Boxed in on a round hole fail - Pic

[Steve Mathews]

I had the bright idea today to hog out the majority of a 5" diameter blank with a 2 1/4" Forstner bit. The short sighted plan involved removing more material to reduce the wall thickness in some way. After successfully boring the hole I realized I couldn't come up with a way to proceed other than to make gradual scraping cuts on the inside with a skew. That's when the tenon (Yes, that's right John, not a recessed tenon but a real one) I made to chuck on the opposite end broke off. It wasn't that big of a deal because the piece just rolled off the lathe and I was not in the line of fire. So, was the bored hole a bad idea? If not, what is the proper way to reduce the wall thickness? Here are a couple of pics of the failed attempt.

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PS I plan to work on some non-glued pieces of construction lumber tomorrow as suggested by Mr. Canfield.

[Adam Petersen]

Hi Steve,
I'll preface by saying I'm not a pro. That being said, a lot of turners do exactly what you did, which is bore out the middle to the correct depth and work from there. There's no reason not to unless you enjoy hollowing. From there you used the skew inside a bore hole on a "faceplate" turning. I wouldn't recommend that personally. The only time I use the skew in faceplate orientation is to scrape or help fine tune my tenon. I'd never use it to bore. What other options do you have? The cheapest tool to use would probably be a simple scraper. You "could" use a bowl gouge for some of the cuts depending on your grind and skill with it. I wouldn't be comfortable with that for very long. There's lots of stuff online for homemade scrapers or hollowers too which could be a good place to start. Hurricane turning tools makes good scrapers at a reasonable price too.

[Allan Ferguson]

A sq. scraper would work well to remove the excess wood. Cut with the left corner of the tool. Too much tool hanging over the tool rest can become problematic. Richard Raffen DVDs on box turning are very good.

[Grant Wilkinson]

There is no problem with boring out the middle. From there on, just use a bowl gouge. The hole down the middle doesn't need to change the way you hollow out the inside. It just means you have less material to remove.

When boring with a bit that size, be sure to back out the bit and clear the chips frequently. That is putting a lot of torque on the tenon, and that tenon didn't look very big.

[Barry McFadden]

I hollow out with a bowl gouge after boring a hole with a Forstner bit. I also use this termite tool https://oneway.ca/products-category/turning-tools-handles/The%20Termite%20-%20End%20Grain%20Deep%20Hollowing%20Tool which works great for both end grain AND face grain bowls...I wouldn't be without it..

[Pat Scott]

Your tenon is too small, I would have made it a larger diameter for drilling and hollowing. There is quite a bit of force on the tenon when drilling a 2-1/4" hole. After you have the inside done and the wall thickness where you want, then you can reverse the piece to reduce or remove the tenon and finish the outside profile.

Your piece of wood doesn't look too deep, so I would have probably used a bowl gouge to remove more of the inside bulk. Judge your own skill level when doing this, and if you're not comfortable presenting the tool and bevel then pick up a different tool. Cutting the inside (especially with the wood you are using) will give a better finish than scraping.

A skew would not be my first choice given how much wood needs to be removed. If you must use a skew, lay it flat on it's side and use the toe of the skew and push straight in. Go slow and only try to take off a little at a time. A scraper or hollowing tool can remove more wood than a skew used this way. I will use a skew flat on it's side when I want to enlarge a hole from 1" to 1-1/16" for example when making peppermills - and it takes me several passes to give you an idea of how little I take off at a time.

This piece can still be salvaged so don't throw it away. It looks to have plenty of thickness in the bottom, so I would jam chuck it and cut a new tenon. You don't have to do a full on tenon like you made originally, just cut a shallow notch (or dovetail) in the bottom like this:

[Jimmy Edwards]

Steve I use forstner bits to do a lot of hollowing. However you must start with a 1/2 or 3/4 bit and continue in increments of, 1/8 all the way up to 2 1/4 or so. Jumping on it with a 2 1/4 first is just dangerous. You will break the tenon, shank, or your head.. The lathe must be going slow, very slow. Don't go full depth with the bit. The bits sharp point will take up 1/4 in. to get rid of the little hole. Bottom thickness disappears. Also please never use a skew inside of a bowl. Also dangerous and inefficient. A sharp 3/8 bowl gouge looks perfect for your bowl. You may get a Robust bent tool rest that reaches all the way in the bowl. You can finish cleaning up the inside wall with a 1/2 or 3/4 sharp scraper.

