Calculating Total Number of Speeds on Drill Press

[bostonman]

Good to know.

If I gave it more thought, I would have probably known other brands would work too. Think I got excited the bearings actually had a part number stamped on it and focused more on just buying a replacement.

[jpanhalt]

I am not an expert, but size (inner and outer diameter and height) are obvious or it won't fit.  Grade/class is important depending on application.  Then whether there's shielding and whether the inner race extends past the plane of the outer race must be considered.  The full part number should suffice, but it's worth confirming visually.  I suspect your bearings are shielded and permanently lubricated.  The specific type of shield (metal or rubber) is probably less important in that application.

[bostonman]

NTN replied to my email and stated one of their factories is in Taiwan, so these bearings seem legit (i.e. not counterfeit).

Earlier I measured the outer, inner, and width, of the bearing. From what I can tell, the part number stamped on it and the datasheet on their website are a match. I didn't measure from the inner to the outer (whatever that is called), but now I'll investigate grade and pricing.

If the price difference isn't much, it only makes sense going higher quality.

[jpanhalt]

I have found that McMaster bearing costs are quite a bit higher than what I can get locally with a brand name.  McMaster doesn't usually give you the brand, but I haven't checked recently.  I mention that just in case that's where you are are looking.

[bostonman]

That's good advice, and thankfully I wasn't planning to look on their site for bearings.

My reasons for not looking on their site are basically the same.

[mendip_discovery]

6203 is a standard bearing. The z refers to the seals. Z iirc is open. There will he a guide on the internet. You might want to go for a ZZ or a LLB. I often find talking to a local bearing supplier about what you want to do they can give good advice.
https://www.ntnglobal.com/en/products/catalog/pdf/3015E.pdf

If you buy a good brand of bearing it should be fine. I have loads of these in the shed and they are often the bearings used for motorcycles.

[bostonman]

6203 is a standard bearing. The z refers to the seals. Z iirc is open.

If I'm understanding correctly, 6203 is arbitrary as I don't see a connection between these numbers and the size. The 'Z' apparently is sealed on one side whereas 'ZZ' is sealed on both sides.

Update: After looking, '03' represents the bore size which is 17mm. Think I found the correct part number break down on the NTN site.

The upper shaft in the drill press has been removed and the bearings are back-to-back, so their inner sides may be open (I'll press them out to confirm), but I can't see. The STEP file for a 'Z' bearing has one side open, and initially I assumed they did this to show the bearings, but a 'ZZ' CAD has both sides sealed. Plus one of the PDFs supplied in this thread seem to confirm a 'Z' bearing is open on one side (not sure why someone would want one side open).

Since 6203 defines the bearing size, what other factors should I consider besides sealed on one side versus both sides? I tried to follow the PDF on bearing quality, but it looks like ISO 492 has classes that are tied to dimension tolerances only.

My assumption is I need to consider quality, grease, and seal type. Since they probably get more expensive, and this is only a drill press, it probably only needs some basic bearings.

Update: that PDF of the NTN catalog actually somewhat outlines the things to consider and I see LLB (also LLU that looks better).

[CatalinaWOW]

Though I doubt it applies in this case, back to back bearings sometimes are specified as a matched pair, with the races ground to provide a specific preload when clamped tightly together.

More likely, but not necessarily true in a low cost drill press is the need to shim or adjust clamping pressure on the pair during installation.

[jpanhalt]

6203 is a standard bearing. The z refers to the seals. Z iirc is open.

If I'm understanding correctly, 6203 is arbitrary as I don't see a connection between these numbers and the size.

Not entirely arbitrary, but in accord with a metric table:
https://www.skf.com/us/products/rolling-bearings/principles-of-rolling-bearing-selection/general-bearing-knowledge/bearing-basics/basic-bearing-designation-system

They have been that way for a long time.

[Kleinstein]

The 1 Z series allows it to apply grease later if needed and with something like a gear box that has grease inside anyway this can be handy.  However the 1 side closed bearing are a bit rare and may not be as easy to get. It should be OK to also use the ZZ (or 2Z depending on the manufacturer) that are more common.

As the drill press is likely running at a more moderate speed one could likely also use a fully sealed version like LLB/LLU (the naming here depends on the manufacturer). The price difference may not be large.
Chances are one wants the normal (C2) clearance and not the more loose C3 type for high speed.

[jpanhalt]

As I mentioned, one needs to look at the exact standard applied.  My introduction to BB standards was with the McMaster Carr paper catalog in about 1970.  It used the ABEC system (https://www.emersonbearing.com/resources/abec-rating-guide/) and similar, which are roughly the opposite of ISO.  A very low class (1/2???) was described for inexpensive electric motors.  Class 1 allows -0.005" tolerance, which is huge in a machine spindle with 2 bearings a few inches apart and both much further from the workpiece.  Spindle speed is generally not an issue. 

Example:  If drilling a PCB, a small carbide drill, e.g., #71 (o.026"), may be needed.  0.010" in spindle runout may be problematic, but that would be perfectly OK for a 1/2" spade drill in wood.