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Magnaloy Coupling Company

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Couplings


Installation Gap for Magnaloy Couplngs


 

Keystock/Drive Lug Interference Potential

On Bored and Keyed Magnaloy Couplings, the keyway is located between the drive lugs on each hub.  When the coupling hubs are assembled, each half will have one drive lug located in-line with the keyway of the opposing hub.  In each model size, particular bore/key combinations have the potential for interference between the keystock and the drive lug of the opposing hub.

This interference will result if the bore/key size is greater than listed in the table below AND the  keystock on this shaft extends into the insert cavity of the hub.

CORRECTIVE ACTION:  The interference can be eliminated by shortening the keystock so it does not extend into the insert cavity of the hub.  Failure to correct this situation can cause assembly difficulty resulting in coupling failure and damage to the drive or driven equipment.

Model Size

Shaft Diameter Keyway Size

PM 90

7/8

1/4

100

7/8

1/4

200

1 3/16

1/4

300

1 5/16

5/16

400

1 1/2

3/8

500

1 15/16

1/2

600

2 1/2

5/8

700

2 3/4

5/8

800

3 1/2

7/8

900

4 1/2

1 1/4


Magnaloy Coupling Shaft End Spacing

During the design of mounting systems and coupling installation on these systems, the spacing between shaft ends is an important parameter.  Shaft engagement in the coupling bore is important to insure adequate load bearing surfaces for the keystock or spline teeth.  A good 'rule of thumb' is one times the shaft diameter for shaft engagement.  However, 'additional engagement when available' is the first corollary to this rule.

In our Dimensional Specifications for the Magnaloy Flexible Drive Coupling, the dimensions 'W' and 'X' are given to assist in the proper design of these mounting systems.  The dimension 'W' is the minimum shaft separation recommended to prevent contact between the shaft ends.  Dimension 'X' is the maximum shaft end separation to insure full engagement in the coupling.  This dimension results in both shafts being flush with the inner surface of the coupling and 100% engaged through the shaft length.  While this situation is ideal, because of shaft length consideration, it is sometimes not possible to achieve.  In these cases, we recommend following the above corollary to the 'one times shaft diameter' rule.  The full engagement condition resulting from dimension 'X' is NOT necessary for satisfactory performance of the Magnaloy Coupling and is shown for illustrative purposes only.


Clamp Style Coupling Installation

On some Magnaloy Coupling Clamp Style coupling hubs there is a setscrew in addition to the clamp bolt.  This would be the case, for example, with a bored and keyed coupling hub with the clamp feature.  When installing these hubs it is important to tighten the clamp bolt to the required torque value BEFORE tightening the setscrew to it's torque value.  Failure to follow this procedure could result in inadequate retention of the coupling on the shaft. 


Clamp Style Coupling Maximum Bore Limitations

To allow clearance between the bore surface and the clamp bolt on Magnaloy Couplings with the Clamp Option and between the Steel Bushing keyway on Magnaloy Couplings with the Steel Bushing Option, the following maximum bore limitations are noted:

 

W/Clamp Option

W/Steel Bushing Option

Model Size

Maximum Smooth
Bore Diameter

Maximum Spline
Major Diameter

Maximum Smooth
Bore Diameter

Maximum Spline
Major Diameter

100

1.00

1.00

.625

.625

200 1.125 1.250 .750 .8125
300 1.500 1.500 .875 .875
400 1.6875 1.750 1.00 1.125
500 2.00 2.00 1.375 1.500
600 2.500 2.5625 1.625 1.750
700 2.875 2.875 1.750 1.875
800 3.875 3.875 2.500 2.5625

 

Magnesium Machining Practices and Precautions

The possibility of fire when machining Magnesium is always a real concern.  However, if proper precautions are taken, this risk can be reduced greatly.

Magnesium fire result from combustion of the metal due to heat generation beyond the "Heat of Incipient Fusion".  A magnesium fire is very violent and burns with a bright white glow.  It has the ability to extract oxygen from liquids and damp powders, so extinguishing by suffocation is necessary.  Use of water containing fluids for coolants is not recommended.  In fact, coolants are not recommended or necessary in most cases.  Where coolants are desired, only mineral oit cutting fluids should be used.

The following list of safety precautions and machining tips for machining magnesium are recommended in conjunction with normal safety practices.

  1. A Class D (Ansul metal fire) Fire Extinguisher should be in the immediate vicinity of the machining activity
  2. Cutting tools should be kept sharp to prevent excessive heat generation
  3. Cutting tools should NOT be allowed to dwell on the magnesium part being machined.  This will result in formation of very fine particles of magnesium which can be easily heated to combustion by friction from the cutting tool.
  4. Generally, high speeds, heavy feeds and heavy depth of cuts help reduce the fire hazard by reducing heat generation and the creation of heavy chips and turnings.   Due to magnesium's high rate of thermal transfer, heat is dissipated rapidly and it is virtually necessary for the entire chip to be heated to the point of combustion for a fire to result.  So, the larger the chip, the greater the amount of heat necessary for combustion.

If a fire does result, confine it to a small area and smother it with the extinguisher media.  Do not blast it and spread it over the shop.  For this reason, we use Dry Ansul Sand in moisture proof containers for pouring directly on any small fire that may occur.

