I will be turning fine tolerance tenons for woodwind instruments. I would prefer to machine these joints for precision instead of cutting with hand held tools. I am wondering if anyone has experience using metal lathe tooling for turning wood.
I will be using a wood lathe, and plan on setting up a cross slide vice or table to hold the cutter so I have cross axis movement of the tool across and into the work.
Specific questions:
-There are many grades of lathe tool bits available, and I am particularly interested in brazed carbide bits. These are commonly available in C2, C5 and C6 carbide, and quite cheap. Any recommendations for particular carbide grades? I will be cutting pretty hard dense woods like south american bloodwood and Jatoba.
-Any specific recommendations for tool angle into the work. If I can use a horizontal mount for the bit, I can use a standard tool holder, but if I need to angle the bit, I will probably have to custom make a tool holder.
-I’d also be very appreciative to hear any other experiences/tips from anyone who has done this.
Thanks
Replies
I could find only one reference for tool angles for turning wood on a metal lathe and the angles were very high compared to metal cutting, which would suggest that the relatively blunt angles of carbide tooling for metals might not work well.
I'd suggest grinding steel bits so you can experiment with various angles and tip radii. The angles are: side relief 15 to 20 degrees, end relief 20 degrees, side rake 30 degrees.
John White, Shop manager, Fine Woodworking Magazine
A metal lathe will turn wood. The lathe you want would be a pattern makers lathe which has the speeds of a wood lathe and the cross slide of a metal lathe.
When I was working as a Metalsmith we did the occasional wood, delrin, etc turning on our "Precision Enco Lathe". We used the brazed carbide cutter as well as the high speed steel ones. We did glass work as well so we had a bunch od diamond wheels so we could sharpen and modify tips on the carbide tools. C2 is best for cast iron and non-ferrous metal which would be the equivalent in wood. I
I do a lot with brass, aluminum, copper, zinc, etc and use many standard woodworking tools to machine the metal. Negative hook saw blades are used to cut non-ferrous so I wouldn't worry so much about the angle on the tooling for the lathe work. Try it first. You can always modify it. I see no need for a special tool rest form my experience. Typically those tool holders sit in a tool post which is on a curved bottom wedge on a dished wahers so angling the tool isn't a problem. I think you are worrying about things that you don't need to worry about. I can tell you haven't done much of this. Get some books at the library about basic metal lathe work. Older books are probably better.
Consider using the square HSS stock which fits in the same tool holders the carbide brazed tooling fits in. Easy to sharpen and modify with tools you probably already have. You can cut steel and non-ferrous with it so wood isn't a problem
Delta used to sell a retrofit cross slide tool rest for wood lathes. Don't see them as still available but you might find one somewhere. Look also at lathe duplicators. It would give you the control you want to copy and keep things straight and precise. Vega makes one of the better ones. The tooling is HSS.
Some instrumnet makers have been using modified gun drills for the holes. We were looking into it for our timberframe projects but have manged to find ways to drill 11' holes in timbers with pretty good accuracy...yes...eleven feet!
Mountain,
Rick is on the money suggesting HSS for your application. I prefer eight or ten percent cobalt. I've experimented considerably with different cutting geometry for milling wood on metal type machines. In fact, we run a whole range of custom tooling we've made or ground for machining/turning wood with machines normally thought of as metal machines.
Someday, I may write an article because I've learned a lot after years of experimenting. I'd rather not give that away right now. One thing I will warn you about is making sure you have clearance angles of 20ยบ or more. There's potential hazard for both you and your material if clearance angles aren't adequate.
Don't worry so much about running at a high rpm, instead think of taking clean shavings. Also pay attention to cutting tip radius, it's easier to smooth sand with the palm of your hand than a finger tip.
As others have said, there is no need for either carbide orexpensive disposable tipped tools. They will certainly machine hard smooth woods like African Blackwood,(but not really well due to lack of suitable clearance and the inability to be very sharp) but they are not necessary, and you can get a perfect finish using HSS tools like this Eclipse set pictured. You can easily grind these to any shape and modify the clearance angle which needs to be increased, and you can touch them up with either an oil stone or preferably a diamond plate, to keep them sharp.
The tool on the left is the most versatile-good for turning down to inside shoulders and inside tubes, flat bottoms etc. In fact you can do most things on your wood instruments with just that one.
I think the oriental gentlemen have churned out a lookalike set-which will be much cheaper and do your wood just fine after you have tweaked them. You should easily get a surface that may only benefit from a burnishing with steel wool if it is a Dalbergia like wood , or a sanding with 800 for something like Jatoba.
Concerning the tool holder and the compound slide: if you are thinking of one of those compound vices this is not great, because of all the backlash they have (at least the ones I have seen do). You need to get a proper compound slide to suit your wood lathe which can mount a swivel post to hold the tool-you will need to swivel it.It might be more cost effective to buy a small oriental metal working lathe....
Having seen demonstrations by The Society of Ornamental Turners, I would be inclined to seek their advice regarding the precision turning of wood by mechanical means. The degree of accuracy achieved is truely amazing.
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