P4 ball screws that don't violate the bank or my behind...

So I called Thompson to price check C3 grade ball screws or my cnc conersion of my RF45. I would like to make the machine as accurate as I reasonably can. However when the lady told me 2600 for one screw and double nut preloaded I just laughed. Anyhow, does anyone have a source for a P4 ish grade ball screw? The ebay ones are C7. I would like to keep precision less than 0.001/ foot if I can. I was thinking about possibly just retro fitting nicer ball screws later and getting the chinese c7 stuff to start with . Let me know i you guys have found a source for less expensive reasonable precision screws. I don't care if they are made in china. I just am looking for P3/ C5 grade if possible.

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Originally Posted by ApexMotorsports

So I called Thompson to price check C3 grade ball screws or my cnc conersion of my RF45. I would like to make the machine as accurate as I reasonably can. However when the lady told me 2600 for one screw and double nut preloaded I just laughed. Anyhow, does anyone have a source for a P4 ish grade ball screw? The ebay ones are C7. I would like to keep precision less than 0.001/ foot if I can. I was thinking about possibly just retro fitting nicer ball screws later and getting the chinese c7 stuff to start with . Let me know i you guys have found a source for less expensive reasonable precision screws. I don't care if they are made in china. I just am looking for P3/ C5 grade if possible.

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I bet the C5 is half that price... Still a bit overkill since that's still probably 2-3 times the accuracy of the ways. Also I believe a single nut will be just fine, they're usually preloaded for precision ground screws.

Try HiWin or PMI. Still a set of 3 will cost as much as your machine. Check THKs online store...

I researched that before and found that the C-7 grade are mass produced for a lot of uses, so are pretty cheap. When you get into P-4 ground stuff, its usually custom made for a specific machine, so its really hard to find any in the " bargain bin". The C-7 units can be tweaked by measuring and increasing the ball size and get to about 0.001" lash. Its a bit fiddly, but a heck of a lot less expensive.

I don't understand why someone wants to put ultra precision ball screws on a machine that was never designed to use them and will never be able to take advantage of the increased accuracy. from my understanding on the error on ball screws is that its not compounding. so if your tolerance is +/-.003 over 12 inches, then on the next 12 inches your out only +/-.003 as well. if the error kept growing then the screws pitch would change and that's not how this works. also that's a max error. most of the screws I've measured for my cnc's have been in the +/-.001 to +/-.0015 range of error. also if your machining a part that is 6 inches long you don't get the whole error of the .003 in that six inches. and even if you did you can adjust it out in other offsets. rarely have I needed to machine something at home that is so precise that I can use it in a nuclear power plant.

I'm really confused about the P4 rating for ballscrews? The P rating is for the balls screw bearings. The screws have a C rating. So I assume these "manufacturers" that tout P4 ballscrews are using the wrong nomenclature? Or are they pulling the wool over people's eyes using C5 or C7 screws with P4 bearings? C7 is what is commonly called "transport" grade and is what it's name implies. Although for most uses C7 should be good enough. With the stiction and inherent precision (or lack thereof) in the ways it would seem at first a waste of money and time to install ground ballscrews, unless you're also regrinding the ways (if they were even ground properly to begin with) and making or enlargening oil channels or retrofitting linear rails.

I got a quote from a vendor from AliExpress for my machine that seems pretty reasonable. I'm not sure what precision the screws are or if they come with the necessary nuts or not (I'm not ready to order mine yet, so I haven't asked those questions yet), but you might contact him and get some info. I ordered some linear rails, 20mm with the bearing blocks and got them within a week from China. He is also very good at getting back to you. Usually got back to me within 24 hrs.

Here is what he quoted me for ball screws:
32mm Dia, Pitch 5 mm
2x Length 1524mm Price $167
1x Length 1830mm Price $95
1x Length 710mm Price $54

25mm Dia, Pitch 5mm
2x Length 1524mm Price $105
1x Length 1830mm Price $59
1x Length 710mm Price 36

32mm Dia, Pitch 10 mm
2x Length 1524mm Price $175
1x Length 1830mm Price $102
1x Length 710mm Price 59

25mm Dia, Pitch 10 mm
2x Length 1524mm Price $110
1x Length 1830mm Price $61
1x Length 710mm Price $38


The website is AliExpress.com. The vendor that I used was J&G Hardware Supermarket. I'm not sure how to search for vendors. I'm at work and the website is blocked for me.
The particular person that I talked to was "Jack GU" and his personal email is "[email protected]"

In case you still need linear bearings, here is what he quoted for me:
SBR20 Rails

2x Length 610mm

2x Length 1220mm

2x Legnth 1524mm

12x SBR20UU Carriages

Total price $353 USD (including the shipping cost to USA)

They shipped out on a Monday from China, and I got them on the following Friday. The packaging was less than desired, but I didn't see any major damage (small ding on a corner or two) and all the lengths were over what I requested by ~1/16 - ~1/8 as opposed to under.

Hope this helps.

Quote:

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Originally Posted by dfaszer

I got a quote from a vendor from AliExpress for my machine that seems pretty reasonable. I'm not sure what precision the screws are or if they come with the necessary nuts or not (I'm not ready to order mine yet, so I haven't asked those questions yet), but you might contact him and get some info. I ordered some linear rails, 20mm with the bearing blocks and got them within a week from China. He is also very good at getting back to you. Usually got back to me within 24 hrs.

Here is what he quoted me for ball screws:
32mm Dia, Pitch 5 mm
2x Length 1524mm Price $167
1x Length 1830mm Price $95
1x Length 710mm Price $54

25mm Dia, Pitch 5mm
2x Length 1524mm Price $105
1x Length 1830mm Price $59
1x Length 710mm Price 36

32mm Dia, Pitch 10 mm
2x Length 1524mm Price $175
1x Length 1830mm Price $102
1x Length 710mm Price 59

25mm Dia, Pitch 10 mm
2x Length 1524mm Price $110
1x Length 1830mm Price $61
1x Length 710mm Price $38


The website is AliExpress.com. The vendor that I used was J&G Hardware Supermarket. I'm not sure how to search for vendors. I'm at work and the website is blocked for me.
The particular person that I talked to was "Jack GU" and his personal email is "[email protected]"

In case you still need linear bearings, here is what he quoted for me:
SBR20 Rails

2x Length 610mm

2x Length 1220mm

2x Legnth 1524mm

12x SBR20UU Carriages

Total price $353 USD (including the shipping cost to USA)

They shipped out on a Monday from China, and I got them on the following Friday. The packaging was less than desired, but I didn't see any major damage (small ding on a corner or two) and all the lengths were over what I requested by ~1/16 - ~1/8 as opposed to under.

Hope this helps.

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I would almost guarantee those prices are for rolled screws. Also round rail is normally not used for metalworking due to their relatively light load ratings as opposed to profile rail.