Following are the particulars on tool sharpening, feeds, speeds and depth of cuts recommended for magnesium.  These cover the basic machining operations of Drilling, Reaming, Boring and Milling.

Drilling:  Shallow-hole drilling (depth is less than 5 times drill diameter) presents few problems and consequently, only a few modifications are necessary for high quality drilled holes.  Standard point angels of 118 degrees and chisel edge angles of 120 to 135 degrees which give a relief angle of approximately 12 degrees will give the best cutting action.  It is extremely important, regardless of the type of drill used, that the cutting edges be kept SHARP.  Deep-Hole drilling can be performed with great speed and precision due to the excellent machining characteristics of magnesium.  To extract chips from the hole, it is recommended to use high-helix drills of 40 to 45 degrees.  If standard drills of low helix angles are used, it will be necessary to withdraw the drill frequently to clear the chips.  The standard drill point angle of 118 degrees is the most satisfactory.  Drilling speeds in the range of 75 to 400 surface feet per minute are satisfactory and higher speeds can be used.  The feeds used in drilling magnesium should be heavier than those for other metals to secure proper chip formation.  Small drills work best with light feeds, as they give slightly coiled or ribbon-like chips which feed out through the drill flutes without jamming.  Heavier feeds should be used on large drills to prevent jamming of the chips.  Some recommended feed for a few drill diameters are:

Speeds and Feeds for Drilling Magnesium

Drill Diameter
Inches

Speed
FPM

Feed - IPR

Shallow Holes

Deep Holes

1/4
1/2
1
300
to
2000
.004 to .030
.015 to .040
.020 to .050
.004 to .008
.012 to .020
.015 to .030

 Reaming:  Reamers for magnesium should have fewer flutes than normal for best results.  Under 1 inch diameter - four flutes and over 1 inch diameter - six flutes are best.  Reaming feeds used for brass and steel work satisfactorily on magnesium.  A definite cut (approx 1/32 inch on the diameter) should be taken to prevent compression of the metal and resulting in undersized holes and poor surface finish.  Cutting speeds commonly used in commercial practice vary from 100 to 400 feet per minute.  High cutting speeds and medium feeds give the best finish and most accurate holes.  The following table gives some recommended ream characteristics for use with magnesium.

Reamer Characteristic

Recommendation

Helix Angel 0 or 10 degrees
Rake Angle 5 to 8 degrees
Relief Angle 4 to 7 degrees
Clearance 15 to 20 degrees
Margin .010 to .025 inch
Flutes 4 to 6

Boring and Turning:  Lathe set-ups, with due consideration of the more careful chucking pressures for magnesium and a slight difference in tool design, are similar to those used for brass or steel.  It is important in all types of lathe tools that the relief angles be sufficiently larger to eliminate rubbing of the tool flanks.  Rake angles may vary considerable, but best results are obtained on high-speed steel tools with side and back rake angles of 0 to 15 degrees.  Carbide tipped tools should have slightly smaller rake angels to provide more support for the cutting edge.  A wide range of cutting speeds, feeds and depths of cut are possible in turning and boring magnesium.  Depth of cut as high as .50 inch and feeds from .003 to .002 inch per revolution can be used.  The depth of cut, of course, depends upon the amount of stock to be removed, but for all practical purposed any depth of cut can be taken, providing the work is of sufficient size and is properly secured.  Heavy feeds provide a very quick means of removing metal, but do not give the best surface finish.  However, extremely fine feeds should be avoided as the tend to heat the work more than heavier cuts.  Cutting speeds for magnesium up to 5000 feet per minute are appropriate for turning or boring.  The following table provides recommended depths of cut, feeds and cutting speeds for turning and boring.  The general rule is to turn and bore magnesium as fast as the machine tool, fixtures and work will allow.

Speeds, Feeds and Depths of Cut for Turning and Boring Magnesium
Operation Speed
FPM
Feed
IPR
Maximum Depth of Cut
Inches
Roughing 300 to 600
600 to 1000
1000 to 1500
1500 to 2000
2000 to 5000
.030 to .100
.020 to .080
.010 to .060
.010 to .040
.010 to .030
.500
.400
.300
.200
.150
Finishing 300 to 600
600 to 1000
1000 to 1500
1500 to 2000
2000 to 5000
.050 to .025
.005 to .020
.003 to .015
.003 to .015
.003 to .015
.100
.080
.050
.050
.050

Milling:  Milling operations provide an opportunity to take full advantage of the excellent machining characteristics of magnesium.  Heavy feeds and extremely high milling speeds can be used to remove metal rapidly with excellent surface finish.  The following table illustrates some typical machining parameters with magnesium.

Speeds, Feeds and Depths of Cut for Milling Magnesium
Operation Speed
FPM
Feed Depth of Cut
Inches
in/min in/tooth
Roughing up to 900
900 to 1500
1500 to 3000
10 to 50
10 to 60
15 to 75
.005 to .025
.005 to .020
.005 to .010
up to .500
up to .375
up to .200
Finishing up to 900
900 to 3000
3000 to 5000
5000 to 9000
10 to 50
10 to 70
10 to 90
10 to 120
.005 to .015
.004 to .008
.003 to .006
.002 to .005
up to .075
.005 to .050
.003 to .030
.003 to .030

 

 

 

 

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This Page Last modified: July 12, 2012 05:08 PM

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