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.
A face driver earns its place on shafts that are turned over their full length. It is not the answer for every part:
| Method | Best for | Limitation |
|---|---|---|
| Face driver | Shafts turned over their full length in one clamping | Not for flanged, short or unbalanced parts |
| Chuck | Short parts and flanges | The clamped length cannot be turned, so the rest of the shaft needs a second clamping |
| Driving dog between centres | Occasional one-off shafts | Slow to load, and the dog blocks one end of the part |
The centre point locates the part and the pins carry the torque, so the two have to work together. If the centre hole is too large, the part rides on the pins; if it is too small, the point bottoms out before the pins engage. Both show up as run-out on the finished diameter. Send the part drawing with the enquiry and Mongtec confirms the centre-hole size before you drill a batch.
The end face itself rarely needs machining first. On a standard MFC the pins float, so each one finds the surface of a sawn or forged face. When the face is visibly out of square, the self-compensating MFCDST corrects a tapered end face of up to 1.5 mm and keeps the pressure even, so pins and point wear evenly.
| Question | Mongtec range |
|---|---|
| Diameter at the driven end | MFC10 ø18–38, MFC20 ø27–55, MFC30 ø39–75, MFC40 ø55–100 mm |
| Tailstock mounting | MFC: MT3 / MT4 / MT5. MFCST: straight shank |
| Workpiece weight | 55, 60, 70 and 100 kg for the four sizes |
| End-face condition | Sawn or forged and out of square: MFCDST self-compensating |
Where two sizes overlap, the part weight and the tailstock taper usually decide. Full article numbers and dimensions are on the Mongtec face driver product page.
Usually not. The driving pins self-adjust to the surface, so a sawn or forged face can normally be driven as it is. For a face that is clearly out of square, use the self-compensating MFCDST.
Yes. The MFCST straight-shank execution covers the same four sizes.
Yes. All eleven parts of an MFC face driver are sold separately.