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Forum topic by Karda posted 07-08-2017 08:59 PM 490 views 0 times favorited 7 replies Add to Favorites Watch
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Karda

821 posts in 392 days


07-08-2017 08:59 PM

Hi, got a question: how fast can I run my chuck with bowl blanks. Instructions don’t say much. one speed is 600 rpm for 10” x 4” blank but what about smaller and lighter. My chuck is a Nova G3 how do you judge


7 replies so far

View LeeMills's profile

LeeMills

461 posts in 1140 days


#1 posted 07-08-2017 10:19 PM

Probably not a lot of data; I would just use the suggested range for a particular size.
Someome stated the range should be Diameter X RPM = 6,000 to 9000.
I make it a little simpler: instead of 6,000-9,000 I just use 7500.
To make the calculation simpler change it to 7500/diameter = Speed
So 10” would be about 750 ; 8” about 950…. Of course the deeper the slower for safety.
My gson (8) turned a top a few weeks back and it was about 2100 rpm with spigot jaws in a G3. At a little over 2” it could have been the highest (3600?) but no need to.

-- We cannot solve our problems with the same thinking we used when we created them. Albert Einstein

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LeeMills

461 posts in 1140 days


#2 posted 07-08-2017 10:30 PM

Here is a better chart from Teknatool. Quite a bit of difference in round and unbalanced.

-- We cannot solve our problems with the same thinking we used when we created them. Albert Einstein

View johnstoneb's profile

johnstoneb

2641 posts in 2011 days


#3 posted 07-08-2017 10:36 PM

You run it up until the chuck can’t hold the blank then back off a little.

-- Bruce, Boise, ID

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Nubsnstubs

1207 posts in 1569 days


#4 posted 07-08-2017 11:38 PM

I’ve done 14” blanks at 1750 rpm….... If anything changes while chucked, like a sudden vibration, or wobble, shut’er down….... If you choose to go by the manufacturers directions, you’ll never get anywhere. They are protecting themselves, but you should still exercise caution after you learn all there is to know about your tool…... Jerry (in Tucson)

-- Jerry (in Tucson) www.woodturnerstools.com

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bigJohninvegas

383 posts in 1300 days


#5 posted 07-09-2017 12:02 AM

Turning tends to work best at the fastest speed that you can go SAFELY. its common to only be able to turn at around 500rpm when starting, but as you true up the blank and it gets more stable turn up the speed. At the same time as you turn, lets say almost finished and your turning starts to get thin. Then slow it back down some. don’t want to blow it apart. You get that vibration when you get to fast, sometimes you can speed up a little and get through the vibration. Sometimes you just got to slow down. But you will find the best, smoothest cuts at speed.
I will be up at, and over 2000 rpm almost every turning I do, but I don’t start or finish there. And sometimes never get that fast.
Jerry is spot on, Exercise Caution. SAFETY!!!
Every now and then, BANG, ya loose a bowl. That has not happened in a long time now, but when I was starting out, I had a few.

-- John

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Karda

821 posts in 392 days


#6 posted 07-09-2017 01:13 AM

thanks, I need reality and you gave it, I don’t trust instruction as you said they are in CYA mode. The chart is very helpful thanks

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Planeman40

1035 posts in 2600 days


#7 posted 07-09-2017 07:53 PM

johnstoneb has pretty much got it.

I remember a few years back when I was turning a 30” dia. mold to vacuum form some milky white Plexiglas for a flying saucer to be used in filming a television ad. I had to do it on the outside side of the lathe head of my old 1940s vintage Delta lathe. All turnings are unbalanced when beginning to turn, but this one was something else! It danced that heavy cast iron lathe around the floor! I had to weigh my lathe down with sand bags to get the turning started.

I would recommend using a lathe chuck only for smaller turnings. The larger ones really need to be attached better than a chuck can do it.

-- Always remember: It is a mathematical certainty that half the people in this country are below average in intelligence!

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