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Vibration dampening characteristics.....stainless steel vs cast iron

Odie

Odie

Panning for Montana gold, with Betsy, the mule!
TOTW Team
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We've all heard that cast iron has superior vibration dampening characteristics over steel......Is it true?

Has anyone done any practical experimenting, to see if there is a difference? I suppose the only real way to know for sure, is to take one individual turning, and spin it on two lathes of similar weight and swing.......anyone done that?

This would be conclusive as to how the weight handles balance conditions. Now, the vibrations occurring when a lathe tool cuts wood is entirely different, with entirely different considerations......most of which can be dealt with by fine tuning technique, tool choice, and sharpness.

-----odie-----
 
odie said:
Has anyone done any practical experimenting, to see if there is a difference? I suppose the only real way to know for sure, is to take one individual turning, and spin it on two lathes of similar weight and swing.......anyone done that?
Click to expand...

I would think you’d have to have two identically designed lathes to make that any kind of valid test; otherwise there are too many variables to narrow the difference to materials only.
 
odie said:
We've all heard that cast iron has superior vibration dampening characteristics over steel......Is it true?

Has anyone done any practical experimenting, to see if there is a difference? I suppose the only real way to know for sure, is to take one individual turning, and spin it on two lathes of similar weight and swing.......anyone done that?

This would be conclusive as to how the weight handles balance conditions. Now, the vibrations occurring when a lathe tool cuts wood is entirely different, with entirely different considerations......most of which can be dealt with by fine tuning technique, tool choice, and sharpness.

-----odie-----
Click to expand...

The choice between cast iron and steel is a trade-off. Many forms of cast iron have considerably higher damping characteristics than mild steel, but mild steel has a far greater tensile strength than most of them. High damping is mostly of value when the source of vibration has a strong frequency component near a resonant frequency of the lathe lathe structure/rotating load. Generally you have some control of the latter by adjusting the lather speed. Tensile strength determines how far things are going to bend under the forces of an unbalanced load. In theory. if the tensile strength of all parts of the lathe were extremely high and the lathe were bolted down, the lack of damping would not be a problem. I would guess that the main reason for employing cast iron in a lathe is its lower cost of fabrication compared to steel.
 
Odie - while I’m not an engineer, I did a little research into this a few years back when deciding on a new lathe. The design of the equipment plays a huge role in its performance. Info on weldments is available and seems to indicate that properly designed and constructed weldments help dissapate vibration while providing a stiffer base than cast iron.
Robust and Oneway both incorporate extensive weldments into their lathe designs with the effect that I’ve seldom heard complaints from owners of either on vibration from a properly setup lathe. They may make different ‘noises’ as I’ve seen reference to, but that’s just getting to know a new piece of equipment.
I’d be glad to hear from someone with materials engineering experience weigh in.
 
I would think the only way you could tell a difference is if it was a metal lathe and you are taking very precise cuts. At that point vibration may induce some chatter. On a wood lathe you get more chatter from the uneven densities of wood against the tool that you ever would on the difference between cast iron and steel. Of course that isn't based on any kind of fact or experiment, just my brain working overtime
 
The resonant frequency of a rotating piece of equipment is dependent on several variables one of them being the mass and density of the machine, cast iron usually increases the mass and weight of the machine which helps in dealing with resonant vibrations. This is why adding weight to a lathe will decrease the vibration of the machine and allow turning a larger or out of round blank without having the machine dance across the floor. Some machines are designed to be filled with sand or water to increase the weight of the machine to allow turning larger out of balance pieces. The wood blank is the one variable that is constantly changing while turning which sooner or later will match the resonant frequency of the lathe and create vibrations which will then require changing the speed of the lathe to decrease the vibration or add or remove weight to the machine to resolve the vibration.
 
odie said:
We've all heard that cast iron has superior vibration dampening characteristics over steel......Is it true?
Click to expand...

Vibration damping in the context that we are interested in is a structural characteristic. The choice between using cast or or steel on a lathe is primarily an economic consideration based on the number of items produced, complexity of a casting and cost of a welded assembly. Any subsequent claimed vibration damping benefit of iron versus steel is just marketing BS. Material thickness, ribs, corners, webbing along flat surfaces and designs that avoid repetitive dimensions that could reinforce standing waves (the first Tacoma Narrows bridge) are a few things that matter when designing a lathe that is acoustically flat.

There are valid reasons for choosing steel or cast iron, but perceived vibration damping of cast iron vs welded steel isn't one of them.
 
I spent 40 years running cast iron machinery and for me there is a difference between cast iron lathes and steel fabricated lathes. There is a big difference to me between cast iron tool rests and steel tool rest with the bar on top. That difference is why all my lathes are cast iron, could have any lathe I want, I choose cast iron. Vibration dampening is a real thing.
 
With lathes motor placement and headstock design are important too with respect to vibration.

In line motors less vibration
And surround motors even less.
A well designed lathe with an off set motor will have less vibration the lower end lathes with in line motors. The designer has to make compensation to set the motor out of line.

The 16” Nova DVR has least substantial bed of any lathe it’s size.
The headstock and motor surround the spindle and the lathe has less vibration than any comparable sized lathe I have used. Our club has one for a demo lathe. Everyone complains about the controls. No one has a problem with vibration.
 
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Depending on the type of cast iron alloy many of them have a granular consistency compared to a steel which has a "crystalline" like consistency which can carry vibrations much like a tuning fork. Cast Iron has a more random pattern structure that does not carry vibrations as well.
 
