Introduction: Row count changes how a gearbox shaft shares load, uses axial space, and fits inside the housing, so single row and double row bearings are not simply interchangeable by size alone.
When a gearbox shaft is rebuilt or reworked, the bearing at each support point has to match the shaft, the housing, and the load path through the gears. A single row bearing and a double row bearing can both look like round steel rings from the outside, but their internal ball paths change how they distribute force and how much axial room they need. Understanding that difference helps maintenance technicians and product researchers compare replacements without treating row count as a simple strength rating.
A gearbox shaft usually runs on two or more support positions, and each position can hold a single row bearing, a double row bearing, or a pair of single row bearings. The structure begins with the ball path. In a single row design, one row of balls sits between the inner and outer rings. In a double row design, two rows of balls sit inside one bearing unit, often with a shared outer ring, two inner rings, or a one-piece inner ring depending on the design. The outside width and the shoulder positions on the shaft often reveal which kind of space the bearing was made to use.
A single row ball bearing has one inner ring, one outer ring, one row of balls, and a cage that keeps the balls spaced. Load passes through that single ball path every time the shaft turns. That simple layout gives the bearing a compact axial width, which matters when the gearbox housing has a narrow seat or when the shaft needs a bearing at a defined shoulder. A deep groove single row bearing can carry radial load and a useful amount of axial load in both directions, because the groove shape lets the balls take some thrust as well as downward force. The axial capacity still depends on ball size, contact angle, clearance, and how the bearing is mounted. In many gearbox shafts, two single row bearings are placed apart from each other so the shaft has two support points and can resist bending along a longer span.
A double row ball bearing packs two ball paths into a single unit. The two rows can share radial load, so each row and each ball may carry less of the total force than a comparable single row design. Some double row bearings also take axial load in one or both directions, depending on their internal arrangement. The trade-off is axial width and complexity. A double row bearing often needs more room along the shaft than a single row bearing of similar bore, and it may need tighter alignment because both rows must work together. Two rows can improve load sharing, but capacity still comes from internal geometry, ball size, contact angle, clearance, and the way the shaft and housing hold the rings.
Load direction is the first practical question. A gearbox produces radial load from gear mesh and shaft weight, and it can also produce axial load from helical gears, thrust forces, or thermal movement. A single row deep groove bearing can handle both radial and axial load, but its axial capacity is limited compared with a bearing designed with a wider contact angle or two rows. A double row bearing can be a good fit when one support position must take a combination of radial and axial load, especially when the housing has room for a wider unit but not for two separate bearing seats. The key is to match the bearing to the load path, not to assume that more rows always mean more capacity. Shaft space works together with load direction. A single row bearing uses less axial width at one point, so it can fit a narrow shoulder, a short housing seat, or a shaft end where the gearbox cover limits how much room is available. A double row bearing uses more width at one point, but it can replace two separate ball paths in a single mounting position. Two single row bearings spread along a shaft can create a wider support base, which helps control shaft deflection and keeps gears in better alignment. That layout also lets each bearing be positioned closer to the load it supports. A double row unit can save a separate seat and simplify assembly in some designs, while two single rows may be easier to fit, replace, and adjust in others. Row selection therefore depends on load direction, shaft length, housing width, and the number of support points that the gearbox design allows.
The 62/38-2RS/C3 bearing from Smart Bearing is a single row ball bearing with 38×85×18 mm dimensions, C3 clearance, and 2RS seals. Those facts define how it can fit a gearbox shaft. The 38 mm bore, 85 mm outer diameter, and 18 mm width set the shaft seat, housing bore, and axial space. The single row structure places one ball path between the rings, so it suits positions where the shaft layout calls for a compact support rather than a wide double row unit. The C3 clearance and 2RS seals are part of the listed configuration and need to match the original position. A maintenance technician comparing a replacement should treat those details as part of the fit, not as optional extras. The 62/38-2RS/C3 remains a defined single row support, not a universal substitute for every double row bearing. It fits gearbox positions where the load direction, shaft spacing, and housing dimensions match a single row support. In some shafts, two single row bearings are used at separate points, and a 62/38-2RS/C3 can serve as one of those supports if the seat and load path match. In other shafts, the original design may use one double row bearing to take combined radial and axial load at a single position, and a single row bearing would need a different shaft layout to do the same job. The practical comparison is structural: count the ball paths, check the load direction, measure the axial space, and confirm how the shaft is supported. The product reference for 62/38-2RS/C3 gives the dimensions, clearance, and seal details needed for that comparison.
Single row and double row ball bearings differ first in structure: one ball path versus two ball paths inside the bearing unit. That structural difference changes load sharing, axial width, and the way a gearbox shaft is supported. A single row bearing can carry radial and limited axial load while using less axial space, and two single row bearings can support a shaft across a longer span. A double row bearing can share load across two rows inside one unit, but it needs its own width and alignment conditions. The right choice depends on load direction, shaft space, and the surrounding shaft arrangement. For the 62/38-2RS/C3, the single row structure, 38×85×18 mm dimensions, C3 clearance, and 2RS seals suit defined gearbox positions where those facts match the original layout. Comparing structure and load path before treating two bearings as interchangeable is the safer repair habit.
A：A single row ball bearing has one row of balls between the inner and outer rings, while a double row ball bearing has two rows of balls inside one bearing unit. That changes load sharing, axial width, and how the bearing fits on a gearbox shaft, but row count alone says little about final capacity.
A：Yes. A single row deep groove ball bearing can carry radial load and a useful amount of axial load in both directions. The axial capacity depends on ball size, contact angle, clearance, and mounting, so it suits many gearbox positions where thrust is moderate and the shaft layout supports the load properly.
A：Two single row bearings can be spaced apart to create two support points along the shaft, which helps control deflection and keeps gears aligned. They can also fit narrower individual seats and be easier to replace. A double row bearing may be chosen when one position must share load across two ball paths or take combined radial and axial load within a wider housing seat.
NIST SP 960-17: Rolling Element Bearings Technology and Applications
