KOMEL grinds this ring in Hefei, at a 12,000 square metre plant that has run bearing production for more than ten years. Most buyers arrive with a load case that moves: a shaft that starts out carrying only its own weight picks up an axial push once a gear set engages, or once an arm changes direction. Two separate bearings would solve that, but the housing has no width to spare. What follows deals with that narrow situation only, from ring section to the fits that decide whether the clearance survives mounting. The plant is a manufacturer of this family in seven inch series, and the Four Point Contact Thin Section Bearing for Radial and Axial Loads is the version quoted when both load directions appear in the duty.
The Four Point Contact Thin Section Bearing for Radial and Axial Loads is ground from bearing steel to a near square section: the radial wall, the axial width and the land diameters hold one proportion through a whole series. Moving from a 1.000 in bore to a 40.000 in bore does not change the section, so a housing drawn around one size can accept another without a redesign.
The wall between bore and outside diameter stays thin against the diameter itself, which is where the space saving comes from. That thinness is also the limit: the ring is not a substitute for a heavy duty cylindrical roller bearing in a mill stand, and it is not offered as one.
Both raceways are cut as pointed arch grooves rather than the single radius used in a deep groove bearing. Each groove is ground so that the ball can touch at two points, one on each side of the arch. The inner ring therefore offers two contact points and the outer ring two more, four in total.
Which pair carries load depends on the direction of the force. Radial load presses the ball into the lower part of both arches. Axial load tilts the ball onto the opposite pair, and the load path runs diagonally through the section rather than straight across it.
1. Radial only: shaft weight, belt pull and the separation force of a gear pair sit on the lower contact pair, with the ring acting much like a deep groove bearing of the same section.
2. Axial in one direction: thrust is taken on the upper pair, so a one way push needs no separate thrust bearing.
3. Axial in both directions: because the groove is symmetrical, a reversing thrust is carried by the same ring without a second seat.
4. Radial and axial together: a combined load resolves on all four points at once, which is the case the Four Point Contact Thin Section Bearing for Radial and Axial Loads was designed around.
Friction stays low because the ball rolls rather than slides, and starting torque stays low for the same reason, which matters on a lightly loaded positioning axis.
The table lists six sizes across the KA series, stepping by 2.000 in of bore, dimensioned in inches. L1 and L2 are the land diameters on the inner and outer ring and are the numbers a housing bore is usually matched against.
| Number | Bore (in) | OD (in) | L1 (in) | L2 (in) | Weight (lb) |
| KA020XP0 | 2.000 | 2.500 | 2.186 | 2.314 | 0.10 |
| KA040XP0 | 4.000 | 4.500 | 4.186 | 4.314 | 0.19 |
| KA060XP0 | 6.000 | 6.500 | 6.186 | 6.314 | 0.28 |
| KA080XP0 | 8.000 | 8.500 | 8.186 | 8.314 | 0.38 |
| KA100XP0 | 10.000 | 10.500 | 10.186 | 10.314 | 0.50 |
| KA120XP0 | 12.000 | 12.500 | 12.186 | 12.314 | 0.56 |
Every size in the table shares the same 0.500 in section between bore and outside diameter. Where a deeper section is needed for a heavier axial push, the KB and KC series cover the same bores with more material, and a Four Point Contact Thin Section Bearing for Radial and Axial Loads can be quoted from either without changing the numbering system.
A Four Point Contact Thin Section Bearing for Radial and Axial Loads is sensitive to the fits it is pressed into. A bore fit that is too tight closes the internal clearance and the ring runs hot; one that is too loose lets the outer ring creep. Shaft and housing tolerances should therefore be stated on the drawing, together with the clearance class and the precision grade, so the quotation can be made against a defined part rather than a catalogue number alone.
Mounting is usually a light press on the shaft and a slip fit in the housing, with the clamping done through the adjacent shoulder. Axial clamping should bear on the ring face, never on the seal or the ball path.
1. Two load directions, one seat: shaft weight and thrust in either direction resolve on the same four contact points, so the drawing needs one bore, one shoulder and one clamping face instead of two.
2. Section that stays put: the wall holds one square proportion from KAA through KG, and a 1.000 in bore and a 40.000 in bore are specified the same way.
3. Low drag: the balls roll on the arch grooves rather than slide, which keeps starting torque low on an axis that reverses often.
4. Weight spread: catalogue parts run from 0.026 lb to 30.80 lb, so the same geometry is available for a small wrist or a large frame without changing the mounting logic.
The honest limit is capacity. One ring is rated as a single angular contact bearing, not as a duplex pair; where the duty needs the stiffness of two bearings, two bearings remain the right answer.
Three operations sit under one roof at the Yaohai industrial park in Hefei: grinding, heat treatment and testing, in a 12,000 square metre base that has made roller and ball bearings for more than ten years. A ring that takes radial and axial load in one seat depends on both arch grooves being ground to the same geometry, so the plant that grinds them is part of the product rather than a detail of the invoice.
All processes, from raw material selection to finished product inspection, follow international standards, and the company holds ISO9001 and ISO14001 certification. The technical team reviews the load case before a series is fixed, production progress is tracked against the delivery date, and technical support continues after delivery. Where a bore, outside diameter and width fall outside the tables, the company states that it supplies customised bearing solutions for special needs.
A: A single ring rated for bidirectional thrust carries roughly what one of the two bearings in a back-to-back pair would carry, not the sum of both. If the axial load was sized against a pair running at full capacity in each direction, check the single ring against the larger of the two directions.
A: Not for most positioning duties. Preload raises stiffness but also raises torque, and on a thin ring the torque penalty shows up quickly on a small servo. Set the clearance class first, then add preload only if the application shows deflection under load.
A: In most housings yes, provided the axial load is within the four point rating. The section and the mounting dimensions are close enough that the change is usually a part number swap, but the axial capacity and the stiffness differ, so the load case should be rechecked.
A: Grease for life is normal on small sizes, oil where speed or heat calls for it. The choice should follow the duty cycle rather than the catalogue, and the grease quantity should stay low on a thin ring because there is little free space inside.
A: The catalogue is built on inch dimensions. A metric bore and outside diameter can be quoted as a custom ring from a drawing, since the plant grinds to order as well as to stock sizes.
One ring, four contact points, two load directions, and a section thin enough to fit where a conventional pair will not. The limits are honest ones: it carries what a single angular contact bearing carries, not double, and it needs defined fits to keep its clearance.
Send the bore, the outside diameter, the axial load in each direction and the housing drawing to info@komelbearings.com, and the reply will name one series and one part number with the fits marked on it.
