Frease Bimbal Bearing Tolerance Ring For Installation

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  1. Frease Gimbal Bearing Tolerance Ring For Installation Diagram
  2. Frease Gimbal Bearing Tolerance Ring For Installation Tool

This Tool is similar to P/N 91-805475A1 which used to be P/N 91-57797A3.Tool is made from high quality 1045 Steel, and includes an eyebolt which gives you the option of hanging the tool.Gimbal Bearing Installation Tool. Bellow Ring/ Retainer Sleeve Installation Tool made from PVC Plastic. Gimbal Bearing with housing and tolerance ring. Grease able type. Your transom should have a grease zerk on the side. Drive shaft Bellow. Shift Cable Bellow. Stainless steel hose clamps. 3/4' water hose 5/8' water hose Mounting Gasket. Zip tie for the shift bellow small end. Standard grease zerks: 2. Predrilled and tapped lubrication hole: 3. Screw clockwise until finger tight: 4. Tighten one-quarter turn or 90° clockwise: Thank you for your purchase from the Silverthin™ slewing ring bearing product line - your business is appreciated! Before installation please note the following: Silverthin™ slewing rings. Re: Gimbal bearing install I have a bunch of rings laying around, and i needed it for a job on an older unit.the one you have linked still has to be lined up on the tiny grease hole in the bearing.using the ring eliminates that issue as long as you dont put it in/on/after the welded area. VOWAGH Gimbal Bearing Grease Seal Install Tool Compatible with Mercruiser Alpha Bravo One Gen Two $18.95 $ 18. 95 LOSTAR Outdrive Coupler Alignment Tool Fits Mercruiser Alpha, Bravo, OMC, Volvo SX 91-805475A1, 91-57797A3, 3851083, 18-4442.


Thin Section Ball Bearings for Gimbal Applications

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2021 ©

Service Factors

To determine if a Silverthin™ Slewing Ring bearing is appropriate for an application, a SERVICE FACTOR is applied. Refer to the table below for a guide to the service factor to apply to your application. The load rating curves shown in this catalog are approximate, and represent an application service factor of 1.00. To determine the required bearing rating, multiply the applicable service factor by the applied loads on the bearing, and compare the resultant loads to the load rating curves.

Class of
Typical ConsiderationsApplication ExamplesMinimum
LIGHTWell defined loadingTire mounted light duty construction1.00
Loading well below capacityLight duty Index table1.00
Rotation slow, <10% of time and intermittentLight duty industrial manipulator or robot1.00
Light duty hand operated mechanism1.00
Light duty medical devices1.00
Light duty aerial platforms1.00
Welding positioners1.00
Rotating signs, displays1.00
MEDIUMWell defined loadingTrack mounted light duty construction1.10
Loading near or below capacityScrap yard construction1.25
Rotation slow, <30% of time and intermittentMedium duty industrial manipulator or robot1.25
Rotary tables1.25
Capstans and turnstiles1.10
Wastewater treatment1.10
HEAVYLoading not well definedForestry handling equipment1.50
Loading beyond machine capacity can occurHeavy duty index tables and turntables1.50
Shock loading can occurExcavators1.50
Rotation intermittent, up to 100% of time
SPECIALLoading not well definedAlternative energy (wind, hydro, etc)TBD
Continuous rotationOffshore applicationTBD
High speed rotationAmusement ridesTBD
Heavy loads, shock, impactSteel mill applicationsTBD
High precision, positioningPrecision roboticsTBD

If you require any assistance in determining an applicable service factor, or would like a more detailed load rating curve (recommended if your service factor adjusted applied loads fall close to, or beyond, the load rating curves shown in this catalog), please contact Silverthin™ Engineering for assistance. Please note that the equipment designer is responsible for determining the correct service factor, often validated by testing.

