Ever seen a spindle brake on a Deckel type mill ?

Not as in stopping the spindle but as in adding resistance during milling. I don't think I have....the Mikron has one. Manual is in German but from what I can tell it apparently is useful if using a cutter that might cause a bit of vibration, like a fly cutter...yes ?

Yes, my Deckel FP2 and FP3L vertical heads have this. According to manual it is standard.

Never used it...

L7

My (second generation) Deckel FP2 has it on the vertical head, but not on the horizontal head. On the vertical head, on the top of the spindle, just below the drawbar cap, is a knurled steel ring. If you turn this knurled ring clockwise (viewed from the top) then it pushes down on an internal bronze "shoe" which applies pressure to the smooth top of the bevel gear that drives the vertical spindle. That acts as a brake. The additional friction can be used to reduce (for example) the chatter that results when using a large diameter planing or facing head at low speed. I do use it from time to time, but not often, and not happily. I would rather set up cuts that don't need this.

Note: in some cases, users inadvertently tighten this brake and then complain that their vertical spindle is overheating.

Thiel 159 has this. My reading of the manual is that it is supposed to help reduce the recoil(and noise) from highly interrupted cuts as ballen describes. I can't say that it is entirely successful in this on my mill.

Aciera had a different solution to the same problem on the f4 and f5 a big flywheel you clamped to the drawbar on the vertical head to add inertia.

Sent from my SM-G973F using Tapatalk

My Schaublin 53 and 53n also have five different weights from 11.5 to 15.7 kg to dampen vibration.
They can be added to the vertical head and the horizontal arbor.

Of course they have. The standard vertical head on the FP2 has, the 90deg angled head does, not 100% about the high speed, I guess there isn't a point in that having one.

BR,
Thanos

While the Mikron acts on both hor and vert the Deckel "brake" is more effective IMHO as it is on the last gear

Peter