Dumb Lathe Question...

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I don't have a lathe, and am not sure if I need one yet, and have never used a wood lathe. 35 years ago, I did some work on a metal lathe in a research lab. Here's the dumb question: Why wouldn't I use a metal lathe for wood so I could produce identical cylindars, etc using the screw feeds rather than try and "freehand" the parts and hope they are the same size?
Thanks for any answers.
Rich.....
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I a duplicator unit that essentially does that; it has a guide that follows a template and a cutter much like that used on metal lathe.
But, and I hope I don't sound goofy, doing it that way isn't much different than buying it; since it takes no skill, there is no enjoyment in doing it. Maybe that's not important to you, but it is 90% of why I do woodworking.
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You could for cylinders. It's hard to use the metal lathe to cut curves (o.e. bowls). There are toolrests (for the 7x12) and you can get a ball turning attachment for a metal lathe. But this takes longer than freehand.
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Another answer is that when you are cutting metal, you are essentially doing a scraping cut. A scraping cut on wood, especially on spindles requires a LOT of sanding to make presentable.
To get a good wood finish, you have to do a shear (slicing) cut, which I don't think is programmable.
That being said I visited a manufacturer of oboes who turned the very intricate and precise inside of his wood oboes using a metal cutting lathe with a power feed.
Old Guy

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Since when? I've been turning metal professionaly for 20 years. The only time I ever use a scraping cut is for large form tools. In other words, seldom.

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CW wrote:

Since you stuck a tool ground for metal turning into a piece of wood. Change the grind angles and it's not so bad.
You'll also find few metal-turning lathes with high enough speeds to be ideal for spindle turning, and those that do have them generally don't appreciate a coating of damp woodshavings.
I don't turn wood on a metal turning lathe, except occasionally using one for boring. http://quercus.livejournal.com/122184.html I do turn metal by hand on a wood lathe though, or at least brass. If you're doing Victorian repro it's the easiest way to get the flowing curves on some parts --- the originals would have been hand-rutned too.
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AFAIK - The Oland tool and a metal lathe bit is essentially the same, right?
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writes:

tooling bit, but the turner often uses the edge to shear rather than scrape. Darrell Feltmate is one of the internet-available advocates as you know. http://www.aroundthewoods.com/ Problem is that without rigid tool hold and a bevel, things can roll or jump and get away quickly.
Other people shear with their gouges, which gets the bevel into play to steady everything, like this guy. http://s108.photobucket.com/albums/n28/MichaelMouse/?action=view&current=CherryPeelIn.flv
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In that they are both made of steel, yes.

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It's more than that. I'm talking about the tool described here
http://www.aroundthewoods.com/oland.shtml
To quote Darrell,
"The tip is a 1/4" x 2 1/2" HSS cutting tool, standard in the metal lathe industry."
I can take the same exact bit with the same profile and use it in Darrell's tool, Then I can move it to a metal lathe. The bit doesn't change.
"Old guy" says it's a scraping cut in a metal lathe. It should also be a scraping cut in a wood lathe as well, right?
So I guess the question is
Is the Oland tool a scraping cut? Do all scraping cuts require a lot of sanding afterwards?
As Darrell says
"Some people object to the Oland tool because it looks like a scraper and they want to make shaving"
To be precise, Darrell says the Oland tool should be used with the bevel rubbing (for support I guess). That will change the cutting angle a little, but it still looks like a scraping cut to me. One could eassly add a negative rake to get the exact cutting angle as the Oland with the bevel against the wood.
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You could, but that would be solving a non-problem.
You misunderstand how "freehand" is done. Lateral reference lines at measured from the end of a spindle to mark the begining, end or middle of a shape. Those reference lines are then cut to a reference depth. From there, it is a simple matter of connecting the dots.
That's how you make four matching table legs "freehand". It is no more "freehand" than a child's "connect the dots" drawing.
Regards,
Steve
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Duplicators work fine. BUT... they essentially scrape the wood, not cut it. No razor sharp cuts when using a wood lathe duplicator. The tear out from these things can be just gawdawful since you are dragging that bit along the profile template.
Making four parts that are exactly the same isn't as easy as connecting dots for me or the others in my club. In fact, one of our challenges was to make fancy, profiled, candle sticks as close to each other in dimension as we could. Two wasn't bad. No one got to four.
But on table legs, that would be different. It is plain spindle turning, and you could put witness marks and depth cuts as needed. It IS similar to connecting the dots in that respect. But the good news is this: If you are off a little, who will know? On our candlesticks we set all of them next to each other and got out calipers to check. YOUR legs will be on four different side of a table.
And if you cut them with a normal gouge, you cut way down (maybe eliminate) tearout and cut down on your sanding. Plus, you're not in for a few hundred dollars for a good duplicating attachment. And it is more fun.
Robert
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Metal-cutting tools are slower than wood-cutting tools. It is possible you can use a metal lathe, but the holders, jaws, etc are different.
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The metal lathe I have in the garage will do 3000 rpm. The two (manual) lathes at work will do 2000 rpm, the CNC will do 4000. The Delta 12" variable speed wood lathe tops out at 2000 rpm.
wrote:

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Speed range on most metal lathes is generally from 50 to 1500 RPM. which is generaly too slow for wood turning. I have known people to profile cut cabinet knobs on a metal lathe with success using hard tight grained timbers with no sanding required but thats about a metal lathes limit. For general turning you require a slicing motion. Although it would be possible to set up a chisel in the tool holder to slice for turning cylinders it would be much slower than turning them by hand on a wood lathe. It would not be quite as good a result 'off the chisel' as you could not 'fine tune' the cutting angle for a bit of difficult grain.

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Nope. Takes the same effort to sever the fibers regardless the speed. Makes anything above that mere convenience mixed with danger. It's that MV squared thing. Use your tool properly and 1500 is all you'll ever need. And that's for buffing.
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Yes.

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Speed as little to do with effort required to sever fibres. That come down to torque which will change with speed changes and actually becomes less torque at higher speeds. Speed only relates to being able to do a cleaner cut while working at a faster pace. I rarely turn spindles below 1400rpm. As a general rule the only time I turn below 1400 is for roughing down square stock, spindles larger than about 4" Dia.or on long slender spindles to cut down on whip. Use your tool properly and there is no increase in danger at higher speeds. Naturaly enough if you are doing something that is a little bit 'tricky' or difficult turn at lower speeds. As a metal lathe has a greater selection of speeds (typically 9 -> 15 speeds) than a wood lathe (typically 5 speeds) it would be more useful for larger faceplate work but the bulk of a metal lathe makes access a little more restrictive.
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Speed only relates to being able to do a cleaner

Faster, perhaps. Cleaner, hardly. My carving gouges make exceptional cuts at zero RPM. Ol' Roy demonstrates the proper cuts by rotating by hand as well.
Use your tool properly and there is no increase in danger at

Newton disagrees. Potential energy of a departing fragment or the piece itself is proportional to the square of velocity. If it never happens, dandy, but use your tool properly and you don't need to take the risk.
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That should have read "clean cut at faster pace"

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