Upgrading from 4" column mill to Knee Mill -- Looking for advice.

My self would vote for doing both. The RF 30 type mills have enough power for a lot of jobs the main complaints I hear on these forums is lock of higher in the z axis and the position moving when the column is moved.

If it was me provided I had the space I would get a used knee mill (Bridgeport) and use it for that reason. Even if I had to layout bolt patterns and such on the CNC RF 30. The main reason I say this is unless you have a working knowledge of electronics maintaining that mill would be a challenge. So a lot of home guys would shy away.




Sent from my iPhone using Tapatalk
 
There a good point of having a bench mill is milling a key at end of a 240" shaft
Ther no knee to rise or lower You set bench to set shaft

Dave

Sent from my SAMSUNG-SM-J320A using Tapatalk
 
Perhaps run through the usual list of constraints, such as: available space, available power, budget, transport, load/unload. Also, what is your intended use: work envelop, existing resources, planned projects. Obviously you are not new to this activity. Is it your ambition to do the CNC conversion, or do you want to take on the sort of projects that would really benefit from the capabilities of a CNC?

I just picked up a 20 year old industrial VMC. I think the cost & effort vs the capability is very favorable (Duh, if I didn't believe that I wouldn't have bought it). You can end up with competencies that a person probably would not build on a converted knee mill: ball screws, spindle drive interface, chip conveyor, full enclosure, flood coolant, very robust way covers, automated lube system, tool changer & air blast cleaning, air padded spindle seal, 4th axis, 40 tools . . . . and so on. Of course, you can walk into a store and buy all that and more most any day of the week - just consumes far more money than I was prepared to spend. However, at a a bit over $12K for a working machine that simply has a less efficient programming interface than a current machine, will provide a lot of capability that would be difficult to develop on a converted knee mill.

The base machine you linked in your first post will be half of what I spent, you'll spend additional time and money (and have a good time doing it) and end up with a pretty modest CNC. I am always very impressed by people who convert a machine they way you have. To me, it seems like an expensive (time and money) approach for the resulting capability.

Let us know how you make out.


Thanks for your comments. I plan to do a CNC conversion on the new mill, I have minimal experience with machining (just a fun hobby). I have an electrical engineering background so the electronics side is fairly trivial and only costed about $200 per axis when done on a budget i.e. buying the steppers and drives off ebay and I cobbled together a power supply from scrap parts. Motion Industries provided the gears and belts. I order circuit boards all the time so I just included the control board with another order.

This was more or less out of necessity as I doubt anyone sells a conversion kit for this particular mill, however after watching a video or two promoting the conversion kits for similar Grizzly models, my conclusion was I'm going to have to modify the kit to make it work on my mill, may as well just order the parts separately on the cheap and make the brackets. Making the brackets became easier as I added each axis and now I can't imagine not having the CNC aspect.

Summary for me the journey is the fun part.

BTW, visited local surplus machinery warehouse yesterday. They have about 30 or so used mills; Bridgeport and clones as well as new TopWell models. After speaking with the sales guy, I'm inclined to try and find a barely used 8 x 30 as this will be located in my basement and the Bridgeports simply look to beefy to get into a basement at near 2 tons. I can likely manage to get a 8x30 that should be < 1000lbs into the basement with some patience, rollers, a few 4x4 braces and a pinch of luck;-)

Cheers
 
Last edited:
Looking forward to seeing how this progresses.
 
If you need to work a machine down into the basement, that is a pretty hard constraint. I paid $6000CAD, no GST, for the VMC 1000 (with a fair amount of tooling) - which is probably cheaper than the CX603 that you linked. I paid a significant moving cost and there are going to be significant costs for the power (which should be cheap for the CX603) - which is why I estimated the total at $12K. Although I saw the machine run, I have no doubt there will be plenty of cleaning and repairing - in your words, still a "journey" to ending up with a decent working machine.

You seem to be very comfortable with the electronics. I may be contacting you - HELP, the smoke came out!
 
Think about where you’d be if awhile back you had spent all that work converting an old Bridgeport. Ok, maybe not the most helpful thought. But for the rest of us, worth considering, no?
 
P.S. the Bridgeport comes apart surprisingly easy, so the head is separate, the table comes off, and then it’s just a big hunk of metal that can go down the stairs.
 
Slo-poke: what software are you running currently?
mark
 
Back
Top