Need for speed.

[Al Chavez]

I've been turning on a Powermatic 2014 that has three belt positions. That allows for 15-900 rpm with high torque, 30-1800 rpm, and 60-3600 rpm.
I am a relative newbie and have been turing around a 12 months in the last 18 months.

Up until recently have not changed the belt from the lowest setting.

Now I am chasing after an extremely smooth finishing cut. What speeds and tools do you all recommend for finishing cuts?

I am using a reground 1 1/4" round nose scraper with a 25° negative rake angle. I have been sharpening both faces (80° and then 25°) and using a 600/1000 grit diamond stone to remove the burr left from the wheel. I then use a carbide rod to raise a burr on the 25° face. Now I am using it at between 1800 - 2500 r.p.m.s. I have noticed that the burr does not last very long. I've also noticed the scraper will catch on the tool rest so now I've rounded the bottom edges of the negative rake scraper and I have started filing my tool rest smooth and then applying that green lubricant stick for sharpening tools onto it. That helps.

In addition to the negative rake scraper I have been using a two faced skew with both faces ground to 35° (70 ° total). This works as well... maybe better.

Lastly I will use my5/8ths" bowl gouge with a 55° bevel and long swept back wings. Good results.

What speed do you use with these tools for finish cuts?
Any other tool that seems to cut better at 2500 r.p.m.s?

I have not joined a local club and may not until things settle down a bit. I do watch many Y.T. demos so even a few of those would be appreciated if they are especially good.
What tools do you use for 2500 + r.p.m.s or tools to absolutely avoid at faster r.p.m.s.

Thanks in advance.
Al in Texas~

 

[hockenbery]

What ar3 you turning?

Turning speed is dependent on the diameter of the pieces.
Larger diameter -> slower speed.

Feed rate of the tool is dependent on speed and diameter
Faster speed -> Faster feed rate
Larger diameter -> faster feed rate.

This last part is important if you are cutting on the wrong line a lot more of the bad line will be cut at a higher speed.
Bad things happen faster at higher speeds.

Try the 2nd pulley position after roughing round it should do well below 900 rpm and let you experiment with higher speeds.
For bowls & hollow forms the middle belt works best for me.


2500 I use a skew and spindle gouge. This speed is for spindles and finials. Small diameter higher speed.

 

[Kevin Jenness]

Rotational speed absolutely depends on the size of the workpiece. 2500 rpms on a 3" diameter spindle may work well, but could lead to disaster on an 6" bowl with a hidden crack. A rule of thumb I refer to suggests finishing speeds according to the formula diameter in inches x rpm =6000-9000. That's not gospel but should keep you out of trouble with sound workpieces. Sometimes a relatively lower speed can work to cut down chatter, sometimes faster is better. Vibration is bad. Toolrest height is also a factor.

Negative rake scrapers are generally said to work with an included angle of <90 degrees. You might want to change the bottom angle on yours to 60 or so and see if it works better. The burr doesn't last long, it's the nature of the beast. I tried the burnishing process you are using for a while but have gone back to using the burr off the wheel as I don't see a great deal of difference.

 

[Dean Center]

For spindles, the official number is 6000 divided by the diameter in inches. Not sure about face grain turning. Your lathe manual has a suggested speed for turning in it. I suspect most of us turn at the speed that seems 'comfortable' (unless we've just had a class with Jimmy Clewes, then we feel obligated to turn at an uncomfortable speed )

 

[robo hippy]

About 3 years ago, I got my first lathe that actually had a read out for rpm. That means that I learned to turn 'at the correct speed'. Some turn at scary fast speeds, some turn slower. With my American Beauty, I have 3 speed ranges, and I had the speeds changed so mid range is from about 15 rpm up to about 2200. This suits my bowl turning range just fine, and being on the mid range gives me plenty of torque for coring. I might turn a 6 inch bowl at around 2000 rpm. A 14 inch bowl at maybe 1000 rpm, but again, I don't know for sure. Some of determining the 'correct' speed is learning what feels best. Most find it easier to get cleaner cuts at higher speeds. Important thing to remember is that accidents get much more 'spectacular' at high speeds.

