Turning speeds

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Jans husband

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I can't find the answer (so far) on the IAP Site about this, so how do you determine the turning speed of a pen blank, whether wood or acrylic ?

How does it vary depending on the wood or type of acrylic being turned?

There must be some general rules, but what are they?

Any help appreciated!!

Thanks

Mike
 
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jttheclockman

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Fast as you can go or at least at top speed of your desired belt setting. Makes the tools react better when speed is increased if you have sharp tools.
 

Jingle57

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IMHO you have to go with the combination of tool used, material being turned and your experience. I've watched a number of videos from a lot of turners and it seems turning with acrylic at the highest speed your lathe will turn and using tools with carbide inserts does well for them. I started turning acrylics and cutting with carbide works well for me at about 2800 RPM, care must be use to not overheat tool and material. I've also used HHS skews, roughing gouges, and spindle gouges, on various material with some success. Sanding at lower speeds seem to work well for me. I haven't done much with unstabilized material but I adjust speed to what woks best with the tool/material combination. In either case sharp cuttings weather it be HHS skews, spindle gouges, or any carbide tool, is essential.
 

Jingle57

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My fingers don't work so well sometimes so excuse the spelling, where's the spell checker when you neeeeed it.
 

Dehn0045

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For me the only downside to 'fastest my lathe will spin' is that I TBC with no bushings and when I kick on the lathe the blank sometimes spins a little while the live center gets up to speed. I also don't have VS, so I go with the second highest speed (I think it is around 2400, maybe 3200...). At this speed I am able to kick the lathe on with the blank reasonably snug between centers and it usually doesn't spin relative to the live center. If it is not holding well between centers I'll snug up while its spinning, but in general faster is better when TBC.

Also, consider that low speeds on a non-VS will give you more torque, but on most inexpensive VS lathes low speed will reduce torque.
 

Jans husband

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Thanks for the speedy responses,
But does the best speed vary for different materials?, and we hear very often about keeping materials cool during turning and especially drilling, (I do all my drilling on the lathe)
I tend to drill quick through acrylic-2000- and slow-800rpm-through wood, and turn at those speeds as well, but sometimes I get smoke or smell!!
 

Dehn0045

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I drill at 500 on the lathe for everything, would go slower with some materials but that is the slowest speed on my lathe. I've never had a need to go faster. Faster speeds while drilling can definitely generate more heat, some materials (snakewood, buffalo horn, etc) can't take much heat. Smoke while drilling is probably not great for any material.

If you are getting a lot of heat while turning at fast speeds it is probably more likely due to dull tools IMHO. Carbides tend to be less sharp compared to honed HSS. Slower speeds may help, or sharper tools. When talking pen blank sizes, 2000 to 4000 rpm shouldn't be a problem while turning.

I don't turn a lot of plastic, but a 'melting plastic' smell is pretty common while turning even though the blank is fairly cool.

High speeds while sanding will definitely generate more heat.
 

Jingle57

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I generally use NOVA Pen Plus jaws or a collet chuck, Pen plus for square blanks, collet for round, I'll center the blank with a live center, push a dimple into the blank, replace the live center with a drill chuck and drill appropriate size hole for my requirements, cut blank to size. I'll mount the blank on a mandrel, with appropriate bushings, install my mandrel saver, tighten everything then start turning. I don't usually experience any slipping at start-up. This is what woks for me.
 

Paul in OKC

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I drill around 700-800 on my drill press, mostly because I'm too lazy to change the belts, but it is a good speed for about any blank. I clear often. Turning......full tilt boogie. The only time I might slow down is when I am turning a piece of a tree branch that may start out 'wonky'. Once I cut the OD down a bit I go full rpm. (Non VS Jet lathe)
 

peter1958

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I can't find the answer (so far) on the IAP Site about this, so how do you determine the turning speed of a pen blank, whether wood or acrylic ?

How does it vary depending on the wood or type of acrylic being turned?

There must be some general rules, but what are they?

Any help appreciated!!

