FAG36620B-3Tapered Roller Bearing Cup 7-5/8 in OD x 0.9063 in Wide Class 3 Precision 36600 Series — Cup Only, No Cone

Product Description

What this part is

This is a tapered roller bearing cup — the outer ring on its own, with the tapered raceway ground into its bore. It is the 36620-B cup from Timken’s 36600 inch series, 7.6250 in (193.675 mm) outside diameter by 0.9063 in (23.020 mm) wide, supplied to Class 3 precision. A cup is one half of a tapered roller bearing. The other half is the cone assembly — inner ring, tapered rollers and cage — which is separately numbered and is not part of this listing.

What is and is not included

This listing is the cup alone. There is no cone, no roller set and no cage. You receive the outer ring only. If you need a complete bearing you must also source a 36690 cone (5.750 in bore), or one of its siblings such as 36691. This is the single most expensive mistake made when buying tapered roller bearings: cup and cone are separately numbered halves of one bearing, and an order placed against a cup number brings you half a bearing.

Cups and cones are separable by design, and replacing one without the other is normal practice rather than a compromise. The cup presses into the housing and the cone onto the shaft, so the two wear at different rates and in different failure modes. A cup-only replacement against a sound cone is a routine and much cheaper repair.

Decoding the designation

36620 — Timken inch-series cup number in the 36600 series. Within an inch series the cup and the cone are numbered separately; 36620 is a cup, 36690 and 36691 are cones.B — a Timken design-revision letter on the cup. In Timken’s own catalogue the 36690 / 36620-B pairing is listed under TSF, Tapered Single with Flange, and Timken publishes a flange outside diameter (D1) of 7.7772 in / 197.541 mm and a flange width (C2) of 0.1563 in / 3.97 mm for it. A flanged cup locates axially against the face of the housing instead of relying on a machined shoulder inside the bore, which is how you get a repeatable seat in a through-bored or thin-walled housing. If you are matching an existing part, check the flange against the photographs before ordering — a flanged cup will not drop into a housing bored for a plain cup, and a plain cup has no shoulder to register against a flange-faced housing.−3 — Timken precision Class 3. The notations 36620B-3, 36620B #3 and 36620B *3 all mean the same thing. This is not a quantity, a revision or a packaging code.K- prefix — K-36620-B and K36620B are Timken component-order forms of the same cup number, used when a cup is ordered as a loose component rather than as part of an assembly. They appear widely in OEM parts lists and are cross-referenced below.The cone number, not the cup number, selects the bore. A 36620-B cup fixes the 7.6250 in housing fit; the 36690 cone fixes the 5.750 in shaft fit.

What Class 3 precision actually buys you

Timken supplies inch tapered roller bearings in graded precision classes — Class 4 is the standard commercial grade, then Class 3, Class 0, Class 00 and finer. Each step up tightens the tolerances on outside diameter and width, and critically on radial and axial runout of the ground raceway.

A Class 3 cup therefore runs truer in the housing than a standard cup of the same nominal size, and it is specified where housing-bore runout translates directly into a product-quality problem: machine tool spindles, precision gearboxes and index drives, printing and converting rolls, gear grinders, paper machine positions. It costs more than a standard cup and it is stocked far less widely, which is exactly why a surplus batch of them is worth finding.

The commercial consequence cuts both ways, and both directions matter. A standard 36620B will fit where a 36620B-3 is called for, but it will not run the same, and substituting down a precision class in a precision position is a common and expensive error. In the other direction, if your position only ever needed a standard cup, a Class 3 part is a free upgrade at no fitting penalty. Note that this listing does not reproduce the numeric Class 3 runout limits, because those come from Timken’s precision tolerance tables and were not read for this reference — ask if you need the figures certified.

Correcting the source data

Two errors in the original listing data have been corrected here. The brand field carried FAG while the part number, the title and the markings are all Timken — 36620B is a Timken inch designation and the brand has been set to Timken. The cup width was given as 0.9036 in; Timken’s own catalogue entry for 36690 / 36620-B gives the outer ring width (C) as 0.9063 in / 23.020 mm. The 0.9036 figure is a digit transposition and should not be used for a stack-up calculation.

Published ratings and mounting data

The figures below are Timken’s own published data for the complete 36690 / 36620-B single-row assembly. They describe the bearing as a pair, not the cup alone — a cup has no load rating in isolation, because capacity is a property of the roller set running between both races.

