Machining wood on a metal lathe...

[ckm]

I'm wondering if anyone knows what kind of tooling you might use on a regular metal lathe to machine hardwood.

I tried some indexable inserts I usually use on aluminum, but it leaves a slight grove and it seems like it's tearing rather than cutting, esp. when against the grain. Although it does seem that hardwood (walnut in this case) is much harder than delrin.

Yes, I know I could use a steady rest, but I don't have one and then I can't use the power feed...

I did search all over CNCzone and Google, but it's all about wood lathes, not wood on metal lathes....

Thx.

Chris.

[ger21]

From my experience trying to turn Delrin in a wood lathe, I'd say that Delrin is much harder than walnut. What you want is the sharpest possible tools.

[Geof]

I have found the best approach is to grind a HSS tool with a very steep top rake so you do get a cutting action, make the cutting edge about 1/16" wide but do not have it exactly straight and level with the centerline, cant it an an angle off about 10 degrees so it crosses the centerline facing toward the direction of cut. This allows it to have a somewhat sideways shearing action as it cuts.

Before machining wood on a metal cutting lathe it is a good idea to wipe all the excess oil off the ways, etc,. The wood dust will stick to everything and make a horrible gummy mess when mixed with oil.

[ckm]

Originally Posted by ger21 From my experience trying to turn Delrin in a wood lathe, I'd say that Delrin is much harder than walnut. What you want is the sharpest possible tools.

I don't know. I machined a similar section in both materials and the delrin version has MUCH more flex and you could mark it with your fingernail. There is no comparison. I showed it to some other people and everyone was shocked at how hard it actually was.

Maybe it's the delrin I've used. Anyway, that's not really what I was asking, I'm not interested in turning delrin on a wood lathe and I already know what tooling to use on a metal lathe ;-)

Chris.

[ckm]

Originally Posted by Geof I have found the best approach is to grind a HSS tool with a very steep top rake so you do get a cutting action, make the cutting edge about 1/16" wide but do not have it exactly straight and level with the centerline, cant it an an angle off about 10 degrees so it crosses the centerline facing toward the direction of cut. This allows it to have a somewhat sideways shearing action as it cuts. Before machining wood on a metal cutting lathe it is a good idea to wipe all the excess oil off the ways, etc,. The wood dust will stick to everything and make a horrible gummy mess when mixed with oil.

I assume you keep the rotation towards the tool? What about speeds and feeds? My assumption has been 'as fast as possible', as this is the case with routers?

Thx.

Chris.

[Boots]

Geof has the right approch here-and the tip of the tool should have a large radius (not pointed). You will need to get underneath the surface and scoop the wood off like a spoon but not that radical. Yes turn towards the tool with the highest RPM you have got with a moderate feed rate. Experimentation will yeld you the best results. He is also correct about getting the oil off the ways and lead screws or you will have a big mess to clean-up. Delrin (like Teflon) has it's own lubricity (making it easier to cut) where as wood does not, so be sure your tool is very sharp. True your grinding wheel so the edge of the tool is smooth and not jagged. If your tool is bouncing whilst grinding it won't work well. To my knowledge there are no inserts that will do this as they are too dull on the edge. HSS works great.....

[Geof]

Originally Posted by ckm I assume you keep the rotation towards the tool? What about speeds and feeds? My assumption has been 'as fast as possible', as this is the case with routers? Thx. Chris.

Normal rotation but maybe not as fast as possible, especially with the feed. Wood turning lathes that I have seen rarely go over 1500 rpm and what wood I have turned on a metal lathe I did around 1200. For the feed you have to feel your way to some extent. If you push it too fast you may get chipping or tearing. If the tool is really sharp and is slicing the wood off nicely you will find it just floats along up to a certain level of feed then starts to push back a bit.

[daisydog]

This may be a bit more than you want to do but if you plan on turning a lot of wood consider using a laminate trimmer in a holder made to attach to your tool post. I build cue sticks and this what I use.

If you want to see pictures go to azbilliards.com and look in the tools for sale.

Good Luck,

Ddog

[ckm]

Originally Posted by daisydog This may be a bit more than you want to do but if you plan on turning a lot of wood consider using a laminate trimmer in a holder made to attach to your tool post. I build cue sticks and this what I use. If you want to see pictures go to azbilliards.com and look in the tools for sale.

Thanks for that. Couldn't find the particular tool, but I can imagine what it looks like.... Much like a grinder attachment and it might work a lot better than fixed tooling.

The big problem I am having right now is workholding. I need to machine a hole through a ball, and I though of drilling a pilot hole and using a regular chuck with inside jaws, but that doesn't actually hold strongly enough. I think I might have to machine the hole through first (probably on a drill press), then make a ball.

To be honest, it's quite an unbalanced and scary operation all around and I'm probably going to have to figure out a better way... Maybe a six jaw chuck would work better, but I don't have one handy.

Thx for all the tips.

Chris.

[Geof]

Originally Posted by ckm ...... I think I might have to machine the hole through first (probably on a drill press), then make a ball. ...Chris.

This is very likely the best approach but hold it on a mandrel rather than gripping it with inside jaws.

[ckm]

Originally Posted by Geof This is very likely the best approach but hold it on a mandrel rather than gripping it with inside jaws.

I was using inside jaws as the ball in question was already machined and that's the only way I could figure out to hold it...

But, yeah, it was not the best way to do it.

Chris.