Thanks

Mike
Hello Mike,
Drilling as slow as the machine goes, 400 rpm is my slowest but my drillbits warm up. So sometimes drilling in 2 stages.
Turning the blanks as fast as the thing goes, mine 3200 rpm. sanding 800-1600 rpm in my case. dry sanding at 1600 rpm, but carefull with temperatures, 800 wetsanding, CA application at 400 rpm. But i have to say that the lathe has 4 pulleys, no electronics.
first pulley 400 and 800 rpm (400V machine fast and slow) second 1000 and 2000, third 1200 and 2400, last one 1600 and 3200 rpm
 

leehljp

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I'm not into cast material that much, but there is one (cast material) that is somewhat brittle, and those new to it complain that chunks come out instead of smooth turning. The regular reply for those that do turn it is: SPEED. 2500 - 3000 rpm. But this applies to other acrylic and wood of different kinds also.

Some long time bowl turners come into pen making and are used are used to slower rpm. But overall, 2500 to 3500 rpm are used for turning down to size and even finishing. There is not much difference in the speed for cast material (generically described as acrylic) and woods of different kinds.

There are differences of the tools used. Skews do better on soft wood than scrapers do. Both do equally well on hard and dense woods.
An old timer long since departed wrote the following a few years ago:
RussFairfield said:
What is always left out of any comparison of tool finishes is the wood. All things being equal, shear scraping can leave a better surface finish than a skew chisel on the very hard dense and close grained species, but it can't come anywhere close on everything else.

If you really want to see the extreme differences, try using a both scraper and skew on Cocobolo, Blackwood, or Desert Ironwood. You will find that the scraper might be the better tool for these very hard species. At the opposite extreme, the scraper will be a disaster on a soft wood like Douglas Fir or Pine, while a sharp skew can leave a smooth clean cut and polished surface that doesn't need sanding.

The reason I am referring to tools, you asked about turning speeds for the different kinds of material. Overall, speed differences between material are not as relevant (except higher speeds) as tools for different wood densities. Even then, with skilled experience, even the drawbacks can be overcome.

Example of speed differences on soft wood:

The next is bowl turning chart - diameter as it relates to safe speed:

Bottom line: The material is irrelevant, it is the diameter in combination with the speed.

BUT - There IS a difference when metals are involved.
 
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peter1958

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I looked in some old manuals, 1985 it says.
There they talk about 3 meters/second for turning and 5 meters/second for scraping.
On a pen 20 mm thick it is 3/(0.02*3.14159)*60=2865 rpm for turning.
So if thinner (most are) faster if you can.




2864,791​
 

harik.raif

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Some long time bowl turners come into pen making and are used are used to slower rpm.
I think this is what is happening to me. A simple "I'd like a nice mechanical pencil" from my brother has led to a great deal of expenditure, new tools mandrels the whole 9. Now that I'm actually turning, I keep breaking through the blank at about 3/32s (maybe :) ). I'm turning around 1800 which seems blazing fast :) but I guess I have to turn it up to 11. The wood is zebra wood which is pretty open grained and pretty hard. Perhaps my tools need to be sharper too. You can get away with more perhaps with green bowls.
 

howsitwork

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As Hank said it comes down to tools, technique and sharpness as much as to speed. With a 3/4” square blank I’d guess Im starting off at about 700 rpm with a freshly sharpened hss roughing gouge until the corners are removed the. I up the ante to probably about 1500 and might switch to my round hss skew or stick with the roughing gouge until I’m down to say 3/8 “ diameter.

I like the mass of the roughing gouge as it dampened any vibration as well as taking a nice shallow cut . I’m in no rush and seem to get fewer breakouts that way. On Acrylic Or other plastics I again start with the roughing gouge but am VERY GENTLE until the corners are removed and the size reduced somewhat. If I start to get chipping , I either resharpen and / or re hone and gently go back in.

Drilling I doubt I ever exceed 700rpm , usually slower with frequent withdrawal of the drill bit to keep the flutes clear of chips.
 

qquake

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I "knock" the corners off on the bandsaw before I turn acrylic blanks. Makes it much easier to rough them. I use a carbide chisel at an angle so I get a "shearing" cut. I turn at 2000 rpm for roughing, shaping, sanding, and finishing.
 

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leehljp

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Yep, Most bowl turners turn too slow
I think this is what is happening to me. A simple "I'd like a nice mechanical pencil" from my brother has led to a great deal of expenditure, new tools mandrels the whole 9. Now that I'm actually turning, I keep breaking through the blank at about 3/32s (maybe :) ). I'm turning around 1800 which seems blazing fast :) but I guess I have to turn it up to 11. The wood is zebra wood which is pretty open grained and pretty hard. Perhaps my tools need to be sharper too. You can get away with more perhaps with green bowls.

