A crazy thought and potential project.

Squatchhhammer said:
That is something I was looking into. Also I was wondering if High carbon steel would work just as well for rigidity vs cast iron. On top of that, I am looking into what paint to use. I've seen people use Sherwin-Williams metal paint but I was also wondering what paint did the beaten metal look. I've seen some machines with it and I would like to use that style of paint.
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Cast iron is a lot easier to produce than steel. Manufacturers use it for the excellent dimensional stability and the vibration damping of the flake graphite structure.
 
Squatchhhammer said:
That is something I was looking into. Also I was wondering if High carbon steel would work just as well for rigidity vs cast iron. On top of that, I am looking into what paint to use. I've seen people use Sherwin-Williams metal paint but I was also wondering what paint did the beaten metal look. I've seen some machines with it and I would like to use that style of paint.
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To be radical, have you considered concrete? Magnetite concrete with steel fiber (i.e., chopped up steel wire) is very dense and rigid and provides better vibration damping than cast iron.


Is the paint you are looking for "hammertone"?
 
Squatchhhammer said:
That is something I was looking into. Also I was wondering if High carbon steel would work just as well for rigidity vs cast iron. On top of that, I am looking into what paint to use. I've seen people use Sherwin-Williams metal paint but I was also wondering what paint did the beaten metal look. I've seen some machines with it and I would like to use that style of paint.
Click to expand...

Steel varies very little in stiffness (Modulus of Elasticity) from low carbon up through the expensive alloys, so I wouldn't bother with high carbon steel, just go with 1018 or A36. Steel gives you about twice the stiffness of cast iron and about 3 times the stiffness of aluminum. I think the main reason it is not used for machine bases more is just cost of fabrication, and also the fact that you need at least one cast iron surface on sliding members (steel on steel has problems). I think a steel tube based gingery machine would be quite stiff, but getting it flat may be dificult. I have never tried scraping steel, but I hear that it is dificult.
 
Scraping steel is... unsatisfying. It also makes a pretty horrible bearing surface (at least mild steel does). If you go with a steel structure, I would recommend linear rails rather than box, V, or dovetail ways.

Course, you could go steel and coat them with turcite...
 
Everyone on the CNC forums loves the linear rails for building machines. They do it for the low friction, so they can get really high movement rates on the machines using small steppers and cheap drivers. Never mind that the machine can't cut at anywhere near those rates. I think that the hydrodynamic bearing (traditional V, square or dovetail ways) bring some definite advantages to the table. They are low cost. They provide better coupling of the structural elements of the machine to dampen vibration. They are strong. Even with a bad crash, you are very unlikely to damage a way, more likely the head of the machine will come apart. Their performance in dirty environment is on par or better than the linear rails, they both need protection. As far as using steel, I think using steel on one side with something else on the other, such as turcite (or one of it's competitors) or cast iron would work out fine. Even the aluminum on steel that the Gingery machines use seems to work well, for what those are. Steel on steel for sliding surfaces is just a bad idea.
 
Interesting, I thought steel on steel would be fine since any bearings I had used, I.E. ball, flat, needle, etc., had steel surfaces all around and just need lubrication to keep them running true and seizing. On top of that, since steel used more often I thought it would be cheaper to get a casting done instead of iron. I thought they only used iron on most brakes to have them wear out faster and make the consumer pay more. I wish I had a machinists handbook ( I know its the machinery handbook but I only heard of it in machining) to look up the information I will need.

So on top of that, if steel is used for the main structure but then cast iron was used for most of the "bearing" surfaces like the ways and the spindle.

Also would actual bearing assemblies would make a better spindle assembly than bushings, or would that not work as well and cause more slop within the cuts?

John Hasler said:
To be radical, have you considered concrete? Magnetite concrete with steel fiber (i.e., chopped up steel wire) is very dense and rigid and provides better vibration damping than cast iron.


Is the paint you are looking for "hammertone"?
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YES IT IS!!! Thank you very much. I couldn't find exactly what it was called, but I want to paint every machine I will own in that style. I love the look of it on different machines I have seen before, and I will have to get some when doing a restoration project if I'm lucky. I was looking to do a restoration project as a way to study how a machine was designed and built, since I'm more hands on. Also if I'm lucky, I might hook engineering student from a near by University; MSU or Michigan State University, to look into doing a project of that sort.
 
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The bearings you are familiar with are designed to roll not slide, steel on steel sliding surfaces are not great. With the exception of cast iron you usually want one material harder than the other for sliding surfaces to prevent galling,
Hardened steel is used on the bed of Hardinge lathes with the mating carriage being cast iron on the early models and I believe a teflon sheet on the newer ones,
Greg
 
Mild steel is never (hardly ever?) used as a bearing surface. It's far too soft. When steel is used, it is usually hardened, and used in conjunction with a plain bearing made of a softer material such as brass, bronze, or babbitt.

Lots of older lathes used plain bearings to great effect. They have some benefits, buy you will notice that nobody makes new lathes with plain bearings (to my knowledge), and there is probably a reason for that. A lot of it likely has to do with cost (lots of adjustment needed to get plain bearings working "just right"). Plain bearings also tend to have a lower top speed, but if you are not running at 6k RPM, it's probably not an issue.

Regarding the use of steel in machine tools, try this experiment. Take the handle of a screwdriver and tap it against a bar of steel. You will hear a distinct "ring", like a tuning fork. Now try the same think with a piece of cast iron. You will hear a dull "dunk" sound. CI is much better at absorbing vibration than steel. Something to keep in mind.
 
I was trying to find Timken bearing prices for their super precision bearings, but there's a problem with that. Every site I went to had a "you must sign up to get a quote" just to roughly see a price. So I went on ebay, and what I had found out there for any price is that I might be looking at a 500 USD to a 1000+ USD price tag PER BEARING!! So probably back to using bushings. I was hoping to make it more precise and modular for the test piece, but seeing the price what bearings are, I now understand the reason why the manufactures went with bushings.
 
Try VXB. They carry NSK angular contact ball bearings in ABEC 7, which are what are used on modern machine spindles. Depending on the size, they are quite a bit cheaper than what you are finding on Timkens. They still aren't cheap, just not quite that high. Also, the quality of the bearings, from a runnout perspective, matters much less if you finish the spindle while it is running in those bearings.
 
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