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Forum topic by Mark posted 01-28-2020 07:17 PM 327 views 0 times favorited 10 replies Add to Favorites Watch
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Mark

1032 posts in 2605 days


01-28-2020 07:17 PM

Morning all. I followed a web site from a turning club in Pennsylvania. The project they where high lighting was a lidded box with over lapping concentric rings using offset centres. While the article was fairly well detailed, the author made no mention of lathe speed. I did try my hand at turning one with a piece of yellow heart, with variable success. I was turning at around 900 rpm. I cut several of the rings to deep and caught several edges with dissastorous results. But I will try it again. Maybe with a bit of Cherry.. but the question is…What speed would you use? I’m thinking a bit slower? Whatcha think?

-- Mark


10 replies so far

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BurlyBob

7044 posts in 2896 days


#1 posted 01-29-2020 01:06 AM

I have no idea about your speed question. But both those photos of your work are incredible!

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Mark

1032 posts in 2605 days


#2 posted 01-29-2020 02:14 AM

I hope I haven’t given the wrong impression. The pics are NOT my work. They are from the article I spoke of and were for sole purpose of demonstrating what I’m trying to achieve.

-- Mark

View Bob Collins's profile

Bob Collins

2750 posts in 4314 days


#3 posted 01-29-2020 04:06 AM

I tried one of these years ago but can’t remember what speed I used, possibly around 750rpm. It could be a matter of experimenting on some scrap pieces. Have you checked ytube? Look forward to seeing your results. Cheers.

-- Bob C, Australia. Your best teacher is your last mistake.

View Mark Wilson's profile

Mark Wilson

2704 posts in 1694 days


#4 posted 01-29-2020 08:46 AM

A rule of thumb in turning is that you turn as fast as you dare, or, as fast as you’re comfortable. With offsets like the second photo, of course, one mustn’t go so fast that the lathe walks across the room. However, with my eccentric goblets, I’ve gone as fast as 2000. I learned some time ago that, as you speed the lathe up, when the world starts to shake, you speed it up a little more. Most of the time, it stops shaking once you get through that initial oscillation. Speed is good, most of the time. At lower speeds, you’re tool will want to jump. That’s asking for a catch.

-- Mark

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Mark

1032 posts in 2605 days


#5 posted 01-29-2020 03:49 PM

Thanks for the suggestion Bob. I took a look and found several videos with different applications.
Mark. Thanks for your input. One of the videos was from Captain Eddie. He started 1600 and finished 3200…I think. But yer right about the slow speed, as I found out

-- Mark

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TheDane

5740 posts in 4294 days


#6 posted 01-29-2020 03:49 PM

Speed should be as fast as you feel safe … it is more important to have sharp-sharp tools.

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View HokieKen's profile

HokieKen

12196 posts in 1769 days


#7 posted 01-29-2020 04:54 PM

I’m with Mark and Gerry. Crank it up as high as you can without it trying to run away from you.

-- Kenny, SW VA, Go Hokies!!!

View OSU55's profile

OSU55

2542 posts in 2620 days


#8 posted 01-29-2020 05:21 PM

Estimating that piece to be ~ 3” dia, and following wood machining surface speed recommendations (which the 6000 – 9000 rule of thumb is in line with) roughing at ~ 2,000, finish cuts ~ 2,800 rpm. I find these surface speed recommendations to be very good starting points for balanced blanks. The off-center cuts I’m unsure about because I haven’t done any. Lathe vibration will be your guide as well as any guidance from a mfr if using an off-center chuck. That appears to be a special ground tool, possibly a scraper?

View LeeMills's profile

LeeMills

699 posts in 1932 days


#9 posted 01-29-2020 06:00 PM

I would go faster given the small size. By my chart (Teknatool) I would go to the 2180 belt position
Here is the chart from Nova (Teknatool); most mfgs give similar ranges.

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

View Underdog's profile

Underdog

1445 posts in 2666 days


#10 posted 01-29-2020 06:03 PM

Two things (not just for your benefit, but the benefit of others reading this).

1) Face shield! Always use a face shield, but it’s even more important when turning something that’s likely to blow up or come off the lathe.
2) Stay out of the line of fire! Don’t stand where it might grenade right into your body. Stand to the side.

As for speed, I have no idea. I’d just have to see how it went. If the sections are thin and likely to come apart at speed, then I’d stop at an RPM below the point where centrifugal force tears it apart. Hard to tell without doing destructive testing, yes?
Maybe contact that club and ask them?

-- Jim, Georgia, USA

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