If you turn shafts and you are doing it in two setups, the second setup is where your concentricity error comes from. A face driver removes it by driving the workpiece from the end face instead of from a chuck.
Hardened pins bite into the end face of the workpiece. The centre point locates it, the pins transmit the torque, and the entire length of the shaft is free for the tool. There is no chuck in the way, so you turn the whole part in one clamping.
The pins self-adjust to the surface of the material, which is why a saw-cut or forged face is usually acceptable without preparation.
Every re-clamping introduces a new datum. On a shaft, that shows up as concentricity error between the features turned in setup one and setup two. You can chase it with a steady rest and careful indicating, or you can not create it.
The time argument is the obvious one. The accuracy argument is the one that usually decides it.
| Model | Morse taper | Workpiece | Max load |
|---|---|---|---|
| MFC10 | MT3 / MT4 / MT5 | ø18–ø38 | 55 kg |
| MFC20 | MT3 / MT4 / MT5 | ø27–ø55 | 60 kg |
| MFC30 | MT3 / MT4 / MT5 | ø39–ø75 | 70 kg |
| MFC40 | MT4 / MT5 | ø55–ø100 | 100 kg |
| MFC | Morse taper shank — the standard range. |
|---|---|
| MFCST | Straight shank, for machines without a Morse taper tailstock. |
| MFCDST | Self-compensating. Corrects a tapered end face up to 1.5 mm with even pressure in every direction. Pin and point life goes up and maintenance goes down. |
All eleven components of an MFC face driver can be bought separately — cover, point, pins, roller, head, urethane, shank, spring, end cover. A worn pin does not mean a new face driver. Ask for the parts list when you order, not when something wears out.