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Forum topic by Karda posted 12-17-2017 08:02 AM 660 views 0 times favorited 18 replies Add to Favorites Watch
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Karda

877 posts in 429 days


12-17-2017 08:02 AM

I am turning nice piece of dried cherry but am getting a lot of tear out and tool marks I didn’t get before, could it be lathe speed. I no longer have my 4th gear 2200 RPM I am limited to 1600 and under could slow speed be part of the problem or is it technique thanks Mike


18 replies so far

View walnutles's profile

walnutles

2 posts in 72 days


#1 posted 12-17-2017 09:42 AM

No Mike its not your speed, you should be able to get a clean cut at 1000 rpm or lower.
You don’t say if your using a scraper or a bowl gauge, so a little more information would help us to advise you on what we think the problem is.
some woods do suffer from torn end grain when turning in one direction so turning from the other direction will help with this and are you turning with a sharp tool as a sharp tool with light cuts will also help.
I hope that this helps. Les

View Wildwood's profile

Wildwood

2204 posts in 2010 days


#2 posted 12-17-2017 01:14 PM

Already said speed is not your problem! 1600 RPM’s should provide a smooth off the tool finish if using sharp tool. Thnk you are forcing the cut with dull tools!

-- Bill

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Karda

877 posts in 429 days


#3 posted 12-17-2017 05:52 PM

It happens the most when I am working on the bottom. The scrappers are the worst probably dull but it happens with the bowl gouge but not as much, speed must be technique thanks

View LesB's profile

LesB

1448 posts in 3318 days


#4 posted 12-17-2017 10:17 PM

RPMs can be relative because the surface speed of the object being turned varies with the diameter. The outer surface of a 12” diameter blank has a much faster surface speed than a 3/4” pen blank at the same RPM. So the larger the blank the slower you need to go in RPMs. My normal range is 600 to 1500.
As a “general” statement the faster speeds work better with SHARP scrapers at avoiding tear out. Light passes help and if your lathe is reversible I find I can remove some tear out by reversing the cut…especially on the inside of a bowl. With gouges your are cutting not scraping and a slower speed works fine.
I have never completely mastered the skew but it gives the least tear out and the smoothest finish.
Some wood is just more susceptible to end grain tear out and there are times I just sand it down with 60 or 80 grain sandpaper. That does makes it hard to get fine sharp details it that is what your are going for.

By the way. The carbide tipped scrapers do not give as fine a cut as a HSS scraper. So while I use the carbide scrapers for roughing I usually end up finishing with the HSS tool. Also when sanding the slower speeds work better and leave fewer deep scratches with coarser grits.

-- Les B, Oregon

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Karda

877 posts in 429 days


#5 posted 12-17-2017 10:46 PM

thanks les that helps I got the outside sanded and finished now I am working on the inside most of the tear out I think was the scrapers on the bottom but on the side it cleaned it up some. some of it sanded out. thanks ike

View LeeMills's profile

LeeMills

489 posts in 1176 days


#6 posted 12-18-2017 01:07 AM

Are you keeping the scraper flat on the rest or are you sheer scraping for the final passes?
Brian Havens has some very good videos on sheer scaping (usually the tool is about 45 deg).
https://www.youtube.com/results?search_query=brian+havens+woodturning
Just look up sheer scraping or sheer cuts.

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

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Karda

877 posts in 429 days


#7 posted 12-18-2017 02:23 AM

I am using a half inch round scraper flat on the rest with handle slightly elevated. I watch Brian havens videos. I wish I could ask him questions

View Lazyman's profile

Lazyman

1565 posts in 1262 days


#8 posted 12-18-2017 04:48 AM

Check out the section at this link about sharpening scrapers, particularly about raising a burr. Getting a burr on scraper makes a huge difference on the smoothness of the finish.

http://www.docgreenwoodturner.com/scrapers1.html

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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Karda

877 posts in 429 days


#9 posted 12-18-2017 07:25 AM

thanks for reminding me that is a good article

View LeeMills's profile

LeeMills

489 posts in 1176 days


#10 posted 12-18-2017 05:11 PM

I think you may help somewhat by using a sheer scrape instead of flat (conventional scrape per Havens terms). If you link to the minute mark in the video that you have a question(s) about maybe folks here can give enough info to form a consensus of possible problems/answers.
It will also be a harder cut in dry wood than in green and the distance over the tool rest may be more important.
With a 1/2” wide you can set up chatter pretty quick if it is the standard thickness (1/4”) tool.

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

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Karda

877 posts in 429 days


#11 posted 12-18-2017 06:51 PM

got the inside done now to sand butt a couple cracks to fill. i sharpened my scraper that helped a lotmy 1/2 inches is 3/16 thick I was scrapping about 2 1/4 deep. This is the thinnest bowl I have ever done. The lip is very thin. when I scrape there the wood whines like a banshee. I’ll post a pic when I am done

View LeeMills's profile

LeeMills

489 posts in 1176 days


#12 posted 12-18-2017 07:43 PM

If you take a look at the Havens or the Stuart Batty videos (on Vimeo) their 1/2 wide scrapers are 8/16 thick.
May be a little extreme but Stuart also recommends 7/1 overhand for scrapers. So 2.5” deep would require tool and handle behind the rest of 17-18” to maintain good control.
Looking forward to the pic.

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

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Karda

877 posts in 429 days


#13 posted 12-18-2017 09:58 PM

ok

View LKaan's profile

LKaan

11 posts in 35 days


#14 posted 12-19-2017 02:21 AM


If you take a look at the Havens or the Stuart Batty videos (on Vimeo) their 1/2 wide scrapers are 8/16 thick.
May be a little extreme but Stuart also recommends 7/1 overhand for scrapers. So 2.5” deep would require tool and handle behind the rest of 17-18” to maintain good control.
Looking forward to the pic.

- LeeMills

Wow great information. Thank you. Never could figure out why sometimes I see Turner’s using extremely long handled tools. That explains it perfectly.

-- Learning the wood whisper.

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Karda

877 posts in 429 days


#15 posted 12-19-2017 06:07 AM

here are the pic of the cherry bowl i was working on. The finish is mineral oil and beeswax

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