Press Fit Question 1

[rfhall]

Have used several calculators ,formulas and other threads from this forum to determine the force required to press fit a pin in to a block of material.

Every formula and calculator requires the diameter of the disk or hub. I am inserting the pin into a rectangular block. I am assuming the outer diameter to be the distance from the hole center to the nearest side.

Is this the best method to determine the outer diameter of is there another method to calculate the force.

 

[CESSNA1]

RFHALL: The equations for determining the force required for a press fit are based on definable geometries, ie circles. Once you leave that geometry the problem changes and it becomes more difficult or impossible to solve using hand calculations. Having a hole in a rectangular beam certainly exceeds the circular shape assumption. You may need to use trial and error methods to get the force you need. You may want to run several experiments to get curves for your situation. FEA may also help.

Regards

Dave

 

[ewh]

Is the hole your inserting the pin into circular or rectangular? You only state that the block is rectangular.

 

[rb1957]

usually the force to install an interference fit bush is very low, 'cause usually they're frozen with LN or LCO2.

 

[eromlignod]

At a certain point, the hub thickness doesn't matter anymore. It's an asymptote. Generally this point is considered to be when the hub diameter is at least twice the diameter of the shaft/hole. Past this it doesn't matter if your hub is 3" dia. or 300ft dia.; the press fit is approximately the same.

As long as you don't need a super-accurate figure, you can use the standard "pressure factor" table in the Machinery's Handbook or look here:

http://www.engineersedge.com/manufacturing_spec/press_fit_force.htm

Hope this helps.

Don
Kansas City

 

[rfhall]

Thanks for the replies

The hole in the block is round.
Don't have access to FEA.
Can't do test as the block is made from Beryllium $$$.
The pin is SS 303 at .0626 diam. I used .243 as the outer diameter. This is greater than 2 times the diameter.
My customer is basing his calculations on the yield strength of the pin only.
His calculations gives an answer of 107 lbs.(Fy* Area of pin) Using the press fit calculator and hand calculations I get 247 lbs.
Don't know which is the better way. His method doen't take in to consideration that Be has a higher modulus and no friction factors.
I reviewed the machinery handbook but it doesn't apply to the materials I am using.

Any more suggestions or thoughts.

 

[Sunilp]

Fit is based on the surface area around the material that comes in contact with the mating part. The nearest thing to calculate force for press fit can be made be converting the available area aound the rectangular component and then finding the diameter equivalent in order to use in the Force equation. The answer obtained would be very comparable to the actual results.