Ballscrew Basics

[DAVINCHO]

Thanks a lot,

Great article !!!!!

[R!f@@]

nice article

[kurniawan]

hallo

[headsmess]

phwoar! i read all that!

is that there "warner red label" a 2 start thread? me sees two return tubes and the pitch is waaaay steep for the depth.

which raises an interesting point...do the balls recirculate on the same track or keep crossing over in a multi start system?

[dustin1706]

Great write up!

Thanks!

[beaker152]

newbie questions:
i note that many of the items on ebay are described as having "signs of cosmetic wear"... is it a false economy to buy used ball screws for precision CNC applications?

are there any nuts to stay away from with the THK ground ball screws? i've had a hard time correlating markings i see in the item images with listings in the THK catalog (THK KX 80376, for example).

are the differences between BIF, DIK, BTK, etc. important to the performance of the unit or is it just a different nuts/seals?

lastly, how much of the shaft needs to protrude from the fixed end for attaching to the motor?

thanks!

[louieatienza]

Originally Posted by beaker152 newbie questions: i note that many of the items on ebay are described as having "signs of cosmetic wear"... is it a false economy to buy used ball screws for precision CNC applications? are there any nuts to stay away from with the THK ground ball screws? i've had a hard time correlating markings i see in the item images with listings in the THK catalog (THK KX 80376, for example). are the differences between BIF, DIK, BTK, etc. important to the performance of the unit or is it just a different nuts/seals? lastly, how much of the shaft needs to protrude from the fixed end for attaching to the motor? thanks!

BIF : Offset preload
DIK: Offset preload, slim design
DIR: Rotary nut
BNFN: Double nut preloaded
DKN: Doubel nut preloaded, slim design
BLW: Large lead (1x screw diameter), preloaded
BNF: Single ball race
BNT: Square nut
DK: Slim version of BNF
MDK: Miniature
BLK: Large elad, no preload
WGF: Super Lead (1.5x-3x screw diameter)
BLR: Large lead rotary nut

These are all precision ground ballscrws....

[Bear5k]

Originally Posted by louieatienza BIF : Offset preload DIK: Offset preload, slim design DIR: Rotary nut BNFN: Double nut preloaded DKN: Doubel nut preloaded, slim design BLW: Large lead (1x screw diameter), preloaded BNF: Single ball race BNT: Square nut DK: Slim version of BNF MDK: Miniature BLK: Large elad, no preload WGF: Super Lead (1.5x-3x screw diameter) BLR: Large lead rotary nut These are all precision ground ballscrws....

To add on: A couple of the screw models (e.g., BNT, IIRC) are available as both a rolled and as a ground screw. Just knowing the product line of the screw may not be enough to determine rolled vs. ground (and a seller may not know the difference).

[louieatienza]

Originally Posted by Bear5k To add on: A couple of the screw models (e.g., BNT, IIRC) are available as both a rolled and as a ground screw. Just knowing the product line of the screw may not be enough to determine rolled vs. ground (and a seller may not know the difference).

Yes true... You must do your homework as well. One seller even has videos on his auctions showing the ballscrews' movenment, which helps. Check Swede's first post here for pics; there's good info there. Look for package markings or markings on the nut that say C0, C1, C3, C5; good chance they're ground, though I saw some rolled ballscrews that claimed to have C5 accuracy. After looking at a few auctions, it should be pretty easy to determine which is which.

I've been fortunate to find ground ballscrews in their original packaging, still sealed, and I guess that's the best way to insure you're getting something that works right. Of course that's no guarantee and there's always a small risk involved with online purchasing. But the more you look, the better you get at spotting the good stuff. Particuarly with the THK stuff, the rolled ballscrew nuts look very sumilar to the ground ballscrew nuts..

[UserJ]

Ive looked at the prices at they are way too steep for me at this time. Having a budget of about $300, Im looking for what would be the next best thing. Is it possible to find a ACME anti-backlash ballscrew with somewhere between C7-C5?

[mike_Kilroy]

typo

Originally Posted by UserJ Ive looked at the prices at they are way too steep for me at this time. Having a budget of about $300, Im looking for what would be the next best thing. Is it possible to find a ACME anti-backlash ballscrew with somewhere between C7-C5?

u shud be able to get c7 with good rolled screw. depending on length, dia, etc, u may buy it for that price. list this info if u want more info.... pm me with the details if u want a quote from ballscrews.com (thomson or bs&a).

[harryn]

Hi, I was under the impression that in order to obtain "zero backlash", it required a double nut. Nonetheless, I have seen a variety of ballscrews listed on automationoverstock that are single nut, double nut, and a range of screw specs from C2 to C7, all claiming "zero backlash" nuts.

1) Am I confusing ball screws with other types of screws that need a double nut for zero backlash ?

2) Surely, a C2 ballscrew has less backlash that a C7, even if they are both called out as zero backlash nut types ? I guess then it is a question of spec / price for new one, but in the NOS market, that gets distorted a bit.

3) I assume that the NSKs with "zero backlash" are better than the hiwins with an "anti backlash" nut ?

Thanks

Harry