ER Insert Bearings Explained

An ER bearing is a Gold Line ball bearing insert sold without a housing: a wide inner ring ball bearing with a cylindrical outside diameter and a snap ring, made to be pressed into a housing the machine builder supplies rather than into a cast pillow block or flange. It carries many of the features of the housed Gold Line units, including the shaft locking, the zone hardened inner ring and the felt seal, and its number states the shaft size directly. This guide explains what the bearing is, where it is used, how to read the number, what the ERX-TREME options add, and which series are stocked.

What is an ER insert bearing?

ER stands for a cylindrical OD bearing with a snap ring. The outer ring is black oxided, has a plain cylindrical outside diameter with a locating snap ring, and carries a lubrication groove and lubrication inlet; the inner ring is wide, extends past the outer ring, and is zone hardened only under the ball path so the extended portion stays soft for the setscrews. The bearing is pressed into a housing, typically a steel plate or a conveyor roll, and locked to the shaft by setscrews or a Skwezloc concentric locking collar.

The rest of the construction is the Gold Line insert used in every Sealmaster housed unit: Grade 10 steel balls in a land riding retainer that floats on the ground lands of the outer ring, 52100 bearing steel races, an ABEC 1 precision rating, and a felt seal with a rotating flinger that directs contamination away from the sealing surface with less drag and heat than a rubber contact seal. The outer ring race profile is tapered toward the raceway rather than parallel to the axis, so lubricant flows back to the ball path more easily. A standard-duty ER-16 is a 1 inch bore insert with a 2.0472 inch outer race diameter and a 0.75 inch outer race width, and its product page lists the inner race profile as a wide inner ring, the internal clearance as Standard and the maximum operating temperature as 220 F.

Where are ER bearings used?

ER bearings are used wherever a bearing has to sit inside a roll or a plate rather than on top of a base: conveyor rolls, live rolls and nip rolls, unit and bulk material handling, and the printing, packaging and converting machinery whose webs run over hundreds of rolls. The cylindrical outside diameter lets the insert be pressed straight into a roll assembly, and the snap ring locates it there.

The application list for the series runs from agricultural processing equipment, metal slitting and winding, plastic film transfer and packaging equipment through ink rollers, plate cylinders, dampening rollers, blanket cylinders, forming rollers, collecting cylinders and calendar rolls to printing webs, spindles, veneers and winders. In the web applications the material has low strength, and if the rotational torque of the roll bearings is excessive the sheet tears and jams the machine, which is what the low drag ERX-TREME options below exist for. Housed Gold Line units, which share the locking and sealing features, are in the mounted ball bearings category.

How does the ER number encode the bore?

An inch ER number states the shaft size in sixteenths of an inch: ER-16 is a 16/16 or 1 inch bore, ER-20 is 20/16 or 1-1/4 inch, and ER-32 is 2 inch. A metric standard-duty number is 2 followed by the bore in units of 5 mm, so ER-205 is a 25 mm bore and ER-206 a 30 mm bore. Letters after the size are options: T for the Skwezloc collar, M for metric hardware, C for a contact seal, and an X directly after ER for an ERX-TREME option.

The suffix R marks the reduced outside diameter version, which is made for the 1-1/4 inch and 2 inch bores only: an ER-20R has the 62 mm outer race of the 1-3/16 inch size instead of the 72 mm race of the plain ER-20, and an ER-32R has the 90 mm race of the 1-15/16 inch size instead of the 100 mm race of the ER-32. The table gives every inch size, the metric insert that shares its outer race, the outer race diameter, and the housing bore for a stationary housing.

The housing bore is the published fit for a light load conveyor roll application with a stationary housing; a revolving housing uses a tighter bore, and a tighter press fit than the table calls for a review of the bearing internal clearance.

How is an ER bearing locked to the shaft?

Two ways. The standard ER insert locks with two diamond faceted setscrews spaced 120 degrees apart, which gives a balanced three point contact on the shaft, minimises distortion of the inner ring and resists backing out. The T version locks with the Skwezloc concentric collar, a clamp that centers the shaft in the bearing bore, holds near perfect ball path roundness, eliminates the shaft damage of setscrew locking and reduces fretting corrosion, tightened with a TORX Plus head cap screw.

