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Description
Left-hand parting tool 20X20 4 mm T20 Smoxh
Technical data for the holder for Korloy MGMN 400 inserts
| Technical data | |
|---|---|
| Designation | BDKT L 2020 K4C T20 |
| 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 | 20 mm |
| Max. parting diameter D max | Ø40 mm |
| Insert pocket | MGM. 4C (MGMN 400, width 4 mm) |
| Hand | L – left-hand (right-hand version: SM09554) |

BDKT-L 2020 K4C T20 Smoxh – insert clamping and cutting depth
What this tool can do, screw clamping and a double-edged insert
In this line, Smoxh offers a left-hand parting tool 4 mm BDKT-L 2020 K4C T20 with screw clamping of the insert. The holder parts off bars up to Ø40 mm and cuts external grooves 4 mm wide. The MGMN 400 insert sits in the pocket under a flexible lip tightened by a BKTV M6x25 screw.
Dimension S = 20.4 mm means that the cutting edge projects 0.4 mm beyond the side of the 20 mm wide shank. This allows cutting close to the chuck jaws without the shank rubbing against the workpiece face. The 20x20 mm shank with a length of 125 mm is a common size for tool posts on conventional and CNC lathes.
The MGMN 400 insert has two cutting edges at opposite ends. When the first becomes dull, rotate the insert by 180° and use the second.
The insert is supported by the narrow blade of the head, 20 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 4 mm slot. This limits the tool to parting off bars up to Ø40 mm, or twice T max.
Parting off bars up to Ø40 mm and cutting 4 mm grooves
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 Ø40 mm, a 4 mm kerf, and material loss limited to the insert width.
Cutting external grooves
A 4 mm groove between shaft shoulders or a retaining ring groove at the end of a journal, up to 20 mm deep. Cut wider grooves with several adjacent passes.
Screw clamping from above
The BKTV M6x25 screw draws the flexible lip of the head against the insert. Change the insert with an AA5 key without removing the tool from the tool post.
Double-edged insert
MGMN 400 has a cutting edge at both ends. One edge dull? Rotate the insert by 180° and use the other.
Material loss: 4 mm
Each parting cut turns only 4 mm of bar into chips. For 100 parts, this consumes 10 cm less bar than a tool with a 5 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
Measure T max from the insert tip to the point where the blade transitions into the wider head. Grooves up to 20 mm deep can also be cut in bars larger than Ø40 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.
Designation decoder for BDKT L 2020 K4C T20
Five elements of the Smoxh code, read from the left

holder type
BDKT

hand
L

shank
2020

insert pocket
K4C

depth
T20
Parting data – speeds and feeds for a 4 mm insert
Starting values with coolant; refer to the insert grade data sheet for definitive data
The table provides starting values for coated MGMN 400 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 | 120–200 | 0.07–0.15 |
| PAlloy steel | 130–180 | 0.07–0.15 |
| PHardened steel | 70–130 | 0.07–0.12 |
| MStainless steel | 120–160 | 0.07–0.15 |
| KCast iron | 130–210 | 0.07–0.15 |
Starting spindle speed: n = (1000 × Vc) / (π × D). For a Ø40 mm carbon steel bar at Vc = 170 m/min: n = (1000 × 170) / (3.14 × 40) ≈ 1350 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 Ø40 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 400 insert in 3 steps
the BKTV M6x25 screw with the wrench AA5, 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 Ø40 mm
Cutting insert not included
COMPATIBLE WITH:
| ✓ | MGMN 400 parting inserts (Smoxh: MGM. 4C) – width 4.0 mm, length 21 mm, height 4.8 mm |
| ✓ | BKTV M6x25 clamping screw (spare part) and AA5 wrench |
| ✓ | Right-hand version BDKT-R 2020 K4C T20 (SM09554) with the same dimensions |
Smoxh parting tools and boring bars for MGMN 400 inserts
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Inserts from other grooving systems, such as DGN, GTN or KGM, do not fit the pocket. The left-hand 4 mm BDKT-L 2020 K4C T20 parting tool combines a 20x20 mm shank with quick insert changes in a screw-clamped jaw. Its 20 mm cutting depth and compatibility with MGMN 400 inserts make it a basic tool for parting and grooving bars up to Ø40 mm. In metalworking and fabrication shops, it parts off pins, spacers and bushings from bar stock.
Frequently asked questions
An MGMN 400 parting insert (in the Smoxh catalog: MGM. 4C) with a width of 4.0 mm, length of 21 mm, and height of 4.8 mm. It is double-ended, so one insert provides two cutting edges. DGN, GTN, and KGM inserts do not fit this pocket.
Ø40 mm, which is twice the cutting depth T max = 20 mm. For larger bars, choose the 2525 K4C T22 version (up to Ø44 mm) or 2020 K4C T25 (up to Ø50 mm). Grooves shallower than 20 mm can also be cut on larger diameters.
Yes. The holder cuts external grooves 4 mm wide and up to 20 mm deep. An insert with -M or -T geometry also allows turning with the side of the insert, but with a depth of cut up to 0.8 × 4 mm = 3.2 mm per pass.
Up to 20 mm, which is the holder's T max. In a single pass, the groove width equals the insert width of 4 mm; wider grooves require several adjacent passes. For deep grooves, retract the insert every few millimeters to clear chips.
Product accessories
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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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