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Description
Internal trapezoidal threading insert 16 IR 3 TR
Technical data for a full-profile insert for trapezoidal threads with a 3 mm pitch
| Technical data | |
|---|---|
| Designation | 16 IR 3 TR MTA |
| Brand / part number | Horn / 15170 |
| Type | internal threading insert, right-hand |
| Profile | full, trapezoidal Tr, 30° angle |
| Pitch | 3 mm |
| Profile height | 1.75 mm |
| Thread tolerance class | 7H |
| Insert size | 16: edge 16 mm, IC 9.525 mm |
| Cutting edges | 3 |
| Tool holders | right-hand internal SIR, size 16, holes from Ø16 mm |
| Grade | MTA: submicron carbide, PVD TiAlN |
Pitch3 mm
Profilefull Tr 30°
Depth1.75 mm
Tool holdersSIR 16
Internal trapezoidal threading insert 16 IR 3 TR turns the full internal thread profile with a 3 mm pitch: flanks, roots, and crests. It can produce threads from Tr 22 × 3 to Tr 60 × 3 in bores starting at Ø16 mm. It works in size 16 right-hand SIR boring bars. It has three corners for successive use.
Full Tr 30° profile – flanks, roots, and bore diameter
The insert finishes the thread crests in the same cycle
This insert
16 IR 3 TR – full profile
Crests trimmed to diameter D1.
Axial cross-section of a Tr 24 × 3 thread after the final pass. Gold highlights the insert; the red line indicates the surfaces machined by the insert.
The trapezoidal profile has a 30° flank angle and flat roots and crests. The internal thread profile height H4 is 0.5 of the pitch plus the crest clearance ac = 0.25 mm, giving 1.75 mm. The insert turns the flanks, roots, and crests at the bore diameter in the same cycle.
The Tr 24 × 3 thread has a bore diameter D1 = d − P = 21 mm and a root diameter D4 = d + 2 × ac = 24.5 mm (PN-ISO 2904). Tolerance 7H is specified in the trapezoidal thread standard. Bore the hole slightly undersize beforehand. An oversized bore will leave the crests unmachined and the profile too shallow. Check the finished thread with a thread plug gauge or a screw.
Threading with the 16 IR 3 TR insert – passes, feed, and cutting data
Feed of 3 mm per revolution and 8–17 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 – 3 mm of feed
The workpiece rotates while the boring bar with the insert moves along the hole axis by 3 mm per spindle revolution. In a typical setup, the right-hand insert feeds toward the chuck and turns a right-hand thread. During the final passes, its side cutting edges trim the crests to the hole diameter.
Schematic of the passes for a Tr 24 × 3 thread. The lines show successive cutting edge positions.
Successive passes to a depth of 1.75 mm
The insert reaches a profile height of 1.75 mm in 8–17 passes; use 12 as a starting point. The first pass removes the most material; the final pass removes 0.05–0.08 mm. Use flank infeed at an angle slightly less than 15°, which is half the profile angle: the insert then cuts mainly on one flank.
In a blind hole, make a relief groove at the end of the thread at least 3.2 mm wide and no shallower than the infeed depth.
Cutting speed for MTA grade
MTA grade is a submicron carbide with a PVD TiAlN coating for steel, stainless steel and cast iron. The speeds in the table apply to thread turning.
| 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 |
Spindle speed and feed for Tr 24 × 3
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 = 3 mm/rev.
Example: Tr 24 × 3 in a bore in low-alloy steel, vc = 100 m/min
n = 1000 × vc / (π × d) = 1000 × 100 / (π × 24) ≈ 1330 rpm
vf = n × P = 1330 × 3
3990 mm/min
feed rate
d – thread diameter (24 mm), n – spindle speed, vc – cutting speed from the middle of the range in the table, vf – feed rate.
Calculate the helix angle β using tan β = P / (π × d), where P is the pitch and d is the thread diameter. For Tr 24 × 3: 3 / (π × 24) = 0.040, giving β ≈ 2.28°. Standard threading holder shims tilt the insert by 1–1.5°. This thread has a larger angle, so select a shim with an inclination closer to 2.3° using the holder manufacturer's table.
