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Here's a good article on this. It's about ceramic bearings but it applied equally to steel bearings. So the Cx is a specification, and not an indication of quality which would be more about production tolerances or deviation from them and materials used.myerslawnandgarden wrote: ↑Wed Aug 25, 2021 10:35 pm I am also not knowledgeable regarding C1/C3, could you expound?
The suppliers that I use do reference EMQ quality bearings which we supply for the mechanical pto clutches, EMQ stands for "electric motor quality"
Bob
The suffixes C0 through C4 in a bearing part number refer to a bearing’s internal clearance value and have to do with what’s called “radial play”. Radial play is the radial internal clearance between the balls and races, and is the measured value of the total movement of one ring with respect to the other in a plane perpendicular to the bearing axis. Radial play can also be referred to as“internal clearance”.
The following is a list of bearing clearance values and what they mean:
C0 – Referred to as “standard clearance”. Normally, there are no markings on a bearing with a C0 clearance value.
C2 – Refers to a “less than standard clearance”. Bearings with this type of clearance are uncommon and have very limited uses.
C3 – Refers to a “greater than standard clearance”. This is the most common type of bearing, and is the correct choice for the majority of applications.
C4 – Refers to “greater than C3 clearance”. Not as common as C3, but often specified in small engine crankshaft bearings.
In any bearing, including ceramic hybrid ball bearings, some internal clearance is necessary to the ensure that the bearing turns freely, without binding. But note that these clearance values are very small. For example, a 25mm bearing with a “standard fit” will have an internal clearance of about a half a thousandth of an inch. The same bearing with a C3 fit will have about one thousandth of an inch clearance. This value is less than the diameter of a human hair! Internal clearances are also relative to the bearing’s bore size (the amount of radial play will increase as the bore size increases).
The radial play for a given bore size is not an exact value, but a range. For example, a 6205 C3 bearing (25mm bore) has a radial play value that falls between .0006” and .0010”. The same bearing in a C4 clearance has a clearance range of .0011” to .0015”. In a properly assembled bearing, the clearance will generally fall in the middle of the tolerance range.
A small amount of extra clearance is usually not a problem, but any amount of negative clearance (interference) can be a big problem, resulting in increased friction, heat, and ultimately in early fatigue failure. Therefore, it is always better to err on the side of a bearing that is a little loose, rather than one that is a little tight. It is also important to note that the radial clearance value that matters most is that when the bearing is installed and up to operating temperature.
How old was the shot one Matt?MattA wrote: ↑Sat Dec 04, 2021 10:02 pm I finally got my deck off today and cleaned up about a month behind schedule. The top center spindle bearing was shot and the top left was a little noisy. I replaced them both with some Fafnir 204RR6 bearings I had saved from a previous rebuild. Nice and quiet now. Earlier this fall I replaced both right side spindle bearings. I'll probably get a full set of Fafnir 204RR6 bearings on order from Bob for the next rebuild.
I replaced all 6 spindle bearings at the start of the 2020 mowing season. The bearings were around 2 years old when I replaced them. I replaced them because the center spindle bearings had seized up over the winter while stored in my garage. I also replaced the center spindle at that time.Eugen wrote: ↑Mon Dec 06, 2021 10:39 pmHow old was the shot one Matt?MattA wrote: ↑Sat Dec 04, 2021 10:02 pm I finally got my deck off today and cleaned up about a month behind schedule. The top center spindle bearing was shot and the top left was a little noisy. I replaced them both with some Fafnir 204RR6 bearings I had saved from a previous rebuild. Nice and quiet now. Earlier this fall I replaced both right side spindle bearings. I'll probably get a full set of Fafnir 204RR6 bearings on order from Bob for the next rebuild.