RETAINING COMPOUNDS

TOPIC 1

RETAINING COMPOUNDS

Learning Outcome

Describe and use, retaining compounds.

Assessment Criteria

You will:



1. Identify types of retaining compounds.

2. Describe the action of retaining compounds.

3. Identify where retaining compounds are effective.

Demonstrate the correct use of retaining compounds.

RETAINING COMPOUNDS

There are a large range of compounds available to perform functions such as thread locking, and sealing.entering thread

There compounds come in the from of liquid retaining and sealing products. They can perform the following jobs :

? Prevent fasteners from working loose.

? Seal leaky threaded fittings.

? Keep bearings from spinning on shafts or housings.

? Restore fit between worn bearings, sleeves, gears and pulleys.

? Seal flanged assemblies.

For each of the tasks listed above a specific compounds is required.

Threadlocking and Sealing

Vibration and shock result in the loosening of threaded fasteners, causing the loss of clamping force and ultimately, machinery failure. Lock washers and other mechanical means of threadlocking, are still susceptible to failure.

Threadlocking retaining compounds eliminate the need for expensive and complex mechanical locking devices in most cases, as well as sealing against rust and internal corrosion, machinery fluids, gases and most chemicals.

They prevent seizure of threaded fasteners through corrosion by preventing moisture


The sealing and locking liquid finds its way into all of the tiny imperfections of the thread surface. At the are of metal contact, the cured resin forms “thousands” of tiny mechanical “keys” resisting any rotational movement of the fastener, and generally “jamming” the threads with a cured, high compressive strength material.

Using Threadlock.
Two things are important when using thread lock.

How Threadlock Works

Threadlock:

? Components must be clean.

? Compounds must be allowed to cure or dry properly.

Components must be cleaned of all oil or grease using a cleaning solvent and a clean cloth.

To apply Threadlock, simply apply from the bottle nozzle or tube to one part, either the bolt, the nut or the threaded hole.

Apply sufficient amount to fill the gap between the parts

Note:

Threadlock/sealant will not harden while in contact with air. The compound will only harden when air cannot get to it. Because of this it is called an anaerobic compound.

Screw the nut or bolt into place and apply the correct torque.

It is now important to allow the compound to cure properly.


Factors Influencing Speed of Cure

The curing or hardening time necessary for these compounds depends upon the following.

Surface Cleanliness

• Grease, rust inhibitors and other contaminates slow or limit cure.

• Anaerobic compounds cure speed varies with different metals:

         * Steel - medium.

         * Aluminium -slow.

         * Brass - very slow

Finished Surfaces

• Anodizing or plating will slow or prevent curing.

Clearance

• Large clearances require more compound, reducing the speed of cure.

 Surface Roughness

• Rougher surface finishes will assist compounds to cure faster by exposing a larger surface area. Grit or Sanding is a very effective surface area preparation.

 Part Size

• Strength develops faster in large parts which have a larger surface area .3 mm fasteners will not be finger tight as quickly as 10 mm fasteners.

 Part Shape

• Threads - fast cure time

• Slip fits - medium cure time

• Gasket surfaces and tensile joints - slow cure time.

Temperature

Temperature is most important in the curing process, (however the average temperature in Sangatta is good for encouraging fast curing time).

Cure speed of anaerobic products decreases with decreasing temperatures and increases with increasing temperatures.

Anaerobic products can be accelerated to cure faster by applying heat. As a rule, they will cure even outside the joint, if temperature

exceeds 95oC despite the inhibiting effect of air. Curing temperatures up to 150oC are practical.

The time/temperature guide is a general guide to curing rates. Time commences from when the part has reached a stabilised temperature at the bond line and excludes heat up time. Heat sources also influence cure rate with greater intensity, as with induction heating, producing cures on moderately sized parts in a matter of a few seconds.

Bolts, studs, nuts and threaded holes may be re-used. The old compound can be removed

Temperature Influence

On Curing Time and the threads cleaned with a wire brush or similar tool.

Failure of Threadlock to work.
If the threadlock compound does not work as expected three things could have happened

• Sufficient material was not applied to fill the joint.
• Sufficient time was not allowed for curing.
• Parts were excessively oily, dirty or greasy, which may prevent the compound from curing.

If the correct curing does not occur:

• Clean all parts thoroughly.
• When all parts are clean and dry, apply a Quick Cure Primer to the threads. Let them dry, then apply Threadlock compound again and allow sufficient time to cure.

Applications for Threadlock

Some places where threadlocking is necessary are;

• Wheel studs
• Assembly mounting bolts
• Crankshaft bearing nuts
• Flywheel to crankshaft bolts
• Master link bolts
• Radiator guard bolts
• Final driver housing studs
• Roller guard bolts
• Sprocket hub set screws
• Outer bearing retainer screws

Always check and follow the workshop manual for the equipment you are working on and follow their recommendation on the areas that must have thread lock.

Packaging and storage
Anaerobic products require a continual supply of oxygen to maintain their liquid state while in storage. To achieve this, they are packaged in special polyethylene containers.

The container is never filled to its total capacity. The remaining air space is the source of oxygen needed by the product.

Note:

Make sure bottles of compound always have an air space inside and never empty one bottle into another without leaving an air space

Safety With Compounds
When using any sealing or adhesive compound, extreme care must be taken not

Written Activity #1
Answer all of the following questions.

1. Name five (5) things for which retaining compounds can be used.

    1. ___________________________________

   2. ____________________________________
   3. _____________________________________

   4. ______________________________________

   5. ______________________________________

2. What do you use retaining compounds in place of?

      _____________________________________
 
3. How does a retaining compound work?

     ________________________________

4. What are two important things which must be done when using Threadlock?

    1. ___________________________________

    2. __________________________________
5. Will a retaining compound cure if in contact with air ?

