Is there a chart or formula for sanding speeds vs project diameter?

[Brian Brown]

I am trying to break some of my bad habits, and start turning more safely, and using methods/techniques that are more consistent and reliable to get consistent results, and faster completion of projects. I have lots of bad habits to break. Craft Supplies USA publishes a chart of minimum and maximum lathe speeds for turning.

Formula: Diameter x RPM = 6,000-9,000


Example- A bowl blank that is 8 inches in diameter.
8" x 750 RPM = 6,000
8" x 1125 RPM = 9,000

Therefore the slowest recommended spindle speed is 750 RPM, with the highest recommended speed being 1125 RPM.

This makes setting a safe spindle speed easy.

We all know that to make sanding more efficient we need to slow down the lathe. Does anybody have a similar chart or formula for the best speeds for sanding, depending on the diameter of the piece? I have heard all kinds of guesstimated speed like turn at 1/2 turning speed for sanding, etc. A lot of people seem to have a rule of thumb, but few agree. When sanding a bowl or vessel, the max speed would vary depending on how close you are sanding to the center vs the outside of the piece, but speeding up to compensate for the slower turning center is a little over the top in terms of practicality. Does the sanding speed chart below seem to be reasonable, or do you have a better formula/method to determine speed, or you do what I have done in the past, and just wing it.?

Screen Shot 2024-03-06 at 4.58.33 PM.png

[alan weinberg]

Interesting question. Every sanding discussion I’ve seen mentions slower being better, 500-600 rpm max, but nobody mentioned different speeds for different size objects. Didn’t know such a chart like you showed existed. Will be interesting to read the replies.

[Richard Coers]

SLOW! https://www.youtube.com/watch?v=STxottay2P4

[Brian Brown]

Full disclosure... The sanding speed chart here is one that I made from a similar formulation as the turning speed chart. I calculated it with a roughly (very rough) 1/3 sanding speed vs Cutting speed. I have my doubts as to the suitability of the calculations on the chart. I think is is probably too slow on the large diameter end, and maybe a little high on the other end. That's why I asked the question.

The max speeds of the two situations exist for very different reasons. In the case of turning, the max speed it to give a greater chance that the piece will not fly apart from centrifugal force as the wood spins. In the case of slower sanding speeds, that nasty explosion is rarely the issue. The slower speed is to keep the heat build up from being so bad, and allowing time for the sand on the paper to drop down in between the wood fibers, rather than gliding over the top. Robo Hippy likens this to the traction of car tires. When they spin, you get no grip, but when they turn slower, they grab the road better. That's where my question comes in regarding speeds. Because the travel distance is so much greater on larger diameter pieces, it seems that setting the speed based on diameters would make more sense than one single speed. I guess the real question I am asking is; is the maximum sanding speed the same for all situations and diameters, or will the sand paper have better efficiency with different speeds for different diameters. I know the type of wood is a variable, and there are many other variables. Now my head is starting to hurt, and I am having a bad case of math nausea. Maybe I should give up turning and take up bonsai.

[Dan Hunkele]

My theory is that the grit needs a chance to bite at the wood and speed diminishes the chance. Turn the speed up if you want to burnish the wood.

[James Baldwin]

I usually sand at about 800 to 900 RPM either in forward or reverse except when I'm using my Cole chuck. It says don't exceed 600 RPM. Jim

[Edward Weber]

Not a clue as to what speed I sand at.
After time and experience, you get a "feel" for it. You know when you're cutting, not just simply skating accross the surface.
Start slow and use a backing pad.

[Richard Coers]

I go by feel. If I can't feel the sandpaper actually cutting, I slow the lathe down. Just think if your random orbit sander was sanding a board that is sliding by at 15mph!

[Bill Howatt]

If you have a good cloud of dust flying up, you are cutting.

[Maurice Mcmurry]

I found a believable article on the web that states 60 miles per hour is ideal for power sanding. I also have an interactive pulley calculator bookmarked that makes quick work of the calculations. I will find those and post a link...

[Edward Weber]

The problem with charts (static numbers) are, they don't work well with natural materials, too many variables.
Every species of wood is different and will abrade at a different rate. The grit and the speed must be adjusted to compensate for all those variables.

[David Walser]

I think a speed chart would be nice for newbies. However, I follow a rule that may be simpler: Sand at the maximum speed that allows your sandpaper to remain cool. If the paper is getting hot, then you're sanding too fast (or pressing too hard)!

One of the many reasons I like wet sanding is that it allows me to turn up the speed when sanding. Wet sanding is faster and the sandpaper lasts longer. Other than the mess, what's not to like?

[jack duren]

Shops I know run one speed. As fast as it will go..

https://www.google.com/url?sa=t&rct=...T&opi=89978449

[Brian Brown]

David, I like simple, and this rule sounds like an easy on to use, as well as an easy one to teach.