[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

[s_c_engineering]

you may as well forget about using the stock setup. your either going to have to attach ballscrews to the spindle clamp. or lock the spindle in place and figure out a way to make the entire head move up and down. counterweighting it or using a gas spring. my idea revolves around what this guy did to his drill press. http://www.pathcom.com/~vhchan/cnc/cnc.html

[jhowelb]

No large secret on the spring. Just pick one up at Home Depot and hook it to the collar on the spindle and some place handy inside the casting hollow.

This guy, however has a better idea. I will pattern my notion after his!

jb

[dgoddard]

Interesting idea. Do you have the web site where this is located or if a CNCZone member, their member name?

[jhowelb]

I must confess to being an electronic pack rat. I have a 300 gig hard drive nearly filled with pics of different mechanical "ideas". They are catagorized according to subject matter but beyond that all data is lost.
I'v got other spinning nut designs pictured but that is about the neatest and best execution of the lot.

[jhowelb]

One of you guys wanted a picture of the Z backlash spring. Here it is, no great shakes really!

[s_c_engineering]

thats an interesting concept. but you said you lose steps with it this way no?

[jhowelb]

It loses z position because there is a clutch that makes the connection between the worm gear and the spindle crank. the clutch will slip if motor move the axis faster than the bit can cut. Nothing to do with the spring, just have to keep the feed rate on z axis slow enough to be sure the machine is not crowded.

btw, no mentors in Bakersfield.

[Preston E]

Hi JB...In the picture of the fellows Z drive...and yes I've seen that one before the likely problem will be with the long arm attaching the screw to the quill deflecting under load. Either triangularating the bracket to strengthen it or moving the screw as close as possible to the quill will help greatly...

Just fome food for thought.

Regards,

Preston

No large secret on the spring. Just pick one up at Home Depot and hook it to the collar on the spindle and some place handy inside the casting hollow.

This guy, however has a better idea. I will pattern my notion after his!

jb