Bowl turning Harmonic vibration adjustments for the "perfect cut."

[Odie]

There is the vibration your lathe will produce at any given rpm and combine that with the vibration a chunk of wood spinning will produce at any given rpm......along with the effect a sharp tool has on the vibration at that rpm. If you can control all those things, it's possible to get a perfectly clean tearout free cut......provided the tool is sharp and the presentation of that tool is correct.

It cannot be stressed how much rpm effects the cleanest of cuts, and rpm must be adjusted precisely.

It also cannot be stressed enough just how much sharpness contributes to the "perfect cut".

One very good method of infinitely adjusting the rpm beyond what us mere mortals can is with a vibrometer.
You can't buy one of these, but you can easily make one, and here is a thread that will tell you how:

Thread 'Lathe vibration detector ideas please!'

Apr 21, 2019

I am looking for ideas for devices, or inventions for detecting minor vibrations on the lathe.

The purpose is to adjust the rpm to where the least possible vibrations are present.

Right now, I use my fingertips on the lathe bed, plus there is one long neck spot lamp that consistently gives me some good indications. Other lamps and fixtures on the headstock also help.

Assuming the best location would be connected to the headstock, but entertaining input, if any.

I have tried an antennae like affair that was not very successful.

I also have experimented with a jar of water, that was...

• Odie
• Replies: 103
• Forum: Woodturning Discussion Forum

=o=

 

[hughie]

There would be so many variables in this that makes it a quest of epic proportions. It seems everything would have a part to play in it, on top of species, wall thickness, toolrest, length of tool projection,tool thickness, sharpness, bearings, motor condition, belts, lathe construction,condition of lathe bed, stand construction, and floor to name a few. There probably would be a lot initial work to secure and remove other possible sources on the equipment before moving onto actually the cutting of the blank. This should prove to be a very interesting thread, a bit of a can of worms Odie

 

[Jason Matisheck]

All cell phones have a 3 axis accelerometer. Look for a vibration measurement app for your cell phone. (Not a vibration creation app, which is also a thing.) Figuring out how/where to mount it and what the data means is the real problem.

Here's an example: https://apps.apple.com/us/app/vibration-analysis/id817385888

 

[Odie]

There would be so many variables in this that makes it a quest of epic proportions. It seems everything would have a part to play in it, on top of species, wall thickness, toolrest, length of tool projection,tool thickness, sharpness, bearings, motor condition, belts, lathe construction,condition of lathe bed, stand construction, and floor to name a few. There probably would be a lot initial work to secure and remove other possible sources on the equipment before moving onto actually the cutting of the blank. This should prove to be a very interesting thread, a bit of a can of worms Odie

Yeah, I hear ya, Hughie......

Eliminating as much vibration as possible is only a piece of the puzzle.....but, the puzzle isn't completed until all the pieces fit together!

=o=

 

[Odie]

I'm surprised there isn't more discussion about the importance of eliminating any vibrations a lathe, the spinning wood, or the interaction between the two have in getting a perfect tearout-free cut.

I can tell you that I'm using my homemade vibrometer on every bowl I make ever since I first made mine in 2019. The results I'm getting now should be some indication to other turners just how valuable this can be in pursuit of that ever-elusive "perfect cut".

The perfect cut allows a bowl turner to eliminate aggressive sanding.....and when that happens, it's possible to maintain geometric integrity of the bowl. Side grain bowl turning is particularly subject to the effects of aggressive sanding because of the alternating long grain and end grain as the wood spins. The resistance to the cut is pulsating for your final finish cuts. The tearout free cut is important, because it allows the turner to accomplish many fine details that look good to the eye.

When you eliminate the harmonic vibrations (a very basic requirement for getting the perfect cut), the only thing that can hold you back is your skill level in other aspects of tool preparation and tool handling.

=o=

 

[hughie]

I think in some respects its a highly involved thread and not for the faint hearted. Back in the day I was involved in sound isolation and the national standard and it proved to be quite complex although not quite the same but there are some parallels I suspect, with mechanical isolation, equipment construction ie steel versus cast iron etc. We may have to assume that lathe, stand etc is in perfect condition and that we only need to concern our selves wood, tooling and the toolrest. I might start with sharpening, on a previous thread here it was discussed various types steels for gouge tips. The testing was based on duration of the cutting edge using known wood species and what we found that the finer the grind the longer the edge lasted and we ended up with 1000grit diamond lapping disc proved to be the most durable grind. I suspect much of this depends on artisans experience and ability as well as rpm's and whats being turned ie spindle or hollow vessel and wall thickness that this might be a nirvana type quest, but lets see what turns up - pun intended

 

[Odie]

equipment construction ie steel versus cast iron

Howdy Hughie.....I'm interested to hear of your conclusions regarding steel vs cast iron.

the finer the grind the longer the edge lasted and we ended up with 1000grit diamond lapping disc proved to be the most durable grind.

I'm currently using 600gt diamond hones, and I can concur with the edge lasting longer with a finer grit to create the edge. Also of note, is the edge seems to last longer with very fine cuts vs heavy cuts.

I also feel the very tip of the cutting edge is finer when the hone forms the edge from multiple directions. This pretty much makes a statement about the quality of the edge while hand honing vs from a spinning wheel.

=o=

 

[Kim Huggins]

If you could convert your vibration sound into an audible harmonic or a visible sine wave that should do. I just use my fingertips and the feel of the tool against the wood.

 

[hughie]

Howdy Hughie.....I'm interested to hear of your conclusions regarding steel vs cast iron.

I'm currently using 600gt diamond hones, and I can concur with the edge lasting longer with a finer grit to create the edge. Also of note, is the edge seems to last longer with very fine cuts vs heavy cuts.

I also feel the very tip of the cutting edge is finer when the hone forms the edge from multiple directions. This pretty much makes a statement about the quality of the edge while hand honing vs from a spinning wheel.

=o=

Cast has the ability to absorb vibration due to its microstructure, which contains graphite flakes that act as natural dampeners. Steel on the other hand transmits as it carries vibrations through its structure due to its high elasticity and rigidity as a metal. Interesting though if you fabricate a tool rest with several tack welded layers of mild steel it will act like cast iron.

 

[hughie]

Howdy Hughie.....I'm interested to hear of your conclusions regarding steel vs cast iron.

I'm currently using 600gt diamond hones, and I can concur with the edge lasting longer with a finer grit to create the edge. Also of note, is the edge seems to last longer with very fine cuts vs heavy cuts.

I also feel the very tip of the cutting edge is finer when the hone forms the edge from multiple directions. This pretty much makes a statement about the quality of the edge while hand honing vs from a spinning wheel.

=o=

one of the reasons why many if not all professional turners will highly polish the flute. Potentially, the finer the surface the finer the edge.

 

[Isaac Litster]

Maybe I am missing something, but what is the "perfect cut"? I think Ulf Jansson in Sweden has the perfect cut, as he can start sanding at a very high grit, and often the finish is glossy off the tool. He does sharpen tools past 600 grit I believe. Is this necessary for all woods? A wood such as a mountain mahogany, with nearly no pores, extreme hardness, fine grain, etc. is easy to cut. With a screwdriver (which I use often) I can get a polished-looking surface with no sanding. I would then assume there would be no incentive to put much effort into sharpening, lathe speed, lathe construction, tool rest, or other factors. On the other hand, a wood-like western redcedar is nearly impossible to cut with a freshly sharpened skew. But I don't see anyone turning western redcedar, so why is this a struggle? On most woods, even softwoods like yellow cedar, I haven't noticed a problem with tear out on a freshly sharpened tool, even with fine details. What species are you using that this is a concern?

That being said, from the miniature carving I do, I have grown to notice details that everyone else who sees the final product doesn't notice, so am I not noticing what the perfect cut is? Have I been striving for a mediocre cut, without realizing that I could be achieving the "perfect cut"? Is the polished surface off the tool possible with most woods?

As someone who doesn't care for sanding (I don't really have sandpaper to sand properly), I am interested in a "perfect surface". My 10x18 lathe doesn't have variable speed, and it stays at about 2000 rpm. Is it possible that I could get a better cut by reducing the speed with certain woods? Possibly on thinner pieces? Is there more to a "perfect cut" than having a freshly sharpened tool, taking a minuscule cut extremely slowly with a perfect technique?

 

[hughie]

Maybe I am missing something, but what is the "perfect cut"? I think Ulf Jansson in Sweden has the perfect cut, as he can start sanding at a very high grit, and often the finish is glossy off the tool. He does sharpen tools past 600 grit I believe. Is this necessary for all woods? A wood such as a mountain mahogany, with nearly no pores, extreme hardness, fine grain, etc. is easy to cut. With a screwdriver (which I use often) I can get a polished-looking surface with no sanding. I would then assume there would be no incentive to put much effort into sharpening, lathe speed, lathe construction, tool rest, or other factors. On the other hand, a wood-like western redcedar is nearly impossible to cut with a freshly sharpened skew. But I don't see anyone turning western redcedar, so why is this a struggle? On most woods, even softwoods like yellow cedar, I haven't noticed a problem with tear out on a freshly sharpened tool, even with fine details. What species are you using that this is a concern?

That being said, from the miniature carving I do, I have grown to notice details that everyone else who sees the final product doesn't notice, so am I not noticing what the perfect cut is? Have I been striving for a mediocre cut, without realizing that I could be achieving the "perfect cut"? Is the polished surface off the tool possible with most woods?

As someone who doesn't care for sanding (I don't really have sandpaper to sand properly), I am interested in a "perfect surface". My 10x18 lathe doesn't have variable speed, and it stays at about 2000 rpm. Is it possible that I could get a better cut by reducing the speed with certain woods? Possibly on thinner pieces? Is there more to a "perfect cut" than having a freshly sharpened tool, taking a minuscule cut extremely slowly with a perfect technique?

lol more worms Yes species play a huge part. I have some 100 year lignum Vitea it turns like plastic and a glass finish every time. Details, yes! What I have found about details is that most folks cant see them, maybe. But if have too identical pieces one is finished to the 'nth degree we shall say the other is finished well. I have found often they will choose the 'nth degree over the other but explain why

 

[Odie]

Maybe I am missing something, but what is the "perfect cut"?

Good question......What I feel is the perfect cut, is a surface straight from the tool, without tearout, that can be start-sanded at 180/240gt, or higher.

That being said, from the miniature carving I do, I have grown to notice details

The "details" I speak of are those intersecting edges and grooves that are done while spinning on the lathe......not carving. As previously stated, the quality of these details can shift dramatically once the geometric integrity is altered. This "geometric integrity" can be further understood when considering perfect concentricity within multiple perfect circles

My 10x18 lathe doesn't have variable speed, and it stays at about 2000 rpm. Is it possible that I could get a better cut by reducing the speed with certain woods?

Absolutely!......My 33-year-old Australian made Woodfast lathe originally wasn't a variable speed....had to change belts for quite a few years before I converted it to variable speed. After converting it to variable speed, one thing I noticed almost immediately, is the vibration resulting from the combination of wood and lathe could vary with small rpm adjustments.....much more pronounced with major rpm adjustments. By these rpm adjustments, the quality of the tool finish was also a variable. This tool finish variable is directly related to fine tuning of rpm in order to minimize any vibration. The rpm can change with species of wood, size, and denseness......but, the lathe vibration at any given rpm is static, until the block of wood of the moment enters the equation.

=o=

 

[Odie]

Cast has the ability to absorb vibration due to its microstructure, which contains graphite flakes that act as natural dampeners. Steel on the other hand transmits as it carries vibrations through its structure due to its high elasticity and rigidity as a metal. Interesting though if you fabricate a tool rest with several tack welded layers of mild steel it will act like cast iron.

Hughie.....I have heard similar explanations concerning the value of cast iron vs steel from other sources. I tend to think there is something to the notion that cast iron is a better material for wood lathe construction, but I have no personal experience to validate the concept.

=o=

 

[Odie]

If you could convert your vibration sound into an audible harmonic or a visible sine wave that should do. I just use my fingertips and the feel of the tool against the wood.

Kim, that could very well be the case. Whether it is a better method of determining the vibration level than my homemade vibrometer is a question unanswered. I'd say it is about 15' the laser beam transmits to the opposite wall, and thus makes even the smallest rpm adjustments very apparent.....and very applicable to my purpose in searching for the best rpm, and therefore the perfect cut......

=o=

 

[Ron Solfest]

Good question......What I feel is the perfect cut, is a surface straight from the tool, without tearout, that can be start-sanded at 180/240 or higher.

Slightly off of the original topic of this thread, but I’m interested in your thoughts on something I’ve observed.

All else being equal, I find that using a shear scrape or negative rake as the final pass makes initial sanding easier. If my last pass is a clean push cut it leaves a nicer looking surface than the shear scrape, but I think that surface is burnished a little and it takes longer for my initial sanding to ‘bite’ or often I drop down a grade for that initial sanding just to cut quickly.

Stated more succinctly: for the same surface (no tear out) a final push cut looks nicer than a shear scrape but requires me to start a grit lower to sand than the shear scrape. Does this make sense?

 

[Odie]

Slightly off of the original topic of this thread, but I’m interested in your thoughts on something I’ve observed.

All else being equal, I find that using a shear scrape or negative rake as the final pass makes initial sanding easier. If my last pass is a clean push cut it leaves a nicer looking surface than the shear scrape, but I think that surface is burnished a little and it takes longer for my initial sanding to ‘bite’ or often I drop down a grade for that initial sanding just to cut quickly.

Stated more succinctly: for the same surface (no tear out) a final push cut looks nicer than a shear scrape but requires me to start a grit lower to sand than the shear scrape. Does this make sense?

Very interesting, Ron......

My experiences are similar, but not exactly the same.

Let me contemplate this before I respond in depth.

Thanks for bringing this up.....

=o=

 

[Odie]

Slightly off of the original topic of this thread, but I’m interested in your thoughts on something I’ve observed.

All else being equal, I find that using a shear scrape or negative rake as the final pass makes initial sanding easier. If my last pass is a clean push cut it leaves a nicer looking surface than the shear scrape, but I think that surface is burnished a little and it takes longer for my initial sanding to ‘bite’ or often I drop down a grade for that initial sanding just to cut quickly.

Stated more succinctly: for the same surface (no tear out) a final push cut looks nicer than a shear scrape but requires me to start a grit lower to sand than the shear scrape. Does this make sense?

Sorry for the delay, Ron......had other things going on.

For my bowls, I hardly ever use NR scrapers on the exterior, but do extensively use them for finish cuts on my interiors. For finishing cuts on exteriors, I've come to rely on manually raised burs on scrapers used in the shear mode. (For exteriors generally, I use scrapers flat to the tool rest to bring a roughed bowl to round. I then transition to gouges for general shaping and then go to the scraper in a shear mode for the final cut just prior to sanding.)

For interiors, I use NR scrapers quite a bit for a final sand-able surface, and whether it's a push or pull cut depends on the bowl shape and species of the moment. As the cut proceeds closer to the exact center, where the speed of the cut slows down considerably, there seems to be a point where a push cut is better controlled by reversing the NRS direction to a pull cut. There doesn't seem to be a hard fast rule about what direction is best, but listening to the cutting action tells me when it's time for a change in direction. On the side walls of the bowl interior, the best cut seems to generally be a push cut, but there is always exceptions.......for instance, my extreme undercut rims where directions can change, as well as NR vs standard scrapers. (For initial shaping of the interior, I generally rely on gouges.....prior to transitioning to NR scrapers.)

Note: On interiors, if I could get my tool rest closer to the cut without a long overhang, I could possibly use scrapers in a shear mode much more than I do.......and, that seems to be the reason why I don't very often.

=o=

 

[Ron Solfest]

Thanks Odie.

It sounds like your process doesn’t often (ever) end with a gouge push cut (floating the bevel) which I think is where I’ve notice a slight burnishing that makes sanding take longer. I’ve really mostly noticed this on the exterior of bowls.

FWIW - my process on the exterior usually ends with a shear scrape using the gouge I turned the exterior with, lately I’ve added a negative rake (flat on tool rest) over the exterior often.

On the interior I used to similarly use the gouge upside down to shear scrape before sanding, but a “surprise” doing this at the transition a few years ago where I got too much edge involved made me a little more nervous about this. I still do this for shaping, but virtually all of the time now I finish with a negative rake, whichever direction is cutting better (usually push down the side to the transition, and pull across the bottom into the transition). As often as not I use a nearly flat regular scraper in the dead center area, just because it does better than the very rounded negative rake that I have.

After adopting the negative rake I seldom shear scrape with normal scrapers anymore, some but not often.

I grind the wings on my gouges with pronounced convex wings which allows me to easily use them to shear scrape.

More info than you wanted, but presented in case you have some advice to offer

 

[Doug Rasmussen]

It cannot be stressed how much rpm effects the cleanest of cuts, and rpm must be adjusted precisely.

Think about how as a young kid I was able to get the cleanest of cuts barely needing very fine sanding on my dad's old metal lathe with a max of only 500 rpm on the spindle. Two words come to mind for me.

 

[hughie]

Hughie.....I have heard similar explanations concerning the value of cast iron vs steel from other sources. I tend to think there is something to the notion that cast iron is a better material for wood lathe construction, but I have no personal experience to validate the concept.

=o=

The theory is cast iron will absorb the vibration and if we look at metal turning lathes are all cast iron for the same reason as well as the mass.

 

[hughie]

Some of the species I turn have problems with scraping. Some require the razor sharp shear cut with a burr, others only negative angle will work , it sort of horses for courses. I have some curly Blackwood [ Acacia Melanoxylon] that requires turning the external from each end with razor sharp tools and some scraping in the centre to get a good finish, inside is a whole different kettle of fish.

 

[Alan Weinberg]

Isn’t there more vibration if a piece is farther from the headstock than if it were closer? I noticed that you use a fairly tall waste block on some pieces, Odie. Would there be less vibration with a shorter piece? I’m just trying to think of a variable not yet mentioned. @Odie

 

[Raif Harik]

Taking the sophistication down a notch or ten, vibration is not something I have heard much about as I was coming up. I've learned things somewhat intuitively, but not really consciously so this thread is really helping solidify som concepts.
I have noticed, obviously, that as I turn up the ramps it can start to really shake. I've also noticed that as I keep turning up the Rpms it can even out again. And I have kinda noticed that when making the cut I can get sort of undulations that result in a sort of spiral. I know that push on the bevel can cause this. Still some times with no pressure on the bevel I can get that. So perhaps this is what Odie is talking about with HF created but the tool on the wood.
I think an important takeaway for the more novice of us is: work to get as smooth a rotation as you can by messing with the Rpms. Then if you are getting a weird cut with a sharp tool, try and mess with the Rpms some more.
I'm guessing, depending on your level of OCD perhaps, as you get better at this process, you may find a vibrometer helps you take it to a new level.
So thanks Odie for bringing this up and sort of inadvertently solidifying the importance of adjusting Rpms to get an improved cut, in my mind.

 

[Odie]

Isn’t there more vibration if a piece is farther from the headstock than if it were closer? I noticed that you use a fairly tall waste block on some pieces, Odie. Would there be less vibration with a shorter piece? I’m just trying to think of a variable not yet mentioned. @Odie

Yes, the height of the wasteblock could make a difference if the height was significantly larger. I use standard 2x4's and 2x6's for my wasteblocks, so the actual difference isn't that much over using a modern scroll chuck. Any difference at all would probably add to vibration, as you have suggested......and, since I've been using my homemade "vibrometer" for the past few years, I've been adjusting the vibration level down to the gnat's a$$! I think this device allows me to make these fine adjustments much more refined than anyone who doesn't use a vibrometer. Of course that is my opinion, but I can tell you that I believe I've been able to get finer, cleaner cuts with my tools since I've been using the vibrometer. (I should state that fine tuning the rpm's is only one component of the total equation in the search for the "perfect cut".......but, without it, the entire equation is significantly handicapped in that search.)

=o=

 

[Odie]

The theory is cast iron will absorb the vibration and if we look at metal turning lathes are all cast iron for the same reason as well as the mass.

Isn't cast iron also used because it is less susceptible to warpage caused by time and temperature variations?????

=o=

 

[hughie]

Isn't cast iron also used because it is less susceptible to warpage caused by time and temperature variations?????

=o=

True, as far as I know

 

[Mike Novak]

And I have kinda noticed that when making the cut I can get sort of undulations that result in a sort of spiral. I know that push on the bevel can cause this. Still some times with no pressure on the bevel I can get that.

Raif

I have been struggling with this lately. I have heard that I need to “float “ the bevel to get best cut, but it never occurred to me that bevel pressure might increase vibration. I will try lightening up the pressure next time it happens. Thanks!

 

[Raif Harik]

Raif

I have been struggling with this lately. I have heard that I need to “float “ the bevel to get best cut, but it never occurred to me that bevel pressure might increase vibration. I will try lightening up the pressure next time it happens. Thanks!

My understanding is that one wants to push down on the tool rest and not at all forward into the wood. i.e. you don't push into the wood at all just guide the tool in the right direction, while putting all the pressure down into the tool rest to provide stability. And I guess, check the RMPs if that doesn't work

 

[Doug Rasmussen]

Isn't cast iron also used because it is less susceptible to warpage caused by time and temperature variations?????

It's used because it's easier to make a casting than a weldment. Anybody with a home shop and a welder can make a weldment. Castings need a foundry. Both methods require about the same amount of machining for headstock/tailstock mounts, etc. Cast iron does warp, Bridgeport milling machines frequently have sagging tables at the unsupported ends. With casting it's easy to make large fillets and bracing at key places for structural integrity. Weldments will have internal stresses and sometimes warpage from the heat of heat of welding.

