CNC lathe conversion (again, sorry!)

[kong]

Ok guys, i got the lathe, and am in the process of cleaning the gunk off of it. I am considering the cnc conversion, which should be quite straight forward, but need a little help on the x-axis leadscrew. One end is not supported, but I would like to add a bearing or two to stiffen it up. Now if the saddle were made of ali, I would dive straight in and bore a hole through, and whack a mounting plate on the outside for the bearings (obviously the leadscrew will be replaced with a longer one). But, since I have never even thought about cutting/drilling cast iron, your opinions/experience would be a great help. I have NO access to a mill, so it's pillar drill only I'm affraid. What to do?





The thickness of cast iron I would need to get through is about 1". Thanks

[sp00k1e]

Im no expert, but on my machine I just used a hand drill, it cuts very easily but produces a fine dust which gets everywhere, it taps easily as well.
Paul

[Stevie]

Well a hand drill will screw this up for sure; unless you can guide it somehow

I'd be inclined to just use the leadscrew as is; if you have no access to a milling machine to make even a guide to steady the drill bit from the handwheel side; trying to drill this without a mill from the opposite end will result in disaster

If you re-placed the lead screw with a ball screw and nut the project would be much more accurate; but I'll have to say somewhere in the process a machine shop will have to be found to help you

If this route is the way you go; the old nut could be used as the guide for a long drill to punch through the cast iron; then "maybe" you could bore it up to a brg dia with a drill press; I hope you have at least a finger dial to pick up the hole center

[Bloy2004]

If you're adding bearings "whacked" on the outside, just drill out a hole oversized so your ballscrew will clear it. Then make your bearing plate/block with adjustment for alignment. All you want is support at that end, right? If this is going to be your business end then the bearing mountings/CNC motor will all hold the shaft end in alignment.
Don't know what the casting surface is like on that end...it may have to be faced or surfaced.
At any rate, the casting will drill fairly easy at a speed that won't fling the granual cuttings all over.....just from my experience..

Another thought if your casting is uneven....and your drill press has an accurate depth stop... to counter bore the tapped mounting holes to receive short stand-offs thus creating an even plane perpendicular to the ballscrew.

[kong]

Thanks guys, Stevie, you're thinking is way too advanced for me! Bloy, you got it, I was planning on drilling an oversize hole, and machining an aluminium bearing block (which I can do on the cnc router) which can be bolted onto the outside, with some sort of adjustment to align the screw. I'm just planning at the moment, so as long as the iron will be "easy" to drill through with the drill press from the outside, I am happy. I will have plenty more questions as the plan comes together!

[HuFlungDung]

You could make a drill jig like this sample, if you wanted to do a good job of centering the hole. One end of the block is a close fit over the end of the existing screw, the cutout part fits over the casting at the end of the saddle, and the other hole is the guide bushing for your drill bit. Kind of a pull yourself up by the bootstraps sort of way to make it work

[balsaman]

Cast iron drills easier than aluminum in my experience.

Eric

[kong]

Hu, thankyou That is an excellent idea!

[Stevie]

I think like a tool and diemaker (because I am one)

There is no such thing as close enough with me! it's right or it's scrap