Cone part number: 36690 — Cup part number: 36620-B — Series: 36600Cone bore (d): 5.7500 in / 146.050 mmCup outside diameter (D): 7.6250 in / 193.675 mmCup outer ring width (C): 0.9063 in / 23.020 mmCone inner ring width (B): 1.1250 in / 28.575 mmOuter ring flange outside diameter (D1): 7.7772 in / 197.541 mmOuter ring flange width (C2): 0.1563 in / 3.97 mmDynamic radial load rating C1 (1 million revolutions, ISO method): 44,200 lbf / 196,000 NDynamic radial load rating C90 (90 million revolutions, Timken method): 11,400 lbf / 50,900 NDynamic axial rating Ca90: 7,220 lbf / 32,100 NStatic radial load rating C0: 88,600 lbf / 394,000 Ne factor 0.37, K factor 1.59, Y factor 1.63G1 factor 366, G2 factor 121, geometry factor Cg 0.177Housing backing shoulder diameter, frontface (Da): 7.50 in / 190.5 mmShaft backing shoulder diameter, frontface (da): 6.02 in / 153 mm; backface (db): 6.1 in / 155 mmMaximum housing fillet radius cleared: 0.06 in / 1.5 mmMaximum shaft fillet radius cleared: 0.06 in / 1.5 mmEffective centre location: 0.19 in / 4.8 mmCage location relative to frontface (Ab): 0.13 in / 3.3 mm; relative to backface (Aa): 0.04 in / 1 mm

Weight is not stated here. Timken publishes no cup-only weight for this reference, and the assembly weight shown on the catalogue entry is not consistent with a bearing of this envelope, so no figure is carried rather than repeating one that looks wrong. Assembly width (T) is likewise left out: the TSF catalogue entry lists a Width (T) of 0.375 in, which cannot be reconciled with a 1.1250 in inner ring, and the plain 36690 / 36620 assembly width of 1.125 in comes from a distributor mirror rather than from Timken. Measure the part you are replacing.

What these specs mean in practice

The K factor of 1.59 is the number that tells you what this bearing is for. K is the ratio of radial to thrust capability set by the cup angle: a higher K means a shallower cup angle and a bearing that is radially strong and comparatively thrust-weak. At 1.59 the 36600 series sits in the middle of the tapered roller range, carrying a genuinely useful axial component alongside its radial load. That is the mix a gear-driven shaft produces, which is why the series turns up in gearbox and roll positions rather than in pure thrust duty.

The e factor of 0.37 is the threshold in the equivalent-load equation: below an axial-to-radial load ratio of 0.37 the thrust component drops out of the calculation, above it the equation changes. With e = 0.37, K = 1.59 and Y = 1.63 all published above, plus C1, C90, Ca90 and C0, you have everything needed to run a bearing life calculation on this position without asking anyone for data.

Quantity and configuration

Forty-one pieces are on hand and each piece is one cup — not a set, not a cone-and-cup pair. Order the count you actually need, and remember that a complete bearing needs a 36690 cone as well. Forty-one Class 3 cups of one production vintage from a single source is an unusual position: if you run a machine with several identical roll or spindle stations, this is the batch that lets you bring them all to the same precision class at once instead of mixing classes and suppliers across the machine.

Fitting notes

The cup presses into the housing bore, and the 0.06 in maximum housing fillet radius must be respected at the shoulder or the cup will not seat square. Drive it in from the large end of the taper, square to the bore, with a fitting tool that bears on the cup face and never on the raceway. A hammer blow on a ground raceway brinells it, and on a Class 3 part that throws away the entire reason you paid for the precision class.

Tapered roller bearings have no built-in internal clearance. The operating endplay or preload is created at assembly by how far the cone is drawn up against the cup, and that setting governs bearing life more than any other single variable. In a precision position the machine builder normally specifies it tightly. If you are fitting a new cup against an existing cone, re-measure and re-set endplay to specification — a new cup has an unworn raceway and changes the stack-up, so the old shim pack no longer gives the old setting.

Interchange guidance

36620 is an industry-standard inch cup designation rather than a proprietary Timken code, so it is manufactured by several bearing makers and a 36620B from any reputable source is dimensionally interchangeable. That widens the sourcing options considerably in both directions — and it is also why the precision class has to be checked separately: the class is not part of the base number, so a plain 36620B from any maker is a standard-class part and is not equivalent to this 36620B-3.

Cross-references: 36620B, 36620-B, 36620 B, 36620B-3, 36620B #3, 36620B *3, 36620B CL3, K-36620-B, K36620B, K-36620B. Base cup without the B revision: 36620. Related cup forms: 36620D and 36620DC double cups, 36620P. Mating cones: 36690 (5.750 in bore), 36691. Related assemblies: 36690/36620-B, 36690/36620, 36691/36620, 36690/36620D.

Central Surplus also stocks the matching Timken 36690 Class 3 cone under SKU B-BS3#LAQ8WA, and the complete 36690-3 / 36620B-3 Class 3 cone-and-cup set under SKU CF4#JTOIVS. If you need both halves, buy the set rather than sourcing the two numbers separately — and if you need the pair matched to the same precision class, that is the listing to use.