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Segmented bowl Turning Issue

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Forum topic by Mcron003 posted 06-25-2018 10:49 AM 466 views 0 times favorited 10 replies Add to Favorites Watch
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Mcron003

3 posts in 25 days


06-25-2018 10:49 AM

Topic tags/keywords: segmented bowls woodturning issue wood douglas fir jet lathe tools question

Just to preface this I am very new to wood turning.

I made a segmented bowl blank (4 in diameter) very easily, however when I went to turn the inside of it I could not take off any wood or it would fly off the lathe.

I used Douglas fir, I have a jet 12in lathe and I have tried to used a full size turning tool with a carbide cutter and a 1/2 in bowl gouge to try and rough the interior out and nothing is working.

Am I using the wrong tool?
Are there any special techniques to make this workable?


10 replies so far

View John Smith's profile

John Smith

1130 posts in 217 days


#1 posted 06-25-2018 11:29 AM

can you post some photos of the tools that you are using ?

-- Graduated Valedictorian from the University of HardKnocks --

View OSU55's profile

OSU55

1737 posts in 2044 days


#2 posted 06-25-2018 12:15 PM

Some pics of how your are attempting to hold the bowl on the lathe would help also. It could be many things

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Lazyman

2185 posts in 1442 days


#3 posted 06-25-2018 02:06 PM

It is most likely a problem with how you have it mounted. How is the piece mounted on the lathe, chuck, faceplate, glue block or between centers? It is a good idea, if possible, to keep the tail stock engaged until you just cannot proceed without backing it away. If you are using the bowl gouge for hollowing the inside, it may be that it is dull or not sharpened well. Some pictures of the tip will help us see if that may be part of the problem. The most common problem when learning to use a bowl gouge, for me anyway, is catching the wings or corners of the gouge because you are holding the gouge at the wrong angle or being too aggressive with your cut. Carbide on the other hand is pretty forgiving so unless the cutter is old and dull, that would indicate a problem with how the bowl blank is mounted.

Also note that, though it seems a little counterintuitive for a beginner, a faster speed is actually less likely to get a catch than a slower one. The reason is that when you turn a slower speed, you are more likely to push further into the gaps and take a bigger cut causing a greater impact and are more likely to catch the wing of the bowl gouge.

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

View LeeMills's profile

LeeMills

564 posts in 1356 days


#4 posted 06-25-2018 03:40 PM

As others said, a pic would help.
How is the blank mounted… spindle orientation with the grain in line with the ways or bowl orientation with the grain perpendicular to the ways? The grain dictates the direction of the cut.
You should be able to use those tool even thought a 1/2 bowl gouge is pretty big for a 4 inch bowl.
My guess is it is mostly in the presentation rather than the tool.
More info would help with suggestions or links to videos which show the “proper” techniques.

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

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Mcron003

3 posts in 25 days


#5 posted 06-25-2018 04:55 PM

The tools that I tried to use were two different full-size carbide tools (square and round cutters), this was the second time that I’ve used these carbide tools so I made the assumption that the cutters were still sharp.

After failing with the carbide tools I went to woodcraft and bought a 1/2 in bowl gouge, I have a tormek so I bought the sharpening jig for gouges as well, I watched a youtube tutorial on how to set up the jig and I believe that I got the gouge very sharp. I practiced with the gouge quickly on some scrap wood and did not have any problems. I only sharpened it twice because the bowl flew off the first time I started cutting the bowl, I tried a couple more times (with the chuck) but that was the point that I destroyed the bowl.

Unfortunately, I cannot show how I mounted it because the final time it flew off and cracked the bowl, I got frustrated and threw it away, the trash was picked up this morning.

The first two times I mounted it I used the stock 3in faceplate with 1 1/2in screws into the waste block. (I rotated the faceplate and offset from the original screw holes) The last time I mounted it I had enough waste block rounded that I used the chuck with the largest set of jaws(~3.5in).

I turned the outside with carbide tools pretty easy, I mounted it between centers and made sure the tailstock was engaged, it was secure.

My guess is that I used to short screws with the faceplate, doug fir is very soft so the screws ripped out easily, my speed was to slow and my bowl gouge technique is not very good. Any more suggestions would be helpful.

I looked up “how to turn the inside of a segmented bowl” and one of the websites said to start out with a scraper, is that right?

