K2 Review, KT-3925

[ballendo]

Taus,

Yes, ballscrews designed for use where their reduced friction and increased efficiency are the main concern; are often less than ideal when pressed into use for precision positioning. IOW, there are ballscrews that really weren't meant to be used the way we use them in DIY-CNC. And the "actuator grade" that are likely used by K2--and most others at teh low end of CNC, really WILL be better if you do a bit of work to them.

I'd suggest following the advice Jeff D gave about disassembling each one and cleaning with a wire brush and or scotchbrite pads.

BTW, if you spread out a sleeping bag, then put a WHITE sheet over it, then SIT down in the MIDDLE of it, you'll likely not lose any balls when you disassemble.

Roland Friestad had an article about assembling ballnuts to the screws in HSM magazine. The idea you used with vaseline is pretty much what we all do, just using white lithium or --in my case-- Krytox grease (Grainger's has it.)

Point is, even tho you don' wanna. IMO you'll be glad--in the long run-- if you DO take these apart and clean 'em up...

The factory guy who said .008 is a clue; this is DEFINITELY NOT a motion control grade screw/nut.

You asked where to get balls? Bal-tec in Los Angeles, CA, USA is an EXCELLENT source. (I tend to use oversize balls in a single cheap ballnut with the low grade rolled screws; and it works well. there is a bit of time where the balls are "running in"; then that goes away and things work well.

Hope this helps,

Ballendo

Are ballscrews very gritty?

I find if I turn the screw counter-clockwise it's pretty smooth. However when I change direction (clockwise) it is tough. It like they are getting stuck and I feel like I am going to break them. They loosen but get stuck again.

So far I don't see the luxary of ballscrews or are these Nook ones just cheap? They list thompson on the website but nook is what I have. The leadscrew on the Z axis is silk.

There has to be some grease they need...

UPDATE:
I called Nook and they said to use E-900 lub. The ballscrew is a standard roll screw and the info on the nut is here (SBN10325)http://nookindustries.com/ball/BallSRTInfo.cfm?id=15

taus

[ballendo]

Forgot to add that since you have a lathe; make yourself a short rod the same diameter as the root of the ballscrew. This is used when you reload the nut (when you buy a ballnut by itself it comes with a shart cardboard tube of this diameter inside to keep the balls from falling out. You then put the nut against the end of the screw and turn the nut onto the screw--and off the cardboard tube...

Another item you can make which helps immensely is a set of two collars that fit the OD of the ballscrew and are milled (for square body ballnuts) or turned(for round body ballnuts) to locate the ballnut exactly concentric to the ballscrew.

You put the empty ballnut on the screw; add these collars on each end of it, and now the ballscrew is in the center. This makes adding the balls REALLY EASY. Worth the time to make IMO.

Ballendo

[DieGuy]

Forgot to add that since you have a lathe; make yourself a short rod the same diameter as the root of the ballscrew. This is used when you reload the nut (when you buy a ballnut by itself it comes with a shart cardboard tube of this diameter inside to keep the balls from falling out. You then put the nut against the end of the screw and turn the nut onto the screw--and off the cardboard tube...

Another item you can make which helps immensely is a set of two collars that fit the OD of the ballscrew and are milled (for square body ballnuts) or turned(for round body ballnuts) to locate the ballnut exactly concentric to the ballscrew.

You put the empty ballnut on the screw; add these collars on each end of it, and now the ballscrew is in the center. This makes adding the balls REALLY EASY. Worth the time to make IMO.

Ballendo

Those are great recomendations! that keeps the balls from getting out on top of the thread!

[tauscnc]

Hey Ballendo,

Man you always seem to find me and help out. You have been with me since I started this whole machining thing. I think you where the one to answer my question about shank dia vs flute diameter and what the heck that is. Also you confirmed that the Sherline laser ingravings on the Y axis are indeed backwards. Remember? Gezzz, we have come a long way.

Great ideas too. I will get a large sheet out and give the screws a good overlook. I am interested in making this machine as smooth as possible. Do you think scotch brite pad or #0000 steel wool?

I was able to get 3-4 paper towel worth of grit and dirt out of the ballnut. I will also make a rod for the nut to load it and also those collor things. That is what happened to mine the 2nd time I tried to load it...the 2 balls road on top of the ballscrew and got stuck. Man o man.