As for tools to use, I use a scraper for all of my roughing. I will use a NRS for sweeping cuts across the bottom of the bowl, but seldom use them for the transition or coming up the sides of a bowl. Scrapers tend to pull on the fiber more than gouges. This includes NRSs as well. I prefer a shear scrape for my finish cuts. I do have videos about this up on You Tube. Check out 'Scary Scrapers' and Shear Scraping, under robo hippy. A bunch on sharpening and gouges too.... Haven't done one on the NRSs yet though, hopefully this fall some time. One side note, I will NEVER use a scraper for a finish cut anywhere near the rim of a bowl, especially ones over about 6 inch diameter. The wall will start to wobble, which can lead to a massive catch and destruction of your bowl. "My bowl made this strange screeching and howling sound and then it blew up!"

You may want to consider new weapons for your arsenal, well maybe more weapons. The swept back gouges are kind of a one tool does everything type. I like the more specialized tools. I have a bunch of 40/40 grind gouges, and a bunch of BOB (bottom of bowl) tools. They just seem to work better.

robo hippy

 

[Al Chavez]

Thanks for all the replies.
I typically have been turning small hollow forms and bowls 6 - 8 inches in diameter. I have started turning smaller spindles and finials so all the guidelines above will be easy to apply. I will try a 60°/25° on my negative rake scraper. Reed, I'll be watching your YT videos to hone my skills especially the shear scraping one.
Thanks everyone.
Al

 

[Doug Freeman]

Speed - machine cutting (vs hand, a knife, etc) is a function of surface speed. Others have commented on rpm vs dia and the “thumb rules” work pretty well.

Dont doubt you havent had much success with nrs angles of 80/25. Just too blunt. 60/25 will do better. I prefer the same angle on both so that the tool can be used either direction. I settled on 35/35, but anything from 40/40 to 25/25 will work.

I have great success honing off the grinding burr and using a carbide burnisher to raise the burr - stronger, sharper, longer lasting. If its a bit rougher cut I’ll use the grinder burr till it wears out, then hone and burnish. If its the last little bit just prior to sanding I always use a burnished burr. The edge needs to be sharp prior to burnishing - if it isnt then the edge wont do much. Typically use a 600 gr dia hone last to get an edge, more coarse may be required 1st to get the bevel planes to meet in a sharp edge.

 

[Dean Center]

Al, if you're doing spindles, you will get a better surface from a skew than a NRS on most woods. And the upper end of the official speed formula is 9000 divided by diameter in inches.

 

[Tim Connell]

Good comments above on tools and the sharpening of them. As to speed, I paid attention to the "rule of thumb" that everyone mentioned for the first few months I was turning, had no experience, so I needed something to go by. Now, I do similar to what Reed mentioned, turn at the speed that feels right. I'm sure I'm probably turning faster than the "rules" say I should, but so what, I've never been one to follow rules anyway.

My midi Rikon has three ranges: the lowest I use for very unbalanced work, the middle for most bowls and hollow forms, and crank it up on the third range for almost all spindle work.

As long as you aren't getting excessive vibration, try increasing the speed over your normal range and carefully work the piece. If you never work outside your comfort zone, you'll never discover what you are capable of achieving. Of course, always keep in mind that there is a difference between uncomfortable (when you are developing skills) and dangerous.

 

[Al Chavez]

Thank you everyone.
I changed the bevels on my negative rake scraper to 40°/40° yesterday. It makes sense to be able to use both sides to use in either direction. I haven't had a chance to use it yet but I am excited about it.

I have a much better idea about the ranges of speed for my lathe and what circumstances to use them. I like the advice and general consensus about what speeds most use for bowls and hollow forms since that is what I mostly do now. And the general rule of thumb for spindles is helpful to as I am starting to do more finial work. I appreciate all the replies.

