Threaded Connection

[ChrisConley]

Hello all, I don't know if this falls exactly under gears and pulleys, but I figured some Machine Design professionals would find this an easy problem.

I have a general threading question which I will attempt to describe as accurately as I can.

I need a device that will allow small adjustments in a table's orientation. This strut will allow for a one time adjustment of a large magnet. To this end a threaded shaft inserted into sockets, one socket is attached to a fixed support, the other is . As the shaft is rotated small movement in the shaft allows for fine tuning pitch,rotation, etc.

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This is a quick representation of the shaft with two threaded ends. My questions are: what combination of handing will allow for the greatest accuracy of adjustment (RH-RH,RH-LH, etc.), Secondly is there a formula for calculating the amount of torque required to turn a shaft such as this one through one rotation. And finally is there a way to determine (once the handing is determined) how much distance will be covered by one rotation of the shaft.

I hope that I have been clear enough but feel free to request additional information.

 

[GregPerry]

Chris,

The smalles adjustment I think will be obtained useing RH-LH threads. The threads must be of a different pitch, for example.

RH - 2mm pitch
LH - 1mm pitch

One rotation will result in the RH screw going out 2mm and the LH screw going in 1mm resulting in a total movement of 1mm. By selecting pitches that are closer together the resultant movement is decreased.

The distance can be determined as shown above by subtracting the thread pitches (single start threads) for RH-LH threads.

To determine the torque apply 'power screw' theory. It is normally in any mechanical design book.

Greg