[John K Jordan]

...2 1/4" Forstner bit....
...scraping cuts on the inside with a skew.


The bored hole is a great idea. The Forstner bit is used by many expert turners to remove some wood to depth before hollowing. Others use a big drill bit - for goblets Rudy Lopez showed a 1" taper drill he cut off short and resharpened. I often use a 3/8" drill for my boxes, goblets, and things but the Forstner bit could save a lot of time - I keep bits mounted on short wooden handles with an adjustable depth collar for make it foolproof. Also, a common "old" way to drill a starter hole was simply push a spindle gouge into the end of the wood as a drill bit.

The tenon does look too small. It would probably have been fine for end-grain turning since the wood is strong in that direction. But for face turning like this piece the wood will split off easily at a ring, especially for some types of wood. (I prefer to turn things like this as end grain if possible, with the grain running down the axis of the lathe.) The thing to do is make the tenon much larger and just plan on finishing more of the base after reversing and jam chucking. You can save this one by making a wide flat spot (perhaps by reversing and turning) then gluing a larger glue block on the end. I would use a strong wood for the glue block.

As for hollowing, I'd be afraid to put a skew chisel inside a piece like that. I rarely use a skew for any kind of scraping. I do often use a diamond profile parting tool for hollowing certain small things - it works well since the cutting edge is so small and the side force is almost nothing when pushed straight into end grain. That's what I use for these little bells - 30 seconds of hollowing with the parting tool, then clean up by shear scraping with a wing of a spindle gouge or a small Hunter tool. (This one cut in half to show the profile)
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Let me get something straight - was your intention A) to end up with straight walls from the opening, like a cup, or B) did you want to hollow by undercutting the at the top and making the inside wider than the opening?

If A), straight walls, a square ended scraper pushed straight in usually works well, removing a little at a time. A bowl gouge is perfect, scooping out and perhaps cleaning up the bottom some kind of scraper. These would be "conventional" scrapers, flat on the top, profile ground as desired. I like the little teardrop scrapers for a rounded bottom. Very useful are the rounded negative rake scrapers for cleanup of rounded insides of boxes and bowls. A box scraper such as Packard shows is perfect for cleaning up the sides, and the bottom if it is flat.
http://www.packardwoodworks.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=packard&Product_Code=108784&Category_Code=
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Note that any way you hollow you don't want to remove too much material on any one pass since the side stresses could be too high. That's the reason people who do hollow forms often use very small cutting bits. These are often made from 1/4" or smaller HSS square or 1/2 round bars and fastened to a tool end with screws or brazing. Look at the bits in the tools that the other John Jordan uses on all of his hollow forms, held in place with set screws:
http://www.johnjordanwoodturning.com/John_Jordan_Woodturning/Tools_and_More.html
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If B), then a combination of straight tools and crooked tools is the thing to reach in under the opening. The Jordan tools show these, I also have some made by Sorby and some other makers. You can easily make your own. (Google "make hollowing tool) My favorite swan neck tools are those Mike Hunter makes - I keep some in various sizes. Some people make their own using cheap carbide cutters. But be careful - as mentioned before, the smaller the cutter, the less side forces on the piece while hollowing. I am a big fan of the Hunter carbide tools - the bits he uses are amazing: razor sharp and can be used in bevel-rubbing or scraping modes depending on the situation. For hollowing, I often reach for his swan-necked tools, especially a very small one for small turnings. I took this picture to show some handles I made, but it also shows one of the tools for reaching inside under the opening. I have an even smaller one now good for ornaments and things.

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JKJ

[Michael Schneider]

I was watching YouTube and came across a nice video of a Trent Bosch hollowing presentation to a turning group. He used a gun drill (something I had never seen before). He talks about drilling the hole down the middle at 59 minute mark https://www.youtube.com/watch?v=bPqZz-PDa4A


It is a great video on hollowing. I am an newby at that and learned quite a bit.

Have fun, there are always many ways to solve a problem
Michael