Internal trapezoidal threads with a 3 mm pitch – from Tr 22 × 3 to Tr 60 × 3
One insert, many diameters with the same pitch
Hole diameters shown at the same scale. The tooth profile and thread depth are the same for each.
The pitch and tooth profile are independent of diameter. The profile height of a thread with a 3 mm pitch is always 1.75 mm, for both Tr 22 × 3 and Tr 60 × 3. The bore in the workpiece determines the thread diameter, not the insert.
The 16 IR 3 TR insert can cut trapezoidal threads listed in the PN-ISO 2902 table with a 3 mm pitch and bores from Ø16 mm. Threads from Tr 11 × 3 to Tr 14 × 3 have bores smaller than Ø16 mm and require a smaller insert.
| Group according to PN-ISO 2902 | Thread sizes with a 3 mm pitch |
|---|---|
| Tr threadsPN-ISO 2902, pitch 3 mm | Tr 22Tr 24Tr 26Tr 28Tr 30Tr 32Tr 34Tr 36Tr 38Tr 40Tr 42Tr 44Tr 46Tr 48Tr 50Tr 52Tr 55Tr 60× 3 |
Tr 24 × 3 is highlighted in gold – the thread shown in the drawings and calculation example in this description.
Decoding the 16 IR 3 TR designation – element by element
Size, operating hand, pitch, profile and grade in the insert designation, holder selection
Dimensions according to catalogs for inserts of this standard. Enlarged corner detail.
16 IR 3 TR insert dimensions
Size 16 indicates an edge length of 16 mm and an inscribed circle IC of 9.525 mm, or 3/8 inch; it is not the thread diameter. Dimensions X = 1.3 mm and Y = 1.5 mm specify the cutting tip position relative to the sides of the insert. The corner reproduces the trapezoidal profile: a 30° angle, a flat root, and crest clearance ac = 0.25 mm.
16
Insert size
Edge 16 mm, IC 9.525 mm.
I
Internal thread
Turning inside holes with a boring bar.
R
Right-hand version
SIR boring bar, feed toward the chuck.
3
Thread pitch
3 mm; one insert for one pitch.
TR
Tr trapezoidal profile
Angle 30°, full profile, class 7H.
MTA
Carbide grade
Submicron, PVD TiAlN, P20–P40 and K20–K30.
Only for a pitch of 3 mm and internal threads
The insert profile matches a single pitch. At a different feed, the insert flanks will not align with the thread flanks, resulting in a distorted thread. A boring bar for size 16 inserts fits bores starting at Ø16 mm, which determines the smallest thread size. Threads from Tr 11 × 3 to Tr 14 × 3 require a smaller bore.
Mount the threading insert in right-hand SIR boring bars for size 16 inserts, e.g. SIR 0013 M16, SIR 0016 P16 or SIR 0020 P16. A right-hand internal insert works only in a right-hand boring bar.
The 16 IR 3 TR internal trapezoidal threading insert finishes an internal trapezoidal thread with a 3 mm pitch, including the crests. A single insert can produce more than 10 sizes, from Tr 22 × 3 to Tr 60 × 3, always with the same profile height of 1.75 mm. It is suitable for lead screws and nuts with this pitch.
16 IR 3 TR – selection and application questions
Key information before selecting an insert
You can produce internal trapezoidal threads with a 3 mm pitch from the PN-ISO 2902 table: from Tr 22 × 3 to Tr 60 × 3.
Yes. The full profile trims the thread crests at the bore diameter, e.g., 21 mm for Tr 24 × 3. Simply bore the hole slightly undersize beforehand.
The profile height is 0.5 of the pitch plus the crest clearance ac: 1.5 + 0.25 = 1.75 mm (PN-ISO 2904). It is the same for every diameter with this pitch.
Right-hand SIR boring bars for size 16 inserts, e.g. SIR 0013 M16 (holes from Ø16 mm), SIR 0016 P16 (from Ø19 mm), SIR 0020 P16 (from Ø24 mm) or SIR 0025 R16 (from Ø29 mm).
Usually 8 to 17 passes; start with 12. For harder materials, add passes instead of increasing the cutting speed.
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