Typical Application

“Typical application” of Silverthin™ Slewing Ring Bearings will exhibit the conditions listed below. Special consideration must be given to bearing selection and features whenever the application conditions differ from those considered “typical”. Those typical application conditions are:

  • Vertical axis of rotation. Essentially, the bearing mounted “flat”.
  • Compressive thrust and moment loads being predominant compared to tension loading.
  • Radial load limited to less than 10% of the thrust load.
  • For single row bearings, intermittent rotation (not continuous) should not exceed a pitch-line velocity of 500 feet/minute.
  • Operating temperature between -40ºF to +140ºF.
  • Mounting surface geometry and installation procedures to assure roundness and flatness of both races. An example approach would be to apply a centered thrust load while tightening the bolts using the alternating star pattern method.
  • Periodic checking of mounting bolts to verify proper tension is provided for.
  • Periodic lubrication is provided for.

Load Capability

Silverthin™ Slewing Ring Bearings are designed to accommodate significant radial, thrust and moment loads as shown below:

This is accomplished in most cases by the unique four point contact raceway geometry, which is similar in concept to Silverthin™ X-Type Thin Section bearings. This allows a single bearing to accommodate all three loading scenarios noted above, either individually or a combination thereof.

For more detailed information on SilverThin™ slewing ring load capabilities consult the load curves charts.


Silverthin™ Slewing Ring Bearings are used most commonly where rotation is slow, oscillating, and/or intermittent. For speed limit calculations please contact Silverthin Engineering.


Silverthin™ Slewing Ring Bearings are not typically provided with diameter tolerances. Some slewing ring applications require a higher degree of accuracy. For engineering and design support on special applications please contact Silverthin Engineering.


Silverthin™ Slewing Ring Bearings are often used indoors, and outdoors where exposure to moisture and significant contamination is possible. Normal temperature ranges -40°F to +140°F (-40°C to +60°C) are standard. Slewing rings designed to operate in harsher environments are available from Silverthin, contact a Silverthin Engineer early in your design process to identify the best bearing system solution for extreme environments.

Mounting – Tension versus Compression

As mentioned earlier, it is best to mount the bearings in “compression” as shown below. This ensures that the load is carried by the balls, which is represented in the load curve provided. Tension mounting has significantly less capacity, as then the bolt strength becomes the primary consideration for capacity.


Mounting surfaces need to be machined accurately for proper function of the bearing. Where standard bolt patterns cannot be accommodated, contact Silverthin Engineering for alternative options. Consideration must be given to mounting in tension or compression. In tension, BOLT strength becomes the limiting load consideration, the load curve no longer applies, and special considerations must be made. See additional guidelines below.

Minimum Mounting Structure Guidelines

/install-car-battery-free-near-me-at-home/. Generally, this rule of thumb will provide adequate structural integrity.

Flatness & Mounting Surface Dish (Mounting Surface)

Flatness of the bearing mounting surface is critical to optimal performance. Frequently mounting structures are welded or worked in a way to induce stresses into the structure. These stresses must be relieved, following which the bearing mounting surface must be machined flat. Flatness must be considered:

  • Circumferential Direction (δr): The amount of out-of-flatness allowable in the circumferential direction for four-point ball bearings is shown in the figure below. This amount of out-of-flatness must not be exceeded in a span less than 90°, and not more than once in a span not more than 180°.
  • Allowable Dish or Perpendicularity Deviation in the Radial direction (δp): For four-point contact ball bearing designs, this amount of dish allowable can be approximated using the formula:
    δp ≈ 0.001 ∗ Dw ∗ P
    P=radial dim of the mounting structure face (in)
    Dw=rolling element diameter (in)

Note that if an application requires greater precision or low rotational torque, it may be necessary to reduce the values of δr and δp. For roller bearings, the amount of flatness allowable is approximately 2/3 of that for an equivalent sized four-point contact ball bearing.


Grease is the most common lubricant used in slewing ring bearings and gear applications. Regular lubrication through provided grease fittings or grease holes is required for proper operation on standard slewing rings. For special lubrication options, contact Silverthin.™

Friction Moment (Rotation Torque)

The Friction Moment can be estimated for a slewing ring bearing using the formula noted below. The resulting values assume that the bearing is mounted according to the guidelines outlined in this catalog. This estimate only applies when load is applied to the bearing, and does not reflect starting torque in an unloaded condition. Also not considered are frictional torque generated by the lubricant, seals and weight of the components. This does however provide a starting point, and with additional experience adjustments can be made in the assembly to accommodate for additional torque.

