# Travel speed



## Shandit66 (Feb 2, 2010)

This might off topic, but I'm guessing this is "kind of" a CNC question.

I have a large lathe, to which I'm mounting my router on a home made cross slide.
There's a (manual = hand crank) setting to move the router in/out from the centre line (Z-axis?) and an automated (motorized) setting to move the slide along the length of the lathe (X-axis?)

The intent is to take really large chunks of rough cut wood (> 24" dia), mount them, spin them, and use the router to trim them down until they're somewhat round and fairly balanced.

As background to the problem:
- these are all "green" wood. Freshly cut, sopping wet. VERY Soft wood in this state.
- basically tree trunks = not round at all
- these are typically 100 to 200 lbs 
- they're often 20 to 50 lbs out of balance.

Hence if I try to get the lathe up to a "normal" cutting speed of 100 to 500 rpm, the vibrations are enormous. Picture a 2000 lbs lathe bouncing up and down, and/or a 100 lbs block of wood flying, bouncing off the ceiling and across the room (it happened - once. And I hope not to repeat it!!!)

So I've cut the speed to about 7.5 rpm using a gear motor and a pulley gear system. So on a 24" dia log, that's about 3 inch per sec of travel. I can't slow it down any more - without major rebuilding.

I will use the router to trim these up. Since they are not round, the bit will sometimes be cutting, sometimes hitting dead air.

During the cutting stage, I have 2 variable to work with:
1 - depth of cut (I guess you could call this the Z-axis?)
2 - rate of travel along the length of the lathe. (X-axis?)

Assuming, I'm using a 3/4" spiral bit and a 2 hp router, is there any way to approximate how I should set these two?

(I know I do the old trial and error, but I'm a little afraid of blowing up the jog/router etc...)

Thanks

Olaf


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## bloomingtonmike (Dec 13, 2011)

My first thought is that doing this with a router will take a huge huge amount of time and would be very dangerous. I would be looking at building som kind of parallel jig and use a chainsaw. Something you can use to spin the log in indexable degrees and then, lock it in place, and have the saw take a slice off. Make it so you can lower the saw and repeat until you have some sort of multisided round log. Then take it to the lathe.

I do not see this being safe with the log rotating under power being that far out of round. 

BTW - a 3/4" spiral bit typically has a 3/4" shank and will not fit in any 2hp router that I know of.


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## Shandit66 (Feb 2, 2010)

I know its pretty slow doing this. And I do use a chain saw (off the lathe) to get the pieces roughly 8 sided. That's fastest, but its clearly not precision work.

BTW - cutting this with "standard" chisels takes a very long time = hours...

As for a jig that connects the chainsaw to the lathe, thats an interesting thought and I'll mull it over.
Half the point here is not to get everything smooth. Rather, there will be pieces that have holes or gaps in them. Hence out of balance. The point is to reduce the mass first and get close to balanced.



And you're right on the bit, its a 1/2" shank, but I think a 3/4" cutting diameter.


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## Shandit66 (Feb 2, 2010)

An example is "Clark CNC Lathe Mill - Roughing Aspen to round" on YouTube


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