Also, any recommendations for tools that can be used in smaller bowls? (5in a below)

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Lazyman

2185 posts in 1442 days


#6 posted 06-25-2018 11:22 PM

The doug fir is pretty soft and brittle so you need pretty long screws to hold it on and with a chuck I would not be surprised if a tenon breaks off if you get a catch. And if you oriented the grain so that the screws were driven into end grain, that will almost guaranteed that the screws will pull out. You’ll have better luck if the screws go into side grain. For brittle wood like that, I find that a recess with an inside grip on the chuck seems to be less likely to break off. Also, it is very important when using a chuck that the end of the jaws (tenon or recess) rest on a flat surface on the bottom of the bowl, If you can see any gap between the jaw and the wood, it is not flat enough.

The carbide is much easier to master than the bowl gouge so I would recommend using them for hollowing until you have a chance to practice with the bowl gouge. Make sure that the top of the carbide cutter is even with the horizontal center line of the turning axis. Some people tilt the carbide tool but most of the time it is best to just keep the cutter parallel to the tool rest. Keep the tail stock engaged as long as you can.

BTW, A great wood to learn to turn bowls with is Bradford pear (or almost any fruit tree for that matter). If they are common in your area, keep an eye out for tree trimmings. BP turns really nicely, especially when green and wet, and is very forgiving when you are still learning how to use a bowl gouge. BP is a pretty wood too.

EDIT: a 3/8” bowl gouge would probably be easier to use with a smallish bowl than the 1/2”

-- 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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Mcron003

3 posts in 25 days


#7 posted 06-26-2018 02:48 AM

Nathan,

That’s some great information, I have been keeping an eye out for tree trimmings. I just found a nice chunk of monkeypod wood that I turned down into a bowl blank. Thanks.

-Matt

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OSU55

1737 posts in 2044 days


#8 posted 06-26-2018 12:24 PM

While work attachment may have been part of the problems (1-1/2” screws should be adequate) Segmented turnings create interrupted cuts, and its easy for a beginner to move the tool in the air gap and then create a deep cut, similar to a catch. Low rpm just makes it even easier to to this. Try to take very light cuts and build your experience. Yes it will take longer but its a learning task, dont be in a hurry.

I started with scraping tools, carbide and hss, on segmented turnings. They create more impact forces during interrupted cuts. Once I learned how to properly sharpen and use a bowl gouge, the scrapers were put away. I use hss scrapers for sheer scrape finish cuts, but hardly touch carbide tools anymore – sharp hss cuts so much better.

View Steve Peterson's profile

Steve Peterson

381 posts in 3137 days


#9 posted 06-26-2018 04:49 PM

It is a bit hard to tell what happened without pictures. Keep trying and don’t give up. Turning gets easier.

I learned by practicing on scraps of hardware store lumber. Douglas fir was difficult because of the coarse grain. It tends to chip a lot and tears out in big chunks. Hemlock or other “white” lumber is a bit cheaper and has a finer grain than DF. I would suggest starting slower and don’t expect a masterpiece on the first try. This means don’t bother taking the time to glue up a segmented blank. Just glue a few 2×6’s together to form a cube and practice with that. Even better is to find a source of tree trunks. Turning green wood is much easier.

I have not mastered the round carbide cutter on the inside of a bowl. It grabs way too easily, although the online videos make it look easy. Bowl gouges are much easier for me because they have a much larger bevel.

-- Steve

View gwilki's profile

gwilki

210 posts in 1528 days


#10 posted 06-27-2018 12:43 PM

As with the others, I have some questions.

You say that you mounted your face plate to a waste block with screws. How did you mount the waste block to the bowl?

When it flew off, did the waste block come off the bowl or did the face plate come off the waste block?

Then you say that you used a chuck to hold the waste block, but it flew off again. Did the chuck let go of the waste block or did the waste block come off the bowl?

Finally, you say this is a segmented bowl. Is it open segment? If so, you have gaps to catch tools. If it’s simply a segmented, closed ring, that cannot be the issue.

Keep in mind that with segmented pieces, you have very hard, rigid glue that you are cutting. You need a very light touch to prevent the glue lines from grabbing your tool and ripping the piece off the lathe. DAMHIKT

-- Grant Wilkinson, Ottawa ON

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