The choice shows in the number and on the product page: an ER-16 lists its shaft locking as set screw with a 1/4-28 thread, and the ER-16T lists concentric locking with a 10-24 cap screw; both are 1 inch bore inserts with the same 2.0472 inch outer race. The Skwezloc collar is the recommendation for applications with strict run-out requirements and for stainless steel shafting. The metric inserts carry the collar with metric hardware and all-metric dimensions, and the contact seal is standard on them, so a metric number usually ends in TMC: an ER-205TMC is a 25 mm bore Metric-Skwez insert with the same 52 mm outer race as the ER-16.

What does ERX-TREME mean?

ERX-TREME is the family of ER inserts built for a specific operating problem rather than for fatigue life: low drag, high temperature, and relubrication through the inner race. The X after ER marks the family, and the suffix at the end of the number names the option. Most bearing problems are not fatigue related but come from contamination, lubrication starvation or other environmental issues, and each option changes the seal, the grease or the clearance to meet one of them.

Low drag (LO) cuts the felt seal down to reduce drag and uses a channeling grease that lubricates with low friction, while the felt still retains grease and filters debris; an ERX-16 LO is the 1 inch size. Extra low drag (XLO) uses the same cut down felt soaked in oil, which acts as a lubrication reservoir and lowers seal friction, and the bearing is oil lubricated. High temperature (HI) uses a Nomex felt seal, Krytox grease and an increased internal clearance to accommodate thermal expansion of the components, and an ERX-16 HI lists a 400 F maximum operating temperature and Increased clearance on its product page. The expansion version (HIY) adds a half-dog setscrew and lock wire that engage a slot in the shaft, so the shaft can grow in length with temperature while the inner ring still turns with it; every expansion bearing must be paired with a fixed bearing.

Re-lube (RL) is the one ER insert with a lubrication fitting built into the bearing: grease enters at the inner race extension, runs through a groove in the bore and into the bearing chamber, so the insert can be relubricated without any groove or drilling in the housing. It is made for stationary shafting only, where the shaft and inner ring do not rotate. An ERX-16 RL lists the option as inner race relubricatable. Every other ER insert is relubricated through the groove in its outer ring, which needs a passage from a fitting on the machine to the groove. High contamination (DRT) is a Custom Select option rather than an ERX-TREME one: a heavy duty multi-lip contact seal, double lip or triple lip depending on size and series, with a 100 percent fill of GoldPlex HP grease.

Which ER and ERX inserts do we stock in each size?

The table below lists every ER and ERX insert we hold, grouped by the size code its number carries, and each number opens that part's own product page. Take the size code from the shaft size in the size table above — a 1 inch shaft is an ER-16 — then read across its row for the version you need. The plain number is the setscrew insert, T is the Skwezloc collar, C the contact seal, and the ERX numbers are the ERX-TREME and Custom Select options set out above; an ERX-PN number is phosphorus nickel coated for corrosion resistance. The codes from 204 up are the metric inserts.

The rows state the numbers we hold now, not every number the series publishes: a size code with no row of its own is one we do not carry, and the next code up is a different bore. The other insert families in the insert bearings category are numbered differently and are not listed here.

Which ER series are stocked?

The insert bearings category carries the Sealmaster Gold Line ER setscrew insert in inch bores from 1/2 inch to 4 inch, the ER-T Skwezloc insert, the Metric-Skwez ER-TMC insert in 20 mm to 60 mm bores, C contact seal versions, and the ERX-TREME LO, XLO, HI, HIY and RL options, along with the DRT high contamination and 3C triple lip seal variants. Filter the category by bore to see every insert for a shaft size, or open the mounted bearings category for the housed Gold Line units in pillow block, flange and take-up form.

The number on a bearing already in a roll gives the shaft size and the options, and the guide to mounted bearing nomenclature reads the housed unit numbers the same way. Internal clearance on an insert is stated as Standard or Increased, which the guide to bearing clearance codes sets against the C classes used on unmounted bearings. When the number cannot be read, measure the shaft and the housing bore and send both through the bearing selection form and we will confirm the insert before you order.