# RF-30 clone CNC started, need some guidance on ball screws and motors please



## kilohertz (Apr 1, 2022)

Hi guys,

I bought a Craftex 30 a few weeks ago, 1999 model RF-30 clone made in Taiwan, dirty but good shape with some tooling and accessories but buried in a garage for a few more weeks. Then last weekend I bought an unused 2010 King PDM-30 again RF-30 clone, Taiwan, that a machine shop bought new and started a CNC conversion but didn't finish, it's been sitting in storage ever since. Missing a number of items for it to work as a manual mill and would be about $600 to restore it to a full manual machine, so I decided instead to spend the money on finishing the CNC conversion.

Electronics and computers have been my whole life so that side of it will be easy for me, what I need some help with is identifying what I already have here and what I need to complete the mechanical side of it. I have been reading various build threads and will continue to do so, many of them on this site, but that will take some time and I would to at least start sourcing the parts.

As mentioned the machine is a King PDM-30 and is missing the following key items, 2 hand wheels, X- axis lead screw bearing holder on one end, quill return spring, quill hand wheel, motor, motor pulley, and a few other non critical items probably not needed for the conversion, even the hand wheels are probably not required. What it came with are ball screws already mounted on the original lead screw nuts with thrust bearings, the matching lead screws already mounted in the end bearing holders, most of the ball nut balls which fell on the floor when I removed the lead screw to get the table off to move it. 

My plan is to find a 3~ motor and VFD it using a single pulley on the motor and still have 3 pulley speeds.

The items I need some guidance on are how to support the end of the X axis lead screw (LS) opposite the bearing end, probably machine another plate to hold a bearing. Should I direct drive the LS or cogged belt and pulleys? Are the ball screws suitable for this machine? They are .2" pitch, 5/8" diameter, smaller than the original. I'm thinking of using a similar LS for the quill rather than driving the sloppy fine control with a belted motor. The ball screws only have a short threaded end where the thrust bearing preload is adjusted, and has a locking collar. There is no room for a pulley or direct drive connection. The end is hollow so maybe a rod could be machined and inserted/welded on for an extension. I'm not sure how the mfr intended this to be driven. Ideas?

Thinking NEMA 34 or maybe 23 motors, controllers and such I can work out later, same with computer and software. I have various 24 and 48VDC supplies suitable for the motors, 12-20amps.

I have two lathes and will have the complete Craftex mill/drill machine in a week or 2 so I can machine some of the parts that may be required.

Hopefully I am off to a good start. Look forward to building this and getting some guidance from you fine folks.

I'll attach some pics of the ball screws and nuts.

Thanks in advance for any help and guidance you may be able to offer.


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