Polski 
- 98% satisfied customers
- 72h delivery
- 30 dni na zwrot
Description
M8 DIN 371 C machine tap – with straight flutes
Technical data and dimensions to DIN 371
| Technical data | |
|---|---|
| Thread | M8 x1.25 (metric coarse thread, right-hand) |
| Standard | DIN 371, reinforced shank |
| Flute | straight |
| Chamfer | form C, 2–3 threads |
| Thread tolerance | 6H |
| Material | HSSE (HSS-Co5) |
| Overall length | 90 mm |
| Threaded section length | 20 mm |
| Length to shank | 35 mm |
| Shank diameter | 8 mm |
| Square drive | 6.2 mm |
| Tap drill | 6.8 mm |
| Manufacturer | Narex |
M8 machine tap The Narex straight flute tap cuts threads in cast iron, brass, bronze, and steel. Chips removed by the cutting edges remain in the flutes and leave the hole with the tap. A straight flute moves chips neither upward nor downward.
The form C chamfer ends 2–3 threads from the tip, allowing the tap to work in through holes and blind holes. Cobalt-alloyed HSSE steel and a 6H tolerance produce threads for M8 screws.
MaterialHSSE, 5% cobalt
Flutestraight
ChamferC, 2–3 threads
Tolerance6H
Where chips remain in a straight-flute tap
The flute holds the chips until the tap is reversed out
A straight flute runs parallel to the tap axis. It has no helix to carry chips upward. The chamfer cutting edges are not ground at an angle, so they do not push chips downward. Short chips break into fragments and remain in the flute next to the cutting edges that removed them. They leave the hole only when the tap is backed out.
1
Straight flute – chips remain in the flute, next to the cutting edges that produced them.
2
Form C chamfer: 2–3 incomplete threads on the tapered lead.
3
The tap rotates clockwise to cut a right-hand thread.
4
Individual fragments exit at the top, onto the workpiece surface.
5
A few fragments fall below the tip and exit through the bottom of the hole.
6
Feed 1.25 mm/rev, equal to the pitch of the M8 thread.
Straight flute – thick core and chip space
Straight flutes are shallower than spiral flutes, so the tap core is thicker. A thicker core withstands torque better, making the tap less likely to break during machine tapping. Each flute acts as a small chip pocket. It works best with short chips that break into fragments on their own, as in gray cast iron and brass.
Form C chamfer – full thread 2–3 threads from the tip
The chamfer is the tapered lead of the tap, which removes material gradually. Form C has 2–3 tapered threads, equivalent to 2.5–3.75 mm, since each thread corresponds to a pitch of 1.25 mm. In a blind hole, the full thread therefore ends close to the bottom. In a through hole, the chamfer only needs to extend approximately 4 mm below the workpiece.
DIN 371 shank and machine mounting
Reinforced 8 mm shank with 6.2 mm square
DIN 371 specifies machine taps with a reinforced shank. For M8, the shank diameter is 8 mm, the same as the thread diameter. There is a reduced neck between the thread and the shank, and the length from the tip to the shank is 35 mm. The 6.2 mm square at the end of the shank transmits torque from the holder to the tap.
Mount the tap in a tapping chuck with a 6.2 mm square socket or in a tap collet. On a drill press or machine tool without rigid tapping, use a chuck with axial compensation. It compensates for the difference between the machine feed and the thread pitch, preventing the threads from being stretched or compressed.
▲
Clear the flutes when tapping deep threads
Chips remain in the flutes until you back the tap out. In a deep hole, tap halfway, back the tool out, remove the chips, and finish the thread. An overfilled flute jams the tap and can break it.
Cutting data and tap drill hole for M8
Cutting speed, spindle speed, and feed for HSSE steel
These values apply to HSSE taps. Spindle speed and feed rate were calculated for a diameter of 8 mm. Feed per revolution always equals the thread pitch, which is 1.25 mm. In a deep blind hole, reduce the speed by 20–30%.
| Workpiece material | Cutting speed [m/min] | Spindle speed [rpm] | Feed [mm/min] |
|---|---|---|---|
| PMedium-carbon steel 500–700 MPa, e.g., C45 | 8–12 | 320–480 | 400–600 |
| PAlloy steel 700–1000 MPa | 6–10 | 240–400 | 300–500 |
| KGray cast iron, e.g., EN-GJL-250 | 10–18 | 400–720 | 500–900 |
| KDuctile cast iron, e.g., EN-GJS-500 | 8–15 | 320–600 | 400–750 |
| NFree-machining brass and bronze | 20–30 | 800–1190 | 1000–1490 |
Spindle speed = 1000 × 12 m/min ÷ (3.14 × 8 mm) ≈ 477 rpm; feed = 477 rpm × 1.25 mm ≈ 597 mm/min
12 m/min is a cutting speed in the lower half of the range for gray cast iron. 8 mm is the tap diameter, and 1000 converts meters to millimeters. 1.25 mm is the pitch of the M8 thread – the distance the tap advances into the hole per revolution. Set approximately 480 rpm and a feed rate of approximately 600 mm/min.
