Safe Lathe Speed for Bowl Turning?

[leehljp]

I have a 12 inch Rikon lathe and have learned from both reading and experience the relation of turning speed to the diameter of the blank. I am also thinking of turning bowls larger than my 12 Rikon will allow. That means a new lathe in the future. However, the HF and low end Grizzly ($300 - $500) range only goes down to 600 RPM. And 600 RPM seems fairly high and dangerous for 14 to 16 inch blanks. After the low end Grizzly and HF, the price jumps to well over $1000 for any lathe that will turn at 200 - 400 RPM.

Is there a chart or generalized opinion of what is a safe speed for particular diameter? I know that once roughed turned and balance is achieved, the speed can be increased, but rough just mounted blanks are outright dangerous as speed increases.

Opinions and wisdom on the speed vs diameter relationship?

(BTW, This is a next year project at the earliest. Just trying to get my head around it,)

[atgcpaul]

+1 on seeing said chart, too. I have a Rikon mini-lathe as well as Delta midi-lathe with Reeves drive. I think the Rikon can go down to 430rpm and the Delta to 600rpm.

I'm wondering if you can put a plug-in speed regulator on these like people do with routers to slow them down.

[Bill in Buena Park]

Hank,
Check out this website:
http://www.docgreenwoodturner.com/lathespeed.html

I've also attached the graph from that website.

I try to get the blanks as round as possible at the bandsaw before mounting on the lathe, this helps some. I haven't gone beyond 13inch blank start size on the HF (started outboard, on faceplate), and final turned size was a hair under 12 inches (turned inboard after completing outside, for hollowing.) I would not try this with non-round or severely imbalanced blanks of this size on the 34706. If I get the itch to turn bigger, I've got the G0766 on my radar.

[JoeyGee]

Hank, thanks for asking the question and Bill thanks for that chart and link. I have my first bowl blank sitting on my band saw after rough cutting it round, just waiting for me to find the time to ruin it on my lathe 😃.

[woodturner]

That means a new lathe in the future. However, the HF and low end Grizzly ($300 - $500) range only goes down to 600 RPM. And 600 RPM seems fairly high and dangerous for 14 to 16 inch blanks. After the low end Grizzly and HF, the price jumps to well over $1000 for any lathe that will turn at 200 - 400 RPM.

The answer is "it depends" ;-) It depends on the equipment, user, and blank. A mostly round blank on a heavy lathe and an experienced user can turn at higher speeds (for example, Richard Raffan). A lighter lathe, more out of round blank, etc. requires a lower speed.

One good option is to look at used lathes - Powermatic 91's are great bowl lathes, for example, and go for a few hundred dollars in good condition. They don't seem that popular any more among turners, so they are heavily "discounted".

I recently bought one and am pretty happy with it - my only complaint is that the top speed (2500 RPM IIRC) is too low for my preference. I typically turn faster than many people, however. I typically start a spindle turning in the 2000 RPM range and jump up to 5000 RPM or so once it is turned round. A 12" bowl that is reasonable round I'd start at maybe 1200 RPM and move up to 3000 RPM once it is roughed round.

The charts look reasonable and are probably a good guide, maybe a little on the slow side but better safe than sorry. It's really one of those things that depends on your comfort level and equipment. Best advice is don't turn faster than your comfort level.

[Bill in Buena Park]

One good option is to look at used lathes - Powermatic 91's are great bowl lathes, for example, and go for a few hundred dollars in good condition. They don't seem that popular any more among turners, so they are heavily "discounted".

Sure wish I could find one around here like that. No luck.

A 12" bowl that is reasonable round I'd start at maybe 1200 RPM and move up to 3000 RPM once it is roughed round.

You have more confidence in your blanks than I have in mine. 3000rpm on that size bowl would give me major pucker factor as I imagine hidden weaknesses and centrifugal force conspiring against me. I think my top speed on this size 1200-1500!

[leehljp]

THANKS Bill! I had to yell that. It is a GOOD yell! That is THE information for which I was looking. This is very helpful.

WT. Thanks for that information also. I am totally aware of out of balance blanks, - and how they can be managed. I was in Branson Mo over the weekend and in one of the stores that I go to (when LOML is shopping next door) has lots of wood carving, bowls, vases etc. Many of the bowls are odd shaped and with voids. It is the voids that make for danger, especially if the turner wants the void to be at a certain point. Balance, heavy lathe, speed and strong mount are crucial. The problem comes in for people who start with midi/mini lathes for pen turning and small bowls and then move up to 10 to 12 in bowls and vases 10 to 15 inches long. AS to the speed, critical knowledge and awareness of this from experience is a necessity, or it becomes dangerous and deadly quickly.

Also, I have watched quite a few YouTubes a few years ago of people turning large logs and blanks. Again, balance, lathe weight, speed and mount are necessary.

My question really was generalized and Bill posted the parameters for size vs speed. On the pen forum over 11 years, I have watched skilled bowl and vase turners come in and with their long experience chime in that 600 to 1200 RPM is fast enough for any turning, even on a 3/4 diameter pen blank. Then there is the other side - pen turners who get skilled at making pens (turning at 3000 RPM) and then go to turn a 10 to 12 inch bowl at 3000 RPM in the rough form. Usually this is a post from someone who learned a lesson the hard way.

Speed is OK as long as the person has considerable experience and knows when a sound change and minute' vibration are warnings to back off - with the experience to know when a light vibration means 1. to turn of more rough edges, vs 2. back off or get out of the way!

For me, my first turning experience in the early '90s could have been deadly as I let the skew get caught and flung against the wall. I haven't mastered the skew yet!

BILL: Thanks for the link. That is great information!

JOE: Let us know how your bowl turns out!

[woodturner]

You have more confidence in your blanks than I have in mine. 3000rpm on that size bowl would give me major pucker factor as I imagine hidden weaknesses and centrifugal force conspiring against me. I think my top speed on this size 1200-1500!

You are probably turning different types of wood. I don't turn wet wood or wood with defects, and I turn a lot of segmented and glued up work. So the wood is dry, solid, and lighter weight. In addition, I don't use engineers chucks, I use centers, sometimes faceplates, and vacuum or jam chucks to finish. When I am roughing out a bowl, I have it between a spur and dead center, so it is held well and does not break loose.

[Bill in Buena Park]

You are probably turning different types of wood. I don't turn wet wood or wood with defects

This is likely a large factor, since even though I process the timber myself and keep only what appear to be solid blanks, I can't always tell by looking at the outside of the cut blank what I'll find inside. I've come across hidden inclusions and internal splitting not visible until roughed out. Not as stable as hand-selected segments to glue up, although the chicken in me is still afraid to use speed on those too.