Harbor Freight mill conversion to cnc

[jhowelb]

A while back I started a thread on converying a Grizzly 9 X 19 G4000 lathe to cnc (http://cnczone.com/forums/showthread.php?t=26530) and created a bit of interest but had to put off continuing the project due to health concerns My health has recovered but my shop is cold and I can't risk another infection so it will have to wait till spring.

I love this hobby so much and I want so much to share any gained knowledge and experience before I'm taken away so I've decided to begin sharing the conversion of a Harbor Freight Table top mill with any who might be interested. These are my motives so forgive an old man his fallibility while I pass the time till warmer weather.

After reading an article in Home Shop Machinist I decided to use some of their ideas to convert a manual mill that I'd had in my shop for a number of years.

Using ½ inch plate aluminum, a hole saw and a chop saw I fashioned some stepper mounts as shown in these photos.

I think I'll pause here to invite comments and conversation.

[jhowelb]

For some reason one pic wouldn't attach and without it the post is pointless.
Sorry about that.

[S_J_H]

jhowelb,
I'm not real sure by the pics of just how those parts will come into play later on but they look nice. I would say you are off to a good start. I was following along with your lathe project as I also have a Grizzly 9x20.
I have converted a x2 and x3 mill to cnc and it was well worth the effort.
I'm sure whatever progress you post here with your conversion project will be appreciated by many.
I also want to wish you all the best with your Health.

Steve

[jhowelb]

Hey, Steve!
One picture is worth at least a thousand words.
Keep in mind that these brackets (OSHA un-approved) are an intermediate step.
Aditional steps will make belt guards from 2 X 4 rect. tube.
See, at this time I was "boot strapping" myself out of a situation with no equipment at all. You make equipment help you build itself!

[jhowelb]

Now, because I had worked with this mill for some time, I knew that there was enough backlash in all the lead screws to cause big control problems. Ball screws were going to be a must.

MSC Industrial Supply Co. provided an answer at a reasonable price.

I used the original thrust bearings and be cause I could not cut concentric threads with the lathe I utilized the illustrated "work around" and welded a fabricated end of softer steel in place.

The photos of the ball nut and nut receivers are not mine, I "borrowed" them but they are indistinguishable from my own.

[jhowelb]

Two more pics to finish the mechanical story and then on to controllers.

Notice the modified cheap calipers used as a DRO!

[s_c_engineering]

nice work j!!! i like the way your used the belts. where did you pick up the belts and pulleys? also, hows that z axis on backlash? i have almost the same mill except mines got the geared head on it intead of the belt head. looks like it went together pretty smooth!!!

[ozzie34231]

What are you making?
Parts!
Parts for what?
For the machine.
Why?
So I can make better parts.
For the Machine?
Yep.

Ozzie

[jhowelb]

MSC provided the belts and pulleys, I used the XL (1/5 pitch)

http://www1.mscdirect.com/CGI/NNPDFF...5849&PMCTLG=00

Not real happy with the Z axis, it can lose steps on a heavy cut. The backlash is eliminated with a large spring attached to the back side of the quill. Now that my lathe can cut ands thread ball screws I will design and install an external screw for the Z axis and while I'm at it I'll build X and Y mounts out of 2 X 4 square tubing so that they provide belt guards in the bargain. Maybe even cut new screws for the X and Y!

Yep! Building parts so I can make better parts! But, what the hey!!! What else does a retired gentleman do while his wife is off teaching school?.

Well, I mean, when he's NOT mucking about on the CNCZone!

[s_c_engineering]

so on the z axis are you planning on making a rotating ballnut with a solid mounted screw, or mounting the nut solid and having the leadscrew rotate like normal?

[jhowelb]

I have already made one attempt at a rotating nut. mounting the thing square, right and plumb turned out to be a tussle. This time with the ability to cut threads, things will take on a different look.

The hundred bucks or so for the ball screws is a really good investment. First, that is an eight foot length we are talking. That makes a lot of machine! Secondly, friction is the ultimate enemy in any mechanical application. Remember, ball screws can be run dry or with a small amount of silicone lube.

[dgoddard]

I'm converting a RF31 and been thinking about various ways to eliminate the z-axis backlash. Thought about a spring, gas cyl, or hanging weight. Does your spring setup eliminate the backlash? What size spring did you use? Do you have a source? Photo of setup would also be helpful. Thanks