New Machine Build- one foot lathe

[cyclotron]

Hi all,

I'm almost complete with a design for a one foot long cnc lathe. Its more of a breadboard model for a larger lathe that I would like to build one day (for which I don't have the space or time to tackle!). In any case, I will use this small one to prototype parts for binoculars. I am hoping that it will be able to cut aluminum, plastic, and some composites. Also, I intend on using gang tooling. That's really the part that makes this a breadboard model, as I don't have much experience with setting up tool offsets and such.

my current design is just a standard lathe configuration. There is about 4" of z travel and 5" of x travel. The swing will be around 4.5" over the ways and 2" over the cross slide. This all depends on where the motor couplings get tucked away so the numbers could change.

Anyway, I am using parts from my last cnc build. I will have to cut two linear rails (should be interesting!) And I'll be mixing in a slab of cast iron for the base.

I hope to get down to machining later this spring, as early as mid May. in the mean time, I hope I can get some feedback on the design and really hammer out all the details like limit switch mounts, way covers, etc. This is something that I neglected in my last build and I'm trying to learn my lesson!

Cheers! Andy

[Starleper1]

not a bad design, check out the thread "Parts Bin Micro Lathe" he did a real nice job on a mini lathe.

[cyclotron]

Starleper,

I had been thinking about making a small machine for a while now, but the parts bin lathe really inspired me to seal the deal. I really like the simplicity of the design, namely the single extra wide bearings. I need to look over that thread again to see what he said he was building it to do. Also I would be curious to see that machine in more of a gang tooling mode, with more than one tool on the cross slide.

[cyclotron]

I tweaked the drawings a bit more and I managed to work in another inch of travel in the X. I think 6" should be enough to hold a basic assortment of tools: turning, drilling, boring, and cut off. I will have to do some drawings that mock that up a bit.

[will gilmore]

remember that with gang tooling you sacrifice 1/2 of your z with tooling. if you have 6" of z you can only drill a 3" deep hole

[The Blight]

That is true only if you place the tool at the front of the cross slide. Place it further back and you will have more travel.

[zephyr9900]

Originally Posted by cyclotron I will have to cut two linear rails (should be interesting!)

Andy, that's looking good. I built a similar mechanism to put on my Feeler lathe, and of course Jason's excellent small lathe is a great machine. I cut the 10mm rails for my mechanism with a grit blade in my hacksaw, and it only took a couple of minutes per cut. And I'm sure I didn't disturb any heat treatment as I would have using an abrasive cutoff wheel.

As the Blight said, I've placed my drill chuck holder at the back edge of my toolplate, so that I can adjust the tip of a drill to be pretty much in the same plane as my turning and parting tools. Haven't used it yet--I still need to bore the toolholder in place on the lathe--but that's the plan!

Randy

[cyclotron]

Will,

I'm glad that you pointed this out about the travel and tooling interaction, its something that had not occurred to me at all! I have not really decided about what the the cross slide will be like, t-slots, tapped grid of holes, etc. I can't really hope to design a tooling plate that is perfect right off the bat, but I can at least add the option of moving tooling from the front to the back (right on Blight!) I will load some drawings for how tooling could work. I am leaning towards t slots because they won't interfere with the rails beneath. They also won't let swarf down through like tapped thru holes would. No matter what, I think that thickening the cross slide is in order.

Randy, you said you used an abrasive (?) hacksaw blade? I was planing on using a cut off disc on a dremel or fordam tool and dipping the rail in water when it got hot!! While I feel this method would be more exciting, the abrasive hacksaw method seems most sensible. I am wondering about how to clean up the rails after the cut. Isn't there a thread about this? Anyway, I was going to borrow a carbide end mill from my friend and do some light passes with that to clean things up.

Got to get back to my drawing, I will see about cutting the rails this week.

[cyclotron]

Randy,
I took a look at your feeler lathe conversion(?)
I hope I don't have the same chatter problems that you
were having. I guess you either have enough bearing surface
in a machine tool or you don't! no way around that one!

[will gilmore]

Originally Posted by The Blight That is true only if you place the tool at the front of the cross slide. Place it further back and you will have more travel.

True if the work will clear the cross slide. I think a lot of gang lathes worth with minimal clearance above the cross slide and all the tools hanging off the front.

[LeeWay]

Take a look at my gang tooling.
http://www.cnczone.com/forums/attach...5&d=1231293676

I intend to put another drill bit in, but mounted on the back row. It will have an offset holder and will extend the same length as th other one.

I could easily put another tool on the back side for turning. It is just that my parts are rather simple. A cutoff tool serves two purposes. Turning and cutoff.

I only have 5" travel, but with the table I used, I have the luxury of double rows of tooling.
Just food for thought on gang tooling.
Looking good on the design so far.
It doesn't really matter how much Z travel you have when working with no tailstock.
The X matters the most I think.
I knew 5" would get me the tools that I needed. With 6", you should not need to worry much.

[zephyr9900]

Originally Posted by cyclotron Randy, you said you used an abrasive (?) hacksaw blade?

Yes, Andy, I've had it for at least 20 years, used it less than 10 times. But it's really handy for cutting small hardened things. The linear rails have been its "moment of glory" thus far.

Originally Posted by cyclotron I hope I don't have the same chatter problems that you were having.

With the wide rail spacing you've drawn, you shouldn't have a problem. I had the chatter initially because I was just cantilevering the loads from the relatively narrow THK actuators. Adding the parallel rail to widen the support base made a world of difference.

Randy