Determining the tip speed of a rotating disk

Here is my guess somebody is welcome to correct…

Circumference = pi x diameter, so 3.14×6 = 18.84” circumference (distance around)

If that is spinning 500 times in a minute , that = 9420 inches a minute. That equals 785 feet per minute.

To have more fun… x 60 that equals 47,100 feet per hour…divided by 5280 = 8.92 miles per hour.

How fast is the edge going? 500rpm. :-)

But I guess you wanted miles per hour? Feet per second?

-- Charlie M. "Woodworking - patience = firewood"

Now to have yet more fun…

If a 6” spinning bowl blank leaves chicago at 10:00 a.m heading for new york at 500 rpm, when will a 9” bowl blank leaving Chicago at noon heading toward New York spinning at 550 rpm pass the 6” bowl blank?

(my brain hurts just writing that question…)

In Pittsburgh?

-- Charlie M. "Woodworking - patience = firewood"

I guess I could have worded that better…. The real question would have been regarding velocity….

Tip speed in Feet p/Sec i guess…. versus the rpm. You see the discussion was regarding the proper rpm vs the blank size which kind of morphed into this side question.

-- "Everything that is great and inspiring is created by the individual who labors in freedom" -- Albert Einstein

Do you mean, “for a specified tip speed and diameter, what should your RPM be”? Then it’s just a matter of rearranging the equation (solving for RPM) and boiling down the constants. For tip speed in feet/sec and diameter in inches:

RPM = 229*tip speed/diameter

-- My broker promised me he would treat my money as if it were his own. Trouble is, he did.

13.08 feet per sec.

The next question this raises for me is: What is a good tip speed for shaping a bowl blank?

I did a little research and found several references to this simple formula: The diameter of the blank in inches multiplied by the lathe rpm should fall between 6,000 and 9,000. So, for example, you would want to turn a 10” blank somewhere between 600 and 900 rpm. A 5” blank should be turned at between 1,200 and 1,800 rpm, and so on.

This video explains it:

http://www.youtube.com/watch?v=-3mqZjTgVc4

-- Charlie M. "Woodworking - patience = firewood"

I can answer the safest speed is 0.0
hard to say it depends on the cut your making and the type wood no real rule more of a feel but less viberation is better unless you want texture…chatter time
happy turning

-- Cosmicturner