     ___________________________________

6. Name seven (7) things which affect the hardening/curing time of a sealing compound?

     1. _______________________________________________

     2. _______________________________________________

     3. ______________________________________________

    4. _____________________________________________

    5. _____________________________________________

   6. __________________________________________

   7. ____________________________________________


7. What are three things which could prevent a retaining compound from working
    1. _______________________________________

    2. _______________________________________

   3. __________________________________

8. Name six (6) places where Threadlock can be used.

    1. ____________________________________

    2. ____________________________________

    3. ___________________________________

    4. ___________________________________

    5. ___________________________________

   6. __________________________________

9. What do retaining compounds require when stored to remain liquid ?

        _________________________________

10. What safety precautions must be taken when using a retaining compound?

      _____________________________________


There are range of compounds designed to retain components other than bolts, screws and nuts.

Traditional methods used include keyways, splines, setscrews and interference fits. Each of these purely mechanical methods has inherent problems and limitations.

Splined and keyed fits involve costly machining and require bulky and complex designs. Problems with backlash fretting and corrosion can occur.

Interference fits can offer some cost advantage.

Retaining Methods

against splines and keys, but still have many serious drawbacks. Anaerobic retaining

compounds used in slip fitted assemblies have proven to be a very attractive alternative fitting technique. However major benefits.

are obtained by incorporating such adhesives into the area of traditional fitting techniques, such as with splines and interference fits

Interference Fits

If a shaft or bush is to be pressed into a hole in a component the hole must be made smaller than the shaft or bush. This is called an interference fit.

Interference fits can be assembled by two basic methods: press and shrink fitting

Interference Fits

The term interference fit maybe used to identify another method of assembling parts on shafts in which a hub is stretched when mechanically forced over a shaft larger than its bore.

Retaining Compounds in Action

Applications for Compound
Some assemblies are virtually impossible to make with interference fits. Those involving thin walled components are difficult to press because of their shape and overall fragility.

Application of Retaining Compound.

Some places where retaining compounds are used are:

• Wear sleeves on shafts
• Bearing retainer cups
• Crankshaft lip seals
• Fan hubs
• Impellers
• Pulley sheaves
• Gears to shafts
• Thin walled bushings and housings

Using Retaining Compounds

The steps to be followed in using a retaining compound are:

• Spray parts with quick cure primer and let it dry for 2 or 3 minutes.
• Spread retaining compound evenly.
• Install part.
• Press fits can be used at once. Slip fits require 2 hours curing time.

Bearing mount
Bearing mounting compound operates in much the same way as retaining compound but with a few differences, as follows:

• Bearing mount will help to restore fit between replacement bearings in worn housings and on worn shafts.
• It will fill a clearance of up to .005” (.13 mm).
• The maximum operating temperature is only

          149oC compared with 204oC for retaining compound.


Written activity #2
Answer all of the following questions.

1. Name four traditional mechanical retaining methods.

    1. _____________________________

    2. _____________________________

    3. ____________________________

    4. ____________________________

2. Do retaining compounds bond better to a rough or smooth surface?

     ______________________________

3. Name six (6) places where retaining compounds can be used.

     1. _________________________

    2. _________________________

   3. ________________________

   4. ________________________

   5. _______________________

   6. _______________________

4. List the four (4) basic steps that you follow when using retaining compounds.

    1. ______________________

    2. _____________________

    3. _________________   

    4. ____________________




Written activity 1

Answer all of the following questions.

1. Name five (5) things for which retaining compounds can be used.

    1. Prevent fasteners from working loose

    2. Seal threads

    3. Prevent bearings spinning on shafts

    4. Restore worn parts

    5. Seal

2. What do you use retaining compounds in place of?

    Mechanical means/fasteners

3. How does a retaining compound work?

    Cured resin forms thousands of “keys” and jams the threads

4. What are two important things which must be done when using a Threadlock?

    1. Components must be clean

    2. Components must be allowed to dry properly

5. Will a sealant dry if in contact with air ?

     No

6. Name seven (7) things which affect the hardening/curing time of a sealing compound?

    1. Surface cleanliness

    2. Surface finish - type of surface

    3. Clearance

   4. Roughness

   5. Part size

   6. Part shape

   7. Temperature

7. What are three things which could prevent a sealing compound from working?

    1. Not enough compound to fill the joint

    2. Not enough time allowed for cure

    3. Presence of grease, oil or dirt


8. Name six (6) places where Threadlock can be used.

   1. Wheel studs

   2. Assembly mounting bolts

   3. Crankshaft bearings

   4. Flywheel to crankshaft bolts

   5. Master link bolts

   6. Radiator guard bolts

   7. Final drive housing bolts

   8. Roller guard bolts

   9. Sprocket hub set screws

   10. Outer bearing retainer screws

9. What do retaining compounds require when stored to remain liquid ?

     Oxygen

10. What safety precautions must be taken when using a retaining compound ?

      Must not be allowed to come in contact with your skin or eyes

Written activity #2

Answer all of the following questions.

1. Name four traditional mechanical retaining methods.

    1. Keyways

    2. Splines

    3. Set screws

    4. Interference fit

2. Do retaining compounds bond better to a rough or smooth surface?

     Rough

3. Name six (6) places where retaining compounds can be used.

     1. Wear sleeves on shapes

     2. Bearing retainer cups

     3. Lip seals

     4. Fan neebs

     5. Impellas

    6. Gears to shapts
        thin washed..........and hausing (?)

4. List the four (4) basic stops that you follow when using rataining compounds.

1.

2.

3.

4.

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