Bearing Precision Class Identification

[Graham WhartonParticipant @grahamwharton]

Hi chaps,

These bearings are from the horizontal spindle from a Tom Senior Junior mill that I am refurbishing.

They are Timken Taper Roller Bearings

Front – 2523/2582

Rear – 1922/1975

I'm trying to work out the precision class. Can anyone help from the photos, or know what would be fitted.

Front

Rear

[Graham WhartonParticipant @grahamwharton]

[blowlampParticipant @blowlamp]

I wouldn't spend much time worrying about the precision class of a modern (decent brand) taper roller bearing. They are all manufactured to very tight tolerances anyway.

Martin.

[Graham WhartonParticipant @grahamwharton]

According to the Timken catalogue, Normal precision Taper Rollers can have TIR of up to 2 thou just in the bearing itself whereas the precision grades start at 3 tenths TIR. I dont know about you, but i'd be a bit miffed if I just spent 100 quid on a set of standard precision bearings and ended up with 2 thou runout on the bearing itself.

Graham

[blowlampParticipant @blowlamp]

The thought of spending £100 on a pair of bearings with 2 thou runout would make me look for a different manufacturer. I dread to think how much their 3 tenths and above versions cost, although I actually believe that even their 'standard' bearings would perform much better than their specifications would indicate

As an example, I recently fitted my Mini-Lathe with a pair of standard Koyo 30206 taper roller bearings from Arceurotrade at less than £10 each. As near as I can tell, the runout is zero – this includes clocking the spindle register and also a 'still in place' turned test piece.

As far as I am aware, precision bearing classes are largely confined to angular contact bearings nowadays, with some exceptions of course.

Martin.

[Jeff DaymanParticipant @jeffdayman43397]

Graham if I were you I would check google or yellow pages and find an industrial bearings and drives supply firm near you. Tell them what you are fitting the brg to and see if they have a Koyo or SKF or other cross ref brg. Should not be anywhere near 100 pounds cost for the size and type you show in the pics. You do not likely need genuine Timken.

Both Tim and Ken (founders of Timken brgs) must have been well on the champagne if they ever made a set of tapered roller brgs that had .002" runout per set. Are you sure that tolerance in your catalogue is not a max housing machining error spec?

Happy New Year all.

JD

[Graham WhartonParticipant @grahamwharton]

Thanks for the reply guys.

Timken list the max tolerances for their taper roller bearings as follows

Inner bore Class 4 +0.0005/-0.0000 Class 3 +0.0005/-0.0000

Outside Diameter Class 4 +0.0010/-0.0000 Class 3 +0.0005/-0.0000

Inner Ring Width Class 4 +0.0030/-0.0100 Class 3 +0.0030/-0.0100

Outer Ring Width Class 4 +0.0020/-0.0100 Class 3 +0.0020/-0.0100

Radial Runout Class 4 0.0020 Class 3 0.0003

Sounds as if these are absolute extremes, Youve all made me feel a bit better about the likely outcome if I was to fit standard precision bearings though.

I did look at SKF but they don't do any that will fit.

Prices are Timken RRP, which I believe get discounted by about 50% when they get to the shops.

2523-20024 £31.84 ex vat

2582-20024 £62.48 ex vat

1922-20024 £22.47 ex vat

1975-20024 £67.07 ex vat

Ive sent some emails to some bearing distributors and am awaiting replies and actual prices.

The bearings that are in the machine at the moment are actually in good condition. I removed them with a view to finding out their numbers, and then if they were 30/40 quid for the lot, then I would just put new ones back in. However if they are going to turn out to be 100 quid ish for the set, then i'll probably clean up, repack and refit the existing bearings.

[chris stephensParticipant @chrisstephens63393]

Hi Graham,

There is a firm in Yankee-land that overhauls and modifies Bridgeport heads by fitting 5 instead of 3 bearings and to ensure complete concentricity they re-cut the R8 taper using the quills own bearings. Food for thought if new bearings do actually have that amount of cheapness, which is relatively unlikely.

chriStephens

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