[sudip]

Ball screws are the most important part of the machine. You should choose it and buy it after proper knowledge about it. This can help you

Ball Screw In CNC Machine.

[bigspike]

I plan to use Angular Contact Bearings of a decent grade, cost/benefit/budget, on all fixed ends. As well as floating bearings on the free ends. By floating I mean the shaft will be turned down about 1" with the 1/2" wide bearing centered in that length. Allowing the ball screw to expand and contract in length by sliding in the bearing.

Attached is a drawing of my current plan for the pre-load ball nut mount. All parts steel.

One ball nut is screwed into the mounting block.
On the opposite side a recess holds the spring washers aligned to prevent them from rubbing on the ball screw.
A flat washer distributes the load to the spring washers from the pre-load threaded sleeve.
This secures the flanged sleeve that the other ball nut is screwed into.
The ball nut flanged sleeve and the pre-load sleeve will have holes or slots for a spanner wrench and either loctite, hex set screws or both to prevent loosening.

Doubles the required amount of threading, but should work. Comments?

[michaelthomas]

FWIW......I'm going to grind a new ballscrew to replace my Y axis Roton on my ZX-45.

I work at a shop that does a lot of ballscrew and shaft grinding for the aviation industry. I am in the process of retrofitting one of their older Studer grinders with a new KFLOP control. The machine was not capable of thread grinding with the older control, but as of Friday it seems to be on its way with the KFlop.

I intend to use the roton screw replacement as one of its tests after its fully functional. The newer machine will hold .0001 to .0002 in diameter and pitch, but it has glass scales. The one I'm converting only has rotary encoders on the screws, but should still do a respectable job. Its in a temperature controlled room with temp controlled coolant.

I'm curious how it will work with the stock roton nut. I'll check back in here when i have some results.

It may not relate to this thread entirely, as they would never be cost effective for a benchtop machine.....but its a fun experiment for me.

[bigspike]

This has been very frustrating. I am still waiting for quotes from Motion Industries etc.

This morning I decided to start over searching for Nook sellers. I went back to the Nook distributors web page and visited all five companies listed. I then searched each for local service centers. While there, I checked for online information.

Applied Technology has listings for Nook, but they are limited and the price was higher than I was quoted for the one item that I had a quote for.

Kaman Industrial Technology requires you register to login for pricing, so I created a login. I searched for ballscrews, ball screw, ball nut and came up empty.

I am still waiting for a quote for the XPR ball screws from Kaman in Ft Collins.

Just for the hell of it I searched the Kaman site for the XPR6320R72 part# of the 72" x 5/8" x .200" ball screw. The search returned the product with a price of $145.67, that is $13.82 CHEAPER than the Motion Industries quote of $159.49!

The 48" XPR6320R48 was $9.20 lower
The SRT series single ball nuts were $4.87 lower each for a savings of $29.22 on 6 of them.
For a total savings of $52.24

When searching the Kaman site you must enter the actual Nook part number. Geez, who'da thunk? The description of the ball nut is "Linear Guide System Accessory" bearing type "ball" secondary classification "nut" - of course how could I have been so dense. simple!

eCommerce checkout showed all items back ordered, so I called the Ft Collins office for clarification. This is normal since they don't stock these products. The order will be sent to the local center, they process it to Nook, Nook responds with shipping date, they reply to me with that info (if I'm lucky, considering their track record), Nook ships direct to me.

I dropped the hammer and placed the order, $550.71 plus S&H yet to be determined.

Hey Motion Industries...snoozers are losers.

Gee, I wonder if I will get my ball screws & nuts before I get my quote from Kaman of Ft Collins?

FWIW: I found another place to order online, Control Resources they sell .002" accuracy Chinese ball screws complete with fixed & free end machining and the single ball nut. They have end blocks with bearings, spacers, and seals. They also sell ball nut mount blocks and motor mount ends. Prices look fairly reasonable, if you have no way to machine the parts yourself. Below example for one 24" axis with ball screw, mount blocks, motor mount machining included:
16mm rolled screw, 5mm lead, 650mm overall, 500mm travel $ 118.25
BF15 Simple/Floating End Ball Screw Mount $ 44.00
FK15 Fixed End Ball Screw Mount, Flange Type $ 72.00
Motor Mount, NEMA 23, req FK/BF15 cast iron $ 101.10
Ball nut mount for 28mmØ barrel - steel $ 82.20
Flexible Motor Coupling, 10mm x 6.35mm SS $ 21.50
$ 439.05
My guess is these ball screws are the same as the eBay seller and homeshopcnc people sell.