Well I did cut some stuff last night and this thing with the porter cable router can sure make a mess! That router is so freaking loud. Now I just have to learn how to use Mach 2 better. It was really cool to watch the gantry move! I was cutting pine type wood around 50-60 ipm (I think) with a 1/8" endmill. Butter.

Always something to learn!

taus

[carlnpa]

I'm using a Hitachi MV12VC 2.25hp variable speed. It's really quiet even while cutting and cost is low. TIR 0.0005
steps
(2000/25.4)/0.2(inch/thread)=393.70 step/mm
Was it close?

[cbass]

Hey guys,

Having read all your comments on ball screws, I can't help but feel a bit confused. Why is there so much dirt in these? Aren't they made under relatively clean conditions? As I've ordered preloaded screws, should I still consider taking them apart, or does this only apply to non-preloaded versions?

Hey carlnpa, where did you get your TIR specs for the Hitachi? 0.0005 seems very good, in fact, it puts it in a class by itself. Did you measure this yourself or was it published somewhere? The best stat I've seen for a router is for a Makita RP1101 which is claimed to have 0.0015 TIR. Of course there is probably variations from day to day in the factory. Some might be better than others. Your claim of .0005 is within the ballpark of a Sherline Industrial Headstock (0.0003-4). If this is the case, I may want to reconsider my spindle as the Sherline is about $450-500.

[ger21]

Even if the spindle's runout is .0005, once you tighten a bit in the collet it's unlikely that the runout will still be that low.

As for noise, any good quality router with variable speed will be pretty quiet around 10,000 rpm. And 10,000 rpm should be plenty fast for the speeds you'll be cutting at.

[carlnpa]

The Hitachi is pretty tight. I ended up measuring with a bit in the collet, took readings from the shaft and tool bit. I had been using a 1/4 to 1/8 adapter insert and was getting accuracy issues. Chasing them down the adapter from a porter cable laminate trimmer had .005+ runout.

[cbass]

Like I said, .0005 is in a class by itself. As I think ger21 alluded to, your reading may still be off depending on how you aligned the bit and collet in relation to the spindle. Taking an average of several different alignments would account for this. I often judge a book by its cover, and when I saw the Hitachi I was a bit put off by its running shoe asthetics. Regardless, it sounds like a quality tool.

Any idea if there are fixed tooling systems for a 1/2" router like the Hitachi? From what I've read, the Tormach system requires a drawbar...

[ger21]

Any idea if there are fixed tooling systems for a 1/2" router like the Hitachi? From what I've read, the Tormach system requires a drawbar...

Sears makes some quick change collets for Porter Cable and Craftsman routers, which can be set up for fixed length tooling I think. I think some people here bought some a long time ago, but I've never heard any reviews.

If you use Mach2, it's possible to write a macro so that when you change tools, the router can travel to a switch and automatically set the tool length. Swede had posted about doing the same thing in FlashCUT, but had a few problems. Not sure if he's got it working yet. Tool length sensing!

[carlnpa]

cbass - I went up and measured again, TIR on shank of Belin 1/4 in bit much less than 0.001. Outside of collet and shaft is all over the place ie 0.005. Inside of shaft where collet mates much less than 0.001. Could be I just got a good one. I mentioned the Hitachi because I am getting good numbers and the unit is very quiet. I'll be getting a second one for another operation in a few weeks will post results of that one.
BTW my little HF mill shows 0.0015, grizzly lathe 0.002

[tauscnc]

Hey guys,

Worked on the router some more. I took the Y axis ballscrew off again and tried to shine/polish/buff/ it using a drill and #0000 steel wool. I can say the leadscrew will now fall under its own weight through the nut as long as there is no load on it (but I never tried this before cleaning so I am not sure if it is "really" better). I have to say my biggest disappointment on this machine (and one of my biggest excitments I had about getting it) are the ballscrews.

I dare to take the X one off afraid somewhere I will bent it. I am just gonna leave it alone. I have places where it seems to bind more, etc. I have not measured the backlash yet.

Gotta work on an enclosure for it and also gotta figure out Mach2, sometimes freezes on me.

Well that is it for now.
later
taus