Chinese ball nuts & screw on Ebay

[SSN Vet]

Has any body out there used hardware from this outfit.....
http://stores.ebay.com/linearmotionbearings

They advertise their ball screws as C7 and they certainly look ground, from the photos.

I'm curious just how they are getting the "anit-backlash" features in their ball nuts, as their 16mm nuts only measure ~1-3/4" long (with the flange). Is that long enough to get two seperate tracks? Or are they likely just oversizing the balls?

Limited experience here.....

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[rwestbr]

Has any body out there used hardware from this outfit.....
http://stores.ebay.com/linearmotionbearings

They advertise their ball screws as C7 and they certainly look ground, from the photos.

I'm curious just how they are getting the "anit-backlash" features in their ball nuts, as their 16mm nuts only measure ~1-3/4" long (with the flange). Is that long enough to get two seperate tracks? Or are they likely just oversizing the balls?

Limited experience here.....

I have recently purchased and installed these ball screws on my x2....they are awesome!!! :rainfro: They are replacing the NOOK setup I had previously They are not ground but precision rolled....they get the anti backlash from offset ball track inside the nut, instead of oversized balls...works very well and should last longer than one with oversized balls.

I am very very pleased!!! with the price,service, communication (excellent English) , shipping time (under 1 week, they ship EMS) and defiantly the product,it is 1st rate.But remember these have flanges and it takes a little effort to adapt them to the X axis on the X2, but totally possible.I cut one side of the flange off and milled some material from inside the sadle where the ball nut mounts.

I ordered 3 ballscrews and nuts with machined ends for under 300$,they thew in 2 motor couplers for Free.

Hope this helps..

Robert

[port_huon]

I have some of their ballscrews (1605) Good people to deal with, quick response to any questions and on time shipping. Freight can be a bit high but that applies to most stuff from China
As C7 grade, I doubt they're ground..

I can;t comment on the backlash as I haven't used them as yet. I bought them to build a CNC router but have been sidetracked with a recently bought X2 mill.

[port_huon]

rwestbr,

What size ball screws did you put in your X2? Did you get the supplier to machine the ends to your requirements (apprently he'll do this for a very reasonable rate)

I was planning to CNC an X2 once I get a bit of manual experience with it. nook screws seem to get the most mention where the X2 is concerned but the stuff from lineramotionbearings is better priced - for me in Australia anyway.

[rwestbr]

rwestbr,

What size ball screws did you put in your X2? Did you get the supplier to machine the ends to your requirements (apprently he'll do this for a very reasonable rate)

I was planning to CNC an X2 once I get a bit of manual experience with it. nook screws seem to get the most mention where the X2 is concerned but the stuff from lineramotionbearings is better priced - for me in Australia anyway.

I got the 16mm screws with 1605 nuts, Yes they machined the screws on my request, to my specs. And YES VERY Reasonable...All 3 for under $300USD Shipped....

I'm no Expert, but i cant measure any backlash... the spec I believe is <.015 millimeters = 0.000590551181 inch Backlash.But you can E-Mail them to confirm this....

Robert

[port_huon]

I have recently purchased and installed these ball screws on my x2....they are awesome!!! :rainfro: <snip>.But remember these have flanges and it takes a little effort to adapt them to the X axis on the X2, but totally possible.I cut one side of the flange off and milled some material from inside the sadle where the ball nut mounts.

Robert,
I've been going over the various commercial offerings for X2 cnc conversions to get ideas on doing my own.
I've love to see any photos of your X2 conversion and any details of what you had to do to fit the ballnuts.

[rwestbr]

Robert,
I've been going over the various commercial offerings for X2 cnc conversions to get ideas on doing my own.
I've love to see any photos of your X2 conversion and any details of what you had to do to fit the ballnuts.

I will have to disassemble the X axis....give me a few days and I will show you...but keep in mind that I had to use a cheap drill press to mill out the clearance (not pretty), however it works and is out of sight. I also made an end support with a pressed in 3/8 id bearing for the X axis (a must have!!!)
Here are some pics in the mean time..

Robert

[ellik]

These seem to be the same ball screws and nuts Homeshopcnc is selling. I would be very interested in seeing how you fit these nuts on your X and Y axes, how ugly it might be

EK

[rwestbr]

These seem to be the same ball screws and nuts Homeshopcnc is selling. I would be very interested in seeing how you fit these nuts on your X and Y axes, how ugly it might be

EK

They look similar, but my flanges have 6 holes instead of 4....The Y axis is simple, the flange is long enough for the set screw to engage. The X is more difficult but not that bad.I will get some pics and post in a few days.

Robert

[Hirudin]

I bought some ballscrews from them (I left them their 14th feedback) and as far as I can tell the screws and nuts seem like high quality. Unfortunately I didn't have them machine the ends so they've just been sitting on my shelf since they got here.

[Hirudin]

This same company is selling spindle motors on eBay and there's a thread discussing the quality of the spindles. From the little bit I skimmed it looks like people are happy with 'em.

[renatopub]

I'm no Expert, but i cant measure any backlash... the spec I believe is <.015 millimeters = 0.000590551181 inch Backlash.But you can E-Mail them to confirm this....
Robert

I have those screws fitted to both X any Y on my X2. I measured 50um backlash with the dial indicator. Absolutely no way these screws can get down to 15um unless you use 2 nuts with pre-load. Where do they state 15um?

I had to take one of the nuts out to get the screw machined, amazingly that was not so difficult to get it assembled again. And it was interesting to see the insides of the nut, looks very good as it is precision ground (the screw is just rolled though). There are 3 raceways with one turn each.

