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turnings #10: Newfound respect for hollow-form turners

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Blog entry by Gary Fixler posted 08-25-2009 04:06 AM 2689 reads 0 times favorited 10 comments Add to Favorites Watch
« Part 9: A turned Jacaranda bowler hat Part 10 of turnings series Part 11: first hollow-form failure update - major checking! »

Well, I tried out the tools I got from mom for my birthday recently. Of note:

1) My 1/2” Sorby Spindlemaster was not a good indicator of how the 3/4” and 1” behave. I’ve been using the 1/2” however I liked, never reading up on how to use it, nor watching any videos. I recently watched one and thought “Huh, I’ve been using it entirely wrong.” I’ve been holding it flat, and using a combination of things with both hands and the tool rest to get the curves I want. With the larger versions, these movements I’ve grown accustomed to cause catches, wrenching the tool this way and that. It’s nearly unavoidable. So, I went back and watched the video again. I was out there for awhile trying everything with both new tools, and I passed through the proper methods many times, but didn’t achieve the results seen in the videos most of the time. It’s going to take a lot more work with them to gain comfort. I did get it to act sort of like in the video several times, but could never achieve a smooth curve, nor did I ever get that burnished look (though it’s green wood – so probably couldn’t anyway).

2) The Sorby Sandmaster is pretty cool, save the bearing. The head spins freely, and by letting the work brush the bottom edge of the disc, you get it spinning, so it keeps clearing away dust and presenting different sections of grit to the turning. I found that the bearing isn’t quite the precision engineering I was expecting. The head was a tad rattley. The disc would stop frequently, and need a bit of coaxing to start spinning again, because the head bent ever so slightly, causing the mating surfaces around the bearing to seize up a bit. Once the dust got in the cracks, it gummed up and was scratchy when spun by hand. I sprayed some WD-40 in there and it got a lot better. It works alright, but I was just surprised that such a top tool needed babying right from the first minutes of use. It did give a good finish, and allowed me to round out the hollow form from the poor surface I was getting through my inexperience with the new Spindlemasters. The pad (60 grit only so far) stayed nice and clean, and no burned fingers was a real plus :)

3) Hollow forms are harder than I feared. I don’t really know what’s going on inside yet without being able to see. I don’t have good light set up, nor calipers, so it’s all guessing when turning, then trying to figure things out by feel with my fingers after powering down intermittently to check things out.

Here’s the chunk of Indian laurel fig (Ficus microcarpa) turned cylindrical:

Ficus log on lathe

It’s pretty green still. It’s a branch from a larger log that forked. The grain reminds me of an unsealed utility pole:

Ficus log on lathe

Ficus log on lathe

I was able to drill out a centered hole easily with the Sorby micro holder with boring bar insert:

Sorby micro boring tool

Save for the fluffy bottom – green F. microcarpa logs get huge flaps in certain parts of their grain (a kind of tearout) – the outer form came out well. This is sanded with the Sorby Sandmaster with 60 grit, used to shape the curvature a bit after some wobbly Spindlemaster work:

hollow form exterior turning

I was having a really tough time past the first 2 inches. The micro hollowing tool, which fits in the red insert handle seen above (with the boring bar inserted) worked great at first, but then it was just too deep. I switched to the Sorby Hollowmaster, but it’s just huge. It was like playing Operation getting the head in there without hitting the lip walls, and then it was so hard to maneuver. I needed a hollowing tool halfway between them.

Eventually I lost my grip on the micro hollowing tool and it rattled around in the lip for a second before I grabbed it again, and it made some large cracks down the walls. I carefully tried to turn it a little more (for some reason), and then decided to open the mouth wide and just see what I’d done inside, as it was hard to tell in the dark interior. The 1/2” Spindlemaster made a really ragged edge when I did this, probably because the cracks were causing the whole lip structure to vibrate hard against itself:

hollow form with ragged edge to lip

That’s where I gave up on it for the night. I was a little low on patience. My first half dozen bowls were disasters, too (sent at least 4 of them across the garage after huge catches), so I’m not nearly ready to give up, but it was time to take a rest.

I have finally tried it, and now I have a better sense of what I’m in for. I think I might turn away the top of this thing, reshape what remains into a smaller version of what I made here, and use the micro hollower on what will be a much more properly-scaled turning for its length.

This fig is actually a bit hard. I think I’ve made myself into a wimp with that luxuriously soft jacaranda wood. It melts away like butter, in 1/4” deep cuts. I should probably glue up some oak blocks and strengthen myself up. Hollow forms are tough work!

-- Gary, Los Angeles, video game animator



10 comments so far

View lew's profile

lew

10027 posts in 2407 days


#1 posted 08-25-2009 05:43 AM

Thanks for the description of the tool operation, Gary

Looks like each time you turn you get a new experience and improved skills.

Lew

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View scrappy's profile

scrappy

3505 posts in 2082 days


#2 posted 08-25-2009 09:02 AM

Keep all the great info comeing. Now I know I am not ready to try a hollow form. haha

Will try sooner or later, but still trying other forms that you have shown.

Thanks for the great posts.

Scrappy

-- Scrap Wood's the best...the projects are smaller, and so is the mess!

