DIN 7978 Extractable Taper Pins
Extractable taper pins carry an internal thread in the large end, so a pin seated in a blind tapered hole can be drawn back out with a puller. We supply them in mild steel with a fine ground finish, available across a range of metric sizes - contact us for hardened or special material requirements.
Also known as: extractable taper pin, internal thread taper pin, threaded taper pin, bs 1804 taper pin, din 7978.
DIN 7978 dimensions
| Nominal diameter (small end) | Extraction thread | Thread depth | Counterbore diameter | Counterbore depth |
|---|---|---|---|---|
| 5mm | M3 | 6mm | 3.5mm | 1mm |
| 6mm | M4 | 6mm | 4.5mm | 1mm |
| 8mm | M5 | 8mm | 5.5mm | 1.2mm |
| 10mm | M6 | 10mm | 6.5mm | 1.2mm |
| 12mm | M8 | 12mm | 8.5mm | 1.2mm |
| 14mm | M8 | 12mm | 8.5mm | 1.2mm |
| 16mm | M10 | 16mm | 10.5mm | 1.5mm |
| 20mm | M12 | 18mm | 13mm | 1.5mm |
| 25mm | M16 | 24mm | 17mm | 2mm |
| 30mm | M20 | 30mm | 21mm | 2mm |
| 40mm | M20 | 30mm | 21mm | 2mm |
| 50mm | M24 | 36mm | 25mm | 2.5mm |
Materials & strength
Extraction from blind holes
The tapped large end accepts an extraction screw or slide-hammer adaptor, so the pin comes out of a blind tapered hole without disturbing the reamed seat.
Fine ground finish
The taper surface is finish-ground so the pin beds along its full length and repeats its seating on re-assembly.
Male-thread alternative
A related pattern (DIN 7977) carries an external threaded stub instead of an internal thread, extracted with a nut and packing. It covers the same blind-hole duty where the projecting thread is acceptable.
Related specificationsWhy choose an extractable taper pin?
A plain taper pin is normally driven out from the small end - impossible when the hole is blind. The internal thread lets the pin be pulled from the accessible side, preserving the tapered seat for the next fit.
How is the pin removed?
Wind an extraction screw or puller adaptor into the thread and draw the pin straight along its axis. Because the taper releases as soon as the pin moves, the pulling effort needed is modest.
What sizes are covered?
The dimension table runs from 5mm to 50mm nominal diameter with the extraction thread stepping from M3 to M24. Larger diameters within the table are produced against requirement - send us your requirement for anything above 16mm.
How does DIN 7978 relate to BS 1804?
Extractable taper pins are commonly supplied to DIN 7978 dimensions; where BS 1804 conformance is required, confirm with us.
Need DIN 7978 in a non-standard size or material?
Send us your drawing — specials quoted within 24 hours.