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Some dumb questions for the hollowformers…

Michael Anderson

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WunderKut 10 by Rolly Munro and a Woodcut Pro-Forme
Do you favor one of these over the other? For example, which would you prefer to use for a large endgrain bowl (a la Sally Burnett’s)? I’ve been going back and forth between these two, and eventually will purchase one.
 
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Curious to hear other answers, but I hollow with the Trent Bosch Stabilizer and generally work around 900-1000 rpm.
Depends on the diameter of the piece. For smaller forms (3-4”d), I’ll hollow at 1000-1200 rpm. As the forms get larger, I tend to slow down a bit. I’m hollowing freehand, though, so can usually avoid disaster when I occasionally get a catch
 
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I tend to turn while hollowing at low speeds , 500-800 rpm, what speed do use use Bill?
I generally turn very fast, probably never below 1500 rpm and faster as the piece gets smaller in size. Bigger pieces on the Powermatic and smaller pieces on one of the midis. Turning fast has one drawback that I have found and that is going too thin because the wood starts flexing and you end up with uneven thickness which 90° apart can be very very thin.
 
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I generally turn very fast, probably never below 1500 rpm and faster as the piece gets smaller in size. Bigger pieces on the Powermatic and smaller pieces on one of the midis. Turning fast has one drawback that I have found and that is going too thin because the wood starts flexing and you end up with uneven thickness which 90° apart can be very very thin.
I'll have to try faster to see how it works for me.
 
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Do you favor one of these over the other? For example, which would you prefer to use for a large endgrain bowl (a la Sally Burnett’s)? I’ve been going back and forth between these two, and eventually will purchase one.
Michael, I pay little attention to the pros and cons of end grain etc, rather blank orientation, so I can get the very best out of it for what I have planned for it. So whatever issue the grain my throw up, I just deal with it on the day.
As for hollowers each one has its good points, basically the Pro-Forme will remove wood like no other especially on green blanks where it can be opened up to produce a chip 1.5mm thick while using the full length of the tool. The Wunderkut works best at Rolly's recommended setting of .25mm, and at this setting it will clear its self. Once you have mastered either of these hollowers both are very capably or roughing and finishing cuts and the WunderKut tends to lend its self to smaller vessels as the head is smaller. It is a bit fiddly to adjust, so I leave at the .25mm preferring instead to adjust the Pro-Forme. Sharpening, the Pro-Forme for me is easier to sharpen than the WunderKut which have to virtually strip it down completely and the process of setting the .25mm is not as quick
Which one is best or use the most? I use both all the time on most pieces. So I think it would depend on what you're turning. If you're making small pieces, much like our swap. Then the WunderKut with smaller articulated head would be the one I would go for. On the other hand, if you turn larger pieces with some depth, the heavier bent bar of the Pro-Forme would lend its self better. As a point of interest, my Pro-Forme has a 3/4" bar and the other 16mm or 5/8th and they both work well even with the Aussie hardwood.
The learning curve of the Pro-Forme can be slow for some in finding the sweep spot, and it has a tendency to self feed on heavy cuts with green wet wood. But is readily controlled by simply rolling it over into the cut, whereas the WunderKut is more straight forward, rolling is the simple control method used on both.
I understand about going back and forth, I did the same and ended buying both and do not regret either purchase. As a matter of interest, Woodcut will sell you the head only, and you make the rest the saving is around 60% and its not hard. If think you may want to go this way, PM me and I will put something together, either that or we can catch up online and speak about it.
 
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If you think about it, what is a catch? A controlled cut could be defined as a smooth cut at your desired depth, and in the place you want it. Put a tool to spinning timber at the wrong angle, height, or feed rate and any tool can create a catch, or unpredeictable/uncontrolable cutting. That can vary from instant destruction of the piece (and/or tool) to just a skate, or deeper cut than intended. The key to success is to maintian control and predictability of your cutting action, so you achieve the desired results.

On a bowl or spindle, we use our experience and mostly our view of what we're doing to guide us to make our cuts in a controlled way. We can see the remaining wood, the cutting edge of our tool, it's depth of cut and orientation, and the shavings produced. All of those visual clues are invaluable.

Cutting into the opening of a hollow form is like donning a blindlfold. You quickly lose your view of what shape the wood is inside and how deep the tool is cutting, etc. You have to adapt to using feel and sound. The majority of systems have cutting tips are really just scrapers. To keep from breaking the 90° rule with a scraper, (and to be able to hollow to the center) both captured and articulated systems set the height of the cutter level with the rotational axis. The size of the cutters is kept pretty tiny. Not just for working thru a small hole, but hollowing generally means hanging some length off the tool rest. Engaging the long edge of a teardrop scraper inside a hollowform invites a catch.

More later, got a call to get a large burl. :cool:
 
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In 15 years of turning, I’ve never turned a hollow form of any sort nor have I even held one in my hands. I love to look at them and admire them (and those who turn them) greatly.

Questions from a complete ignoramus:

1. Is it possible to turn a hollow form without special equipment/tools? I would think a swan neck tool is the bare minimum for entry…

2. In the hollow form world, what is most desirable? Thinness of the wall i.e. less weight? Or overall shape? Is it “better” to be very thin with a mediocre shape, or great shape with thicker walls?

3. What is an acceptable thickness for the walls? And are the walls supposed to be uniform thickness? It appears to me, if the bottom is as thin as the walls, many pieces may be very prone to rolling. Is a weightier bottom deemed inappropriate to the form or perhaps crucial to the form?

4. How does one compensate for the amount of tool that is required to hang over the tool rest? I assume this is where captured bar systems are required….

5. Do the hollow forms that are created by cutting blanks in half, turning out the centers, then gluing them back together, less valuable (perceived value or actual value) than the ones bored out with a single hole?

6. Is there a general rule as to what defines a “hollow form” piece? How large can the entry hole be before it just becomes a bowl with a large undercut rim?

7. To my eye, the very best hollow forms are the ones with no embellishments and I rarely see embellishment on the traditional hollow forms. Whether tall rocket shaped or low sitting flying saucer shapes, it’s rare to see turquoise, stone. Milliput, etc features…. Is this because the walls are so thin, or is it rather frowned upon?

8. For those who sell, is there a higher end market for the hollow forms? (I would hope so). How has selling hollow forms compared to your sales of “regular” bowls/platters?

Thank you for indulging me…. I look forward to hearing from you all.
It really depends on the wood and the size as to what you need.
#1 the shape is critical. It should be your top priority.
#2 I only use a swan neck tool. It is generally all you need for most hollow forms until you get to the big stuff. I personally own several different types and brands. Most come with different attachments (blades), but I generally only use a round blade.
#3 thickness is important, but not overly critical. I usually turn smaller pieces down to about 1/8 inch. But bigger pieces I will leave around 3/8 inch.
#4 if your wood has voids in it, you may not be able to turn it as thin as you would like. It really depends on the wood. A trick to hold it together is to turn the outside, get your desired shape, then wrap the whole thing in tape, or Cling wrap. This helps hold it together.
#5 hollow forms do sell for more than a bowl, generally. They are more work, and people will pay for Art Forms.
#6 practice makes perfect. You will get internal catches that will sometimes pull at your wood and shift it in the jaws. It happens. It’s a learning experience. Don’t get frustrated. Try something else.
#7 Good luck.
 

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