Yep, Most bowl turners turn too slow with pens when they start off. Simply do the math, or I will do it for you (But it has been 60 years since algebra class - so I could have punched the wrong formula in):

12" bowl at 700 RPM:

12” x 3.14 = 37.68 inches
37.68” x 700 rpm = 26,376 inches per minute on the outer edge
26,376” / 12” = 2198 feet per minute
2198 FPM x 60 minutes = 131880 ft per hour
131880 ft per hour = 24.97 MPH

24.97 MPH is the cutting speed of a 12 inch diameter bowl (on the outside diameter) at 700 rpm.


3/4" diameter blank at 3000 RPM Notice the speed difference!

.75 x3.14 = 2.355 inches
2.355 x 3000 rpm = 7065 inches per minute on the outer edge
7065 / 12” = 588.75 ft per minute
588.75 FPM x 60 minutes = 35,325 ft per hour
35,325 ft per hour = 6.69 MPH

6.69 MPH is the cutting speed of a 3/4” diameter rod at 3000 RPM

ANOTHER Misconception (Tied to the above): Slow speed causes more catches than Fast Speed.


Even if you cranked the speed up to 4000 rpm, it would be slower than a 12 inch bowl at 700 rpm or even 500 rpm.


PLEASE: someone check my math and formula. I am not interested in being right, I am interested in WHAT is right. IF I made mistake, I want to know it and just get the right/correct information out there. Thanks.
 
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magpens

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I use a metal-working lathe and carbide cutting tool.

I turn pens (both wood and "acrylic") at about 1200 RPM at the fastest ( initial rounding of a square cross-section pen blank), and often lower.

Much lower for drilling (about 300 RPM ?), but I do not have a tachometer so cannot give precise numbers.
 

peter1958

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3 meter/second is 10.8 km/hour = 6.75 miles/hour
Some woodturners (stuart batty) turns bowls at about 40 miles/hour with his 40/40 grind.
On my lathe is a matrix of speeds and diameter, i'll post a picture here.
It has a 4 pulley drive and 2 electric settings for slow and fast, So beltchanges are frequently done.
400 rpm is slowest 3200 is fastest speed.
Then i use all different turning tools, hss gauges and chisels, carbide roun and square scrapers, but my favourite gauge is a spindle gauge about 13 mm or 1/2 inch, very hard kobalt steel. Powder technology of Crown. Extremely hard and touch
 
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peter1958

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Finally took some pictures of the lathe.
1. the table of speeds and diameters on the lathe
2. specs
3. 2.2 meters between centers and some bedstorage.
 

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leehljp

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Thanks Peter, for the picts. One item mentioned but not specifically for the purpose - is sharpness. With the slower CUTTING speed on pens (but higher RPMs) the slower cutting speeds most definitely need tools with sharper edges.

I had a good discussion a couple of years ago on another forum with a friend who had been a bowl turner for years. Sharpness to many bowl turners in his camp said that a very good slow speed grinder with a quality stone is all that is needed. I quoted to him an article by a reviewer of a Tormek system, in which the writer said, "of course, any grinding needs to be followed up with good honing. Sharpness is not complete without honing."

This is especially true for tools used on pens blanks and their slower cutting speed.
 

peter1958

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Thanks Peter, for the picts. One item mentioned but not specifically for the purpose - is sharpness. With the slower CUTTING speed on pens (but higher RPMs) the slower cutting speeds most definitely need tools with sharper edges.

I had a good discussion a couple of years ago on another forum with a friend who had been a bowl turner for years. Sharpness to many bowl turners in his camp said that a very good slow speed grinder with a quality stone is all that is needed. I quoted to him an article by a reviewer of a Tormek system, in which the writer said, "of course, any grinding needs to be followed up with good honing. Sharpness is not complete without honing."

This is especially true for tools used on pens blanks and their slower cutting speed.
Yes, sharpness is necessary, once did see a bowlturner turn a bowl with a spoon, sharpened and honed! that worked well. I like the CBN wheels very much. I tried once to sharpen and turn on such a wheel, what a revelation that was, Now i want to buy a grinder with 2 cbn wheels on it. But need to save some more.
 

