[balsaman]

Ok, I am about to embark on a Enco style round column mill-drill conversion.

This one specifically:

http://www.kingcanada.com/Products.htm?CD=36&ID=121

I just ordered:

3 Gecko 320 drives
3 USDigital 250 CPR encoders
3 Amtek surplus DC motors, 50 volts, 2100 RPM

So, a couple questions:

I have read all the horror stories about the round column mills and the PITA when you need to reposition the head on the column. My question is, if I can live with the 5" quill travel, does this mill do a good job machining with the quill extended?

What are the odds that I can build some sort of external keying (using THK rail and bearings) into the round column and move the whole head up and down on the column as a z axis? If not that, perhaps I can still use the quill for z but use the keying to keep the head in position on the column when manually moving the head?

What do you think of using the stock lead screws? I am considering the Mcmastercarr 5/8" rolled ballscrews but are they any better than the stock lead screws as far as acuracy is concerned? I know they would be more efficient. Also If I used two ball nuts for preloading will they bind because of the fact that the screw is rolled and thus not that acurate?

Anyone with experience out there I would apreciate your feedback!

Eric

[cncadmin]

What did the mill cost you?

[balsaman]

It's used. $800 CAD. They cost $1500.00 here new at www.busybeetools.ca

Here is the link: http://busybeetools.ca/cgi-bin/pictu...0&NTITEM=B1977

Eric

[Bubba]

balsaman,
Looking at the add in your post makes me think the mill I have and yours are almost twins. Only the paint job looks different! As I have/am doing a conversion of a round column mill, I think I can speak from some limited experience.
1. Existing lead screws> for get IT (Don't ask:}) I used Roton rolled ball screws and am perfectly happy. With the original screws due to some problems, I was getting up to .250 backlash (and the mill hasn't seen THAT much use). I made my own pre-loaded ball nuts and the other day, I was doing some engraving and it would have shown up big time if I had any real backlash. Looked good to me. I wasted several months using the existing lead screws.
2. Can you live with the limited quill travel. Well, so far, I have; but it takes a creative setup. For "table" mounting, I made a raised table with a piece of 4x4 tube so I had room at the end to do the necessary tool changes. The vice makes the part raise up sufficiently to handle that part all by it self.
3. Finish, is satisfactory for the stuff that I do. Again, YMMV depending on how accuracte and how heavy a cut you take. I find for my purposes that a 3/8 mill is about as big as I want to go and not have problems with rigidity of the machine.
4. Unless you are a genius (and you may well be), the idea of moving the whole head is a tough nut to crack on a round column. Keeping it in line will be very difficult. If you figure this one out, there are a LOT of us out here that would like to know how you do it. (Keep it in line and do it "cheaply")

If I can give you any assistance, PM me.

Bubba

[trubleshtr]

I was just contemplating the hf 3 in 1 or possibly their version of the same mill you are converting, at 1000 bucks usd, i'd have to drive to buffalo to get it.
Balsaman are you in the GTA? (you dont have to answer), busybee on dixie rd mississauga is around the corner from my work, and if they got more at that price.....
this is what i was contemplating...
http://www.harborfreight.com/cpi/cta...emnumber=33686

[HomeCNC]

Well Balsaman, Welcome to the club

[HomeCNC]

Balsaman,

I have used my cnc drill/mill for a long time. I have never had to reposition the head once my job has started. I think the trick is to get screw machine length drills. Check out my website on how I keep my tool lengths very close to the same length.

[balsaman]

truble,

That's the one. The used one I am buying is a private deal, not buying it from busybee but from an individual who bought it there originally. I am not from GTA, but in Woodstock. An hours drive.

Bubba,

Ok, I will go with the ball screws and two ball nuts per axis. I need to pick up the mill this week and have a better look at it before I know what to buy. Did you use 5/8" ball screws? The ones I am considering are the 5/8" x 13/64" at $1.09 per inch plus $21.04 per square nut.

I will be posting regularly on the progress with lots of pictures so everyone will have lots of time to tell me how to do it.

