Help Please - Turning Speed (RPM) Advice

[BRIAN JACKSON]

Still consider myself a newbie...turned 20 bowls/cups so far, but the more YouTube videos I watch, the more conflicting advice I seem to get. My question this time is turning speed (RPM).

If I mount a chainsaw cut blank from a hunk of raw wood, I tend to spin at 500 RPM to get it into shape(between centers). After getting it close to round, I may increase to 1000 - tops but on faceplate.

If I have a block of pre-cut wood, I typically saw off the corners and start turning around 750 RPM already mounted to faceplate.

Even after getting pretty close to perfect round, I've never turned above 1300rpm. I've been seeing a lot on YouTube where they say to spin as fast as you can. Is this right?

I have a Rikon Variable Speed Midi so I can turn over 3000, but....is this safe? I also use carbide tools. Have experienced a lot of "catches" in the slower speeds and often wondered it is catching because of the speed or just poor tool placement.

So far, I've turned pieces in Spalted Maple, Bald Cypress, and Eucalyptus. Actually tried to turn a green blank of GUM - and that didn't go so well - was very hard to remove excess on the inside of the bowl. Most pieces between 4-6 inches across. Wanting to try something larger soon. Just turning between centers to rough out then use a faceplate while I save up for the chuck.

Thanks in advance!
Brian

[Mike Peace]

Sounds like you have an approach to speed that is safe and works for you. Dale Nish developed a formula of Diam x RPM = 6000 - 9000 and a lower if rough and unbalanced. Here is a video I did on the topic. https://youtu.be/8lq78dWdwH4

[BRIAN JACKSON]

Thanks Mike - great video too.

[Reed Gray]

I never had a lathe with a speed read out till 2 years ago. I still don't look at it because I learned to turn by 'feel'. For bowl blanks, first, turn the speed down to zero. Then you can ease the speed up till things start to shake a bit and then turn it down till most of the shaking is gone. That shaking will transfer to the form you are turning, making it much more difficult to get it round. As a production turner, I was turning 6 to 8 inch bowls in the 2000 rpm range, and I slowly worked my way up to that. Main thing to remember, is that 'accidents' get much more spectacular with higher speeds.

robo hippy

[John K Jordan]

To me, much depends on what I'm turning. You seem to be turning bowls and such where a problem with the wood or technique can be dangerous at higher speeds. High speeds can also make a problem like a catch worse in some cases, at minimum, scarier, or more dangerous at worse case if a bad catch causes the piece to break or come off the lathe. It's wise for a relative beginner to turn at a slower speed until gaining expertise in tool control. (My previous advice still holds - to best develop expertise at tool control learn spindle turning first even if the goal is to turn nothing but bowls.)

I turn a lot of smaller things in spindle orientation (grain aligned with the axis of rotation/lathe bed) and most of the time turn as fast as my PM will go, over 3000 rpm. Maybe 2000-2500 rpm for something like a goblet. I find a couple of advantages to higher speeds: less vibration and a smoother surface with the same tool speed.

I don't often look at the speed control, just set it to what "feels right" but that may just come with experience. I think I often turn face oriented things (grain running across, perpendicular to the lathe bed) like small 8-10" bowls or platters at maybe 1200-1500 for finish cuts, slower when shaping. These are mounted in a chuck. Very slow or stopped when sanding. Higher speed for pieces with wings can result in a smoother surface with less tool bounce when "cutting air."

Other things that might determine lathe speed besides size, weight, and balance are the type of wood, grain orientation, the integrity of the wood (any cracks/voids/rot?), skill level, and the tool in use+the amount of wood being removed, slower for heavier cuts, much faster for shear scraping or NRS use.

Note that a piece can be turned perfectly round and you can still get out-of-balance vibration due to differences in density in different areas. In this case, just like a non-round blank, there may be vibration at certain speeds but changing the speed to a little lower or a little higher might be smoother.

JKJ


Still consider myself a newbie...turned 20 bowls/cups so far, but the more YouTube videos I watch, the more conflicting advice I seem to get. My question this time is turning speed (RPM).

If I mount a chainsaw cut blank from a hunk of raw wood, I tend to spin at 500 RPM to get it into shape(between centers). After getting it close to round, I may increase to 1000 - tops but on faceplate.

If I have a block of pre-cut wood, I typically saw off the corners and start turning around 750 RPM already mounted to faceplate.

Even after getting pretty close to perfect round, I've never turned above 1300rpm. I've been seeing a lot on YouTube where they say to spin as fast as you can. Is this right?

I have a Rikon Variable Speed Midi so I can turn over 3000, but....is this safe? I also use carbide tools. Have experienced a lot of "catches" in the slower speeds and often wondered it is catching because of the speed or just poor tool placement.

So far, I've turned pieces in Spalted Maple, Bald Cypress, and Eucalyptus. Actually tried to turn a green blank of GUM - and that didn't go so well - was very hard to remove excess on the inside of the bowl. Most pieces between 4-6 inches across. Wanting to try something larger soon. Just turning between centers to rough out then use a faceplate while I save up for the chuck.

Thanks in advance!
Brian

[tom lucas]

If it "seems" or "feels" dangerous, it's too fast. But it sounds like you've found a method that works for you on bowls. The bigger the wood the slower the speed. The less concentric the wood the slower the speed. Actually numbers aren't so meaningful.

[Kevin Jenness]

There was a lengthy thread entitled "speed" on the AAW forum not too long ago on this subject, worth a look.

The formula Mike Peace mentioned (diameter x rpm = 6000-9,000) is a useful rule of thumb. At 9,000, the rim speed of the turning is about 27 mph. Impact force if something lets go is proportional to the square of the speed. Adjust the rpms according to the size, balance, soundness and mounting method of your blank.

It sounds like the speeds you are using are within normal limits given the size and attachment method.

As Robo Hippy says, "Stay out of the firing line".

[Brian Deakin]

I struggled to correlate lathe speed in rpm and the diameter of a bowl in inches

I then found this website for tyre speeds and used it to compute lathe in rpm for different diameters and entered the figures into chart

http://www.advanced-ev.com/Calculators/TireSize/

Please note you need to set the differential ratio to one

Example
Set the differential ratio to one

Decide on a peripheral speed in mph ,enter a diameter the chart will then calculate a rpm