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# Taper Shaft and Hub interference Calculation

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## Taper Shaft and Hub interference Calculation

(OP)
Hi, Users...
Shaft and Hub were interlocking with keys. Shaft Taper have a bigger end was 36.80mm and 11.454 degree taper & Hub also Smaller end 29.8mm and 11.450 degree Taper. While i am applying torque on M24 nut, Shaft and Hub are interferenced. Can anyone Suggest me 1. how to Calculate Interference fit and Pressure of Shaft and hub? 2.How to calculate the transmission torque ? 3. Calculate Fricton force and axial force ? 4. Shaft and hub were contact approx. 90 % for New Shaft and hub. How to calculate Theoritical Contact area and Actual Contact area ? IS there any Standards for Prussian blue matching for cotact area verification. Explain by Formula with solution.

### RE: Taper Shaft and Hub interference Calculation

I can address one part of your question. This is a section of our procedure for installation and removal of coupling hubs:

• For hydraulically mounted coupling hubs, refer to the manufacturer’s procedure for hub removal and installation. Before beginning installation, determine the proper interference and pull up for the particular coupling from the coupling drawing or the repair manual. A table of information on taper fit coupling hubs is attached. For critical machines, if no pull up information is available, seek engineering support to determine appropriate values.
• For general-purpose pumps, the following formula can be used to determine pull up:
• Pull Up = 12 x Desired Interference Fit in Inches / Taper
• For many applications, an interference fit of 0.001” per inch of shaft diameter would provide a good fit. If this is the desired interference, the following formula can be used:
• Pull Up = 0.012 x Shaft Diameter / Taper
• The taper should be in inches per foot and the shaft diameter should be measured in inches at the top of the taper. For example a 3 inch shaft with a ¾” per foot taper would require a 0.048” pull up in order to achieve an interference fit of 0.001” per inch of shaft diameter. (0.012 x 3 / 0.75 = 0.048)
• The taper can be determined by measuring the diameter at each end of the coupling hub (D1 and D2) and the length of the hub (L). If all of these measurements are made in inches, the taper would be calculated as follows:
• Taper = (D2-D1) x 12 / L. Most tapers are ¾” per foot (0.75), ½” per foot (0.5), 5/8” per foot (0.625), 1 degree per side (0.419” per foot) or ½ degree per side (0.209” per foot).

Johnny Pellin

### RE: Taper Shaft and Hub interference Calculation

This is a section of the same procedure describing a good method to check for contact using transfer blue:

For tapered fit hubs, check for shaft contact using Prussian blue.
• Clean both the shaft and the hub thoroughly. Apply a very light coat of blue to the bore of the coupling hub.
• Place the hub carefully back on to the shaft. Rap the hub into place with a soft hammer to ensure that it is fully seated against the shaft. Remove the hub being careful not to drag it along the shaft.
• Check the pattern of blue that transferred to the shaft. In most cases, there should be a minimum of 80 percent contact. Check the repair manual for the machine and the coupling drawing to determine if the required contact is greater. Some machines require up to 90 percent contact.
• For extremely large and heavy coupling hubs, the contact should be check between the plug gauge and the hub and between the ring gauge and the shaft. It is extremely difficult to get an accurate contact pattern on the shaft for a hub that weighs more than 100 pound.

Johnny Pellin

### RE: Taper Shaft and Hub interference Calculation

The equation you need for the interference pressure is called Lame's equation. You'd also need to calculate the axial force due to a torque on the m24 nut, which is non-trivial except in homework questions.

Cheers

Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

### RE: Taper Shaft and Hub interference Calculation

No need to calculate torques and forces here. The draw up of tapered couplings is done by distance or temperature. The draw up can be achieved by heating to a specific temperature differential prior to mounting or by installing a dial indicator and measuring the distance traveled as the nut is tightened.

### RE: Taper Shaft and Hub interference Calculation

(OP)
Hii Greg,
Could you please explain

### RE: Taper Shaft and Hub interference Calculation

(OP)
What is Sticking Coefficient ? is there anything inter-relation between Contact pressure?

### RE: Taper Shaft and Hub interference Calculation

Yup, the torque that can transmitted is function of the friction coefficient in the taper, and the axial force, and the diameter and length of the taper. The axial force for a given torque on the nut is a function of most of that and some other things. As I said, it's a textbook problem, not something that can be solved in a post.

Cheers

Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

### RE: Taper Shaft and Hub interference Calculation

Most just copy SKF's OK coupling system but then fail miserably when they add a keyway to it.

But, if you mount your coupling by expansion or draw up the interference is known and the problem is simplified.

### RE: Taper Shaft and Hub interference Calculation

(OP)
Hi Greg,

I am confusing on textbooks..Can you pls send me some reference book names with author name. it will helpful for myself. Could you pls help me regarding this.

Regards
Venky

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