[jharvey407]

I am looking for a good bench top mill to convert to CNC. I have done a lot of reading but I figured you guys could really fill me in on the pros and cons of the machines, especially when it come to the CNC conversion.

I need a 110V single phase machine because my shop only has 110VAC.

I am looking at the G0704. What I like about it is;
110VAC
1 hp
R8 spindle
Variable speed spindle
Good table travel
about $1,000

Is there a comparable mill that might be better?
Are there any major complaints about this mill?
Is it easy to convert to CNC?

Thanks guys,
James

[dugpits]

Only systemic major complaint I've heard on the G0704 and other BF mills is the motors tend to burn up.

I don't know if that problem has been solved or not. I may be suffering the same deal. My controller was tuned down a LOT and my max RPM was around 1800-1850 (supposed to be 2250). When I turned it up, my motor gets hot pretty quick, and I notice - especially at the low end of the rpm range - I get some sparking from my motor brushes. They look fine though so I may call Grizzly to see what the deal is. Not sure that is normal and I'm getting some 'choppiness' in my rpm's (doesn't hold steady and the pitch varies from the motor).

I received my mill about 8-9 months ago, so they may have changed motor suppliers by now.

The spindle bearings also need upgrading. I haven't upped my RPM with a gear mod or belt drive yet, and just running at 2500 rpm for 5 minutes my spindle gets to about 140+. That's with no tooling loaded - so no cutting load.

Yours may vary significantly. These chinese mills vary a lot. Any other model of chinese mill I would guess has the same variability. I don't have any personal experience, but I've heard some people complain about the 'head nod' on the X3 class mills which are pretty close in travel envelope.

On conversion:

I bought Hoss's plans. Not hard to make the parts. I would recommend you measuring areas of your mill before making the parts due to variation in castings. You do have to mill some clearance in areas. I did mine with a drill press and air grinder - it isn't pretty.

FYI - $1,000 is just the start. To get the machine CNC'd, assuming you are starting from scratch (no tooling etc), I would say you need an ADDITIONAL 1,500 - 2,000 to get it CNC'd and ready to go. Tooling is expensive. Machined ballscrews can be expensive too.

On the 110v. Don't limit yourself to 1 phase. I felt that way too. But I've seen pretty reasonably priced VFD converters that will run some 3 phase motors that I'm thinking about if my motor bites it and Grizzly won't give me a new one.

Summary:
I like my G0704. It has enough travel so you can actually make some decent sized parts. It is small enough to move around. Taking it apart to CNC isn't hard - all the pieces are manageable by 1 person. At first I wanted a larger heavier mill, now I'm glad I didn't get one that large for now because it is much MUCH easier to learn when you can put and take the machine apart easy. I have run into unexpected snags - I imagine you will to. I have learned a lot from them, and they make me think more creatively.

Have fun and good luck!

Doug

[jharvey407]

Have fun and good luck!

Doug

Thanks Doug, there's alot of good information there.

[andypugh]

R8 spindle

What are the other options? R8 is inconveniently long, though not a lot worse than MT3. It means you need to raise the head 4 inches to do a tool change. You might find yourself shortening drills to work inside cavities.
The Tormach TTS probably solves this, though I have no personal experience with it at all.