Another X2 Conversion

[acondit]

I have been working on this off and on for some time. One of the problems with too many projects and too little time. Anyway, I thought I would show some of the things I have done.

I will start not necessarily in the order that I did things. So, I am first going to start with the column setback (to increase Y travel). This modification will increase the Y travel from about 4" to about 5.5". It may ultimately require adding a 0.75" to 1.5" thick spacer between the spindle housing and the dovetail slide, in order to move the spindle out further from the column.

I got the idea for this column setback from the work by John Pitkin shown on the GrizHFMinimill group on Yahoo.

Alan

[acondit]

The Y-axis screw mount is made in two pieces. One piece is just a spacer to move the bearing block out from the base. The bearings in the bearing block are 1.125" outer diameter and as a result they were higher than the top surface of the slide (and spacer). So the bearing pockets are spaced out from the base in the bearing block. I originally bought a KDN kit from LMS but it would have required machining the saddle to clear the bearing pocket in the KDN Y-axis adapter and I wasn't wild about that. So I designed my own parts.

At the moment I am using a 3/4"x5tpi precision acme screw with a delrin nut for the Y-axis. Once I get the mill running I may replace the delrin nut with a bronze nut, if I don't add a ball screw. I have enough 5/8"x5tpi ballscrew stock but all of my ballnuts are double ballnuts and they are about 4" long which would significantly shorten the Y travel. So I haven't decided what to do there yet.

The bearing spacer also has 4 holes drilled and tapped for 10x32 allen screws to mount the motor standoffs. I still have to make two new motor mount plates. I used one of the two original KDN plates on my lathe and the other is mounted on the Z-axis (that I will show you later).

Alan

[acondit]

I did the X-axis bearing support on my cnc router. I cut it out of MDF, and hopefully it will be strong enough to last for one project. I intend to replace it with an aluminum one as the first project on the mill when it is running.

It has two bearings, one on each face. It also has four holes drilled and tapped for 10x32 allen screws to mount the motor standoffs.

Next step is to mill a small pocket in the saddle to allow the double ballnut to clear the underside of the table.

Alan

[acondit]

I looked at the rotating ballnut designs by Stirling and Hoss and decided to try a design of my own. I designed it to use an angular contact bearing on top and a thrust bearing on the bottom. I wanted to be able to adjust the bearing preload, so I designed it to use a nut on the bottom to adjust the preload on the bearing.

The inside end of my column was very rough so I used a die grinder to smooth it out. I cut out the bearing support piece out of some 1" aluminum and I machined the bearing pockets before I cut the corners of of the piece of aluminum.

I machined the rotating nut spindle before I converted my lathe to cnc. I turned the piece that was going to be the adjusting nut as a part of the spindle and then parted it off. I ended up with one bearing journal a couple of tenths too small, so I knurled the end of the journal to increase its size and get a better fit. I threaded the end of the spindle for a 32tpi thread. Then I faced and bored the nut piece, and internally threaded it to match the spindle.

Then I centered a 60T XL Belt Gear, turned a shallow pocket to match the diameter of the spindle head and mounted it to the spindle head using 10x32 socket head machine screws. Then I flipped the gear over, bored the boss and threaded it internally (15/16x18) to match the ballnut mounting threads.

Alan

[acondit]

Next step was to test fit the assembly. So here is a picture of the assembly put together temporarily (not the corners have still not been finished). All of the ballnut assemblies that I bought had short stub ballscrews in them (too short to be of any use).

Then here is a picture of the first fitting to the X2 column (note now the corners have been cut). I discovered that with the bigger bearings the assembly interfered with the fit of the belt drive conversion that I bought from LMS.

Also because of the length of my RBN spindle I had to use a 1" spacer to raise the RBN assembly above the top of the column.

Alan

[acondit]

Since I found out that I had interference between the RBN assembly and the spindle motor, I designed a new mounting plate to swing the spindle motor out to the right side of the spindle housing.

I had seen one of these on another website so it is not an original idea. I think it was the KDN website. I designed it so that everything else in the original belt drive kit worked with the new plate.

Alan

[acondit]

This gets me up to date on my conversion. I cut an 18" length of ballscrew stock, finished the ends and drilled and tapped the center of one end for 5/16"x18. Then I used Hoss' design for mounting the end of the ballscrew to the dovetail slide housing. I discovered that my design moved the screw about 1/16" closer to the column than his so I had to mill out a notch in the attaching bracket.

Alan

[acondit]

Today I milled a pocket in the saddle to fit the ballnut for the X-Axis to the saddle. I had to create a pocket 0.060" deep for the whole double nut assembly and two smaller pockets, 0.125" deep to clear the wiper holder and the adjusting assembly.

I used a 3/4" ballnose endmill to clean up the underside of the table so that it would clear the ballnut for the entire travel.

Next step is to machine the ballnut mounting nut. It has to fit in the original saddle pocket and be threaded 15/16"x18 for the ballnut nose threads. Then cut the ballscrew to length and machine the bearing end.

Alan

[cyclestart]

Looking good

Always easier to modify a mill if you have another mill (and lathe ). My own X2 extended Y is waiting for a local machine shop to find time to mill the base. They said the paying customers come first or some such nonsense LOL.

OT/ Hows the lathe doing? Are there any threading videos coming?

[acondit]

Originally Posted by cyclestart Looking good Always easier to modify a mill if you have another mill (and lathe ). My own X2 extended Y is waiting for a local machine shop to find time to mill the base. They said the paying customers come first or some such nonsense LOL. OT/ Hows the lathe doing? Are there any threading videos coming?

Thanks.

Yep, it is always easier to do a job when you have the right tools. Starting when I was in high school, I would find out how much someone else would charge to do a job that needed doing, and I would get my parents to pay for the tools to do the job and I would do it myself. When I got married I continued that with my wife, over time I have built up a good selection of tools.

I have done some threading on the lathe but I haven't made any threading videos. Now that I can cut under cnc control, I am actually finding little things that need to be fixed to make it "right". I recently discovered that the tailstock center is 0.010" higher than the spindle center. I also just discovered that one of my 3 jaw chucks is off center by about 0.003". So I need to fix that before I do anymore turning using that chuck. (And I need to use that chuck to finish the X-axis ballscrew installation.) I have a spare backplate if I cant fix the current one. It seems like every project turns into two more projects.

Alan

[acondit]

Well after almost 2 years, I have done some more on my lonely X2. I'll post some pictures soon. I haven't even built the controller for it and I only built one stepper power cable, so I used my router controller and switched the one cable to test each axis. It worked great.

The X-axis and the Z-axis each have a Thompson double-nut and 5/8"x5 tpi ballscrew. The Y-axis for the moment has a 3/4"x5tpi acme thread leadscrew (there isn't room under the X2 table for a double ballnut).

I ran the x and y at 60 ipm and the z at 37.5 ipm. The controller thought that the z was going 150 but I hadn't created a mill profile to account for the 4:1 gear reduction on the z-axis.

Next step is to mount the limit switches, since for the moment I can use the router controller to run it.

I have been busy lately, trying to get my new/rebuilt router done and it is almost done and seeing the mill move under power is a great incentive to get it finished.

Alan

[acondit]

Here is the X-axis stepper mounted on the temporary MDF bearing support. After I drilled the holes for the standoff bolts, I put superglue in the holes before tapping them. Someone one on the zone (probably in the Router forums) taught me that trick. It gives you much stronger thread support in the MDF.

I haven't done anything about supporting the left end of the leadscrew yet. Given its length it isn't likely to whip much. However, after I get the machine actually running I will use it to make its own supports for both ends of the X-axis.

Alan