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Description
CUTTING WIDTH3 mm
CUTTING DEPTH T MAX18 mm
MAX. BAR DIAMETERØ36 mm
INSERT · 2 EDGESMGMN 300
Parting tool 20X20 3 mm T18 Varel
Technical data for the holder for Korloy MGMN 300 inserts
| Technical data | |
|---|---|
| Designation | MGEHR 2020-3 |
| Type | holder for parting and external grooving |
| Shank height h | 20 mm |
| Shank width B | 20 mm |
| Overall length L | 125 mm |
| Dimension S (to the insert edge) | 20.4 mm |
| Cutting depth T max | 18 mm |
| Max. parting diameter D max | Ø36 mm |
| Insert pocket | MGMN 300 (width 3 mm) |
| Hand | R – right-hand |
MGEHR 2020-3 with screw clamping – operating principle
What this tool can do, screw clamping and a double-edged insert
Parting tool 3 mm MGEHR 2020-3 is a Varel holder for parting off workpieces from bar stock and cutting external grooves. The MGMN 300 carbide insert is held by a screw clamp from above: the screw pulls the flexible lip of the head against the insert. Replacement takes a dozen or so seconds, without removing the tool from the tool post.
The head forms a thin blade 18 mm long, which determines the cutting depth T max. Behind the blade, the head widens to the full shank width and can no longer enter the 3 mm groove. This sets the limit: the tool parts off bars up to Ø36 mm, or twice T max.
The MGMN 300 insert is double-edged: when one edge becomes dull, rotate it by 180° and cut with the other end.
The insert edge projects 0.4 mm beyond the side of the shank (S = 20.4 mm with B = 20 mm). When cutting close to the chuck, the cutting edge engages while the shank stays clear of the workpiece face. The 20x20 mm shank with a length of 125 mm is a common size for tool posts on general-purpose and CNC lathes.
What this tool can do – parting 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
20 mm
WIDTH B
20 mm
LENGTH L
125 mm
DIMENSION S
20.4 mm
T max is measured from the insert tip to the head shoulder. A groove shallower than 18 mm can also be cut in a bar larger than Ø36 mm.
The left panel of the diagram shows the end of the cut: the insert tip is on the bar axis, and the head shoulder touches its surface. The right panel shows cutting edge height: set the edge on the centerline to within ±0.1 mm. Below the centerline, a pip remains; above the centerline, the cutting edge rubs against the material.
Decoding the MGEHR 2020-3 designation
The four parts of the MGT system designation, read from the left
Designation: MGEHR 2020-3
MGEH
Element 1
holder type
holder type
For parting
MGEH
MGEH
External grooving and parting holder for the MGT insert system, with screw-operated top clamping.
R
Element 2
hand
hand
Right-hand
R
R
Standard configuration with the workpiece clamped in the chuck to the left of the tool. The mirror-image version is designated MGEHL.
2020
Element 3
shank
shank
20x20 mm
2020
2020
The first two digits indicate height h, and the next two indicate width B. Fits a tool post for 20 mm tools.
-3
Element 4
insert width
insert width
3 mm
-3
-3
The number after the hyphen is the insert width in millimeters. The pocket accepts MGMN 300 inserts, and T max is 18 mm (bars up to Ø36 mm).
MGT system catalog convention, not ISO 5608 · dimensions: h 20 · B 20 · L 125 · S 20.4 mm
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 values apply to coated MGMN 300 inserts used with coolant. Use the higher speeds with rigid clamping and short overhang.
| 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.
▲
Operating limitations
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
1Loosen
the clamping screw by 2–3 turns
2Seat
clean the pocket, slide the insert in until fully seated
3Tighten
and check that the cutting edge is on the lathe centerline ±0.1 mm
✓Ready
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 |
| ✓ | Left-hand MGEHL 2020-3 version with the same dimensions |
| ✓ | Other sizes in the -3 series available: MGEHR 1616-3 (T max 18.5 mm), MGEHR 2525-3 (T max 18 mm) |
Varel parting tools and boring bars for MGMN 300 inserts
MGEHR/L 1616-316x16 mm | L 100 mm | T max 18.5 mm | Ø37 mmR right-hand
←L left-hand
→
←L left-hand
→
MGEHR/L 2525-325x25 mm | L 150 mm | T max 18 mm | Ø36 mmR right-hand
←L left-hand
→
←L left-hand
→
MGIVR/L 2520-3Ø20 mm | Ømin 25 mm | L 150 mm | T max 6 mmR right-hand
←L left-hand
→
←L left-hand
→
Inserts from other grooving systems (DGN, GTN, KGM) require different seats and do not fit this holder. The 3 mm MGEHR 2020-3 parting tool machines carbon steel at a cutting speed of 140–190 m/min and a feed of 0.07–0.15 mm/rev. When parting off bars up to Ø36 mm, direct coolant into the cut and reduce the feed before reaching the centerline. In the production of fittings and pneumatic components, it parts off connectors, nipples 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.
Start at approximately 1500 rpm for carbon steel, at Vc = 170 m/min with a 3 mm insert. Cutting speed decreases closer to the centerline, so use G96 constant surface speed with a spindle speed limit on a CNC lathe. For stainless steel, use Vc 120–160 m/min.
Up to 18 mm, which is the holder's T max. In a single pass, the groove width equals the insert width of 3 mm; wider grooves require several adjacent passes. For deep grooves, retract the insert every few millimeters to clear chips.
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| 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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