I switch tool rests constantly. I have Robust Rests, Bestwood tools and my powermatic and one homemade one. I cannot tell the difference other that some are shorter than the others. some i like due to their particular shape;
 
I agree with Bill Blasic. Having turned on several of the higher end lathes, I went with a total cast iron alloy unit that is very beefy in its castings, because of its weight and dampening qualities, and I have not regretted my decision. I do use the stock rests, but have a number of Robust rests as well. My other large lathe has a cast rest, but my newest 24x48 lathe has a hardened steel flat bar 1" wide x 1/4" thick, welded into a rabbit in the rest body, and turned on its edge to make the tool surface. I use it as much as any of the Robust rests. Have not noticed it causing any harmonics, nor my Robust rests either.
 
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Well gentlemen......it appears as though the controversy continues. For myself, I can't say that cast iron is better than steel, because the last two lathes I've owned were cast iron. Way back in the beginning, the early 1980's, I started turning on a Shopsmith, but I can't put that in context to this discussion, because I was such a noob then.

I can tell you for sure, that there is a best rpm to minimize vibration, but I don't have the experience with a steel lathe to make any personal judgments about whether iron vs steel would make a difference. (Someone else mentioned there is a zillion other variables, and that's true, too.)

I wonder if there is some analytical, or scientific method of putting this question to rest, once and for all.....?????

-----odie-----

Question: Wouldn't a 20" swing headstock be more stable than a 24" headstock (given everything else equal)......theoretically using the same out of balance blank? To me, it seems like the larger the swing, the more tendency that distance would contribute to the general physical properties that would make a difference.

It also seems like the distance between the forward and aft spindle bearings would make a difference......the longer that distance, the better it would be for eliminating vibration.....no?

.
 
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Seems like this one keeps coming up.... The biggest difference I noticed between my 3520A and My Beauty was that they made different noises when I turn. Slight differences in vibration issues due to headstock design. I have considered putting sand in the tube on the AB, but haven't gotten a-round-2-it yet.... Also thought about the spray insulation foam.... The pressure plates on the bottom of the headstock can make bid differences too. The AB has a full length plate with a full length cam bar, while my old PM had a smaller rectangle plate and single cam like on the banjo. Then there is the argument about fixed headstock vs sliding or pivoting headstock...

robo hippy
 
odie said:
........... I don't have the experience with a steel lathe to make any personal judgments about whether iron vs steel would make a difference. (Someone else mentioned there is a zillion other variables, and that's true, too.)

I wonder if there is some analytical, or scientific method of putting this question to rest, once and for all.....?????

-----odie-----

.
Click to expand...


Odie, if you want some hands on experience with a steel lathe you're welcome to stop by and put a piece of wood on my AB. Maybe you can compare the same piece of wood on your lathe. I'm not too far west of you.
 
odie said:
Question: Wouldn't a 20" swing headstock be more stable than a 24" headstock (given everything else equal)......theoretically using the same out of balance blank? To me, it seems like the larger the swing, the more tendency that distance would contribute to the general physical properties that would make a difference.

It also seems like the distance between the forward and aft spindle bearings would make a difference......the longer that distance, the better it would be for eliminating vibration.....no?

.
Click to expand...

This wouldn't be "everything else equal" but when comparing the 3520b (20" swing) and the AB (25" swing) I would think that the footprint would contribute to the stability of the lathe. The AB, while it has a bigger swing, has a much wider footprint, I cant remember if the Oneway does too. On a personal note based on my own experience with turning on Powermatic 3520b's and my Robust both are very good lathes. Both run smooth and are fun to turn on (though I perceive my Robust as being more smooth and more fun). Both lathes will vibrate and dance across the room when overloaded. I mentor at a retirement community center once a month and turn on one of their several Powermatic lathes. If I have an out of balance piece I do have to go slower on the Powermatic than I do on my Robust when I take the piece home.
 
odie said:
We've all heard that cast iron has superior vibration dampening characteristics over steel......Is it true?

Has anyone done any practical experimenting, to see if there is a difference? I suppose the only real way to know for sure, is to take one individual turning, and spin it on two lathes of similar weight and swing.......anyone done that?

This would be conclusive as to how the weight handles balance conditions. Now, the vibrations occurring when a lathe tool cuts wood is entirely different, with entirely different considerations......most of which can be dealt with by fine tuning technique, tool choice, and sharpness.

-----odie-----
Click to expand...
This feels like deja vu. I believe we already had this discussion...
 
Yeah, every few years it comes up. Fun to dis USS but what it all really boils down to, is can you create what you want with the tools you have. I dont think that Moracon turner worries much about steel vs cast iron. Or for that matter Robin Wood, the spring pole.turner out of England who is one of my idols.
 
Interesting how the Chinese, Japanese and Russians can produce turned pieces quickly with rough hand forged tools using the most basic of forging equipment and archaic machines and tool rests and make it look easy. I just watched a video of a welder fabricator in Mexico that builds custom wood lathes, simple design, easy to use and maintain. I can only imagine what they might be thinking when they look at a western wood turning video.
 
Mike Johnson said:
Interesting how the Chinese, Japanese and Russians can produce turned pieces quickly with rough hand forged tools using the most basic of forging equipment and archaic machines and tool rests and make it look easy. I just watched a video of a welder fabricator in Mexico that builds custom wood lathes, simple design, easy to use and maintain. I can only imagine what they might be thinking when they look at a western wood turning video.
Click to expand...

Once you master the basics you can turn wood with a sharpened spoon.
Many of the better turners use few tools and some a bit primitive in design but high in function.

If you have an opportunity the watch Michael hosaluk turn his pod forms the tools and techniques are very similar
Skew and hook tool

David Ellsworth’s hollowing tools are pretty simple and he makes some of the most ellagant turnings there are.

Of course we all the love to have more tools than our fellow turners
 
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