# lathe speed?



## Rmartin (Mar 18, 2007)

I have been working with wood all my life, but until recently, I hadn't used a lathe in, well, forever. I'm a sponge when it comes to the boards and information, and everything I read said to start turning the square blank at low speed and then switch to a higher speed once it is roundish. So, that's what I do. Or did, because I don't do it that way any more.

I have been starting with my lathe at it's highest speed. Using a gouge tool with little or no pressure, I can go up and down the blank with less effort. I have found I do not have to tighten the blanks as much to the shaft. I also don't get the catching a corner of the blank like I did when using a slower speed.

It seems to work for me, but then I'm unconventional in the way I do things. I use a hasp to turn acrylics/resins.


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## bjackman (Mar 18, 2007)

Richard,
When turning pens I use the highest speed for turning and the slowest speed for sanding and CA application with very few exceptions. Most of my pen turning turning is done with a 3/8 roughing gouge, 3/8 spindle gouge and 1/2 skew.


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## tipusnr (Mar 18, 2007)

All the instruction I have ever had said to turn at the highest speed at which you are comfortable.  You have hit the nail on the head, Richard, the key that most don't master right off is the "light touch".  

Many beginning turners are quite heavy handed, some call it aggressive, and high speed turning tears the tool out of their control.  I think that's how the slow speeds for rounding developed.  But that's just my opinion as I see many excellent turners using slow speed to augment a highly aggressive approach to rounding with the roughing gouge at demonstrations.


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## Lathemaster (Mar 18, 2007)

Richard

The rule of thumb for lathe speed safety is I believe that the 
outer diameter of the piece on the lathe should be moving no more than 
6000 rpm. To quickly calculate this take the diameter of the piece or if not round the longest diagonal and multiply by lathe speed. If less then 6000 then from a safety stand point you are OK - speed relative to the material being turned is another factor.

For pens since the largest diameter or diagonal is usually 1" or less and for example the top speed of your lathe is 2400 rpm then from the safety aspect your are fine.

For me - I turn pens at the highest lathe speed - cut it in half for sanding and go back to highest speed for polishing. Your mileage may vary. Other variances include material being turned - the sharpness of your cutting tool and your personal style.

I didn't go down to the shop and verify the 6000 rpm figure if I'm off there someone please correct.

Enjoy the addiction

Cheers
Mike


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## ericw95 (Mar 18, 2007)

At the woodworking shows, the CSUSA demo recommended that a safe speed is between 6 and 9 thousand.  So during the day, he was turning 8 inch bowls at 1000 rpm.


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## Rifleman1776 (Mar 18, 2007)

For pens you can safely use the highest speed. And that will give best results. For larger pieces is, if it shakes, slow down.


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## its_virgil (Mar 18, 2007)

The rpm's are the same no matter how large the diameter of the stock. If the spindle is turning at 2000 rpm then any piece of timber mounted on it will turn at 2000 rpm. I think you may be referring to the surface speed of the timber, which increases as the diameter increases...maybe in ft/sec or in/sec or some other unit of speed. A 1 in. diameter timber rotating at 2000 rpm has a surface speed (how fast a spot on the surface is moving)of 104.7 in/sec(if my calculations are correct). Diameter times rpm gives (roughly) a number which would be one-third of the surface speed in in/min. A 1" diameter timber at 2000 rpm will give a number of 2000 with your instructions and the actual surface speed of the 1" timber at 2000 rpm would be 6280 in/min or 104.7 in/sec. Now I'm even confusing myself. []

If I'm off base here, someone set me straight.

Basically I do as the others have suggested. I turn as fast as I feel comfortable and sand and finish as slower speeds. When I turn bowls and have to chase my lathe around the bench top, then I'm too fast..sometimes it even shakes the TV in the other end of house...according to my wife.

Do a good turn daily!
Don



> _Originally posted by HotJoe_
> <br />Richard
> 
> The rule of thumb for lathe speed safety is I believe that the
> ...


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## its_virgil (Mar 18, 2007)

between 6 and 9 thousand ???what units??? Numbers without units are just numbers. Diameter x rpm = ????? what is this measuring??? I guess I taught math for too long. Back to the shop.
do a good turn daily!
Don


> _Originally posted by ericw95_
> <br />At the woodworking shows, the CSUSA demo recommended that a safe speed is between 6 and 9 thousand.  So during the day, he was turning 8 inch bowls at 1000 rpm.


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## tas2181 (Mar 18, 2007)

Here is a short article that may help.
http://www.woodturnerscatalog.com/pdf/safe_lathe_speeds.pdf


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## Randy_ (Mar 18, 2007)

It seems there is something wrong with the math here or maybe the units.  If the lathe is turning at a certain RPM speed, then the blank will be turning at that rotational speed as well.  Outer diameter and inner diameter will all be turning at the same speed.  The surface speed will change depending upon the diameter of the blank and larger diameters will result in larger surface speed.

The formula for surface speed(SFM) is:  0.2618 x RPMs x Dia.(in inches) with the result being in feet per minute.

I did an extensive search of the Internet and could not find any information on suggested speeds for turning wood.  Alan Lacer's web site suggested that there is a wide range of speeds that are appropriate for turning wood and depends upon a large number of variables.  At no time did he mention anything about a fixed upper safe limit for turning wood......the implication being that the safe speed changes depending upon the circumstances.

I did find one interesting fact and wonder if this is what HOTJOE was trying to reference.  On a site for a company that manufacturers sheaves for rotating machinery' they warned that the max. safe limit for the rotational speed of cast iron pulleys and gears was 6500 RPMs.  Almost too close to Joe's stated limit to be a coincidence.  I think that we need a few more detains from Joe before we accept the limit he has suggested.