M8 thread in a blind hole step by step
1Spot drilling
90° center drill
2Drilling
6.8 mm drill bit to a depth of 22 mm
3Tapping
feed 1.25 mm/rev, chips exit in the flutes
✓Inspection
blowing out the hole and checking with an M8 6H gauge
Depth 22 mm = full thread 16 mm + chamfer 3 threads × 1.25 mm + allowance 2 threads × 1.25 mm for the tip and chip fragments.
Which materials to choose straight flutes for
Cast iron, brass, bronze, and steel
HSSE is high-speed steel with approximately 5% cobalt. Cobalt helps the cutting edge retain its hardness at high cutting temperatures. Choose straight flutes where chips are short and break on their own: in gray and ductile cast iron, and in free-machining brass and bronze. In C45 steel and alloy steels, it taps through holes and shallow blind holes.
Gray cast iron can be tapped dry or with emulsion. In brass, bronze, and steel, lubricate generously with emulsion at a concentration of 5–10% or with tapping oil.
▲
Long chips clog straight flutes
Stainless steels 304 and 316, wrought aluminum, and soft low-carbon steel produce long, ductile chips. These wrap around in the flutes and jam the tap. For these materials, choose a spiral flute tap for blind holes or a tap with a form B through-hole chamfer for through holes.
M8 machine tap The Narex DIN 371 C tap retains chips in its straight flutes and removes them from the hole when backed out. The form C chamfer leaves the full thread 2–3 threads from the tip, while the thick core withstands torque. The 6H tolerance produces a thread that fits M8 screws with a 6g tolerance. The 6.8 mm drill bit and feed of 1.25 mm/rev remain constant for every material.
Questions about the M8 straight flute tap
Drill bit, chamfer, and hole type
A 6.8 mm drill bit. This is the thread diameter of 8 mm minus the pitch of 1.25 mm. A hole with a 6H tolerance can range from 6.647 to 6.912 mm, so a 6.8 mm drill bit falls in the middle of this tolerance zone.
C is the chamfer form, meaning the tapered lead. The form C chamfer spans 2–3 threads, equivalent to 2.5–3.75 mm, and allows tapping close to the bottom of a blind hole. The longer form B chamfer, spanning 3.5–5.5 threads, is used in through holes.
Straight flutes retain chips until the tap leaves the hole. Spiral flutes carry chips upward along the helix, while the chip breaker on a form B chamfer pushes them down the hole ahead of the tip. Straight flutes provide a thicker core than spiral flutes.
Yes. Chips remain in the flutes, while individual fragments fall to the bottom. Drill the hole deeper to accommodate the chamfer and an allowance: approximately 22 mm deep for a 16 mm thread. Blow out the hole after tapping.
DIN 371 features a reinforced shank – for M8, the shank diameter equals the thread diameter, 8 mm. DIN 376 features a shank smaller than the thread diameter. A practical rule: coarse threads up to M10 – DIN 371, from M12 – DIN 376.
Product accessories
Reviews
No customer reviews for the moment.
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 |
Recommended for you
Viewed products
This website uses its own and third-party cookies to improve our services and show you advertising related to your preferences by analyzing your browsing habits. To give your consent to its use, press the Accept button.
Cookie preferences
Functional cookiesTechnical
Functional cookies are strictly necessary to provide the services of the shop, as well as for its proper functioning, so it is not possible to refuse their use. They allow the user to browse through our website and use the different options or services that exist on it.
Advertising Cookies
These are cookies that collect information about the advertisements shown to users of the website. They can be anonymous, if they only collect information about the advertising spaces shown without identifying the user, or personalised, if they collect personal information about the user of the shop by a third party, for the personalisation of these advertising spaces.
Analytics cookies
Collect information about the user's browsing experience in the shop, usually anonymously, although sometimes they also allow the user to be uniquely and unequivocally identified in order to obtain reports on the user's interests in the products or services offered by the shop.