# Another RF-30 clone followed me home today, a King PDM-30. That's two, now the rebuild starts.



## Kilohertz (Mar 27, 2022)

You may recall my trying to decide which RF-30 clone to get a few weeks ago, I bought the Craftex 30 but haven't picked it up yet, and was contemplating this one as well, and decided to just get the damn thing and be done with it. It's a about a 2010 King PDM-30 that was bought new and dismantled to be be changed to CNC but never done and never reassembled. As a result some of the parts have gone missing over the last 12 years, but I contacted King and they are all available and in stock except for the X axis lead screw bearing housing that goes on the end of the table. Without including the motor or motor pulley, as I am going to put VFD and 3~ on this, parts come to about $600. I got the machine with King stand for $200. I cleaned it up today of it's 10 years of crud sitting in a machine shop unused, turned out pretty nice. Damn this thing is heavy. We removed the table and Y slide, the motor was missing, I'm guessing it was still 450 lbs, got it out of the building and slide it up some ramps into my truck. At home I found that my truck box was the same height as the steel table I have outside so I just slid it onto that for now as my shop needs reorg before I can use the excavator to move it inside.

I need to go thru it in a little more detail and make a final list of things to order...looking forward to getting it going. It was never really used, I think the condition of the ways says it all.

Never too many machines.  More as I make some progress. The machine cleaned up pretty well after an hour of solvent and a brush.

Cheers


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## 6.5 Fan (Mar 28, 2022)

Kilohertz you are correct in saying Never to many machines. A person always has the option to sell down the road, if the price is right jump on a deal. What is the car in the background of 4th pic?


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## Susquatch (Mar 28, 2022)

I think you did the right thing too. I ended up with two BP mills the same way. One of them will find a new home this spring/summer.


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## historicalarms (Mar 28, 2022)

Hmmm one thing I noticed in the top photo, the King has 2 locking bolts to lock the head to the round column,  mine has only one bolt.
     It hasnt been an issue with me only haveing one but others have complained that the head will pivot even when locked....yours will lock solidly I'm thinking.


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## Chip Maker (Mar 28, 2022)

Is that a Firebird in the background?


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## Kilohertz (Mar 28, 2022)

Good morning all,

Thanks for the replies. 

First, Chip Maker wins the prize, yes it's a '68 Firebird I am almost finished restoring. It's going back together slowly as I was having problems getting parts last year. Should be able to finish it this summer. In behind it is a '49 Ford F-47 also being built....the shop is a bit busy/full right now. 

I forgot to post a pic of the only problem with this mill, one of the double column locks has a cracked ear in the casting, I will need to V grind it and weld. Looks like someone got heavy handed with the lock wrench. Otherwise it's pretty much new.

I'll figure out the list of parts it needs and get those moving, giving me time to cleanup the shop.

Cheers


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## YYCHM (Mar 28, 2022)

historicalarms said:


> Hmmm one thing I noticed in the top photo, the King has 2 locking bolts to lock the head to the round column,  mine has only one bolt.
> It hasnt been an issue with me only haveing one but others have complained that the head will pivot even when locked....yours will lock solidly I'm thinking.



That's interesting?  Mine has two.


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## Kilohertz (Mar 28, 2022)

I just discovered something strange with the parts that came with this milling machine, both axis lead screws and brass blocks look like they have been modified. When we took the screws out to remove the block to slide the y-axis table off several zillion balls fell out and I realized that it must be a recirculating ball screw type set up, I had a quick look this morning on YouTube and see that was not original. Has anybody run into a set up like this? I forgot to take pictures of the two axis screws but they are radically different, the fellow included now what I realize are the original lead screws as well. I will get a picture of the originals when I get home tonight, the ones pictured go with the recirculating ball type.

Thanks


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## Darren (Mar 28, 2022)

yup thats a ballscrew. That nut can be reloaded. mic each ball, some ballnuts will have two different sized balls, alternating small/larger.


