How do you undercut a rim?

[Walt Caza]

Good Day Everyone,
As I strive to learn to turn bowls, the next thing
I would like to try is bowls where the hollow inside is a little larger than the rim.

Sifting through the turning forum archives showed me many
projects with undercut rims.
I don't think I wanna undercut the rims proper...
where the wall is thinner than the rim,
just a gentle curve where the inside is wider than the rim.

Poking around in there with a radiused bowl scraper 1/2" thick
proved to be quite grabby...
and the end grain wants to tear-out.(more finese req'd?)

My unskilled hands cannot seem to get a bowl gouge around the corner?
I just wanna explore manually for now, and maybe a rig down the road...

Where do I start my homework?
What tools should I start shopping?
Would finer, closed grain wood better cooperate? (ex: not oak)

LV offers Kelton hollowers and undercutters.
http://www.leevalley.com/wood/page.a...330,49232&ap=1

WoodCraft offers Mike Hunters carbide hollowing tools.
http://www.hunterwoodturningtool.com/index.html

I suspect part of the problem is alternating side grain/end grain on the spin?
And probably the spinning bowl pushed out of round during the cut?
And surely my lack of experience?
I don't know what I should do, nor how to do it!

Any insight appreciated,
see you in the sawdust,
Walt

ps Can anyone share a picture of a bowl like this so we are on the same page?

[Mike Minto]

Walt, glad to see you are experimenting and expanding your woodturning horizon. I've made a couple of forms with undercut rims, and have had good luck using a Sorby HollowMaster. It is the best tool I have for this particular job. Once offered it on eBay for some reason; now glad it didn't sell. Massive toolbar to help control vibration, long handle for control - you might like it. Let us know how it goes, Mike

[Chris Stolicky]

It sounds like you are already wanting to venture into the world of hollowing, albeit the very beginning.

I have actually been able to turn a couple of pretty undercut rims simply by using a 1" round scraper. You are limited by the diameter of the hole (opening), and just have to bring the tool in from the backside of the lathe.

I'll have to see if I have any pics...

[Jim Underwood]

I have used a freshly sharpened gouge, with flute well heeled over toward the horizontal, and the handle well toward the back side of the lathe. Seemed to work for me. Of course some of that depends on how far you want to go down into the bowl.... and how deep the bowl is. Just don't let that left wing get hung...

[curtis rosche]

lay the gouge on its side so that the wings are pointing in the direction of the wood to cut. and hold the handle at an angle. you might find it easier to stand on the other side of the lathe to do it. take a look at some of the hollow forms i have done. they are all done with a bowl gouge

[alex carey]

+1 for sorby hollow master.

Also use the handheld monster hollowsystem.

[Leo Van Der Loo]

Walt I use conventionally ground bowl gouges for it, and it is difficult to get a good clean cut, very often have to do quite a bit of sanding to clean the cut up, scrapers just don't work unless you have some real dense closed grain wood, it will tear the wood worse than a cutting tool does.

It just takes a lot of practice and even then it's not easy.

Here are a couple of pictures I choose to show what I think you meant by undercutting the rim with a gentle curve.

[Walt Caza]

Thanks for all the good replies so far.

Yes Leo, that's precisely what I am hoping to accomplish...
Thanks for posting the pics, your usual amazing work, and right on point!

I guess my real problem is not having done enough 'reps',
which flows from my deeper problem...
not enough turning stock, and not enough shop time.
I heard a quote that 'you need to turn 1000 bowls, not 999 either'.

My whole approach thus far has been suspect.
-precious and spendy waxed blanks from the tool store
-pressure not to waste expensive exotics, instead of practicing technique
-trying to push a turning from start to finish in a short session, so I can bring home a fresh show-and-tell for my wife
-wanting to run before I walk, when I should be crawling

I guess I need a chainsaw, some log sources and
to shift my focus from product to process.