It was a pain to machine the thing in my mini-lathe, but it felt good to do it myself. Next time I would order it alredy machined though The outer 3mm shell of the strew is hard as stone, I had to sharpen my carbide tool every 30 minutes.

I will try to post some pictures today. There was some grinding work to get the Y axis to fit, but it looks good now

[DMF_TomB]

A few things to consider.

1) Lubrication grease can have an affect. Ever oil a micrometer and find it too tight to turn? Dampening grease is a term used for various thick greases designed to smooth motion. If you ever had a large camera lens apart and cleaned it, it would feel dry and rough. The dampening grease gives it the smooth travel feel and tends to resists moving. It is annoying to point a optical instrument down and have it's focus change because the lens barrel is sliding by gravity.

2) All metal objects compress and stretch like rubber, but a smaller amount. In practice backlash compensation using a computer on a CNC is limited as the farther the nut is down the screw the more it will stretch and compress. All backlash measurement should include a force used to push and pull when measuring.
.......Now I am not saying the Chinese ballscrew is within spec. I am just amazed when fellow Americans complain a $10 fake Rolex_ watch doesn't last more than a few weeks. Ever try to make a fake Rolex_ watch? that works for even a week. Even at not $10 but a $100 or even a $1000 to me it is a amazing feat of Engineering.

[renatopub]

Here are the pictures from my X2 mill with Chinese ball screw conversion.

The Y axis (short one) is very easy as the nut fits nicely in place of the original acme nut. The X axis was a bit harder... Had to grind out half of the ball nut flange and gring a 2mm deep recess at the Y carriage. The cast irom from the X2 frame cuts as butter so that is not a big deal, but the ball nut flange ate an entire grinder stone!

Hope it helps.

[rwestbr]

Originally Posted by rwestbr View Post

I'm no Expert, but i cant measure any backlash... the spec I believe is <.015 millimeters = 0.000590551181 inch Backlash.But you can E-Mail them to confirm this....
Robert

I emailed for the specs though Ebay ,and thats what I got back for the spec?

when I measure my backlash with a Dial Indicator (.001in), I get no backlash?
The way I measure is in the pic below...under no load , I turn the X axis back and forth and notice absolutely no play between the turning and dial needle,no pause in the needle , even applying slight force to the table.

I did have problems with the conversion in the beginning, when I tightened down the ballnuts they would cause the axis to bind and not turn smoothly...I had to shim the ballnuts at the flanges to get perfect alignment, now they are smooth as silk.

[port_huon]

Any chance of getting the machining spec you used for the ballscrew ends and the lengths of the X,Y and Z ballscrews themselves? No need for a detailed drawing or PDF, I can produce these as required.

I'm planning to order some ballscrews with machined ends rather than try to cut/machine the ones I already have (they can go into the router I'll build one day ...). I'll ask if he (linearmotionbearings2008) can machine the flanges of the ballnut as well.

[renatopub]

Any chance of getting the machining spec you used for the ballscrew ends and the lengths of the X,Y and Z ballscrews themselves?

I made mine without much planning, kind of design it as it goes. The Z axis is not ready yet and I actualy still dont know how I will do it. The main points I remember are:
- X and Y axis have one trust bearing (actualy the ones that come with the X2) and one self alighing bearing each. Bearing inner diameter 10mm.
- I purchased 3 ballscrews all of them are 30cm long, 1605 type
- I don't remember how much I machinned it, I thing it was like 7cm long or so, I machined it down to 10mm diameter.
- Threads are like 2cm long or so. They are threaded to fit M10 nuts.
- The trust bearings go inside the pulley, I had to machine them to fit the bearings in.

There are several designs in the web. This one I fitted to my particular needs and to the materials I had in hand, not necessarely the best design for everyone. But if you realy want to repeat it yourself I can disassemble it and measure the stuff for you. Just let me know if that would be of any use.

[port_huon]

renatopub,

Thanks for the info. That's more than enough detail so don;t go pulling things apart!

The bearings I have are 10x30x14.2 so turning down to 10mm sounds right.. A threaded section for a nut to hold the bearing on then an 8 mm section for the coupler.
I don't plan to leave the handles on after I CNC the X2 so the total machined length will be about 50mm.

Now to spend some time with a CAD program so I can make some REAL plans.

[renatopub]

Now to spend some time with a CAD program so I can make some REAL plans.

Just some details you should keep in mind:
- You are not using a polley as you talk about coupler (direct drive). A simple thread as I have it might not be the best option.
- Figure out how you are going to fixate and pre-load your thrust bearings.
- I left a little marging for adjustment in the bearing beads so that I could align the bearings with the ball screw, otherwise you will have to shim it. Remember that ballNut + ballScrew + trustBearings, when connected, will produce an over defined assembly. So you either have to increase the degrees of freedom (e.g. by using a self aligning bearing) or you have to aligh the stuff prety well.

I like your idea of getting rid of the handles. What I keep thinking is, what would happen when one turns it by hand with the motors connected to an unpowered driver unit? I mean, the motors will produce spikes of maybe 50V or more (EMF). I guess there is a good chance of killing a driver with that.

Good luck.

[port_huon]

Just some details you should keep in mind:
- You are not using a polley as you talk about coupler (direct drive). A simple thread as I have it might not be the best option.

The end of the ballscrew will be unthreaded so a coupler can be attached. Couplers from the same supplier as the ballscrews.

- Figure out how you are going to fixate and pre-load your thrust bearings.

Bearings are angular thrust bearings [from VXB].

Main reason for getting rid on the handles is to save space. I'm told that using the mill manually once ballscrews have been installed, is not practical and that an MPG is the way to go.

This is all some way off as I want to get some experience with manual milling first. I'll need to improve my skills before I try to make the motor and bearing mounts. First real project on the mill is to fit some sales and a DRO.