The BB5013 metric thin section ball bearing (open four-point Type X, 50 × 80 × 13 mm) from the BB series matches common crossed roller envelopes while running at lower friction torque. Dynamic radial 9.297 kN, moment 227 N·m, clearance 0.030–0.056 mm. Order as LYDL-5013. Compare related sizes and request a drawing or quote from LYDL.
Space is the constraint that decides most instrument designs, and mass follows close behind. The BB5013 answers both: a 50 mm bore inside a cross section of only 15 × 13 mm, in an open four-point (Type X) execution that weighs 0.24 kg. The dynamic radial rating of 9.297 kN and the 227 N·m moment rating let it carry real loads even though the ring is barely larger than a hockey puck.
Because the BB metric family deliberately mirrors the bores and widths of common crossed roller bearings, this smallest of the five LYDL BB sizes slots into envelopes already drawn for RB-style parts — while cutting starting torque and rotor inertia. Designers of gimbals, scanner axes and compact robot joints arrive at this page for that single reason.
A housing of 80 mm across is all the space the BB5013 asks for. The radial section stays constant at 15 mm while the width is 13 mm, and the maximum fillet radius at shaft and housing shoulders is a straightforward 1 mm — no profiled turning, no special tooling. For the machinist this is lathe work, not a project.
| Parameter | Symbol | Millimeters | Inches |
|---|---|---|---|
| Bore diameter | d | 50 | 1.969 |
| Outside diameter | D | 80 | 3.150 |
| Width | B | 13 | 0.512 |
| Cross section (radial × width) | – | 15 × 13 | 0.591 × 0.512 |
| Max. fillet radius | r | 1 | 0.039 |
The inch equivalents are tabulated alongside the metric values because a large share of thin-section demand still originates on imperial drawings. Whichever unit system your BOM uses, the envelope is the same physical part.
LYDL publishes a 9.297 kN (948 kgf) dynamic radial rating, a 12.96 kN dynamic axial rating and a 227 N·m moment rating for the BB5013. The radial and moment figures reappear in the SKF Kaydon BB metric catalog under designation KDN.39322001, which lets you cross-check the specification in a design review. Static load ratings for this size are available from LYDL on request.
| Parameter | Symbol | Value | Notes |
|---|---|---|---|
| Dynamic radial load rating | Cr | 9.297 kN (948 kgf) | LYDL spec = SKF Kaydon catalog |
| Dynamic axial load rating | Ca | 12.96 kN (1,321 kg) | LYDL specification |
| Dynamic moment rating | M | 227 N·m | LYDL spec = SKF Kaydon catalog |
| Standard diametral clearance | – | 0.030–0.056 mm | standard band at this size |
| Inner / outer ring runout (max) | – | 0.013 mm | radial runout |
| Approximate mass | m | 0.24 kg | open execution |
The Gothic-arch raceway gives each ball four contact points, so one row of balls carries radial load, thrust in both directions and overturning moment at the same time. At a 50 mm bore the ball circle is small enough that starting torque stays very low — the property gimbal and encoder engineers chase most. Against a crossed roller bearing of the same envelope, the BB5013 is the smoother-running, lower-inertia choice; the roller keeps the edge in moment stiffness. Where torque and mass are on the budget, that trade usually lands in favour of balls.
| Source | Designation | Notes |
|---|---|---|
| LYDL | LYDL-5013 | internal reference for this size |
| SKF / Kaydon | BB5013 (KDN.39322001) | BB metric thin section series |
| Envelope match | 50 × 80 × 13 mm | matches common RB-style crossed roller boundaries |
Keep both designations on your drawing if procurement ever needs a second source: LYDL-5013 internally, BB5013 (SKF KDN.39322001) against the Kaydon BB metric catalog.
On a 50 mm steel journal, a light-interference or transition fit — roughly j5 to k5 — with an H6 to H7 housing bore is a starting point for steel-on-steel instrument assemblies; the final classes depend on load direction, which ring rotates, operating temperature and precision class, and are confirmed with LYDL engineering. The 0.030–0.056 mm value is the as-manufactured diametral clearance — the operating clearance is calculated from the actual fits and temperatures. Two situations deserve a call to LYDL engineering before the drawing is released: aluminium housings and wide temperature swings, where the operating clearance should be calculated from the actual materials, fits and temperature difference rather than assumed, and any axis that must hold sub-0.02 mm runout at temperature.
Five duties are typical applications for this size. Medical imaging and scanner positioning, where a low-inertia ring lets the gantry servo settle faster. Optical and sensor gimbals, where starting torque sets the achievable stabilisation. Encoder and resolver mounts, where the 0.013 mm maximum radial runout is the figure that matters. Tabletop rotation stages for laboratory automation. And small robot wrist or elbow joints, where every gram saved compounds along the arm.
| Reference model | Bore d (mm) | Outside D (mm) | Width B (mm) | Dynamic radial |
|---|---|---|---|---|
| BB4510 | 45 | 70 | 10 | 5.80 kN |
| BB6013 | 60 | 90 | 13 | 9.91 kN |
| BB7013 | 70 | 100 | 13 | 10.87 kN |
Below the BB5013, the BB4510 runs a slimmer 10 mm width for tighter still envelopes; above it, the BB6013 keeps the same 15 × 13 mm section at a larger bore and a 9.91 kN rating, and the BB7013 continues the same section family. The full ladder from BB3010 to BB90070 is tabulated on the BB series overview page, and the wider thin section bearing category covers the inch-dimension Reali-Slim equivalents.
An open execution has no seals, so contamination control during mounting is the difference between a 0.013 mm runout axis and a scratched raceway. Keep the bearing in its packaging until the moment of installation; use lint-free cloth and clean solvent on the seats; never spin the bearing under finger pressure before it is seated. Check seat diameters and shoulder squareness, then press or tap home with an even force on the ring being fitted. The full inspection and packaging routine is described on the LYDL contact and support page.
Four-point ball contact replaces the line contact of crossed rollers with point contact, so friction torque is substantially lower — for most customers that is the entire reason for the switch. LYDL can supply measured starting-torque figures for your specific preload, fit and lubrication before you commit.
On a 50 mm steel journal, j5 to k5 on the shaft with an H6 to H7 housing bore is a starting point for steel-on-steel assemblies — the final classes depend on load direction, rotating ring, temperature and precision requirements. Confirm them with LYDL whenever the housing is aluminium or the axis sees wide temperature swings, and treat the operating clearance as a calculation, not an assumption.
In some oscillating or low-speed duties it can be — a single initial charge is an option to evaluate against grease life, oscillation angle and contamination exposure, and LYDL confirms the relubrication requirement for your specific duty at order time. For continuous rotation, plan a relubrication interval rather than assuming a fill-for-life design.
Radial runout is verified to the 0.013 mm maximum tabulated above. Dimensional inspection reports, material and heat-treatment certificates are available on request at the quotation stage.
The BB metric series is produced in a sealed (TT) variant at most sizes. If your instrument cannot enclose the axis, ask LYDL for TT availability at 50 mm bore and for the friction penalty the seals add before finalising the torque budget.
Send the quantity, target precision class, clearance band and operating conditions for the BB5013 and LYDL will confirm dimensions, lead time and pricing. A full dimension sheet can be reviewed before ordering — request a quotation by e-mail or use the LYDL contact page, and ask for the drawing package whenever you need the complete sheet up front.
The values on this page trace to the SKF Kaydon BB series catalog entry for cross-reference and the LYDL specification table for manufacturing data. For adjacent precision technologies see the Schaeffler precision bearing catalog (PRG). All figures are reference inputs for sizing, not a substitute for application review.
