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Ed Reiss
14th October 2008, 11:24 PM
Hi All...

Here's a good article on lathe speed selection by Alan Lacer.

http://azwoodturners.org/LatheSpeed.pdf

OGYT
15th October 2008, 01:07 PM
Thanks Ed. I've often wondered how fast the edge of that bowl was spinnin'. :)

texx
15th October 2008, 07:53 PM
its all calculated by peripheral feet per minute .
thats how i worked out the pulleys needed when i built my rip saw and my lathe .
know the revs of the shaft and the circumference of the item ( pulley ,wood what ever )and work it out from there .
by the way any one building some thing pulley driven here is a link to a very handy site .
http://www.pumpcalcs.com/calculators/view/98/

Skew ChiDAMN!!
15th October 2008, 08:37 PM
:? Does it really matter what the RPM or KPH of any given point on the wood is?

Crank it up until it's brown pants time, then back 'er off a tad. Still probably a tad too slow for the best finish, but yer pants last longer between washes that way. :rolleyes:

RETIRED
16th October 2008, 07:39 AM
Been saying the same as Skew for years.

When we are turning the big logs the first question after exclamations asked by visitors is,
"What speed is it doing?"
My reply is, "Fast enough."

Studley 2436
16th October 2008, 11:11 AM
and Skew have it sussed. *LOL* if you have the machine bouncing around then slow it down if not then feel free to speed it up. Just as long as the job isn't in danger of flying to bits.

Had a boss who told me not to run our Mazak metal machining lathe over 700 RPM! Could never believe that. He said the chuck would fly apart! Wasn't true he just wanted a really really quiet workshop so he could listen to the radio and relax. That machine had a top speed of 1600, not that fast but it was a biggish machine so it had less speed and more power. Nice Kitamura chuck too rated to 3000RPM. Rating was stamped on the face.

Studley

Ed Reiss
16th October 2008, 12:43 PM
:? Does it really matter what the RPM or KPH of any given point on the wood is?:

Don't really give a r**s a** what the speed at the circumference or at other points is....this was presented merely as a saftey aid for newbies....and also for us old farts that can't remember from yesterday!:doh::C

Studley 2436
16th October 2008, 01:00 PM
Actually if you really want to know in metric the formula is

1000 x CS then divide the answer by Pi D.

CS is the cutting speed and use D in mm. I have no idea what the cutting speed of wood is. Mild Steel with a HSS tool cuts at 30 m/min carbide tools typically come with a range of 160 to 220 m/min on steel. Want to get scarey fast Cubic Boron Nitride tools will cut HSS at 200 m/min!!!!

Back in the shed though I would just be working it out to 100 m/min on timber with HSS. Every machine and every bit of wood though is different so proceed with caution and pay attention to the results you are getting.

Studley

joe greiner
16th October 2008, 08:42 PM
Surface speed is more important in metalworking than woodturning. For metalworking, tool material, cutting speed and feed rate get into the act, as well as type of cutting fluid. Machinery's Handbook has about 3/4 of a page in the index alone dedicated to this topic. A machinist will consult such info. More often than not, slower cutting works better, especially when drilling..

In woodturning, the best cutting is by slicing fibers, not chopping them off, so higher speed works better.

Note: I'm not a real machinist, nor do I play one on the telly, but I have stayed at Holiday Inn Express.:wink:

Joe

Studley 2436
16th October 2008, 10:10 PM
You can get away with slower speeds on HSS Joe. Carbide is another story frequently problems are caused by going slower. I have seen this many times with plastic deformation of the tool because speeds and feeds and cutting depth are inadequate.

Timber with it's grainy structure I would think benefits from higher speeds and feeds as well as worthwhile depths of cut. The trouble here is rather than being able to set these things on the machine all you can accurately control is the speed. So I reckon you would have to get a decent speed on it and then don't dawdle.

Studley