New Machine Build- X2 CNC choices

[sansbury]

Hi all:

Owing to a lucky break on eBay I now own a barely-used Harbor Freight X2. I already have a CNC'd X1 which I was starting to get used to but the deal was too good to pass up.

Anyway, I am looking at options for CNC-ing the X2 and had a couple questions.

1. Build or buy: I could go with a full kit such as CNC Fusion, or make all or part of it myself. I did the X1 conversion 100% DIY, but it was also very simple--stock screws and skate bearings. Reading stories about trying to turn hardened ball screws and such gives me a little pause. Also doesn't seem to save much $$ when you have to buy the parts retail.

2. To ball or not to ball: Non-precision ball screws do not seem to offer any improvement in accuracy over the stock screws. Is there any advantage in practice to a standard ball screw over the acme-type lead screws, or do you need to go to the preloaded/precision ball screws to see any benefit? In practice I've done fine with the .005-.010" precision which my X1 gives me.

Thanks in advance!

[LongRat]

Conversion kits generally seem to be reasonable value for money, considering the work involved in a 100% DIY conversion. I converted my X2 100% DIY with ball screws, but kits were a rare thing at the time. My advice would be ball screws every time, they are faster and lower maintenance. Plus, you can tolerate things being in slightly worse alignment with ballscrews as they have such little friction. At worst the accuracy will be no better than a good ACME set up, but it will stay that way.
Don't forget you'll need a screw assembly of some sort for the Z axis on the X2, so you might as well take the opportunity to kit out the whole machine with ballscrews.

[hoss2006]

X2 CNC Conversion DIY Cost


Stock and Hardware Kit - Hosmmachine.info --------------------$85
Ballscrew and Nuts - Roton.com ------------------------------- $125
Bearings - Mscdirect.com ------------------------------------- $36
Timing Pulleys and Belt - SDP/SI.com -------------------------- $32
15/16-16 Tap - WholesaleTool.com ---------------------------- $22

Total -------------------------------------------------------- $300

(Cncfusion.com Mini-Mill CNC kit #4 with ballscrews ------------ $559)



CNC 3 Axis Package with 425 oz-in motor and KL-4030 Bipolar
Driver with 24V Power Supply _ Kelinginc.net ------------------- $359
Wiring and Electronics Enclosure ------------------------------- $50


Complete Conversion DIY---------------------------------------$709

(w/Cncfusion Kit ----------------------------------------------$968)
(SyilAmerica Complete Conversion Kit ------------------------ $1695)

You can either save a few bucks and Do It Yourself or spend a few bucks
and save some time.

[sansbury]

Longrat: 'Reduction in fiddling' is a very good reason. I did not think of that but I see it now.

Hoss: Thanks for the detail, you know you are an inspiration to part-time amateur engineers like me.

One thing about ball screws that scares me is the need to machine the ends down. I have a HF 7x10 and have turned 1/2" W-1 drill rod in it but that was an uninterrupted cut. How feasible is it to machine these screws myself? I could get the work done by a family friend who owns a machine shop but it would probably take a few weeks unless I paid for it

Aside: I assume the 15/16 tap is for mounting the nut. Is turning an internal thread not desired for a special reason or do people just like the ease of tapping?

[hoss2006]

The tap is for "latheless" folks, if you can cut internal threads all the better.
For cutting the ballscrews, I use 80-degree diamond Carbide Inserts
with the appropriate Tool Holder.
You also can grind down below the case hardening or anneal the ends as others have done.
Hoss

[sansbury]

OK, well, Hoss sold me on the DIY route. I've ordered some thrust bearings and a set of screw and nuts from Roton. They are charging $20 per for the oversize nut loading which seemed reasonable so I got two that way. I'm assuming the weight on the Z axis will make it less of an issue there?

I've also just picked up some carbide insert tools for my lathe. I ordered a little extra stock on the screws so I can afford to "screw" up once or twice. With a typical 7x10 should I be able to cut through the case-hardening or would I be better off to get out the torch and anneal them?

I figure Roton's a good place to start. With shipping I'm looking at about $180 which seems like half the cost or less of the next closest option.

[hoss2006]

If you have extra stock, try cutting without annealing first.
I've never done anything special to the ballscrews even Rotons before turning them.
I use an 80 degree diamond shaped carbide insert (not the little triangles)
Start with turning (@500 RPM , .025 per pass) with about 1 1/2 inches protruding from the chuck and take it
down to within .050 of finished size.
Move it out and turn down the rest of the screw, then make the finish passes
the full length.
It helps cut down on the noise.
Hoss

[sansbury]

So my ball screws and bearings arrived today. As expected both orders were screwed up. The bearings were my fault (wrong size, misread a number) so there will be an RMA on that. Fortunately it was obvious the minute I opened the box so all nice and sealed for the return.

As for the ball screws, I asked for oversized balls in two nuts when I ordered from Roton, but got none. They didn't charge me for it, either, though. I'm not sure whether to see if I can return them and have them load the nuts or if I should just do it myself.

I cut the first piece of screw for the X axis. Naturally I made a mistake there and cut it too short. I can use it for the Y though and still have enough stock for the X and Z. The bigger problem though was this one cut ate a semi-new bandsaw blade (a Morse bi-metal too, not junk). It just stopped cutting about 85% of the way through. It was enough that I could snap it off but I will have to make three more cuts and I only have one new blade left .

Maybe I should just use an angle grinder with a cutoff wheel!?

On the up side, I chucked the first piece in the lathe and my carbide insert tool actually cut it without shattering as I halfway expected it to. It's a $5 TiN-coated insert so I suppose it ought to cut it. It isn't going to go fast but at least I feel like I can do it.

[The Blight]

I have used an angle grinder several times for cutting ball screws. No problem there. Just take your time, because it gets very hot.

[Crevice Reamer]

Yes! Use a cut off wheel to cut the ball screw to length.

CR.

[sansbury]

Well, I am @#$@! off now.

As I dug in deeper turning the screw down is getting a lot harder, no pun intended. I've gone through and tightened up every piece I can on my lathe but this screw is kicking its @$$. I don't see any chance of getting through the case with the lathe, at least not on the threaded section. I've chipped two insert teeth already with very little progress made. I've turned 1/2" W-1 with very little trouble but this screw makes that look like wax.

Right now as I see it I can either try to anneal the end of the screw or grind it down. When I faced the end off it cut real smooth once I got through the hardened section.

Grinding would be messy as heck but I am leaning that way since I think a big part of the problem is the hammering action caused by the threads. I will be really happy when this is behind me.

[Crevice Reamer]

Try to protect the ways from the grinding dust. Don't let it get under the carriage.

CR.