So in about a month I should have ball screws.

[Padrino]

Bigspike,
I have also been hunting for this stuff as well. Since I work very close to motion, I'm lucky enough to speak with their Linear bearing specialist on a regular basis. I actually have him coming to see me at my work tomorrow. He used to work for THK and if you need his cell number let me know. He is extremely knowledgeable. It is also quite a bit cheaper to go for thompson over nook and if you use the metric line its 23um per 300mm which is the same basically as nook's XPR line.

I have also been looking on ebay and actually ordered some end supports FF20 & FK20 for 68 dollars shipped. I also bought an FF25 and FK25 for 83 shipped. Comes with the bearings, locking nuts ect. Thats is significantly cheaper for the same design than THK.

So you are putting 2 single ballnuts apposing to reduce backlash? How will you know how much to torque it in by? I see your sketch above

Btw what are you building/retrofitting?

[leix_99]

Bigspike,
I have also been hunting for this stuff as well. Since I work very close to motion, I'm lucky enough to speak with their Linear bearing specialist on a regular basis. I actually have him coming to see me at my work tomorrow. He used to work for THK and if you need his cell number let me know. He is extremely knowledgeable. It is also quite a bit cheaper to go for thompson over nook and if you use the metric line its 23um per 300mm which is the same basically as nook's XPR line.

I have also been looking on ebay and actually ordered some end supports FF20 & FK20 for 68 dollars shipped. I also bought an FF25 and FK25 for 83 shipped. Comes with the bearings, locking nuts ect. Thats is significantly cheaper for the same design than THK.

So you are putting 2 single ballnuts apposing to reduce backlash? How will you know how much to torque it in by? I see your sketch above

Btw what are you building/retrofitting?

As soon as they arrive:

1.- Sit and relax
2.- Take those "angular contact" bearings out
3.- Buy a couple of good matched AC bearings
4.- Enjoy!

Just kidding, i bought that kind of supports for my machine too, housings are great, full faces machined, and great finish, but those bearings were the biggest crap i've ever seen. If you're really into making things as accurate as you can and your wallet let, take a closer look to the bearings, maybe yours come up better than mines did.

P.S., I have bought in Spain from a local supplier Hiwin ballscrews and nuts, this was the cheapest brand i could find that had some "name" and from a trusted supplier.

Rolled ballscrews Din 69051 (C7) 20mm, 5mm pitch: 78€/m. (96.7 USD/40'')
FSI ballnut 4 tracks : 89€ (110 USD)

End machining, as stated below, a torch, wet towels, and hours.

[Padrino]

As soon as they arrive:

1.- Sit and relax
2.- Take those "angular contact" bearings out
3.- Buy a couple of good matched AC bearings
4.- Enjoy!

Just kidding, i bought that kind of supports for my machine too, housings are great, full faces machined, and great finish, but those bearings were the biggest crap i've ever seen. If you're really into making things as accurate as you can and your wallet let, take a closer look to the bearings, maybe yours come up better than mines did.

P.S., I have bought in Spain from a local supplier Hiwin ballscrews and nuts, this was the cheapest brand i could find that had some "name" and from a trusted supplier.

Rolled ballscrews Din 69051 (C7) 20mm, 5mm pitch: 78€/m. (96.7 USD/40'')
FSI ballnut 4 tracks : 89€ (110 USD)

End machining, as stated below, a torch, wet towels, and hours.

So your suggesting replacing those internal bearings inside the flange mount end supports? Could you recommend a better brand or this is a common/easy to find items

Cheers

[bru102]

Hi Bigspike...

