Leeroy,
Thanks for the post. Yes the Z-axis is a point of much discussion. I whould have liked to convert the knee to CNC on my machine as the HM-52 also has the horozontal spindle. This whould have allowed me full use of my horozontal spindle and have X as the table left and right, Y whould have been up and down on the knee, and Z whould have been what Y currently is now on the cross slide. CNC gear cutting whould have then been an easy option once I CNC'd my indexing head with the cutter held on the horozontal arbour. (Pictures can be seen of this when I manually cut some timing pulleys). http://www.cnczone.com/forums/showth...t=23872&page=2

With motor controll set up this way then also lets you use the verticle spindle, which is the one you would use. X whold be the table left and right, Y would be the cross slide and Z would be the knee up and down.

It would be very easy to have 2 different setups saved in your software so that when you start your controll computer you simply select the mode you want to machine in for the task and the computer runs the mill in that configuration.

The million dollar question though, is often argued about wether you automate the verticle quill - or the knee. I have seen a lot of people do the knee and on the other hand a lot do the spindle. Both of which work great.
Generally the people who CNC the knee have to put a huge motor drive on it to handle the weight and expensive drive electronics to achieve their result. Some add a Gas strutt, (like on the boot or bonnet of some cars - but bigger) to help oppose the weight of the knee. There is also the option of rigging up a Counterweight arrangement to help lift the knee. I'm sure there are also more options than these, and they all seem to work. There are always little problems with each of them like for instance the cost of a huge drive. The Gas strutt set up is fine untill you go and place a job on your machine and all of a sudden the the knee weighs much more and the drive works hard again to lift and lower it. Steel is heavy so even placing or removing a vice is going to make a difference. The counterweight option caters for the change in weight of the job as you can weigh the job before you put it on the machine and simply add and remove from the counter weight. Works well! The only change that will be encountered is the addition of mass to the load. In this I mean that excelleration and decelleration of the knee will change because you are now shifting almost doubble the total mass of the knee and job. The knee will be sluggy and rappid moves may suffer due to the drive ramping up and down.

I am going to CNC the quill for now. It is a job that is easily in my reach and I have done several sketches of different configurations to come up with the one I'm going to use. The great thing about the quill is that it hardly changes in weight. The only change is a different tool or cutter. This is a big win for me as I can run all the same motors, drive pulleys, belts and control gear for all 4 axis of my machine and also cut down on spares needed to keep the machine running.

My Quill like yours also has a lot of slop as it extends down out of the head. The rack and pinion is un adjustable and has the backlash I would expect from a rack and pinion of this type. I will be adding to this thread as I convert the quill as I am not happy with the amount of runout the quill has when it is extended out a long way. I have already purchased a lenth of Brass 100mm OD and 75mm ID to bush the quill and will be doing that once I have my X and Y axis complete.

Remember there is no right or wrong way of doing the Z axis so please be inventfull and see what suits your set up.
Excluding you Leeroy I dont want this thread to turn into a Z axis debate.

I hope this has been of some help.

Thanks,
Chich.................not Chinch :rainfro: