how fast

[Charlie Knighton]

how fast is a 11 inch wide by 5 inch thick out of round piece of hackberry traveling at the outer circumfance if the spindle speed is 500 rpm

good news: if the tool rest breaks at the post joiunt it will fly in a 90 degree angle from the turner!

 

[woodwish]

Let's see- 11" dia x 500 rpm = 1440 feet minute or about or a little over 16 mph. Now assuming from your post the piece must have come loose or something happened. So the important thing is if the wood's outer circumference is moving a little over 16 mph then the turner must move laterally at least 17 mph :cool2: :cool2:

OK, way too much math - now I have a headache! :mad:

 

[GeorgeH]

The thickness of the material is irrelevant; the circumference works out to a sliver over 34.56 inches so the average rim speed should be about 16.36 mph.Turn slowly, true the edges to balance the work then proceed in normal fashion.
(Because of my rush to attack the mathematics, my first shot at the geometry was flawed.... NEVER rush with math

 

[Mark Mandell]

Math

11" diameter means 34.5" in circumference, 34.5" @ 500 rpm means 17,250 inches per minute or 1,437.5 feet per minute means 86,250 feet pert hours equals 16.34 MPH.

 

[Mr. Don]

Speed

Turn slow enough to be safe, and fast enough to get the job done!!! GAWD...ROCKET SCIENCE!!!! Just do it!!

 

[Leo Frilot]

Yeah, get a bigger gouge and wear a faceshield.

 

[Sky]

Now how's that go..?? An 11" Hackberry @ 500rpm going 16.34 mph and a tool rest moving at an undetrmined rate of speed are traveling towards each other, one leaves Virginia @ 3:22 pm & the other leaves Lynn Haven @ 3:28 pm..... um ... wait... was that toward or away from each other?!!?

 

[john lucas]

I just take the bus, then I don't have to calculate when each train will pass or at what point. Math and I never did get along. 16.34mph is a little slower than my average on a 30 mile bike ride. Not fast but I still don't want a bowl hitting me at that speed.

 

[Steve Worcester]

16.34mph is a little slower than my average on a 30 mile bike ride. Not fast but I still don't want a bowl hitting me at that speed.

I can tell you that it takes less speed on a bicycle to break your neck, but that's a pretty good average speed.

Now how's that go..?? An 11" Hackberry @ 500rpm going 16.34 mph and a tool rest moving at an undetrmined rate of speed are traveling towards each other, one leaves Virginia @ 3:22 pm & the other leaves Lynn Haven @ 3:28 pm..... um ... wait... was that toward or away from each other?!!?

Now thats a big lathe.

 

[dkulze]

Well, to judge the effect of that piece hitting you in the head a such a nice, slow, safe speed, drop said piece on your toe.

Anyone want to calculate the height it would need to be dropped from to approximate 16.34mph?

Dietrich

 

[Charlie Knighton]

ding dong

after lunch ups brough my new tool rest, very fast action by the manufacturer, thanks

put hackberry blank back on, as before it had 8 screws in the faceplate and tailstock pulled up and in use, turned on and ran about 30 seconds, took some wood shavings off and then turned lathe off, hackberry blank has a 10% moisture reading and was very hard, i just was not comfortable with turning it took hackberry off lathe its probably in outer specification limits but why push it

put some ambroise maple vase blank on and turned the outside shape, really did enjoy turning the virginia soft maple

 

[john lucas]

I dropped one 3 inches and caught my finger between it and the ways. You really don't want to do that if you can help it.

 

[Ed_McDonnell]

Well, to judge the effect of that piece hitting you in the head a such a nice, slow, safe speed, drop said piece on your toe.

Anyone want to calculate the height it would need to be dropped from to approximate 16.34mph?

Dietrich

About 9 feet and it would take less than a second to get to your toe.

Ed

 

[Mark Mandell]

About 9 feet and it would take less than a second to get to your toe.

Ed

FEETS, DON'T FAIL ME NOW!!!!

 

[arbud]

Smart move

Begger, you did the correct thing by removing a piece of wood with which you were not comfortable. Rule #1: Always turn safely; that means staying within your comfort zone. If a blank is too heavy, too hard, too big, etc. then put it away until you gain both experience & confidence. One day you'll turn it and get a fantastic result.

 

[Bob Boettcher]

I am at the Utah Symposium, and this topic came up in a Dale Nish Demo. His rule of thumb is this:

Diameter in inches X rpm = 6000 to 9000. [these are just numbers, no units]

For example, a 6 inch piece should run between 1000 and 1500 rpm.

Your 11 inch piece should run between 545 and 818 rpm to meet these criteria, so you are in this zone. The critical thing is most likely the out of round part of the equation, not figured into the formula above.

Dale told of a friend who ended his turning career with a 24" glued up piece mounted outboard on a Delta Lathe with a minimum speed of 800 rpm.

24 x 800 = 19,200!!!

I always set speed by feel, but I think I will make a chart of diameter vs. rpm range that follow these criteria, and post near my lathe. I gives one a starting point at least, and may avoid a disaster.

It turns out that these criteria specify a rim speed range of 26-39 feet per second, or 18-27 mph.

For reference, here are some speed ranges to consider.

1"' diam - 6000-9000 Pen turners have a ball
2" diam - 3000-4500 Still maxed out on the Jet Mini
10" diam - 600-900 Probably slower than most turn this size.
15" diam - 400-600 Starting to sound pretty slow
24" diam - 250-375 Put that baby on low range

I think these criteria are based on the surface speed to deliver an good cut, not necessarily on safety criteria, so out of balance pieces always call for more caution.

Bob

 

[dkulze]

Yeah, those numbers sound good, but with tendancy to exceed them in the 8-12" range.

The tough thing about out of balance and variable edge/face pieces is that they tend to turn better the higher the speed. Makes for a funky equation, as the risk goes up proportionally. I've had some pretty out of balance pieces turned up to relatively high speeds to create a false surface to ride a bevel on. I tend to try and stand out of direct line of fire when making these cuts if I can manage it. Not for the faint of heart or short of insurance.

Dietrich

P.S.(9ft? ouch.)
P.P.S.(feel free to send me that hackberry blank, Charlie)