What's new
What's new

Bearing C3 vs C2

jappietoutou

Aluminum
Joined
Dec 2, 2015
Location
Montreal
Hello
I just bought an old Press Drill R-53, it's a precision machine with a max RPM of 6000.
I want to replace the main bearings, which were New Departure 3203, my local store suggested SKF 6203 C3, but should I go with C2 instead or other ? with a smaller internal tolerance.
Thank You
JP
 
In my experience C3s are used in applications where there might be heating involved (ex fluid couplings) and conflicting thermal expansion of the housing and bearings might cause problems. I'd go with the C2 on your drill press.
Robert
 
Pics please!
I've had a high-speed hammer drilling machine for years. Mine is a Craigslist rescue that might be ex-philly navy yard. I've always wondered about the main spindle bearings but not enough to actually do anything other than use it. Wonderful machines. I made a new flat belt motor pulley & tensioning rig and used a leather belt from a thrift shop and its been drilling for years.
 
The main deciding factor for which clearance to use is are the bearings pressed on to the shaft which will stretch the inner race a tiny bit and is the outer race also a press fit which will shrink the outer race a tiny bit? If so then some of the clearance will disappear and you need C3 bearings. If the bearing slides on to the shaft and is not pressed in to the housing then C2 may be OK.

I have seen cases where C3 bearing were replaced by smaller clearance ones and the bearing was too tight as all the internal clearance was gone from the press fits.
 
The main deciding factor for which clearance to use is are the bearings pressed on to the shaft which will stretch the inner race a tiny bit and is the outer race also a press fit which will shrink the outer race a tiny bit? If so then some of the clearance will disappear and you need C3 bearings. If the bearing slides on to the shaft and is not pressed in to the housing then C2 may be OK.

I have seen cases where C3 bearing were replaced by smaller clearance ones and the bearing was too tight as all the internal clearance was gone from the press fits.
Everything you say here applies to my drill press. Press fits are light in my opinion, but need a press arbor press to remove, but light. Now this is a precision drill press, not much heat involve. I'll go with C3 for now, easier to find than C2.
thank you
 
Pics please!
I've had a high-speed hammer drilling machine for years. Mine is a Craigslist rescue that might be ex-philly navy yard. I've always wondered about the main spindle bearings but not enough to actually do anything other than use it. Wonderful machines. I made a new flat belt motor pulley & tensioning rig and used a leather belt from a thrift shop and its been drilling for years.
I'll post pictures in a couples of week !
JP
 
C2 is below "normal" clearance and can actually have zero play.

NDH 3203 is a 6203 bearing with a 17mm bore so C3 is 11-25 um (4 - 10 tenths), I reball many bearings this size with ceramic balls and find most come on the lower end of the spec so I'd stay with C3.

Untitled.jpg
 

Attachments

  • Bearing checker.JPG
    Bearing checker.JPG
    226.5 KB · Views: 20
How does the inner clearance work when the driven shaft both rotates and slides up & down?. I've never had the bearings apart on mine. Is there an inner sleeve or something between the inner race of the bearings and the keyed shaft?
 
How does the inner clearance work when the driven shaft both rotates and slides up & down?. I've never had the bearings apart on mine. Is there an inner sleeve or something between the inner race of the bearings and the keyed shaft?
There is a hollow shaft with bearings at each ends. The spindle is keyed like you said. There is a 'set screw' that goes through the pulley and through the hollow shaft, that set screw has its end machined to fit the key way of the spindle. very small fit between spindle and hollow shaft inner dia.

Jean-Pierre
 

Attachments

  • IMG_3257.jpg
    IMG_3257.jpg
    2 MB · Views: 10
C2 is two steps lower internal clearance than C3. From larger to smaller, it goes C3, CN (with no clearance markings on the bearing or in the part number), to C2. If you want to have less clearance than C3, normal clearance bearings would be easier to find than C2.

Do the bearings you are taking out have any clearance designations in the part number?
 
C2 is two steps lower internal clearance than C3. From larger to smaller, it goes C3, CN (with no clearance markings on the bearing or in the part number), to C2. If you want to have less clearance than C3, normal clearance bearings would be easier to find than C2.

Do the bearings you are taking out have any clearance designations in the part number?
my original bearings are ND 3203 which don't exist anymore, replacement are 6203, and there is no markings on the originals except N.D. 3203 made in USA. I will go with C3 if my local store does not have the CN .
JP
 
What problem are you trying to solve?
If you want preload, bearing fits is not the way to achieve this.
The ball clearance is for dealing with press fit stretch or shrink
of the races. If you somehow cheat the fit to achieve some
preload internal to the bearing, that really does not help
stiffness of the spindle much. What you want is preload
between 2 bearings, spaced some distance apart. You
need this distance to achieve rigidity. Having loaded balls
in an individual bearing will not make a spindle stiff.
Not to give the result of reduced chatter in a cutting tool,
which is traditionally the primary reason in this industry.

-Doozer
 
The OP did not show us a assembly of the spindle or parts break down. There's a good chance the spacers are there, just have to measure the lengths to determine if there is any difference between the two. Of course, it also depends if the op has some way to measure the differencee with. Dial or digital caliper or rule is not precise enough to use.
 
These drills have an overarm which pushes the spindle from the top. There are normally thrust bearings at the bottom and top of the overarm, so there should be little to no thrust on the spindle bearings.
 








 
Back
Top