Mf = μ ∗ (4.4M + Fa Dpw + 2.2 Fr Dpw) / 2
Mf=Bearing starting torque under load (ft-lbs)
μ=Coefficient of friction (0.006 typically)
M=Moment load (ft-Ibs)
Fa=Axial load (Ibs)
Fr=Radial load (Ibs)
Dpw=Bearing pitch diameter (ft)


It is always suggested that bolts be selected with the advice and assistance of a fastening hardware supplier. Bolt quality, pretensioning procedures, and maintenance can vary widely.

The optimal bolting arrangement has a bolt circle in both the inner and outer races with equally spaced fasteners. This results in a more uniform mounting arrangement, yielding the best performance between the bearing and the fasteners. This is not always possible due to mounting structure arrangements, and holes may be shifted accordingly. In these cases testing is recommended to determine actual bolt loads, validate joint configuration and assembly procedure.

As a starting point to determine the approximate load on the heaviest loaded bolt, the following formula can be used. Please note that Silverthin™ makes no warranty, expressed or implied, regarding bolt adequacy. It is strongly recommended that testing be performed to determine the actual load, as this is the only reliable way to be certain.

Where:Frease gimbal bearing tolerance ring for installation diagram
RB=Total load on heaviest loaded bolt (Ibs)
M=Moment load (ft-Ibs)
r=Rigidity factor. Use 3 for bearings and support structures of average stiffness.
Fa=Axial load (lbs)

If Fa is in tension, the sign is +

If Fa is in compression, the sign is -
Refer to section “Mounting - Tension versus Compression”

BC=Bolt circle diameter (in)
n=Total number of equally distributed bolts
Sf=Bolt factor of Safety. Minimum recommended value = 3. See formula below.
Sf =Bolt Proof Load Rating
Bolt Diameter (in)Proof Load (lbs)
1 - 1/891,600
1 - 1/4116,300
1 - 1/2168,600

Other Bolting Recommendations

  1. Use hexagon head high strength bolts with coarse threads according to SAE J429, Grade 8 or ASTM A490/A490M or ISO 898-1, Grade 10.9 tensioned to 70% of their yield strength.
  2. Use hexagon head coarse thread nuts where applicable according to SAE J995, Grade 8 or ASTM A563, Grade DH or ISO 898-2, Class 10.
  3. For optimal bolt tension, the ratio of the distance from the bottom of the bolt head to the first thread of engagement should be 3.5 or greater. Testing is required for validation.
  4. All mounting bolts in a given ring should have equal clamp length.
  5. The distance between the head of the bolt and the bolt threads should be at least equal to the bolt body diameter.
  6. Thread engagement length of the bolt in the mating steel structure should be at least 1.25 times the bolt diameter.
  7. Bench tests are recommended to validate that the bolt tensioning method achieves desired results prior to equipment testing.

Securing Bearing to the Mounting Surface

When installing the bearing, it is important to ensure that the bearing is as round as possible. This will optimize load distribution and promote the smoothest operation. The following procedures are recommended as an aid.

Use hardened round flat steel washers in accordance with ASTM F436 under the head of the bolt, and also the nut. Lockwashers, and locking compounds on the thread, are not recommended.

Frease Gimbal Bearing Tolerance Ring For Installation Diagram

Install the washers, nuts and bolts in the bearing and supporting structure and hand tighten. Do not distort the bearing in order to install bolts. Apply a moderate centered thrust load to the bearing. Tighten the bolts to the equipment designer’s specifications. A common approach is to use a star pattern to tighten the bolts, sequences as shown in the diagram below. The pattern is usually done in 3 steps at approximately 30%, 80% and 100% of the final bolt torque or tension level specified by the equipment designer.

Frease Gimbal Bearing Tolerance Ring For Installation Tool

Loss of proper tension can lead to premature bolt failure, failure of the bearing and structure, damage to components, and fatality or injury to anyone in the vicinity. The bolts require frequent inspection for proper tension, which is commonly accomplished by measuring torque of the bolt.