm for G 3/8). Where a complete profile is required, select a full-profile W insert for the specific number of threads per inch.
Decoding the 11 IR A55 designation – part by part
Size, cutting hand, profile and grade in the insert designation, holder selection
Dimensions according to catalogs for inserts of this standard. Enlarged corner detail.
11 IR A55 insert dimensions
The number 11 indicates the insert size: an edge length of 11 mm and an inscribed circle IC of 6.35 mm, or 1/4 inch. It is not the thread diameter. Dimensions X = 0.8 mm and Y = 0.9 mm specify the position of the cutting tip relative to the sides of the insert. The corner has an angle of 55° and a radius of 0.05 mm.
11
Insert size
Edge 11 mm, IC 6.35 mm.
I
Internal thread
Turning inside holes with a boring bar.
R
Right-hand version
SIR boring bar, feed toward the chuck.
A55
55° partial profile
From 48 to 16 threads per inch.
MTA
Carbide grade
Submicron, PVD TiAlN, P20–P40 and K20–K30.
Mount the threading insert in right-hand SIR boring bars for size 11 inserts, e.g., SIR 0010 H11, SIR 0010 K11, or SIR 0013 L11. The insert has the same shape as the left-hand external 11 EL insert, so it can alternatively be mounted in a left-hand SEL 11 external holder to turn a thread on a shaft. External inserts are intended for regular threading on shafts. The standard shim tilts the insert by 1–1.5° to accommodate the thread helix angle. The shim only needs to be replaced for a large pitch on a small diameter.
The 11 IR A55 internal inch threading insert covers threads from 48 to 16 threads per inch with a 55° thread angle using a single cutting edge. It is useful for short production runs of various G pipe and Whitworth threads. It requires a prepared hole but eliminates the need for a separate insert for each pitch.
11 IR A55 – selection and application questions
Key information before selecting an insert
You can cut internal threads with a 55° thread angle and 48 to 16 threads per inch in holes from Ø12 mm: G pipe threads in size G 3/8 and BSF 9/16" threads.
Bore the hole to the dimension required for the thread, e.g. G 3/8: bore 14.950–15.395 mm. The insert will turn the flanks and root, while the crests remain at this diameter.
Right-hand SIR boring bars for size 11 inserts, e.g., SIR 0010 H11 and SIR 0010 K11 (bores from Ø12 mm), or SIR 0013 L11 (from Ø15 mm). It has the same shape as the left-hand external 11 EL insert, so it also fits left-hand SEL 11 external holders as an alternative.
The number of passes increases with pitch: 4–8 at 28 threads per inch, 6–10 at 19 threads per inch, and 5–11 at 16 threads per inch. Start at the middle of the range and add passes for harder materials. Some values were interpolated from the manufacturer's table.
This is the insert size: an edge length of 11 mm and an inscribed circle of 6.35 mm (1/4 inch). The hole in the workpiece determines the thread diameter, so the 11 IR A55 insert can cut both G 3/8 and BSF 9/16" threads.
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