 

[robo hippy]

Most of my NRSs are ground 30/60, and I burnish a burr on them. I do have one that is a a 45/45 and burnish a burr on it. It seems to work well. As near as I can tell, you need a certain amount of metal under the burr to support it. Skew chisels are generally 30/30, and that burr is gone instantly. Sorby tools had a 'hard wood negative rake scraper' which was about an 80/25. I did try that grind and didn't like it. Too much metal under the blade, and almost impossible to burnish a burr on it. The nice thing about having the same bevel on each side is it makes the tool easy to reverse. With my 30/60 NRSs, and my platform, it is simple to change angles. I do keep one left handed one for cleaning up the insides of my recesses. The NRS leaves a flatter surface for reversing the bowl so there is less run out than I can get with a bevel rubbing cut.

robo hippy

 

[Tim Starliper]

For spindles, the official number is 6000 divided by the diameter in inches. Not sure about face grain turning. Your lathe manual has a suggested speed for turning in it. I suspect most of us turn at the speed that seems 'comfortable' (unless we've just had a class with Jimmy Clewes, then we feel obligated to turn at an uncomfortable speed )

We had Clewes doing a demo for our club a number of years ago (when they were still going around doing such things). As I recall, he cranked up the lathe, and the lathe started walking across the floor. I forget what lathe it was, but is was one of the big heavy ones (pretty sure it was NOT a Powermatic). Wound up bringing out the floor jack to jack up the ends and put rubber mats underneath to keep it in place. Sounded like a plane engine winding up for takeoff.

Having said that, I do turn some things at 3500 - mainly pens that are either resin or hybrids of resin and wood. I also polish pens at that speed. Bowls and such, I rarely get over 1500 - and that is more for setting a friction polish than turning.

 

[Kevin Jenness]

We had Clewes doing a demo for our club a number of years ago (when they were still going around doing such things). As I recall, he cranked up the lathe, and the lathe started walking across the floor. I forget what lathe it was, but is was one of the big heavy ones (pretty sure it was NOT a Powermatic). Wound up bringing out the floor jack to jack up the ends and put rubber mats underneath to keep it in place. Sounded like a plane engine winding up for takeoff.

I wouldn't sit in the front row at that show.

 

[Tim Starliper]

I wouldn't sit in the front row at that show.

I was at the back. And off to one side.

We did have a shield set up, but that does not guarantee that something won't fly into the audience.

 

[Dean Center]

I wouldn't sit in the front row at that show.

But you want to be up close for when he sets fire to the alcohol soaked piece.

 

[Tim Starliper]

But you want to be up close for when he sets fire to the alcohol soaked piece.

That's why you have a camera up front, that and to record the inevitable carnage!

 

[Bill Boehme]

I've been turning on a Powermatic 2014 that has three belt positions. That allows for 15-900 rpm with high torque, 30-1800 rpm, and 60-3600 rpm.
I am a relative newbie and have been turing around a 12 months in the last 18 months.

Up until recently have not changed the belt from the lowest setting.

Now I am chasing after an extremely smooth finishing cut. What speeds and tools do you all recommend for finishing cuts?

Going at breakneck speed is the best way to be the first one to arrive at the scene of an accident.

In the eleven years that I have owned my Robust American Beauty which also has three drive-belt ranges, I don't believe that I have ever used anything other than the lowest speed range. If your goal is the smoothest possible tool surface, I would suggest working on your sharpening and tool control skills. Despite what one well-known demonstrator says, speed isn't necessarily the answer to a better finish. Unless you absolutely really know what you are doing, turning at high speeds on larger pieces can result in a much worse surface.

.... What speed do you use with these tools for finish cuts?
Any other tool that seems to cut better at 2500 r.p.m.s?

I usually get nosebleed at speeds over 1000 RPM.

... I have not joined a local club and may not until things settle down a bit. I do watch many Y.T. demos so even a few of those would be appreciated if they are especially good.

I understand your concern, but as soon as you feel comfortable, join the San Antonio club and get with a mentor.

 

[Odie]

If your goal is the smoothest possible tool surface, I would suggest working on your sharpening and tool control skills.

Truth here..... ^^^^^

As with many turners who have evolved, there was a time when I, too, felt the need for speed. In my opinion, the one critical reason for giving a turner this impression.....is, not understanding that your tool could be sharper. If you hold up a piece of paper and swipe at it with a reasonably sharp knife, the faster the blade, the cleaner the cut on the paper. To a point, the blade can be traveling slower, and have just as good results......if the blade is sharp-er.

