I've taken the spindle out of the Harrison mill and installed the ETM collett chuck ready for the hob.

Here's the everyday spindle out of the mill and the collett chuck that will replace it.  Very rigid mounting on big bearings, so there will be no problem driving the hob.  I've cleaned the hob up and am making a push to steady the tail end of it.  I've never used the mill in this way before, it'll be interesting.  Think of it as a vertical mill laid on it's back.  I have a big angle plate and have often thought of using the mill like this to generate plane surfaces because the setup is so rigid, far more so than a vertical mill as the castings of the standard are massive.

The bush is made and here's the set-up that will be installed in the Harrison mill with the hob being driven by the collett chuck.  The bushes aren't anchored in the supporting bracket as they won't have any longitudinal forces on them so they won't try to move.  Makes it easier to set up as well if I need a bit more clearance.

Here's the hob set up in the mill.  Getting close now!

All ready for the off.  The mill is on its lowest speed, 67 rpm.  All I have to do is take my courage in both hands and press the button to enter the wonderful world of hobbing!  Can't put it off any longer, now we'll find out if I have got it right!

I'm tempted to say that there's nowt to it!  Here's the test blank I cut and although not perfect, it is a worm wheel.  Funny thing is I'd calculated 75 teeth and it hobbed at 82!  I went back through the calculations and found I'd made a simple arithmetical mistake.  The other thing I've learned is that it will be better to turn a hollow circular groove in the edge of the blank and that the bottom of that curve, less about a third of the tooth depth is going to be the PCD.  I've noticed also that Johnny turned the shoulders off the blank as well before cutting so that there are no delicate feather edges on the gear when cut.  All told, very satisfying and a good test.  The set-up is perfect, plenty of adjustment available and as steady as a rock.  Just goes to show that a bit of time spent on the setup is well worth while.

Now we're talking! After the fascinating preparation and setting-up comes the end result!

Cracking stuff Stanley.

PS Presence of fragrant tobacco device noted!

So what's the cutting sequence Stanley? Do you lower the rotating hob down onto the blank, making he first row of 'teeth'. then raise it, rotate the blank and cut again, repeating until it's complete? That must call for very precise alignment.

Hecky thump no!  Just start the mill, shove the blank into contact with the hob and let it argue its way round (the hob rotates the blank, that's why it's called 'free-hobbing') once you reach the start point give it some more cut and carry on until it looks about right.  Don't forget, this gear isn't meant to drive anything, it is simply a register.

First phase of getting the blank out of the plate I had is to get somewhere near a face, bore it 9/16" for the spindle and then trepan it out.

I've cut the keyway and am half way through making a mandrel to turn it on its own shaft to the blank size.  Then into the mill!