I like your choice of XPR screws and the doubled SRT nuts. I couldn't find any info in the Nook catalog that directly stated they were compatible with each other, but I do see a reference that the (very expensive) SGN nut works on all three screws: ground SGT, precision rolled XPR, and standard SRT. So the "threads" must be compatible, and by implication the SRT nut should work on all of them. Did this come up in your discussions with dealers?? (Sorry if I missed any earlier discussion of this...)

Ray B.

[bigspike]

FYI I ordered Nook XPR ball screw stock and SRT ball nuts.

I was just passing on the info for the end blocks and such. I would assume since they are Chinese made, that the bearings would be junk.

I would probably go with a pair of single row AC bearings to replace them from VXB.com They sell some Japanese Nachi AC's for a decent price.

[bigspike]

Hi Bigspike...

I like your choice of XPR screws and the doubled SRT nuts. I couldn't find any info in the Nook catalog that directly stated they were compatible with each other, but I do see a reference that the (very expensive) SGN nut works on all three screws: ground SGT, precision rolled XPR, and standard SRT. So the "threads" must be compatible, and by implication the SRT nut should work on all of them. Did this come up in your discussions with dealers?? (Sorry if I missed any earlier discussion of this...)

Ray B.

I looked at the specs for the SRT and the XPR and they have the same dimensions. Then when the Nook factory rep called, I asked him if there was any reason not to mix the SRT and the XPR and he said it would work fine. With possible more backlash which can be compensated for easily.

[bigspike]

Bigspike,
I have also been hunting for this stuff as well. Since I work very close to motion, I'm lucky enough to speak with their Linear bearing specialist on a regular basis. I actually have him coming to see me at my work tomorrow. He used to work for THK and if you need his cell number let me know. He is extremely knowledgeable. It is also quite a bit cheaper to go for thompson over nook and if you use the metric line its 23um per 300mm which is the same basically as nook's XPR line.

I have also been looking on ebay and actually ordered some end supports FF20 & FK20 for 68 dollars shipped. I also bought an FF25 and FK25 for 83 shipped. Comes with the bearings, locking nuts ect. Thats is significantly cheaper for the same design than THK.

So you are putting 2 single ballnuts apposing to reduce backlash? How will you know how much to torque it in by? I see your sketch above

Btw what are you building/retrofitting?

Everything I have seen for the rolled Thomson ball screws says they are .003"/foot with the XPR rated at .001"/foot.

When I torque the opposing ball nut against the belleville spring washers, I will be checking for play and smooth operation of the ball screw. I may test with a digital scale and a test indicator to determine the amount of force required to move the table at the point the floating ball nut compresses the washers. Or I will just wing it. LOL

I am converting a G0484 Grizzly RF45 mill.
Also, your motion industries rep won't be able to help me. They have territories and are not allowed to sell outside that area. The Denver office refused to quote me, referring me to the Greeley, CO office which is closer to me.

[Padrino]

Bigspike,
Thanks for the answer and thanks for supplying info on replacing the bearings on the end supports

On the thompson screws, yes the NEFF rolled ball screw metric line has a standard lead accuracy of ±23um/300mm

Jump right to page 118
http://www.thomsonlinear.com/website...lines_cten.pdf

Cheers

[bigspike]

lead accuracy of ±23um/300mm works out to about .001"/foot same as Nook.

But I would be expect the NEFF P5 grade Thomson ball screws to price out at 60% higher.

If you are using the T5 grade then the 23um/300mm is correct only for the first 315mm. Then the permissible travel deviation goes way up. At 1 meter it is nearly 4 times higher than the P5 grade.

The Thomson ball screws I priced above are likely T7 grade.

[steve123]

Congrats on getting your order in. That's a big step. I'm watching how it goes!

I have a metal lathe, but haven't cut a thread in 30 years, and don't want to practice on expensive, very hard ball screws. I am trying to figure out how to choose a machine shop to do the end machining and other milling like my Z plates. I live about 60 miles east of Los Angeles. I have about 20 shops within 15 minutes of me, but I don't know anyone that can recommend one, so I'm kind of lost! I guess I should start a thread!

