For woodworking cloasses, I'm looking for authoritative maximum speed charts for spindle turning and bowl turning. The only ones I've found are in an early Richard Raffan book. Thank you.
[OP]
Member
For woodworking cloasses, I'm looking for authoritative maximum speed charts for spindle turning and bowl turning. The only ones I've found are in an early Richard Raffan book. Thank you.
Contributor
A common rule of thumb says that the product of rpm x diameter in inches should be in the range of 6,000-9,000. A 12" diameter bowl at 750 rpm (12x750=9,000) translates to a rim speed of about 27 mph. For comparison the tip of a 10" sawblade spinning at 4,000 rpm is about 120 mph.
Contributor
In Keith Rowley's book "Woodturning - A Foundation Course" New Edition on page 46 he has two charts on turning speeds base on diameter and length. One chart for spindle turning and one for face plate turning.
Crafts Supplies USA used to have a chart on their old website. If it's there now, I couldn't find it this evening.
Google is your friend! https://www.google.com/search?q=lath...tyu0PEPrLuW4AQ
Last edited by Ken Fitzgerald; 02-17-2022 at 11:13 PM.
Ken
So much to learn, so little time.....
Contributor
Don Stephan, keep in mind that maximum turning speeds probably refer to a piece that is largely balanced. For a piece that has not yet been made roughly "round", you've got to start much slower. It's kind of an intuitive thing - - if your machine is badly shaking or bouncing around you should slow down.
Contributor
Don — There is no such thing as an ‘authoritative maximum speed chart’ for woodturning. Years ago, Dale Nish, the founder of Crafts Supplies USA, developed the often cited rule of thumb Kevin mentioned above. At the time, Dale was a professor of industrial arts at BYU. Among his students were future high school shop teachers and he felt it would be helpful if they had some easy way to teach their charges what speed to use at the lathe. That’s not to say he didn’t give a lot of thought into developing the rule. Nor is it to say it isn’t a good place to start in determining what speed to use. It’s to say there was no scientific study conducted. No mountain of data sorted and analyzed in developing the rule of thumb. It is simply based on Dale’s years of experience at the lathe.Originally Posted by Don Stephan;[URL="tel:3177794"
Of course, since he was a university professor, maybe we should consider it authoritative.
David Walser
Mesa, Arizona
Contributor
I've never owned a lathe with a speed indicator (and have never felt the need for one or missed having one), so I'm prejudiced, I guess. I tell people to turn the speed up until it starts to make them uncomfortable and if they have problems to try first slower then faster. It seems to work, 95% choose too slow a speed to start with, which is fine but demands better technique. I think over-reliance on speed dials rather than looking at what's happening with the wood and the tool is a bad habit that I see way too many intermediate level turners fall into. They do something that doesn't work very well but then don't want to adjust the speed because they have been given a rule about what the "correct" speed is.
Contributor
I turn a lot of banjo rims on my Shopsmith which only goes down to 700 RPM. Especially with a 16" rim it makes me a little nervous, so I am looking forward to a day sometime in the future when I'll have space for real lathe and be able to go slower. My rims are segmented turnings, so luckily they're not too far out of round to start with.
Contributor
Can someone please advise if my logic of using the method below is correct to calculate rpm and appropriate to use for turning
I constructed as a guide a rpm rim speed chart using the website below for diameters of timber ranging from 3 to 17 inches
http://www.advanced-ev.com/Calculators/TireSize/
To use the calculator decide on a rim speed in mph, set the differential ratio to 1 in the calculator, then enter a diameter and calculate a rpm
So as an example you could enter a rim speed of 27mph and calculate rpm for that diameter
Please note this is a general guide and other safety factors must always be considered
Last edited by Brian Deakin; 02-22-2022 at 6:02 AM.
Contributor
Sure, that works as long as the differential ratio is entered as one. I use the rule of thumb mentioned above and do the arithmetic in my head. Your last line, though, is the most important thing. There are a lot of variables involved, most especially the size, balance and soundness of the wood. The rule of thumb is just a check to see if the rpm setting is within a generally plausible range. I would never consider it a hard and fast rule.
There's a much wider range of possible speeds. I have seen videos by Stuart Batty where he talks about rim speeds of over 40 mph, and many a chair leg and bowl has been turned on a pole lathe. I always try to be aware of what it might mean if a blank or chunk of it came off the lathe and hit me at the calculated speed.
Contributor
Different metals, iron, brass, aluminum, have different hardness and thus different turning characteristics and speeds. I have always felt the same about species of wood. I adjust speed to what gives me a good cut for each turning I do.
Contributor
In Stuart video I believe he speaks about up to a maximum of 40mph but this would be under ideal conditions and a very competent woodturner
It would seem wise to regard this a the very upper limit and wise to stay well below this speed
Contributor
the op indicated the question was for classes - what makes anyone think a new turner would have any idea of what mph to use...Dale Nish's formula is, in my opinion, the safest option for new turners.
Contributor
When I was brand new at turning, I just picked a speed that made me comfortable. Admittedly this was probably slower than was necessary and it probably resulted in a lot more sanding than was necessary, but I felt safe. I was turning smaller bowls so it wasn't as crucial since it's much easier to hold a small bowl on the lathe. While I upgraded to a Powermatic 3520C last year and don't have to worry as much about the lathe moving with unbalanced blanks, I still am overly careful. Having said that, I find that the speed chart included in the lathe manual indicates speeds that sometimes seem slow for finish work. For roughing, I think they are OK. Anyway, what I like about the digital speed display is that it gives me an idea if I can up the speed a bit or should lower it, because sometimes I just can't tell. Speed charts are only good for approximating speed and don't take into account capabilities, lathes, etc.
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