On Thu, Aug 22, 2019 at 05:29 PM, Ralph Hulslander wrote:
Ok, when one is facing a end on your lathe the center turns at a different RPM than the exterior,
is that correct??
Ralph,
The surface speed is how fast the material is actually moving at the point where it is being cut.? It is not related to the feed rate of the tool.? The RPM needs to increase as the cutting tool moves towards the center.? In theory, (not practice, of course), the RPM approaches infinity as the cutting tool approaches the centerline.
Example, for which I will use the very rough formula for HSS cutting tools and steel material:
RPM = 300 / diameter (in inches)
If you are facing a 2-inch diameter round, for example, the RPM at the outer edge should be around 150.? As you move towards the center, and are now cutting at the 1-inch diameter point, the RPM should be around 300.? At 1/2 inch, the RPM should be 600, then 1200 at 1/4 inch, etc.
The formula is actually based on calculating for a specific surface speed.? If the RPM is 300 with a diameter of one inch, this means that the surface speed is 1 inch x pi x 300 revolutions = 942 surface inches/minute, or 78.5 surface feet/minute, which is the more common unit of measure.
The desired surface speed depends upon the material, type of cutter, machine rigidity, and a number of other factors, but I personally have always found this formula to give me a good starting point for HSS cutters with steel material.
I hope this helps.
?
--
Regards,
Charlie
New Jersey, USA