View StevenAntonucci's profile

StevenAntonucci

355 posts in 2590 days


#3 posted 08-25-2009 03:22 PM

It always starts that way. Do yourself a favor for #2 and don’t make such a deep vessel. Once you get more than a few inches over the tool rest, things get more exaggerated.

The shape you picked is a good starting shape because 90% of the vessel can be cut with a straight boring bar. The undercut shoulder is right there and relatively easy to get at with an undercut bar or tool of your choice. THE NUMBER ONE RULE IN TURNING HOLLOW VESSELS IS YOU HAVE TO KEEP THE CUTTING TIP ON CENTERLINE. All of the jerkiness and catches you experienced were caused by being somewhere else in the vessel. Also, make sure your cutter is sharp (it should hiss) to reduce drag and cutting forces…

If you are trying to hollow with a scraper, you will find a lot of better ways with some simple tools. Look at the Ellsworth style hollowers, then run down to Home Depot to the steel racks…

Good luck on #2…

-- Steven

View RBWoodworker's profile

RBWoodworker

416 posts in 2004 days


#4 posted 08-25-2009 05:22 PM

Howdy Gary!!

my turning experience starts and stops with just turning the front legs of the rockers I make.. I have never tried bowls or anything hollow.. you are venturing into an area that I never have.. and from the looks of it, your doing a great job so far..I like that vase!! no chucking it across the room either..lol

Listen to those that know like Steven and the other Lj’er’s here.. I’m learning just fom reading their post so I will know when my time comes.. hang in there buddy!!

-- Randall Child http://www.racfurniture.com/

View Hix's profile

Hix

161 posts in 1930 days


#5 posted 08-26-2009 02:46 AM

Great Post! Most of us learn from a combination of trial and error and education. The advice to start w/ smaller forms is right on. Keep at it, the next one will be easier and the one after that and the one…...
It sure is addicting isn’t it?
Keep turning out the posts (and the bowls.) I enjoy reading them.

-- ---call me---- Mark

View trifern's profile

trifern

8132 posts in 2419 days


#6 posted 08-26-2009 05:01 AM

Hi Gary, I would also add the suggestion of having a larger opening. Start by doing a closed bowl type form. This will allow you to use your hollowing tools, but allow more access visually. By being able to see better, you can concentrate on the proper techniques required for your hollowing tools. After some practice and a better understanding of the techniques you can gradually start reducing the diameter of the opening.

Joe

-- My favorite piece is my last one, my best piece is my next one.

View Gary Fixler's profile

Gary Fixler

1000 posts in 2034 days


#7 posted 08-26-2009 05:22 AM

Lew – Yep, learn something new each time, and sometimes that means learning I have a looong way to go :)

Scrappy – Keep at it! We all have to motivate each other. The replies in here psyched me up again after this latest failure.

Steven – Thanks for the tips! I will incorporate them, but I’m also sure it will be awhile before I manage anything nice in the area of hollow forms.

Randall – Thanks for the words of encouragement. Definitely inspiring!

Hix – Will do! I’m going a lot smaller on the next one, whenever I work up the motivation to get back out there.

Joe – I think that’s probably the best idea – start wider, not just smaller. I think my next bit of learning will be something along the lines of 2” deep, and 8” wide, with a 5”+ opening – basically a bowl with a rounded over top, which is what I think you meant by ‘closed bowl form.’ Do you find you can tell where the edges are as you work, or do you have to check with calipers often? Wish me luck!

-- Gary, Los Angeles, video game animator

View reggiek's profile

reggiek

2240 posts in 1922 days


#8 posted 08-26-2009 05:57 AM

Gary, you should also pre drill your vessell with the biggest forstner you can use….l usually use a 2 1/4” chucked into my tailstock with a bit extender (depending on depth of the vessell)...now by taking the bit to where you want to hollow out…you will have a guide to how deep you are going to go….it also gives you the ability to get the hollower into the vessell. You should also have a pair of calipers on hand to measure the thickness as you go.

Hollow forms are actually quite easy once you get the hang of it….and very enjoyable to create…they are art just by themselves (IMO)....

Just keep practising….thats what all of us have to do…..and take it slow and easy…..you will be turning out great hollows in no time….there are also excellent how tos on the internet…and You Tube.

-- Woodworking.....My small slice of heaven!

View Gary Fixler's profile

Gary Fixler

1000 posts in 2034 days


#9 posted 08-26-2009 07:09 AM

Thanks for the tips, reggie! And for the vote of confidence.

-- Gary, Los Angeles, video game animator

View reggiek's profile

reggiek

2240 posts in 1922 days


#10 posted 08-26-2009 07:14 PM

My pleasure….from looking at the pics…I know you will get the hang…..my first hollow looked really bad inside…l wasn’t on LJ’s then or I wonder if I would have had the stones to post it…LOL….but by watching the videos….playing with the chucking….and sending the forstner down the inside….I can turn a nice one fairly easy…Now all I need are some good blanks….therein lies the hard part….good blanks..to buy them is expensive….to make them takes a lot of time…or you need a bit of luck to find some from fallen trees…

Also, look up the staved vessels…its a fairly easy way to make a hollow…without using so much wood…I built the jig…but now I just use a couple band clamps…and wallah!...I should be posting one fairly soon as I am just getting ready to put the finish on my most recent one…

-- Woodworking.....My small slice of heaven!

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