Over and over again, I've heard turners exclaim how sharp their tool is.....after, experienced turners tell them they suspect sharpness could be an issue. For these turners, it's hard to convince them that sharpness is their problem. They will just have to learn by experience, if their inner voice is telling them the truth.....and, they listen to it!

I am foremost a bowl turner who seldom goes any smaller than 6" diameter bowl blanks. My lathe capacity is 16", but I limit the maximum to around 14" diameter bowls. I have my belt setting at 0-1200rpm, and it pretty much stays there. I seldom go over 800rpm, and the rule that governs the speed is eliminating as much residual, or harmonic vibration as possible. Each piece of wood is unique to itself, and there really isn't a formula to determine the best universal rpm according to size. If the bowl has vibration, I don't care how sharp your tool is.....it will be impossible to get that ever elusive "perfect cut". (My definition of a perfect cut, is entirely dependent on the amount of sanding that is required to get the best surface quality prior to applying a finish.)

-----odie-----

 

[Randy Anderson]

Early on I felt I was doing something wrong because I didn't/couldn't turn at super fast speeds like the pros I see online. Like Odie I seldom turn at breakneck speeds. I turn mostly natural edge bowls so 600-800 is my comfort speed for most things. Sometimes you just have to accept that the crotch piece with an odd shape can only spin at 450 and make it work. I may take a traditional bowl or hollow form up to 1000 if it warrants and doesn't start to vibrate. For me a sharp tool, a piece spinning without vibration and cutting at a rate that the speed supports works well, regardless of what the digital tach says. I don't do much spindle work but do turn at faster speeds when I do but still not the near light speed I see some turners go for.

 

[Al Chavez]

Thanks everyone for sharing their experience here.
I feel very comfortable with the lowest belt setting and most of my pieces seem to be roughed out at >500 and finishing cuts made at >1000. I am working on sharpening and now honing my tools more often. I appreciate the feedback about lathe speeds and a need for sharp tools.

 

[Dean Center]

I'm guilty of making fun of turning at heroic speeds, but I don't actually recommend it. Since my lathe doesn't have a tachometer, I can't tell you what speed I turn at, but I'm not brave enough to try 'increasing the speed past the vibration'. As an impatient person, I generally like to be up there just under the vibration speed for roughing, whatever that is for the particular piece of wood. For finishing cuts, where the wood is balanced and I could go faster, I don't find myself turning the speed up, but rather switching to the tools that seem to cut the best in my hands. Freshly sharp, of course.

 

[Kevin Jenness]

Sometimes increasing the speed past the initial vibration point will give a smoother ride - it depends on the piece. This morning I am hollowing out a tall piece less than 4" diameter with a void the entire length held together with plywood hoops on the outside. It rattles like crazy at about 400 rpm, but runs smoothest at about 1000-1200. That said, I like to keep it down to a dull roar - when the lathe is shaking so are my knees. And frequent sharpening is good no matter the rpms.

 

[Tim Starliper]

For spindles, the official number is 6000 divided by the diameter in inches. Not sure about face grain turning. Your lathe manual has a suggested speed for turning in it. I suspect most of us turn at the speed that seems 'comfortable' (unless we've just had a class with Jimmy Clewes, then we feel obligated to turn at an uncomfortable speed )

When I replied to this previously, I didn't address the beginning of your post, just the Jimmy Clewes Breakneck Speed part. If I use the spindle 'formula' for pens (which is essentially spindle turning), then my max would be ~12000 - given that the average size of a pen is 0.5". I think I will stick to 3500 for my pens

The comments about bowls and such - I generally will rough at a low speed. How low depends on the piece - composition and size. Low as in the 400 - 800 range. Once I get it roughed, I generally turn in the 1000 to 1500 range, usually the lower end of that. If I am using a friction polish then I run at 1500 or a bit higher just to generate the friction and heat to set the finish. The actual turning was still under 1500.

 

[Bill Boehme]

A rule of thumb I refer to suggests finishing speeds according to the formula diameter in inches x rpm =6000-9000. That's not gospel but should keep you out of trouble with sound workpieces.

