Turning speed?

[Chasboy1]

Hi Folks, I've been turning stuff off and on since I first tried it in school about 60 years ago now. What I'm curious about is that most videos I watch seem to run at much higher speeds, even during roughing, than I was taught. Has something changed or is my information as antique as I am?

 

[magpens]

I am with you, Charles ! . Slower is better .... for me !!

Typically, I do initial blank rounding at up to 1000 RPM for acrylic-like materials (depends on material), and up to about 1500 for wood.
When I am actually turning a pen, I would go even slower ... maybe even as slow as 500 for plastics and 1000 for wood.

Rarely would I go as high as 1700 for finishing cuts on wood. . Am often amazed at some recommendations given for much higher speeds.

I use a metal-working lathe for everything ... just what I learned on in my youth. . Maybe that makes a difference.

 

[FGarbrecht]

I agree (partly) with Mal. I turn at pretty slow speed on metal lathe (where I turn plastics and ebonite). On the wood lathe I use slowest speed (~500) for horizontal drilling operations but tend to run as fast as possible (around 3400 rpm on a Jet midi) for pen turning, both roughing and finishing. For bigger stuff like bowls I go slower during roughing. I turn things down a bit for sanding on the lathe too because I don't enjoy burning my fingers or melting my alumilite/acrylic/ebonite. From my extensive you-tube lathe video watching experience it seems that the general advice is to turn as fast as you can so long as your machine is stable and not vibrating or rocking too much. That being said, I am no expert, but these things have worked for me.

 

[leehljp]

Hi Folks, I've been turning stuff off and on since I first tried it in school about 60 years ago now. What I'm curious about is that most videos I watch seem to run at much higher speeds, even during roughing, than I was taught. Has something changed or is my information as antique as I am?

Charles,
Yes and No. What you were told 60 years ago probably related to bowls and vases. Spindles could be turned at a little faster speed. Today, bowls and vases turn at similar speeds as then and so do spindles. However, pens are much smaller and require higher speeds.

When I first started pen turning and came onto this forum, which was only 1 year old at that time, I began to notice a few bowl turners complaining about the same thing. The problem is that they did not understand the speed issue in relation to diameter of what was being turned.

Look at the chart below. It gives the lathe speed in relation to the diameter. Notice how 3 inches in diameter is good for 2000 to 3000 rpm. But 12 to 15 inches is safe only at BELOW 750 rpm.

12" diameter bowl is 38.04 inches around X 700 RPM = 26,628 inches per minute, or 2,219 ft per minute, or 133,140 ft per hour divided by 5280 = 25.2159 MPH at cutting speed.

Now imagine if you were cutting a pen blank at that RPM.
3/4 inch diameter is 2.355 inches around, X 700 RPM = 1648.5 inches per minute, or 137.375 ft per minute or 8,242.5 ft per hour decided by 5,280 = 1.5611 mph. VERY SLOW cutting speed for a pen. TOO Slow.

3/4" at 3000 rpm = 7065 inches per minute or 588 ft per minute or 35,325 ft per hour, or 6.6903 mph cutting speed at the blank.

caveat: (My math skills have diminished since moving into the "70+" age. For you mathematicians, please freely correct my mistakes.)


Look at the

 

[lorbay]

With larger objects the faster you go the better the cut. With most of the professionals I have seen they say run as fast as you are comfortable with. Check out Jimmy Clews videos and see how fast he spins.
Lin

 

[Chasboy1]

Thank you all. Very illuminating. !!

 

[howsitwork]

I am with Hank on this one.

Yes faster is better as you get a faster cut and are removing less material with each revolution of the blank. You will only ever get as good a finish as the quality of your tool edge. So keep the tools as sharp as possible , unless you love sanding (???)

I really done know how fast my lathe is going, yes I have variable speed but I've not calibrated it. I turn as fast as I feel safe and happy with , but generally smaller objects = higher speed , all other factors being equal.

If the blank has fracture lines , stress cracks etc then slow it down and take care. Fast also means FACE MASK ESSENTIAL in my book especially if the blanks is of any size eg a bowl blank.

Also bear in mind that the tools you used in school were probably not too sharp and e instructors wanted time to get there before you killed anyone or yourself with them so slower speed was probably a good thing. Depending upon your age it's also possible the lathes being used were not rated for higher speeds as current ones are. No offence intended by that statement just reminiscing myself a bit.