The other part is the end supports. I am glad to hear that people are getting the cheap ones, and perhaps swapping out the bearings. Does BF/BK 15 sound right for the 5/8" ball screws?
My plan is to find a Nook dealer here, get the Nook ball screws, and hand them off with Chinese end supports to a shop, so that they can mill the ball screws to fit the supports.

Another idea is to preload the ball screw, perhaps something like the great master did it (bowing in his direction) Machine frame - MadVac CNC

Cheers,
Steve

[leix_99]

So your suggesting replacing those internal bearings inside the flange mount end supports? Could you recommend a better brand or this is a common/easy to find items

Cheers

Wait to check them, but in my case, and many other people complained about the poor quality of the fitted chinese bearings, i was able to feel the ballscrew moving when everything was bolted, i first tried to preload the bearings with calibrated ss plates, but could not get a decent result. As i said wait for them and check, maybe you're lucky, and i did not want to scare you, just saying it could happen.

You should be able to get the bearings from any common brand for a reasonable price (i got mines i think they were 6 for 60€ in a industrial hardware store next to my job). Those are common sizes, look arround for bearing suppliers.

[Padrino]

Wait to check them, but in my case, and many other people complained about the poor quality of the fitted chinese bearings, i was able to feel the ballscrew moving when everything was bolted, i first tried to preload the bearings with calibrated ss plates, but could not get a decent result. As i said wait for them and check, maybe you're lucky, and i did not want to scare you, just saying it could happen.

You should be able to get the bearings from any common brand for a reasonable price (i got mines i think they were 6 for 60€ in a industrial hardware store next to my job). Those are common sizes, look arround for bearing suppliers.

Sweet thanks. I have a few bearing dealers near me as well. One mistake i think i made was i ordered ff20 & fk20 as well as ff25 & fk25 thinking for a 25 mm and 20mm ballscrew not thinking it has to be turned down still. So i think i would have to swap out the bearings at this point anyways right?

Thanks in advance!

[bigspike]

Still no ETA for the Nook ball screws I ordered 8/6.

I ordered bearings from VXB.com, but the angular contact bearings I wanted are on back order until November. (I am at least hoping to need them before that)
7201 Nachi Angular Contact Bearing Steel Cage C3 Japan 12x32x10 Ball Bearings KIT10011 at $10.88 each.

I know some people suggest ABEC-7 for this but, I just don't see the need for ABEC-7 rated bearings for the ball screws. Or the $600-1000 cost.

Can anyone recommend similar or better AC bearings for this that won't break the bank? Suppliers?

Anyone have any experience with the VXB - 2 Angular Contact Bearing 7201B 12x32x10 Ball Bearings Kit1085? At $12.95 for two it is just 6.50 per bearing which is very very cheap. And no origin is specified.

McMaster has 40° contact angle ABEC-3 bearings, partno 6680K12 at $28.63 each - 6 would cost $171.78 vs $65.28 for the 6-VXB Nachi bearings on backorder, nearly triple!

Are these worth the difference?

-------------------------------------------

FWIW...I also ordered a 36" length of 5/8" Thomson ball screw for my X2 mill. At $61 with shipping, it is a good way to test my ability to anneal & machine a hardened ball screw. If successful, I can extend the X&Y travels of that mill and if not, I won't damage the more expensive Nook ball screws. I ordered it from Reid Supply and they shipped the next day.

[SCzEngrgGroup]

I've used various VXB paired A/C bearings (likely not the same sizes as here) on several projects, and they always worked just fine - no measurable backlash.

Regards,
Ray L.

[bigspike]

Quick Update:

Nook ball screws & nuts delivered yesterday.
Compared to the Thomson I got from Reid supply, the Nook ball screws are shiny, almost polished looking, and the Thomson is smooth and black.
I also got my belleville washers from McMaster.

I went ahead and ordered the cheap angular contact bearings from VXb. I can use then to get started and if they prove to be inadequate, then I will replace them with better quality later.

It will be a few before I can get started machining the ends and I will report back with my progress then.

Thanks to all who participated in this discussion so far.

[Padrino]

Thanks for sharing your selection process with us. Feel free to post some pictures
Rob