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## Kilohertz (Mar 28, 2022)

Darren said:


> yup thats a ballscrew. That nut can be reloaded. mic each ball, some ballnuts will have two different sized balls, alternating small/larger.


Thanks Darren,

They must’ve added that on for a reduced drag for their plans for a CNC set up. As that tray with all the balls on it slid off the stand as we were lifting the machine my son spent half an hour trying to find them all with a magnet, ha ha, so I may need to buy more if I’m going to reuse that. Would there be any disadvantage going back to the original brass set up, as I have the original lead screws as well or is the ball screw a hot rodded zero lash set up and I should keep it and make it work?

Thank you!


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## Darren (Mar 28, 2022)

Yes, its both reduced drag and zero backlash. My mill has ballscrews and they are awesome. Keep them if you can, but you may need to fit a DRO if they have a different pitch than the factory leadscrews.


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## Kilohertz (Mar 28, 2022)

I can see this turning into a hot rodded ultra smooth little mill way beyond the original capabilities.  Column mods coming as well. 

Yes DRO was already in the plans. 

Cheers!


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## PeterT (Mar 28, 2022)

Darren said:


> My mill has ballscrews and they are awesome. Keep them if you can, but you may need to fit a DRO if they have a different pitch than the factory leadscrews.


Maybe I asked you this already but what is the thread pitch of you ball screw?


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## Darren (Mar 28, 2022)

PeterT said:


> Maybe I asked you this already but what is the thread pitch of you ball screw?


Mine are 5.08mm pitch, or 0.200" per rev, so my dials work out. With a DRO you don't need to worry about that though. But course pitches will lead to back driving issues.  Mine have not been a problem


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## Kilohertz (Mar 28, 2022)

I’ll measure when I get home this afternoon, I know the original lead screws are very fine pitch, the ball screws are much courser but again haven’t measured yet.

Appreciate the help


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## Darren (Mar 28, 2022)

the ballnut should be/might be marked with the pitch. Measuring the screw can be harder if it turns out to be a multi start thread.


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## PeterT (Mar 28, 2022)

Thanks, yes it was the potential back-driving (self-feeding) I am curious about. I suspect that's why there are varying opinions about ball screw conversion. Lots of nice inexpensive balls screw systems out there popular for CNC machines, but too coarse a pitch is probably going to create new issues. I'm selfishly thinking more about potential lathe conversion here. I didn't look extensively but I recall looking for 10 TPI equivalent ballscrews to match 0.100"/turn dial range, not as many to choose from & cost rises too.


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## Susquatch (Mar 28, 2022)

Darren said:


> the ballnut should be/might be marked with the pitch. Measuring the screw can be harder if it turns out to be a multi start thread.


I believe his is a single start. See picture #2 above.


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## Kilohertz (Mar 28, 2022)

I can already tell from this discussion that I have so much to learn. Thanks everybody for all of your help.


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## jcdammeyer (Mar 28, 2022)

Nice Score even with the crack.  Hopefully you can get the ballscrew repaired.  At worst buy a new ball nut.


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## StevSmar (Mar 28, 2022)

Boy, that cleaned up very nicely. And with ball screws too!


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## Kilohertz (Mar 28, 2022)

Just got home after a grueling day of work then loading an 18 foot flat deck trailer with fresh cut ponderosa pine for the start of this year‘s firewood, I am dead beat.

However I managed to muster enough energy to drag out the callipers and measure the pitch on both lead screws. The ball screw pitch is .2 inch and the original larger diameter but finer pitch is .1 inch.

And a picture to go with this, including the little balls that fell on the floor. 

Also just realized the hand wheels are the wrong shaft size to work with the ball screw lead screw. Would need to find new ones or maybe, just maybe mind you, make this into a CNC machine and keep the Craftex 30 as a manual machine. 

Hopefully will have more play time after work tomorrow.

Cheers


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