Safety first

Ian

 

[wolf creek knives]

I like what I read here but I think some of those saying a slower speed are using metal lathes. Not sure but that could be a difference. I've been turning for many years (40+) and my instructor, my father in law, taught me to use the lathe at the highest speed possible. He learned to turn when he was in the Navy. For pens (wood) I push it right to 3000rpm and it works just fine. For larger handles i.e. ice cream scoops, coffee scoops I keep it at around 2500rpm. Some may say that's too fast but I'm comfortable with those speeds. I'm working on a very large bowl right now and I might be hitting 1000rpm and it's holding okay. I can't speak to acrylic as I haven't really had much experience with that medium. One important thing that is mentioned here is sharp tools. Sharp tools are a must so keep 'em sharp!

 

[magpens]

@leehljp

Thank you for the graphical info, Hank. . I had never seen those curves before ... and who doesn't like curves !!
But ... if you extrapolate the lower end of the graph below the 3" diameter limit shown ... the speed for a 3/4" pen blank gets ridiculous !!!
I doubt very much that it was the intention of the architect of the graph for us to use that data for that purpose.

I know that some folks play up the speed, even for pens, because by doing so you can achieve a higher quality finish, which approaches (and often reaches) their desired final surface quality. . That is admirable, and great if you can do it. . Factors other than pure speed come into that.

However, I think that a lot of us, especially for pens, rely on post-turning processes, like sanding and micro-meshing, to achieve our goals.
And since I have to do that anyway (for a variety of reasons, one of which is imperfect lathe skills including sharpening skills), there is really no point in speed. . When it comes to so-called acrylic materials, speed can work against achieving fine-finish goals, and skill could be a factor there also.

I am not at all embarrassed to say that I work at lowish speeds !! . A case of... "Do you want it fast, or do you want it good ?" . For me ... maybe !!!

 

[leehljp]

Ian mentioned fracture lines and stress cracks. I did not mention that aspect but one of the points behind the chart is safety. The chart is a "general" recommendation for speed/diameter ratio. At some point the centrifugal force becomes greater than the wood can bear.

 

[JimB]

The speed you choose is determined by multiple factors... your comfort level, your skill level, size of the blank, is it in balance or out of balance, condition of blank, and what your lathe is capable of without vibration.

when I first started turning I turned primarily pens and other small spindles. 1000 rpm felt really, really fast. Over time I started going faster and found it was easier to turn faster and I got a better cut.

I've been turning for 12 years. Now most spindle work is done at 2500 to 3200 (Max speed on my PM). Bowls are a very different story. Blank size and balance are very important consideration. Large out of balance blanks I start at 300 to 500 but below vibration speed. As the blank gets round and better in balance I increase speed. Once round and in balance I will turn bowls anywhere from about 800 to 2000 rpm depending on size.

One very important consideration is your own skill level. Getting a catch at high speed is an experience you will never forget so if you tend to get catches slow down the lathe. Also, a face shield is not optional. I always wear one even when turning something as small as a pen blank.

Most importantly, turn at the speed that is right for you. I have taught many people to turn. I encourage them to try different speeds but I do not recommend they turn as fast as I do As that would be dangerous for them.

 

[Charlie_W]

Pen turning is totally different as the blanks are captured on a mandrel/between centers as compared to turning with a chuck or faceplate and speed can be increased without "too much" risk. For chuck and faceplate turning, one should support the work with the tailstock as long as possible.
If you look at the directions that come with a chuck, it will also give speed recommendations per diameter.
Remember, Turners have turned for generations with a variety of lathes including treadle and pole lathes. Sharp tools, slicing cuts, and operator skill are key. Even with regular spindle turning, wood selection, grain, diameter and length as well as final turned diameter all come into play. Experience will help you decide on speed.
I generally turn on the slower side.....don't think I've ever turned anything at 3,000rpm.

 

[Don Rabchenuk]

I turn my pens about 3500 rpm. from square to round. I get less chatter going at that speed because the tool has less time to bounce off the corners. I drill at 500 and sand somewhere between 500 and 900. Your mileage may vary.

 

[walshjp17]

I'm with Dan (djeljr). I turn pens at 3400 RPM+ regardless of the material. Of course, if there are cracks, inclusions or other abnormalities, they need to be taken care of (filled, cast, etc.) before you start turning. Drilling and sanding speeds are similar to Dan's.

 

[Chasboy1]

Well FWIW, I'm 72 and agree with all that's been stated here. I have a 'manual tachometer' that my Dad gave me. He was a machinist with Norden during WW2 and left me a lot of stuff.