Trying to thread the needle

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sqrrt

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Thanks in advance..
I am trying to understand this relationship...I am not sure how to calculate the problem.

Assumptions: Rod, Allthread , and paper tubing are long enough...As the all-thread turns, the block of wood goes with it.

I have a 3/4" piece of all thread ( COURSE THREADS), 10 threads per inch. Attached to it is a block of wood that slides on its own stationary rod, as not to rotate with all thread.

I am turning the 3/4" Allthread at 10 rpm.

Opposite to the all-thread, I have a 2" piece of paper tubing that is turning at 10 rpm also.

If I attach and center a pencil on the block of wood, attached to the all-thread, and rest it on the paper tubing, and turn each 10 RPM, how many lines will be drawn on the paper tubing in 1 minute?

Again thanks :)
sqrrt
 
Sorry for the lack of understanding.

The attached pic has 10 threads per inch with a 3/4" diameter.

Hope this helps.
sqrrt
 

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I meant a picture of your rods and wood block and paper tubing and everything put together. I'd figured out the threaded rod. Sorry for not being clear myself.
 
Is your setup roughly similar to phonograph equipment, but instead of a wax cylinder yours is paper, and instead of a needle you have a pencil. Your equipment obviously doesn't record sound - it simply draws a nice helix onto the paper cylinder.

If the above is correct, then the answer to your question is that only one line is drawn :)
 
Many thanks for the suggestions. Cubist, it's sorta like a phonograph. You have to keep in mind however that the 3/4" shaft will travel 10 threads in 1 minute. So at the very least, there should be 10 lines on the 2" PVC. Actually I think I figured it out myself. Sorry, I don't have a model to look at.
Nevertheless, With the 3/4" shaft maintaining an rpm of 10rpm, Then lines on the PVC would be proportional to the speed of the PVC.
Ex: With the 3/4" shaft at 10 rpm and the PVC at 10 rpm then 10 lines on the PVC. If I slow the PVC down to 5 rpm then there would be 5 lines.
With the introduction of a rheostat, and small motor one could possibly obtain any number of lines. What do you think Dr. Peterson?
 
It would be so helpful if you could send us a picture as I asked, to confirm the details.

I assume that the wood is "attached" to the threaded rod in the sense that the rod goes through a threaded hole so that the block is moved along as the rod turns. Since the rod turns 10 times per minute and has 10 threads per inch, the pencil will move one inch per minute. Since the paper tube (which I assume is "a length of 2-inch-diameter tubing", not "a 2-inch length of tubing") rotates 10 times per minute, the pencil will draw on it a helix with 10 turns per inch. (Did you miss Cubist's joke that this spiral is a single line? There aren't 10 lines, but 10 turns in the helix, per inch.)

The main thing you are missing in what you've said is "per inch". Yes, if you vary the speed, you could vary the number of turns per inch, which will be proportional to the speed, because e.g. at 5 rpm, the tube turns 5 times while the pencil moves 1 inch.
 
You might also be interested in the technique of using a gearbox instead of a second motor.

I seem to remember cutting a thread into a mild steel rod using a lathe when I was at school. There was a gearbox to control the speed of the longitudinal travel for the cutter. The gearbox setting determines the turns per inch (also known as "thread pitch" in this context, I think). And the mechanism allowed you to retrace the exact same path several times because you make gradually deeper cuts until the helix (thread) is at full depth. You can't cut to the full depth straight away because it would demand the cutter taking too much material and bend the rod/ break the cutter. Actually try "lathe threading" in your favourite search engine!
 
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