Hollowing help?

[Carole Valentine]

I have ended up with an enclosed form (it was sort of unintentional, but I like the looks - sort of like a fat inner tube) and the problem is as a newbie, I have never attempted that type of hollowing before! I am having trouble getting under the rim and making the inside curve follow the outside curve. I can't seem to make a gouge work on that radius. I have a virgin Sorby Hollowmaster, so I decided to break it out and try it after watching the video on Woodcraft's site. No luck...as soon as the tip comes into even slight contact with the wood, it digs in. What am I doing wrong? I have the tool rest set at center, the straight flat of the tool on the rest and am trying to take the most delicate of cuts! They make it look so easy in the video.:confused:

[Blake McCully]

No luck...as soon as the tip comes into even slight contact with the wood, it digs in. What am I doing wrong? I have the tool rest set at center,:confused:

Carole,
Although I'm no expert I have been playing with hollow vessels and I'm really hooked. I'm not familiar with the tool you have, but with the tool I use, basically a home made hollowing tool, I have to play around with the tool rest height to avoid that. Like that silly old cigarette commercial, a silly little millimeter will make all the difference. Also, the distance of your tool rest from the work piece will alter how the tool interacts with the inside. It needs to be close enough to reduce chatter, but far enough away that you can manuver the tip properly. Hmm... lots of help, sorry.

Maybe someone else can give you more help. What I gave was just from my own experience.

Have a great day.

[Jim Becker]

'Need to know if this is an end-grain turning or a faceplate-oriented turning (grain across the axis of the lathe bed), Carole. The techniques are different. If it's the latter, the hollowing tools, such as the Sorby you mention are difficult to use...those are primarily designed for end-grain hollowing where the small tip works great. You need a much heavier scraper designed for an undercut rim with a good burr on it...and the ability to use it with a bit of a shear angle. What you might try is putting the shear scraping (big, rounded, flat cutter) that probably came with your Sorby tool on and with the rounded side of the tool on the rest, work the larger curved edge under that rim at a 30-45º shearing angle.

[Harry Pye]

Carole,

Make sure that you are scraping with a relatively small area area of the tool's edge. Remember as you move from the edge of the work towards the center, the speed of the wood passing the tool changes. I'm talking about the number of feet/minute passing the tool. If you try to cut at two points that have more than a little difference in speed, it will try to twist the tool out of your hand.

You can also swing the tool rest so it is about 45 degrees to the lathe bed and stick on end inside the bowl. Don't go nuts with this, just a little to support the tool while undercutting.

[Carole Valentine]

'Need to know if this is an end-grain turning or a faceplate-oriented turning (grain across the axis of the lathe bed), Carole. The techniques are different. If it's the latter, the hollowing tools, such as the Sorby you mention are difficult to use...those are primarily designed for end-grain hollowing where the small tip works great. You need a much heavier scraper designed for an undercut rim with a good burr on it...and the ability to use it with a bit of a shear angle. What you might try is putting the shear scraping (big, rounded, flat cutter) that probably came with your Sorby tool on and with the rounded side of the tool on the rest, work the larger curved edge under that rim at a 30-45º shearing angle.
Ah hah! So that is the problem. It is a face grain turning. I tried the round blade and had much better luck, but still some catches, but I used it with the flat part of the tool on the rest. If I use the rounded side of the Sorby on the tool rest, that means I have to flip over the round scraper blade from the way it is mounted now, right? I don't have a scraper designed for getting under the rim. I only have a 1" round nosed scraper. If I knew what the profile was supposed to be I guess I could regrind it. This is all new to me. :(
http://www.esva.net/%7Epchousecalls/mahogbowl_opt.jpg

[sascha gast]

you can certainly use the sorby, not the best tool for that, but just bury the cutter tip in the head a bit more, just let 1/8th or so stick out, or the round scraper attachment works awesome for that.

sascha