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Description
DIAMETER Ø25 mm
LENGTH 250 mm
INSERT SNMG 1204rr
ANGLE κr 75°
Technical specifications of the S25 PSKNR 12 boring bar
| Technical data | |
|---|---|
| ISO designation | S25 PSKNR 12 |
| Shank diameter (d) | Ø25 mm |
| Effective height (h) | 23 mm |
| Overall length (L) | 250 mm |
| Functional overhang (f) | 17 mm |
| Min. bore diameter (D_min) | Ø32 mm |
| Entering angle (κr) | 75° |
| Clearance angle | 0° (negative) |
| Clamping system | ISO — lever/pin (P) |
| Insert type | SNMG 1204rr |
| Cutting direction | R — right-hand (L version available) |
| Shank material | Steel (S) |
| Manufacturer | Smoxh |
Boring bar S25 PSKNR 12 – for internal turning of bores
Internal turning tool for machining bores from Ø32 mm
Boring bar S25 PSKNR 12 is an indexable boring bar designed for longitudinal turning and roughing and medium machining of bores with diameters from 32 mm. The round steel shank, ø25 mm in diameter and 250 mm long, ensures cutting stability even with greater tool overhang. The geometry with an entering angle of 75° reduces radial force compared with a turning tool with a 90° angle.
In the lever clamping system (P), the lever presses the SNMG 1204rr insert against the pocket walls through its hole. The negative geometry of the 90° square insert with 8 cutting edges is suitable for roughing and medium machining, providing high cutting edge strength and cost efficiency thanks to its double-sided design. The boring bar is compatible with SNMG 12 inserts in various carbide grades — select the grade to match the workpiece material.
Decoding the PSKNR designation of the S25 PSKNR 12 boring bar
What the individual letters in the ISO designation mean
Decoding the designation PSKNR
P
CLAMPING
Lever/pin (P)
Clamping through the insert hole — quick replacement
S
INSERT SHAPE
Square 90° 90°
SNMG insert — negative, double-sided, 8 edges (4 per side)
K
ENTERING ANGLE
κr = 75°
Longitudinal turning — reduced radial force
N
CLEARANCE ANGLE
α = 0° (neg.)
Negative geometry — double-sided inserts, edges on both sides
R
DIRECTION
Right-hand (R)
Feed to the left — from the tailstock toward the spindle
Shank: Ø25 mm (S25S, steel) · Insert: SNMG 1204rr
Typical applications of the S25 PSKNR 12 boring bar
Cutting operations:
| ▸ | Longitudinal boring — enlarging and finishing cylindrical bores from Ø32 mm |
| ▸ | Roughing and medium machining of bores — negative SNMG geometry provides a strong cutting edge; for finishing, select an insert with a finishing chip breaker |
| ▸ | Internal taper turning — bearing seats, internal chamfers, Morse tapers |
| ▸ | CNC production runs — repeatable cutting edge positioning and quick insert replacement in the holder |
Included
Package contents for S25 PSKNR 12
Package contents:
| ✓ | Boring bar body S25 PSKNR 12 | 1 pcs |
| ✓ | Pin and clamping lever | 1 pcs |
| ✓ | Hex key for insert replacement | 1 pcs |
| ✗ | SNMG 1204rr cutting insert (sold separately) | — |
Compatible SNMG 1204rr insert
SNMG 1204rr
The cutting insert is not included in the set — must be purchased separately. SNMG insert. Negative geometry means that the insert is double-sided and has 8 cutting edges, providing a stronger cutting edge and twice as many edges as a single-sided insert.
Select the insert grade to match the workpiece material: P (structural steels), M (stainless steel), K (cast iron), N (aluminum). You can find compatible inserts in the section "Related products" below.
Insert installation and replacement for the S25 PSKNR 12 boring bar
Instructions for lever clamping (P)
Insert replacement procedure step by step
1 Loosen the lever
Unscrew the lever screw 2-3 turns
2 Clean the insert seat
Remove chips and debris
3 Install the insert
Fit the hole over the pin
4 Tighten the lever
Torque 1.5–2.5 Nm
Important: Do not exceed the recommended tightening torque — this may damage the thread in the seat or crack the insert.
Checks before starting work:
| ▸ | Tool overhang — do not exceed 4×d (100 mm) without support; use vibration damping for greater overhang |
| ▸ | Cutting edge height — set the cutting edge at spindle centerline height |
| ▸ | Insert seat condition — check that the contact surface is not damaged or worn |
| ▸ | Secure clamping — the insert must have no play in the seat |
| ▸ | Indexing — when an edge wears out, rotate the insert to a fresh edge (8 edges in total) |
Note: Use internal coolant (through the spindle) for boring whenever possible. When machining without coolant, reduce cutting parameters by 20–30%. Long tool overhang promotes vibration — if vibration occurs, reduce the depth of cut and increase the feed.
Frequently asked questions — S25 PSKNR 12
The minimum bore diameter is Ø32 mm. In smaller bores, the tool head interferes with the machined wall, preventing proper cutting.
For a steel shank of Ø25 mm, the recommended maximum overhang without damping is 4×d, or 100 mm. Above this value, vibration may occur — reduce the depth of cut or use a vibration-damped boring bar.
The SNMG insert has negative geometry (clearance angle 0°), which means that it is double-sided with 8 cutting edges. When one edge wears out, rotate or flip the insert to use the next edge — this significantly reduces tooling cost per part.
Product accessories
Carbide insert SNMG 120408 MA H6310 Horn
Reference: 0000002922 In stock > 10 items
€5.26
€6.47 brutto
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Shipping
All orders are delivered by courier company GLS. For orders exceeding 369 PLN gross shipping is FREE
| Courier GLS | Przelew24 / Prepayment | 14,76 zł gross | Delivery time 1 working day |
| Courier GLS | Cash on delivery | 17,26 zł gross | Lead time 1 working day |
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