Some weldments need to be stress relieved by heating in huge furnaces prior to machining. Back in the day Delta said they buried all their casting in dirt for a time period to allow them to age and stress relieve, likewise before machining..

Two of the top wood lathes, Oneway and Robust, are weldments. Do they have major vibration issues?

 

[Steve Tiedman]

Part of the story I heard about welded steel lathes, and by extension other machinery, many moons ago was that by welding together steel of different shapes and sizes, and thicknesses, maybe even grades, is that all of these pieces transferred vibrations at different rates, thus naturally dampening the vibrations. I can neither confirm nor deny the claim, but on the surface it at least sounds plausible.

 

[Steve Tiedman]

My understanding is that one wants to push down on the tool rest and not at all forward into the wood. i.e. you don't push into the wood at all just guide the tool in the right direction, while putting all the pressure down into the tool rest to provide stability. And I guess, check the RMPs if that doesn't work

As Richard Raffan has preached to us for 40 years, maintain a very sharp edge, and let the wood come to the tool.

Don't push into the wood. And really, unless you are having to do so during heavy rough cutting of badly out of round wood to control the tool, don't put effort into pushing the tool down on the toolrest. Relax. No white knuckle gripping, no grunting and groaning, no muscle flexing. Relax.

 

[Odie]

Two of the top wood lathes, Oneway and Robust, are weldments. Do they have major vibration issues?

If I'm not mistaken, both Oneway and Robust have cast components. What's being addressed here is more high frequency vibrations that will interfere with a clean cut from a lathe tool. These HF vibrations begin with the spinning wood and pass through the headstock prior to transmitting them to the bedways.

I can't say that cast iron is better, nor those with weldments are better. Majoy industrial manufacturers of machinery are still using cast iron.....so if there was a big advantage to welded structure, why haven't they changed?

=o=

 

[Ron Solfest]

Don't push into the wood. And really, unless you are having to do so during heavy rough cutting of badly out of round wood to control the tool, don't put effort into pushing the tool down on the toolrest. Relax. No white knuckle gripping, no grunting and groaning, no muscle flexing. Relax.

While I agree in general, especially about sharp tools, I disagree with the comment about not focusing on downward pressure on the tool rest. I was just turning a natural edge bowl yesterday and was VERY conscious I needed to put significant downward pressure on the tool rest to keep the gouge from bouncing and ruining my cut. The bevel was “floating” and the cut <1/32” at the time but if I didn’t push the gouge down it would have bounced and ruined a clean cut.

I notice this on laminated bowls that are fully round but have glue lines and different density woods as well. I don’t recall if I’ve consciously thought about this on twice turned bowls, but suspect just the end grain/ side grain density difference would lead to the same.

I concur with the previous post to NOT put pressure on the bevel, but DO put *downward* pressure on the tool rest as needed. But I also agree with your mantra to relax and not white knuckle it.

 

[Doug Rasmussen]

I can't say that cast iron is better, nor those with weldments are better. Majoy industrial manufacturers of machinery are still using cast iron.....so if there was a big advantage to welded structure, why haven't they changed?

Oneway and Robust have weldment beds of tube, round on the Oneway and square on the Robust.

I didn't mean to imply a weldment is better than a casting. But I can make a weldment lathe at home without needing to involve a foundry. Cast iron is still the favorite.

There have been alternatives to cast iron. When home computer disc drives were new to the market parts were turned on ultra precision lathes with massive granite bases. Hardinge used "Harcrete" which was resin and concrete base for vibration damping.

A couple of precision metal lathes used heavy welded bases, maybe 500 pounds, with the lathe having an extremely stiff bed way mounted to the base on 3 hard rubber pads, two under the headstock and one at the tailstock. That was their solution for vibration.

To defeat vibration you need mass in the lathe and rigidity in the tool holder. Mass? A PM 3520 is around 700 pounds. Compare that to some of the old Oliver pattern makers lathes at 3000 pounds. Hard to get rigidity when a human is hand guiding the tool.

There is a way to get rigidity in the tool, add 50 pounds to the tool handle.

 

[Doug Freeman]

I have kinda noticed that when making the cut I can get sort of undulations that result in a sort of spiral. I know that push on the bevel can cause this. Still some times with no pressure on the bevel I can get that

Feed pressure with the front hand, ie pushing the tool any direction except downward onto the tool rest, can cause it. Stuart Batty went over it in a video (dont ask which one, been a few years) Went to the shop to play with and it proved correct for me.