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JM Clipper Shaft Design

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JM Clipper Shaft Design

Proper application design of the shaft assures proper sealing performance. Using the following guide will ensure the best possible sealing environment for your JM Clipper seals.

 

Shaft Recommendations

Material —

JM Clipper recommends a shaft material of carbon steel with a minimum hardness of Rockwell C30 (30 Rc). Soft materials such as bronze, aluminum or plastic should be avoided because they are susceptible to grooving and will cause premature seal failure. If a soft shaft material must be used, a Daemar Shaft Repair Sleeve can be installed over the soft shaft material to provide a durable sealing surface.

Shaft Finish—

JM Clipper recommends a plunge ground finish of 8 to 17 μin Ra (0.20 to 0.43 μm Ra) with zero lead. A shaft finish significantly smoother or rougher will shorten the service life of the seal.

Shaft Profile —

The shaft profile should include a lead-in chamfer per the following example. The leading edge helps prevent lip roll-back and spring dumping. The leading edge and trailing edges should be free of burrs or sharp edges that could cut the contact point of the seal lip. See Table on right for recommended minimum chamfer length.

Daemar DMR JM Clipper seal - shaft design

 

Chamfer Length

Shaft Diam. up to and including Length “w” (inch) Metric Shaft Diam. upto and Including Length “w” (mm)
0.375 0.051 10 1.3
0.750 0.068 20 2.0
1.250 0.085 30 2.2
1.5 0.102 40 2.6
2.000 0.119 50 3.0
2.750 0.136 70 3.5
3.750 0.153 95 3.9
5.000 0.188 130 4.8
9.00 0.239 240 6.1
+18.000 0.375 480 10.0

 

Shaft Tolerance —

To ensure the proper lip-to-shaft interference is maintained, shaft diameters should fall within the tolerances specified in Tables 5-1 and 5-2. Shafts significantly over the tolerance will increase the underlip temperatures and lead to premature failure. An undersized shaft compromises the amount of lip interference available to maintain a positive seal.

Table 5-1. Shaft Tolerance for Inch/Fractional

Shaft Diameter Tolerance
Up to 4.000″ ±.003″
4.001 – 6.000″ ±.004″
6.001 – 10.000″ ±.005″
Over 10.000″ “ ±.006

Table 5-2. Shaft Tolerance for Metric*

Shaft Diameter Tolerance
Up to 10 mm +0 to -.09 mm
Over 10 – 18 +0 to -.11 mm
Over 18 – 30 +0 to -.13 mm
Over 30 – 50 +0 to -.16 mm
Over 50 – 80 +0 to -.19 mm
Over 80 – 120 +0 to -.22 mm
Over 120 – 180 +0 to -.25 mm
Over 180 – 250 +0 to -.29 mm
Over 250 – 315 +0 to -.32 mm
Over 315 – 400 +0 to -.36 mm
Over 400 – 500 +0 to -.40 mm

 

shaft-seal-150

SEAL

dmr-wave-springs-multiturn-single

RETAIN

caplug-500

PROTECT

dryslide-150-2

SLIDE

DMR_SlottedShim_A-075-150x150

ALIGN

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