# Homework Help: Linear speed of the screw

1. Apr 25, 2007

### shurioz

Could somebody help me with this?

Let’s say I have a screw that is 0.25” dia. I want to screw this screw into the wall.
First question: If I turn this screw 2 times around its axis, how far the screw will go into the wall?
Second question: If I rotate the screw at 10 RPM what is its linear speed?
Please help me with question!!! I can’t figure it out.

Let’s pretend that the wall doesn’t resists to the screw at all to go in. I just basically want to know the relationship between linear and rotational speed, when linear speed is parallel to the rotation axis.

Last edited: Apr 25, 2007
2. Apr 25, 2007

### Danger

Welcome to PF, Shurioz. The questions that you're asking depend upon one factor that you didn't mention: the pitch of the screw; that is, how many threads per inch.

3. Apr 25, 2007

### shurioz

It’s a good question. Let’s say the pitch is 20. 20 threads per inch.

4. Apr 25, 2007

### robphy

You can model the screw as "an inclined plane wrapped around a cylinder".

5. Apr 25, 2007

### shurioz

By using the screw example I just wanted to know if the liner speed perpendicular to the rotation axis is the same as linear speed parallel to the rotational axis.

6. Apr 25, 2007

### shurioz

Another question about screw threads.

Let’s say we have a nut with custom threads: 2.0” pitch diameter and pitch-10.
If I rotate this nut by 55 degrees on the bolt, what would be the traveling distance of the nut?
Please help!!!

7. Apr 25, 2007

### Dick

If there are 10 threads per inch then rotating the bolt 360 degrees will advance it one thread or 1/10 inch. Clear now?

8. Apr 26, 2007

### shurioz

2 Dick
Thanks a lot

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