For spindles, the official number is 6000 divided by the diameter in inches. Not sure about face grain turning. Your lathe manual has a suggested speed for turning in it. I suspect most of us turn at the speed that seems 'comfortable' (unless we've just had a class with Jimmy Clewes, then we feel obligated to turn at an uncomfortable speed )

I would like to add clarification for the benefit of beginners who might misinterpret the rule of thumb developed by Dale Nish. When you plug in the diameter and use the constants 6000 and 9000, the range of RPM that you get is not a recommended operating range, it's actually a DO NOT EXCEED range. I wish that the rule of thumb produced just a single number because I feel like that would be less likely to cause misinterpretation.

 

[Pat Patterson]

I would like to add clarification for the benefit of beginners who might misinterpret the rule of thumb developed by Dale Nish. When you plug in the diameter and use the constants 6000 and 9000, the range of RPM that you get is not a recommended operating range, it's actually a DO NOT EXCEED range. I wish that the rule of thumb produced just a single number because I feel like that would be less likely to cause misinterpretation.

Bill, my algebra might be a little rusty can you help me out? With the formula given it would resolve thus:
inches x rpm=6000-9000
rpm= 3000/inches
10inch bowl rpm= 3000/10
rmp=300 ???
Thanks,
Pat

 

[Brian Gustin]

Bill, my algebra might be a little rusty can you help me out? With the formula given it would resolve thus:
inches x rpm=6000-9000
rpm= 3000/inches
10inch bowl rpm= 3000/10
rmp=300 ???
Thanks,
Pat

Actually, think of it more like this: if you have a 10 inch bowl, divide 6000-9000 by that size, giving you 600-900 RPM as a recommended safe turning speed for a 10 inch bowl

In other words 10 inches x 600 RPM = 6000 which is the lower end of the 6000-9000 range

 

[Pat Patterson]

Actually, think of it more like this: if you have a 10 inch bowl, divide 6000-9000 by that size, giving you 600-900 RPM as a recommended safe turning speed for a 10 inch bowl

In other words 10 inches x 600 RPM = 6000 which is the lower end of the 6000-9000 range

Now I get it. The minus sign is what threw me. thanks
Pat

 

[Bill Boehme]

Brian’s explanation agrees exactly with the source of the rule of thumb, the Craft Supplies catalog as shown in the screenshot below.




I may have misspoke in my previous post. Every piece of wood is unique. What is a safe speed for turning one piece of wood might be too fast for another piece so use a rule of thumb for what it is, just a generalization and not something that you can chisel in stone.

My memory isn’t what it used to be, but FWIW it seems like the rule of thumb imight have changed a bit from what it was a couple of decades ago. For the example 8” bowl in the screenshot, the way that I read it is that the lathe spindle speed should fall in the range of 750 to 1125 RPM. My recollection from long ago (which very possibly might be in error) is that the maximum safe turning speed would be in the range of 750 to 1125 RPM, but it is safe and acceptable to turn at a slower RPM. I don’t think that I would feel comfortable roughing an eight inch bowl at 750 RPM or faster. I might increase the speed into that range during the final turning.

 

[hockenbery]

Guideline are nice. My lathe doesn’t have digital readout. Each piece of wood will have a different best speed.
This the process I use for starting unbalanced blanks. Few will ever be totally balanced from the saw.

Balance the weight if you start between centers.
Put the blank on the lathe between centers and shift the tail center to balance the weight.
Put the heavy side up if it falls rapidly shift the center toward the heavy side. Repeat until it

1. Choose a belt position - guidelines are good.
2. Increase the speed from 0 to the unacceptable vibration.
3. Increase the speed slowly -
A. If the vibration gets a lot worse back off to the highest acceptable vibration and start roughing.
B. Usually the vibration will decrease below the acceptable dial in the least vibration and start roughing.

As you get into round the blank vibration will go way down.
Check the tail center and move it if you need to line up the grain, rims, etc. if you shifted for weight to start to probably need to get the grain lined up.
If you shift centers dial to 0 and find the best speed again.
As you rough into round you can increase the speed always seeking minimal vibration.