Bearing Identifcation help!!

[bcromwell]

Can someone help me please, The bearing for my ballscrew is shot and I can't seem to find a replacement. From what I can read on the bearing it looks like it is a Fafnir bearing, With numbers that appear to be 204KT4 or M204KT4, With the only caliper (Very Cheap one) I could find, it is close to 1.845" OD and .779" ID. Can anyone help cross reference this bearing?

[Zumba]

What kind of a machine are you running? Your measurements should have been in MM obviously... it's 20mm x 47mm.

A lot of different bearings will probably fit... NC Cams frequently mentions the NSK 20TAC47. A pair of standard 7204s would probably fit in as well (you'd have to preload them yourself). But your best bet is to call the manufacturer of the machine or Fafnir and get an exact replacement.

[RICHARD ZASTROW]

bcromwell, Fafnir numbers: M = ABEC-3, 204= LIGHT SERIES 20mm(.7874") BORE, 47mm(1.8504") OD, K= CONRAD TYPE (deep groove ballbearing, probably without filling slot) T is supposed to mean felt seal but I do not know what T4 is.

I hope that is the "floating" end. You might want to look at NC Cam's disertations on Ballscrew support bearings. It depends a lot on the application and budget.

[bcromwell]

Originally Posted by RICHARD ZASTROW bcromwell, Fafnir numbers: M = ABEC-3, 204= LIGHT SERIES 20mm(.7874") BORE, 47mm(1.8504") OD, K= CONRAD TYPE (deep groove ballbearing, probably without filling slot) T is supposed to mean felt seal but I do not know what T4 is. I hope that is the "floating" end. You might want to look at NC Cam's disertations on Ballscrew support bearings. It depends a lot on the application and budget.

Thanks for that Richard, Yes it is the floating end. The fixed end bearings are missing from the Previous owner so those might even be more fun...

[RICHARD ZASTROW]

bcromwell, You can probably deduce the replacement for the fixed end bearings. Can you measure/determine the OD of the ballscrew where the bearings fit, the ID and depth of the bore where the bearings fit in the support housing? Is there some type of oil or grease lube holes for the bearings? (if not,the bearings are probably sealed type). Now the bad news, you probably will have to spend a few bucks, the PROPER bearings are expensive. Like Zumba said, these will probably be pre-loaded angular contact ABEC-7's

[NC Cams]

From DZASTR's post, you've already identified the bearing as essentially a 6204 bearing. For the non fixed end, you can pretty much use any 204 series deep groove non-A/C bearing as long as this end does NOT axially locate the ball screw and merely "floats" to support that end.

On some screws, they "stretch" the screw between two precision/semi-precision bearings. In that case, you're going to want to replace it with a like grade/type of bearing.

IF the fixed end has TRUE ball screw bearings, you're probably talking about some high dollar, high preload, high contact angle parts (ala the 24TAC47's or something of a similar design ableit different size/part number). You can replace them with generic stuff BUT you'll lose position accuracy and/or repeatability and/or start having backlash problems.

The true ball screw typ "TAC" bearings are typically high/higher dollar items as they ae truly special for the application. I've already explained the benefit of true ball screw bearings over "generic" items in numerous prior posts so I won't bore people with another diatribe.

The site search engine should enable you or anyone interested in finding the postings.

[bcromwell]

Originally Posted by NC Cams IF the fixed end has TRUE ball screw bearings, you're probably talking about some high dollar, high preload, high contact angle parts (ala the 24TAC47's or something of a similar design ableit different size/part number). You can replace them with generic stuff BUT you'll lose position accuracy and/or repeatability and/or start having backlash problems. The site search engine should enable you or anyone interested in finding the postings.

Thanks to Everyone, NCCams, I did read your very well written post on the ball screw bearings, but I can ask a question. This a old Hurco MB1 cnc Mill that I am trying to get running, While I would love to have the original accuracy it is a hobby machine with a hobby machine budget. What might be get best I can get in the < 200$ price range? Your other post said like 800$ a set (Which is about what I paid for the entire machine) From the other axis it is the same size as the 24TAC47 and is put like a bridgeport (from what I recall) twin bearings face to face, locking tab washer and the nut.
Who has good bearings (and good prices) that sell to private individuals. The best I have found googleing is 7204-ETDULP4 for 105 a pair, but say nothing reguarding ground faces or preload. This is the first time I have ever purchase d bearings so I am a bit lost, Please forgive.

[RICHARD ZASTROW]

bcromwell, Knowing the brand name makes it easier to determine exactly what the part number code means. I've found some Chinese brands such as Peer and AST to be less expensive. I am ignorant of their quality, however. How about posting the mfgr. so we can be more confident in our reply. NC Cams may know those numbers by heart, I do not.

[bcromwell]

Originally Posted by RICHARD ZASTROW bcromwell, Knowing the brand name makes it easier to determine exactly what the part number code means. I've found some Chinese brands such as Peer and AST to be less expensive. I am ignorant of their quality, however. How about posting the mfgr. so we can be more confident in our reply. NC Cams may know those numbers by heart, I do not.

The fixed side bearing are missing and I haven't torn apart the y axis yet to see what the part number is on that set of bearings. The original owner said bridgeport series 1 axis bearings are the same for what that is worth.
If I can find a part number on the y axis I will post it.

[RICHARD ZASTROW]

bcromwell, semi-educated guess (totally inapproriate) the code would indicate a :
7204 = light angular contact 20mm bore
E =
T = CAGE?
DU = DUPLEX UNIVERSAL PAIR
L = LIGHT PRELOAD
P4 = ABEC 7
These, if in good condition, would be a bargain at $105/pair. Maybe those were removed from your machine and are worth "0"? just kidding. Check those numbers with an FAG/BARDEN bearing supplier or on line. Good luck.

[NC Cams]

I don't recall an E code in machine tool bearings. Otherwise, DZASTR"s idendification of the 7204's is pretty much correct.

You really want/need a DUH for ball screws as these are "grunt" type bearings that need a Heavy (H) preload to maintaint low deflection potential. The L preload on the Ebay pieces noted are more suited to high speed/lower load applications such as those used on high speed spindles. Can you use L's or M's? Yes, but don't ***** about backlash or follower error issues.

When it comes to ABEC 7's and/or A/C bearings, you either find/luck into Ebay deals or pay the market price. I don't price shop for bearings outside of calling the typical suppliers when I fix machine tools - either for the home or my business.

It isn't worth the screwing around and/or lame performance to buy unknown/damaged/substandard goods from a bearing supplier with an unknown quality rating.

[hurcojohn]

fafnir p\n MM9306WI-2

barden p\n L078-DF750 (L078H)

mount in db mode (stamped outer faces facing each other)

i have a set of each nos (new old stock) if you cannot find anywhere else...

do not use cheap replacements...

why are you replacing?...

do you have axial slop (loss of motion)?...

btw...x,y and z axis are all the same