Frustrating not to be able to make the things you envision.
I know, it's very early on a looong journey.
Walt

[curtis rosche]

hey, dont sweat it. i kinda tried to do the same thing you are doing, using the really nice stuff to learn on. but it makes the eraly peices lookt hat much better. go to the local sawmill and ask if you can have their cut offs, or some scrap peices. or call a tree removal company or an arborist, tell them you are looking for some wood for a hobby, it doesnt need to be straight or big. (otherwise they might try to get you some peices for boards and try to make you pay for it)

you could always do what David Lancaster does. get a logging trailer and take road trip. he goes from maine to PA just for cherry

[Scott Hackler]

I do a lot of my undercut rims with the lathe in reverse and using a 1.2 HD scraper. This direction allows me to stand on the correct side of the lathe and comfortably come into the underside of the rim. Sometimes if the hole is large enough, I have the rest actually in the bowl, for more support. My 1/2 HD scraper is used a lot and I recommend getting one. Hollowing is a lot easier on some woods as well.

If you want a severe undercut then a hollowing tool is the only real way.

[charlie knighton]

Leo, i like your oak bowl,

Walt, you might want to check out Bob Rosand site, he has an inexpensive bent tool for hollowing xmas ornaments

http://www.rrosand.com/tools.shtml

if you happen to have a 1 inch square tool rest it works even better than on standard tool rest, also this tool not to be used with over 2 inch diameter turnings

i happen to use hollowmaster in certain circumstances and the elbo tool, i like the elbo tool

enjoy

[Chris Stolicky]

Here are a couple of bowls I turned when I first attempted bowls; when I took a short break from making pens. Both were made on my Jet mini. I used a 1" scraper for most of the turning, mainly because I couldn't figure out the bowl gouge at the time and kept getting bad catches. The first is osage orange (~5"x2.75") and the second is figured maple (~6"x3"). So, see, I also practiced on more expensive, bought wood. The osage orange actually bounced across the shop 3 times and has a crack in it! Remember what I said about learning from mistakes? Oh, I was also using the nova midi chuck that has smooth jaws, which isn't the best option when you get a catch.

Note, these pics are also before I ventured into learning how to take pics of my turnings....

comment - I realized after I posted this the maple looks like it has a pedestal, it actually has a flat bottom. It was just sitting up on something.

[Cody Colston]

I'd also recommend the Sorby Hollowmaster. It makes undercutting bowl rims a breeze and will let you get into hollowing for not a lot of money. It's what I still use for my hollow forms.

[Ryan Baker]

If you are using oak, stop doing that (at least for now). Oak is not a very good turning wood and not a good thing to develop skills with. If you can get green wood, that is better for experimenting on as well.

If the undercut is not too severe, you will do better with a bowl gouge than most anything else. Something like a Hunter tool can work well, but is an expensive place to start and not really necessary. If you are having grabbing problems with your scraper, it is probably because you are using too much of the edge. Do not try to use the whole edge of the scraper. You shouldn't be contacting more than about 1/4" of the tool to the wood at any given time. The scraper radius has to be less than the bowl radius. Also, make sure that you are slightly above centerline with the tool shaft angled down toward the bowl (handle up). Shear scraping, instead of flat scraping, will help a lot with tearout. Remember that you should always be cutting 'down' the grain to avoid tearout better. That means that on an undercut bowl, you are better off to be cutting from the widest point of the interior back up toward the rim for a better cut. You may not want to start that way though, since it takes some different techniques, especially with the gouge. The hard part with a gouge is at the widest part where you are transitioning back to cutting toward the center again -- it's easy to lose the bevel there and end up with a nasty catch.

You can also get into the category of hollowing tools, but it doesn't sound like that is the type of thing you are trying to do right now. Hollowing is a whole new world of tools and techniques of its own (and a lot more $).

[Steve Schlumpf]

Walt - lots of good info for you to consider. As you probably have guessed by now - there are lots of ways to tackle that particular problem. Easiest way would be to post a photo of the bowl you are undercutting - so we can see exactly how far back you are cutting into the bowl. Some tools work - some tools work better than others and most all of it relies heavily on experience.