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## its_virgil (Mar 18, 2007)

Thanks. So D x RPM is not an actual measurement but just a reference number of some kind. It is still roughly a third (1/pi)of the surface speed in in/min if the diameter is measured in inches. I think this horse may be close to dead. 
Do a good turn daily!
don


> _Originally posted by tas2181_
> <br />Here is a short article that may help.
> http://www.woodturnerscatalog.com/pdf/safe_lathe_speeds.pdf


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## Randy_ (Mar 18, 2007)

Tom:  Thanks for that link.  I think that explains the mysterious "6000".

Don:  I'm guessing there are a lot of your students floating around who would disagree with you and would have been happy to see you put in a few more years!!  No doubt, there are a few who do not share that view.[}][][}]


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## Rmartin (Mar 18, 2007)

Now I'm wondering where I got the idea to start the blank at low speed. It does feel good to find out by trial and error what everyone else already seemed to know.


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## tas2181 (Mar 18, 2007)

Not that I am an expert or anything--but I read to start roughing a larger piece (such as a bowl blank) at a very slow speed. Mostly because of the piece not being balanced when in the rough stages.


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## its_virgil (Mar 18, 2007)

I turn pens on a jet mini VS lathe. I keep the belt in the mid range position (1700 to 2600 rpm) and do everything there. I turn at top speed..2600 rpm ... start out with a 1 1/2 inch oval skew and when the blank gets close to size I switch to a 1/2 in oval skew. I sledom use a gouge on pens.  I start sanding at 320 and use the low speed of the mid range for applying the CA finish. 
Do a good turn daily!
Don


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## Chuck Key (Mar 18, 2007)

OK, I think I am clear on this now.  The SFPM changes with each rotation of the lathe where material is removed while the RPM stays the same.  Speaking of sanding is there any benifit to sanding in both forward and reverse directions (lathe rotation)?

Chuckie


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## 4reel (Mar 19, 2007)

Just think, all those comments and we are still at turn it at a safe speed. Interesting


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## saltwein (Mar 19, 2007)

Hello All,

I believe this is a simple statement of proportions. If you double the rpm then at any given point on the surface of the turning, the sfm will double.

I believe the 9000 rpm upper turning speed recommendation is an expression of what equivalent rpm would be at the spindle. So it becomes a propotional method of thinking of the speed in terms of distance from the spindle and rpm. Lot easier for us non mathematicians. Please don't correct me if I am wrong! Works for me, LOL!

Regards, Steve


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## its_virgil (Mar 19, 2007)

> _Originally posted by saltwein_
> <br />Hello All,
> 
> I believe this is a simple statement of proportions. If you double the rpm then at any given point on the surface of the turning, the sfm will double.


Yes, as long as the diameter does not change, but as the diameter changes so does the sfm.



> I believe the 9000 rpm upper turning speed recommendation is an expression of what equivalent rpm would be at the spindle. So it becomes a propotional method of thinking of the speed in terms of distance from the spindle and rpm. Lot easier for us non mathematicians. Please don't correct me if I am wrong! Works for me, LOL!
> 
> Regards, Steve


But, the 9000 rpm upper turning speed is not really rpm's.  It is rpm x diameter. 2000 rpm x 2" diameter = 4000 ??? ...  but not 4000 rpm's. I suppose I am being too pickey and I shall start ducking now.
Do a good turn daily!
Don


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## ctwxlvr (Mar 19, 2007)

hmm Max Safe Speed has way to many variables to say there is a max safe speed, what is safe for one material may not be safe for another material of the same size. I turn at the max safe speed for the material I am turning, using the sound and vibration of the lathe to set that speed, I have had a couple of blanks that I thought would shake the house apart, the weight was all on one side of center for the rounded stock.


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## Ron Mc (Mar 19, 2007)

I guess I'm one of the odd ones (leave it alone everyone![]) I have yet to change the belt location on my Jet mini lathe. I learned on it cranked up all the way and there it sits. Same speed for turning, sanding and finishing. I guess it is really a matter of what feels right to you.

OK Don.....Go ahead and add some math formula's to that so my answer looks right![]


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## redbulldog (Mar 19, 2007)

I agree with Ron. 
I feel very comfortable with mine at the speed it is now set to, turning, sanding and finishing. I would have to look at my jet to see what speed it is now set to. I am teaching my daughter to turn pens now and she is learning at the same speed. Ron we must be in the minority, oh well!


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## its_virgil (Mar 19, 2007)

Just for you Ron:
SLS (safe lathe speed) = [{(experience x personal safety quotient) - (# of lathe accidents) + (personal comfort factor)} / {(diameter of timber x  spindle speed)}] + 1 rpm

I too turn at the fastest speed with which I feel comfortable...Turning is no fun if we get hurt. We should all practice safe turning...faster may not be better...nor slower either. Get in your personal "speed zone" and make something.

Do a good turn daily!
don





> _Originally posted by Ron Mc_
> <br />
> OK Don.....Go ahead and add some math formula's to that so my answer looks right![]


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## RussFairfield (Mar 19, 2007)

The  formula that everyone is referring to but getting wrong is that same one that Dale Nish of Craft Supplies has been using for many years. It states that

(Diameter of the wood in inches) multiplied by (RPM of the lathe) = a number between 6000 and 9000

Using this formula would give the lathe speed for a 12" bowl at between  500 and 750 RPM, which seems reasonable; a 20" diameter bowl would be turned at between 300 and 450 RPM, which also seems reasonable; but a 1" pen blank should be turned at 6000 RPM, which is impossible on any commercial lathe that I know of.

The reality is that our personal "Fear Factor" is the best way to determine the proper lathe RPM for any turning job.


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