Threading 1

[ChrisConley]

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.

 

[diamondjim]

The last question can be answered simply.
The pitch is the amount of advance per one
complete turn of screw or shaft. Torque is
ellusive. The more threads engaged would increase
the torque. What kind of fit between shaft and
hub threads?

 

[Hush]

If I understand your set up correctly:

Two RH ends will not move your assembly, the rod will move through both sockets at 1 pitch per turn. A RH and a LH will move your assembly 2 p per turn. One end fixed but free to rotate and the other either RH or LH will move your assembly 1 p per turn.

If you're using UN threads a class 3A will give you the least backlash. If you want more accuracy use an American Standard or Whitworth measuring thread, I believe you can buy measuring thread rod and boxes (nuts)off the shelf but as to who sells them I have no idea.

 

[Kenneth]

Also see thread281-6109 for some more options ...

 

[gbent]

If you are wanting very fine adjustment on a turnbuckle arrangement, without very fine theads, you can use different pitches, with both right hand threads.
For example, a 20 threads per inch RH will give you .050 movement per turn. If the other end is 16 threads per inch RH, one turn will be .0625 inch movement. The movement of the rod will be .050, and the opposite turnbuckle will move .0125 inch. You can play with different pitches to achieve very fine movements. The drawback of this system is the movement of the turnbuckle screw being several times the movement of the opposite turnbuckle. It works well for relatively small movements.