I was looking at a used lathe and noticed the top speed was 3000 RPM, while the replacement model now goes up to 5000 RPM. I think the lathe i have tops out at 3000 RPM. Is 3000 adequate for most turning projects, or would a higher speed be useful to have? My uninformed opinion is that 3000 is plenty for almost anything and it's the lower speeds that get used the most.

3,000 will be plenty.  Most of my turnings are done much lower than that.  Electronic speed is control is a nice asset for a lathe.

Divide 6000 by the diameter of the workpiece to find the correct RPM.  From that calculation, high RPMs are only needed for smaller spindles of the 1 -2 inch range.  That said, I don't think this is a hard rule.  More of a guideline.  

 

From the formula we can extrapolate that a 2" spindle would need a speed of 3000 rpm and a 12" bowl only needs 500 rpm.  That said, much depends on the type of wood, characteristics of the wood, type of cut, and sharpness of the tool.  In some cases, I find I get cleaner finish cuts on a bowl if I'm turning 2x or more of the calculated rpm.  

 

Another consideration is the amount of torque available at higher speeds.  Typically to get the higher speeds, one has to change the position of the belt on the pulleys.  The faster you go, the less torque is available due to the arrangement of the pulleys.  

 

In practice for bowls, I just leave the pulley in the middle position and find a happy place using the electronic speed control. 

 

.40

Edited May 3, 20233 yr by forty_caliber

3000 is plenty fast. I can’t remember ever turning something that fast. 
Paul

Mine tops out at around 3000. So far that's been all I need. I have noticed that carbide cutters do better at higher speeds. I guess if you were doing a lot of polishing, like acrylics, it might be useful.

 

 

For bowls I usually hit 1100 to 1250 after rounding out. All cutters (carbide and tool steel) will bet better cuts at higher speeds. Jimmy Clewes turns at about 2400 to 2700. As to torque you do need more when roughing out the outside and when hollowing so that means changing the belt position and speeds will be slower.

I've never cut anything at 3000 RPM but I have determined that the last Dizzy Bowl which is 12" in diameter did turn better at 1200 RPM than at slower speeds. I think it has to do with the glue joints being harder than the wood... the first Dizzy Bowl I turned a lot slower and the chatter was horrible to say the least. It's been a while since I've turned a solid wood bowl so I'd like to experiment with the RPM on one next.

 

JT