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Description
Left-hand parting tool 25X25 3 mm T18 Varel
Technical data for the holder for Korloy MGMN 300 inserts
| Technical data | |
|---|---|
| Designation | MGEHL 2525-3 |
| Type | holder for parting and external grooving |
| Shank height h | 25 mm |
| Shank width B | 25 mm |
| Overall length L | 150 mm |
| Dimension S (to the insert edge) | 25.4 mm |
| Cutting depth T max | 18 mm |
| Max. parting diameter D max | Ø36 mm |
| Insert pocket | MGMN 300 (width 3 mm) |
| Hand | L – left-hand |

MGEHL 2525-3 – operation with MGMN inserts
What this tool can do, screw clamping and a double-edged insert
Left-hand parting tool 3 mm MGEHL 2525-3 (Varel) parts off bars up to Ø36 mm and cuts external grooves. It uses MGMN 300 carbide inserts clamped from above by the flexible lip of the head. The clamping screw tightens the lip, and the insert can be replaced in a dozen or so seconds.
The insert is supported by the narrow blade of the head, 18 mm long — this is the cutting depth T max. Beyond this point, the body widens to the shank width, so only the blade fits into the 3 mm slot. This limits the tool to parting off bars up to Ø36 mm, or twice T max.
The dimension S = 25.4 mm means that the cutting edge projects 0.4 mm beyond the side of the 25 mm wide shank. This allows cutting close to the chuck jaws without the shank rubbing against the workpiece face. The 25x25 mm shank with a length of 150 mm provides the rigidity required by a narrow cutting edge in a confined groove.
The MGMN 300 insert has two cutting edges at opposite ends. When the first becomes dull, rotate the insert by 180° and use the second.
Applications of the 3 mm parting tool – parting off workpieces and grooving
Parting – cutting a part off a bar
The blade enters the bar all the way to the axis and the part separates. Bars up to Ø36 mm, a 3 mm kerf, and material loss limited to the insert width.
Cutting external grooves
A 3 mm groove between shaft shoulders or a retaining ring groove at the end of a journal, up to 18 mm deep. Cut wider grooves with several adjacent passes.
Screw clamping from above
The screw pulls the head's flexible lip down against the insert. The insert can be replaced without removing the tool from the tool post.
Double-edged insert
MGMN 300 has a cutting edge at both ends. One edge dull? Rotate the insert by 180° and use the other.
Material loss: 3 mm
Each parting cut turns only 3 mm of bar into chips. For 100 parts, this consumes 10 cm less bar than a tool with a 4 mm insert.
Dimensions and cutting reach – dimensional drawing
Side view and top view
HEIGHT h
25 mm
WIDTH B
25 mm
LENGTH L
150 mm
DIMENSION S
25.4 mm
Measure T max from the insert tip to the point where the blade transitions into the wider head. Grooves up to 18 mm deep can also be cut in bars larger than Ø36 mm.
At the end of the cut, the insert tip is at the bar centerline and the shoulder of the head touches the bar surface. The second panel shows the cutting edge height: the edge must be on the centerline within ±0.1 mm. An edge below center leaves a pip; above center, it rubs against the material.
MGEHL 2525-3 designation decoder
The four parts of the MGT system designation, read from the left

holder type
MGEH

hand
L

shank
2525

insert width
-3
Parting data – speeds and feeds for a 3 mm insert
Starting values with coolant; refer to the insert grade data sheet for definitive data
The table provides starting values for coated MGMN 300 inserts with coolant. Select the upper speed range when clamping is rigid and tool overhang is short.
| Workpiece material | Vc [m/min] | fn [mm/rev] |
|---|---|---|
| PCarbon steel | 140–190 | 0.07–0.15 |
| PAlloy steel | 120–160 | 0.07–0.15 |
| PHardened steel | 60–120 | 0.07–0.12 |
| MStainless steel | 120–160 | 0.07–0.15 |
| KCast iron | 150–200 | 0.07–0.15 |
Starting spindle speed: n = (1000 × Vc) / (π × D). For a Ø36 mm carbon steel bar at Vc = 170 m/min: n = (1000 × 170) / (3.14 × 36) ≈ 1500 rpm. At constant spindle speed, the cutting speed decreases to zero at the centerline, so enable constant surface speed (G96) with a spindle speed limit on a CNC lathe.
Do not part off bars larger than Ø36 mm: the shoulder of the head will contact the material before the cutting edge reaches the centerline. Keep overhang from the tool post as short as possible. Over the final 2 mm before the centerline, reduce the feed by as much as 75% and direct coolant straight into the cut.
Installing the MGMN 300 insert in 3 steps
the clamping screw by 2–3 turns
clean the pocket, slide the insert in until fully seated
and check that the cutting edge is on the lathe centerline ±0.1 mm
parting off bars up to Ø36 mm
Cutting insert not included
COMPATIBLE WITH:
| ✓ | MGMN 300 parting inserts (Korloy MGT system) – width 3.0 mm, length 21 mm, height 4.8 mm |
| ✓ | Right-hand version MGEHR 2525-3 with the same dimensions |
| ✓ | Other available sizes in the -3 series: MGEHL 1616-3 (T max 18.5 mm), MGEHL 2020-3 (T max 18 mm) |
Varel parting tools and boring bars for MGMN 300 inserts
←L left-hand
→
←L left-hand
→
←L left-hand
→
Inserts from other grooving systems, such as DGN, GTN or KGM, do not fit the seat. The 3 mm MGEHL 2525-3 left-hand parting tool cuts carbon steel, alloy steel, stainless steel and cast iron when the insert grade matches the material. The bar diameter limit remains Ø36 mm. When parting off hardened steel reduce the speed to 60–120 m/min. In metalworking and fabrication shops, it parts off pins, spacers and bushings from bar stock.
Frequently asked questions
An MGMN 300 parting insert (Korloy MGT system) with a width of 3.0 mm, length of 21 mm and height of 4.8 mm. It is double-ended, so each insert provides two cutting edges. DGN, GTN and KGM inserts do not fit this pocket.
Ø36 mm, or twice the cutting depth T max = 18 mm. Larger bars require a holder with a greater cutting depth T max. Grooves shallower than 18 mm can also be cut on larger diameters.
The left-hand L version is a mirror image of the right-hand tool (MGEHR 2525-3) with identical dimensions. Choose it when the workpiece is mounted on the opposite side of the tool or when required by the tool post arrangement on your lathe. When the workpiece is held in the chuck to the left of the tool, the R version is standard.
A pip remains when the cutting edge is not on the lathe centerline. Set it within ±0.1 mm and check that the insert is fully seated in the pocket. Over the final 2 mm before the centerline, reduce the feed by as much as 75%.
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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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