Eric

[balsaman]

HomeCNC,

I have seen your website. I was glad when this mill turned out to be the same one you did. At least I know it can be done!

Eric

[Bubba]

balsaman,
I used 5/8 screws .2 pitch and got them from Roton.com. I got a 5' length for $43.25 USD and the ball nuts cost $19.40 each. Their wipers are 9.65 ea. Also be aware that they have a $40.00 minimum. I ordered 2 sets of wipers expectimg to get 4 but only got 2. So I used an idea that I got from another group and made my own. Not real pretty, but they work. As for turning the ends of the screw, my atlas is not rigid enough to cut through the hard stuff so I rigged up a tool post grinder out of my die grinder and simply ground the diameter down. Once under the hard stuff, it was easy to thread the ends as necessary.
There are a few pictures on my web site:
http://bellsouthpwp.net/A/r/Arts_home_page/cnc/

Bubba

[balsaman]

Great, thanks. I will order from Roton.

Eric

[anoel]

Hey, Eric... Check out the cost of getting the nuts preloaded. It may be cheaper than buying two nuts.

[ViperTX]

I happend to have a Jet JMD18 (which is really a Rong Fu 30) with round column that I'm planning to CNC. It is the round column and in 10 years of manual machining I've learned to plan my machining and I adjust the column prior to starting a project. http://www.tomsinstitute.com he did a Grizzly 1005 CNC conversion and has an interesting way of creating ballnuts with minimal backlash using 2 ballnuts, a spring and holder. Do you have a website?
I've got the Ametek motors and bought some 500 CPR encoders, haven't bought the Geckos they are on sale at geckodrive.com , I just bought all the parts for the 40 VDC supply, which I'll build this weekend.

[balsaman]

Hey, Eric... Check out the cost of getting the nuts preloaded. It may be cheaper than buying two nuts.

I will. Didn't know they came that way. Thanks.

Eric

[Jkier]

Just posting to keep an eye on this thread. I have that exact mill and have been dying too convert it for the past couple of years. I've been lurking here for quite some time, hopefully following your build will drive me to start.

[Bubba]

I made my own pre-loaded ball nuts and my inspiration was Toms Insititue, however I used a little different approach. I made a "socket" that fits over the back end of the front nut and then a knurled nut which is pinned to the "socket" by one or two 6-32 screws. I used "wave washers" from McMaster to pre-load the nuts. Works great for me.
You can see some pictures of how I did that and made my own wipers also at:

http://bellsouthpwp.net/A/r/Arts_home_page/cnc/

Yeh, I know, a repeat and should have thougt of explaining that the first time:{(

Bubba

[balsaman]

I am waiting for some parts to arrive and I need to pick up the mill. I promise you I will update once I have some more to post.

Eric

[balsaman]

Hmm, motors arrived this morning but I was not home. Gecko's are here. Still waiting on the encoders.

Love those wee little gecko's. Hard to believe they are good for 20 amps.

Eric

[HomeCNC]

I used hot glue to make my ball screw wipers. All you do is oil up the ball screw with some thin oil. make sure you don't get the oil on the ball nut housing. I held the ball nut in my vise with the screw vertical. Heat the ball screw just a little with a torch. Now fill the area where the ball screw enters the nut with hot glue. The glue will conform to the thread of the ball screw and make sure you get glue all over the end of the nut housing. You want the glue to stick to the nut. When the hot glue hardens you give the screw a turn to break it free.

Do the same procedure on the other end of the ball nut.

[cncadmin]

I used hot glue to make my ball screw wipers. All you do is oil up the ball screw with some thin oil. make sure you don't get the oil on the ball nut housing. I held the ball nut in my vise with the screw vertical. Heat the ball screw just a little with a torch. Now fill the area where the ball screw enters the nut with hot glue. The glue will conform to the thread of the ball screw and make sure you get glue all over the end of the nut housing. You want the glue to stick to the nut. When the hot glue hardens you give the screw a turn to break it free.

Do the same procedure on the other end of the ball nut.

That is a great tip, I think I'm going to try that.