NACHI 30305DJ Tapered Roller Bearing 25 x 62 x 18.25 mm, 24°-32° Contact Angle

This NACHI range lists 14 tapered roller bearings in the 30300 series with the DJ suffix, from 20 to 90 mm bore (outer diameters 52 to 190 mm). The 13 sizes from 25 to 90 mm bore are single row bearings with full catalogue figures, shown in the Model Details for each size.

D in the designation means a nominal contact angle over 24° and under 32°; DJ is that larger-angle design with the same ISO sub-unit dimensions (J). The DJ sizes have a constant e of 0.81 to 0.83, against 0.30 to 0.35 for the J bearings of the same numbers, and the same bearing number with J has a higher radial rating and speed limit (see Selecting the right option).

The 30304DJ (20 x 52 x 16.25 mm) is listed by size only. The manufacturer’s catalogue has no 30304DJ row (its DJ sizes start at 25 mm bore), so no load ratings, speeds or mass are shown for it. Please contact AIMS to confirm the exact bearing before you order that size.

A tapered roller bearing carries combined radial and axial load. The cone (inner ring and roller assembly) and the cup (outer ring) are separable, and the internal clearance is set at mounting by the axial position of the cone relative to the cup. A single row bearing takes axial load in one direction, so for axial load both ways fit a pair, face-to-face or back-to-back.

Where this product is used

• Industrial gearboxes and speed reducers
• Wheel hubs, axles and vehicle drive trains
• Transmissions and differentials
• Conveyor drives and general industrial machinery
• Equipment with combined radial and axial loads on one shaft

Features

• Single row tapered roller bearings with a D contact angle (nominal over 24° and under 32°) and ISO sub-unit dimensions (J)
• Combined radial and axial load; a pair mounted face-to-face or back-to-back carries axial load in both directions
• Separable cone and cup: the clearance is set at mounting by the axial position of the cone against the cup, and the bearing can be preloaded for higher rigidity and running accuracy
• Basic dynamic load ratings from 39.8 to 282 kN and limiting speeds from 1,700 to 5,700 rpm on grease for the 13 sizes with catalogue figures
• Constant e, axial load factors, load centre, mass and shoulder dimensions listed for each size in the Model Details

Key specifications

Available sizes

n/a: the 30304DJ has no catalogue row, so no figures are shown for it.

Selecting the right option

DJ or J? The DJ bearing has the same bore, outside diameter, cone width B and overall width T as the J bearing of the same number, but a larger contact angle and a narrower cup (for example C 17 mm on the 30308DJ against 20 mm on the 30308J). The catalogue gives it a lower radial rating and a lower speed limit: the 30308DJ is Cr 80.5 kN with a 3,800 rpm grease limit, against Cr 90.6 kN and 4,500 rpm for the 30308J.

To work out the equivalent dynamic load Pr for a single bearing: where Fa/Fr is at or below e, Pr = Fr; above e, Pr = 0.4 x Fr + Y1 x Fa. For the DJ sizes e is 0.81 to 0.83 and Y1 is 0.73 to 0.74, and the values for each size are in the Model Details.

The load centre a is negative for these sizes (-12.6 to -2.2 mm): the minus sign means the load centre lies outside the cone back face, which matters when you work out shaft and housing loads.

Check the full designation, including the DJ, when you order. The 30304DJ has no catalogue figures, so confirm that size with AIMS first.

Fitting and use

A radial load on a single row tapered roller bearing creates an induced axial load, Fa' = Fr / (2 x Y1), which tries to separate the cone and cup. It is normally balanced by mounting two bearings as a pair or as a multi-row set, so work out the axial load on each bearing, not just the one that carries the thrust.

The internal clearance is set when you mount the bearing, by the axial position of the cone against the cup. The bearing can also be preloaded for higher rigidity and running accuracy, but too much preload raises heat and shortens bearing life, so follow the equipment maker’s setting.

Limiting speeds are given for grease and for oil lubrication. Check the load and speed against the figures for your size, apply a suitable safety factor and contact AIMS if you want a second opinion before ordering.

Related products

The standard-angle J bearings of the same numbers are on the NACHI metric J tapered roller bearings page. Inch series sizes are on the pages for the NACHI LM48548/10 and the NACHI LM11949/10. Other NACHI bearing types: NACHI single row angular contact ball bearings, NACHI spherical roller bearings and NACHI cylindrical roller bearings.