Chasper

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I turns pens at 4,000 which is the max speed for my lathe. Same speed, no matter what material, but mostly I turn resins. If my lathe went faster I would still turn at maximum.
For drilling I set the speed at 500
 

peter1958

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I turns pens at 4,000 which is the max speed for my lathe. Same speed, no matter what material, but mostly I turn resins. If my lathe went faster I would still turn at maximum.
For drilling I set the speed at 500
My max is 3200 rpm which is pen turning speed, drilling at 400 rpm or at the drillpress with 120 rpm, depends on the blank.
 

egnald

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The rule of thumb that I learned was that stock 2-inches or smaller in diameter should be turned at 3000 RPM, but slower until the stock has been turned round. So far I have only turned pens that are 1-inch or smaller so I max out my lathe at about 3500 RPM for turning. Like many others I cut my blanks down with a bandsaw to an octagon shape before starting to turn so they become round very quickly. - Dave
 

Jans husband

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Thank you all for contributing to this thread,
There seems to be a big difference between the various speeds used by the Turners at IAP, and of course it must all come down to personal preference and at what speed you feel comfortable at your lathe with the tools you have available.
What is surprising to me as a relative newcomer is the fact that some turn at twice the speed of others and all produce an excellent pen at the end of it!
So, I suppose it is "what works for me"

Mike
 

monophoto

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So, I suppose it is "what works for me"
Pretty much.

One general rule is that pen turning involves higher speeds than bowl turning. There was a post earlier this week that discussed the relationship between speed and diameter and pointed out that what really matters is the surface speed of the turning as it passes the edge of the tool.

The other general rule is that you should not turn at a speed that makes you uncomfortable. Safety is always a major consideration in turning - turning can be dangerous, and you must take precautions to protect yourself. But as you gain experience, your personal threshold of what is 'too fast' will increase.
 

leehljp

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Thank you all for contributing to this thread,
There seems to be a big difference between the various speeds used by the Turners at IAP, and of course it must all come down to personal preference and at what speed you feel comfortable at your lathe with the tools you have available.
What is surprising to me as a relative newcomer is the fact that some turn at twice the speed of others and all produce an excellent pen at the end of it!
So, I suppose it is "what works for me"

Mike
Mike, the OP is intended to focus on a misconception by more than a few - concerning turning speed. I have been on this forum for 16 years now and read posts regularly. It is not "just a matter of preference" per se - because consistently going back these 16 years, many slow speed users were taught to "never turn more than 1000 rpm" and these turners in particular are the ones that have problems with acrylic and cast blanks. Some questions are from those who are just starting, but an equal amount is from experienced bowl turners. In the past few months, I have or others have replied to queries concerning "how to turn . . . acrylic/cast blank" constantly - because they were having difficulty.

After a few answers then someone, or me in a couple of cases, would ask: "What speed are you turning?" Answer: "1000 rpm."

Well, that was the problem. Their next reply was: I went to . . . for turning lessons and they said never turn more than 1000 RPM. (But the instructor meant that answer for turning bowls." Early on here on this forum, there were discussions in which several from the bowl turning community made comments that pen turners were turning too high - and that was what they were used to for many years. To keep this honest, there were bowl turners here who made excellent pens, but they also were perceptive, observant and intuitive and knew that smaller diameters required faster speed.

Yes, it is up to the individual, but there is also the reality that bowl turning rpm doesn't work as well as pen turning rpm for pen blanks. This was the purpose of this thread. And another honesty, the pen turning jig that was used over a flat bottom router bit in a router table "can work", it will cause problems with quality down the road. So does slow bowl turning speeds. That has been a problem for some here since the beginning. Yes, people can choose their own speed, and slower rpm speed does have more problems when it comes specifically to cast blanks, and in some cases with wood blanks.

I ran into this with a wood pen about 12 - 13 years ago. I made a segmented pen that I learned real quick could not be sanded. I did all kinds of things and it was a combination of two things that made it smooth without the need for sanding on the wood: speed 3000+rpm and razor sharp. No other way to produce that. I have run into a few bowl turners with knowledge and experience and they have made bowls smooth without sanding. Two things for them: Fastest safe speed possible for that diameter bowl and extra sharp tools.
 
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RichAldrich

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With variable speed.
Start at zero.
Increase to 2000 ish.

Turn round gently. Once round.

Raise and lower from 2000 to max.
Listen and feel.
Let the lathe and blank pick the speed.

Do not overstress the blank.
My 2 cent.
 
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