Leeroy,
You and I have had the same toughts. I had also thought of hard chroming the quill up to size but this was going to cost me $890 bucks so that wasn't to be an option. You can very easily purchase ready to go Honed hollow steel tube for making hydraulic cylinders. I was thinging of sleeving the head with a steel bush of this material but that is no good as steel on steel will have bad wearing prpoerties. One option is to bush it with brass so for $150 Inc tax I purchased a piece as described in my previous post. When it comes time to bush the quill I will skimm the OD of the bronz to size, remove the entire head from the mill and bolt it to the cross slide of my lathe, right through it I will place a 70mm piece of high tensile bar between centers as a long solid boring bar. This boaring bar will hold a cutting tool. Using the lathe to spin the boring bar horizontaly I will bore out the inside of the head to siut the OD of the bronz Bush. I will then insert the bush into the head with a chemical lock like "loctite" without moving the head on the cross slide. After that I will bore the inside of the bush to suit the quill. With the length of bronz I have it should pick up the bottom web the mid web and also the top web where the pulley is mounted. After that I will mount the head to the table of my mill and use the horizontal axis to bore out the pinion and lock holes. I would have normally done all of this job in the mill but the Y axis doesn't have enough travel.

A very easy solution to this entire problem provided your quill is straight, smooth and parallel is to use a liquid filler and simply fill up the inside if the head with putty to suit the quill. An excellent product for this is MOGLICE. Examples of it can be seen at http://www.moglice.com/ If you take a look in their "Application Examples" and take a look at "Ingersoll Quill Bore + Elevating Nuts" you will see what I mean. All you have to do is clean everything up, plug up your holes, spray the quill with release agent and put it in the head, inject the moglice in and hey presto..... a perfect fit.

I have no idea what the product costs But I do know someone who has used it many times before and swears by it's accuracy. It is a very attractive solution. If you use a filler or bush it you will retain full travel in the quill.


For your question on the Z axis drive mechanism I am going to use will consist of the following;
I will bolt the head to my table with the quill center axis straight to and square to the column of the mill. I will use the horizontal spindle to mill the side of the head flat where the stop start switch is on the HM-52. This flat surface will be parallel and square to the quill. (I will later include the stop start switch to a movable boom) To the side of the head I will then mount my servo motor and drive mechanism. I will make a large solid steel clamp that will firmly hold the fat part of the quill. It will be a tear drop shape when viewed from the top. The pointy end of the teardrop will have a tube connected to it which contains the lead nut at the top. The motor mount which is bolted tight to the head will also hold 2 preloaded annular contact bearings firmly holding the Z axis lead screw in place. The way it will work is the motor and lead screw will stay stationry to the head and as the screw turns, the nut (anti backlash once again) in the tube will push the tube up and down. The tube is connected to the large quill clamp so therefore the quill will go up and down. All the thrust will be on the 2 annular contact bearings and the lead nuts......... Simple!

I have designed Z this way beacause if I wish to use my mill as a manual machine all I have to do is put the coarse feed handle back on, realease the tube from the Quill clamp and away I go.

Cost so far for my conversion has been $100 each motor times 4, $60 each encoder times 4, ($160 24volt 20amp servo's is CHEAP!) $45 each axis for belts and pulleys times 4

Hope that has not put your head in a spin!

Chich