If there are single row bearings just look at the thickness of the races the workout which direction takes thrust load one side of a race is thin the other thick. Then decide face - face or back - back mount depending on application and required moment stiffness.
-------------------------------------------------- From: "Jan de Kruyf" <jan.de.kr...@gmail.com> Sent: Thursday, November 03, 2011 7:10 PM To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] OT, Ball screw bearings, preload > Oh dear, > I slipped up. (Again) > I clicked on the "preload" link in the speck sheet that Bruce linked to. > and lo and behold SKF puts the link for preloaded bearings on a normal > bearing spec sheet. > So my apologies for not noticing earlier. > > Then in this case you will need to measure your bearings out on the table > and see if the one ring is higher or lower than the other when you support > just one of them and let the other rest on the balls in loaded position. > then you make some sums and make up 2 spacer rings, one for the outer > races > and one for the inner races of the bearing set. > Those rings are turned as accurately as possible and normally ground on > the > faces, but if you turn very well you might get away with just the lathe. > the difference in hight between the outer ring and the inner ring match > the > bearings in such a way that the balls in each of them are comressed by > about 5 um. So if the bearings were perfectly true and the inner ring and > the outer ring were level when one ring is floating and resting on the > balls, then the one distance ring is made 0.01mm shorter than the other so > that when everything is tightened the balls get compressed with the right > preload. > > Asides, perhaps now we see why people are prepaired to pay the premium and > let SKF worry about the right gap for the preload. > > cheers, have fun > > j. > > On Thu, Nov 3, 2011 at 8:27 PM, Andy Ibbotson > <andyi_w...@btinternet.com>wrote: > >> Be careful here, the bearings purchased are BE CB P. The CB denotes an >> axial CLEARANCE class of bearing i.e. >> >> http://www.skf.com/skf/productcatalogue/jsp/viewers/tableViewer.jsp?tableName=1_3_t1&maincatalogue=1&lang=en >> >> If you want preload then you new universally matched pairs (+ lots more >> $) >> which are marked with GA GB or GC depending on preload i.e. >> >> http://www.skf.com/skf/productcatalogue/jsp/viewers/tableViewer.jsp?tableName=1_3_t3&maincatalogue=1&lang=en >> >> GA, GB, GC bearings don't need shims as they are ground to produce the >> correct preload. With type CB bearings you need a spacer between the >> bearings and then some method of applying the preload, i.e. tighten by >> "feel", wave washer etc. >> >> Hope this helps. >> -------------------------------------------------- >> From: "Jan de Kruyf" <jan.de.kr...@gmail.com> >> Sent: Thursday, November 03, 2011 4:08 PM >> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> >> Subject: Re: [Emc-users] OT, Ball screw bearings, preload >> >> > Hallo, >> > look at the picture quickly: >> > >> > >> http://www.skf.com/skf/productcatalogue/jsp/viewers/tableViewer.jsp?tableName=1_3_t3&maincatalogue=1&lang=en >> > >> > the left side picture is normally the situation when there is a big nut >> on >> > the shaft to hold the bearing in place. This nut either has a >> > counter-nut >> > to lock it or it is of a special construction so it can be secured. If >> > this >> > is the case then make sure the nut-face that holds the brearings is >> > perfectly flat and square. >> > The right picture is the case when the outerrings need compressing by a >> > specially made ring (again perfectly flat and square). The shaft >> > locknut >> > does not need to be quite as perfect in that case. >> > >> > In both cases the object of the exercise is to close the natural gap >> > between the rings. This will give the bearings just the right preload. >> > >> > j. >> > >> > >> > >> > On Wed, Nov 2, 2011 at 6:02 PM, Bruce Klawiter <bmkl...@yahoo.com> >> wrote: >> > >> >> I bought new bearings for the ball screws on my mill, SKF 7204 BECBP. >> >> >> >> >> http://www.skf.com/skf/productcatalogue/Forwarder?action=PPP&lang=en&imperial=false&windowName=null&perfid=123002&prodid=1230020204 >> >> >> >> I have read conflicting information on how to install them. >> >> It appears the best way would be installing them back to back, but I >> have >> >> read the inner rings should be clamped tight and also read the outer >> >> rings >> >> should be clamped tight when there back to back. >> >> >> >> I am not sure I understand the proload either and can't decipher what >> >> it >> >> is form the SKF website. >> >> >> >> This is what I think I need to do, find what the preload is (weight) >> >> and >> >> measure the defection of the outer race when this weight is placed on >> the >> >> bearing. >> >> >> >> Take this measurement X 2 and shim between the the races of the two >> >> bearings and clamp tight the inner rings and I will have the correct >> >> preload. >> >> >> >> Do I have this right. >> >> How do I find the preload >> >> >> >> Your help is greatly appreciated, >> >> Bruce >> >> >> >> >> >> >> ------------------------------------------------------------------------------ >> >> RSA® Conference 2012 >> >> Save $700 by Nov 18 >> >> Register now! >> >> http://p.sf.net/sfu/rsa-sfdev2dev1 >> >> _______________________________________________ >> >> Emc-users mailing list >> >> Emc-users@lists.sourceforge.net >> >> https://lists.sourceforge.net/lists/listinfo/emc-users >> >> >> > >> ------------------------------------------------------------------------------ >> > RSA(R) Conference 2012 >> > Save $700 by Nov 18 >> > Register now >> > http://p.sf.net/sfu/rsa-sfdev2dev1 >> > _______________________________________________ >> > Emc-users mailing list >> > Emc-users@lists.sourceforge.net >> > https://lists.sourceforge.net/lists/listinfo/emc-users >> >> >> >> ------------------------------------------------------------------------------ >> RSA(R) Conference 2012 >> Save $700 by Nov 18 >> Register now >> http://p.sf.net/sfu/rsa-sfdev2dev1 >> _______________________________________________ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users >> > ------------------------------------------------------------------------------ > RSA(R) Conference 2012 > Save $700 by Nov 18 > Register now > http://p.sf.net/sfu/rsa-sfdev2dev1 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
