Bowl transituation

[Jerry Lear]

I have been turning for awhile but still have trouble on the inside of the bowl on turning onto the transition and across the bottom. I use a side ground bowl gouge with a 60 degree bevel and the heel is relieved.
I know this is end grain but I was hoping someone could give me some pointers to help control the tool when making the transition.
Thanks

 

[Zach LaPerriere]

For starters, I'm no expert. To a certain extent I find that the blunter your bottom of the bowl gouge is, the easier it is to control. When I started with this grind I used a bit over 80 degrees. Now I'm favoring 70 degrees for most, but I still use the 80-ish degrees for finer cuts on some difficult woods.

Relieving the bevel is great. I don't let my primary bevel on these grinds get over a 1/16". Good luck.

 

[Owen Lowe]

I have been turning for awhile but still have trouble on the inside of the bowl on turning onto the transition and across the bottom. I use a side ground bowl gouge with a 60 degree bevel and the heel is relieved.
I know this is end grain but I was hoping someone could give me some pointers to help control the tool when making the transition.
Thanks

It’s certainly a tricky endeavor to get the side and bottom to blend well with a good finish. One of the issues is that when you transition to the bottom, as you said, you’re going against end-grain and it tends to leave a poorer finish than the sides. A very short bevel, like Zach ^ mentioned, helps the angle of the tool as well as supporting the cut fibers. You might try doing a center outward cut when working the bottom if it’s relatively flat. In my experience that can really help with the quality of the cut. Don’t go too far or you’ll be hitting the end-grain of the side! It’s a very delicate balance between the two. I sometimes run my lathe in reverse doing this center-out cut because it’s easier getting and supporting the tool handle at the proper angle.

I find that once I get the transition between side and bottom fairly well shaped a very, very, light high-angle shearing cut with a curved wing side-ground gouge or just-sharpened scraper blends the two pretty well. I’ve also experimented with a gooseneck cabinet scraper, also held at a high shearing angle to blend and that also works well.

 

[hockenbery]

Hi Jerry,

Shape of the bowl, depth of cut, and speed of cut all contribute making cut from rim to bottom center.
a hemisphere shaped bowl is probably the easiest to cut through the transition sincethe cut is always across the fibers until dead bottom center.
Even with these bowls there is more resistance as the angle across thhengrain becomes more acute
With wider bowls there is more cutting into the end grain.

There are lots of ways to cope with thus issue. I find it more problematic when roughing.
Here is what I'd do.

The speed of the wood coming past the tool is much slower a 1/3 from the bottom than it is at the rim
If you are doing step cutting you can speed up the lathe a bit as you work on the Bottom 1/3.

You can see this in a a video of a roughing demo. Fast forward to 22:50 to get in the neighbohood.
Roughing green bowl -

View: http://www.youtube.com/watch?v=Lo0bGSafZq4


What I do when roughing is to start my cut removing 1/2" to 3/4" of wood.
Then mostly by feel when the cut meets more resistance just pull the tool back a bit an cut half the thickness to bottom center then cut the part I left.
Usually this is 2/3 of the wall at full cut and the last 1/3 repeated twice with a 1/2 cut.

When I'm doing the finish cuts they are to light to halve so I just slow down as I get closer cutting into the end grain.
In the same demo I return a dried bowl.
Fast forward to 26:26 to see the finish cuts.

Mounting and turning a dried bowl -

View: http://www.youtube.com/watch?v=sCZWsHB4vlM

 

[odie]

Jerry......another thing you might want to consider trying is a traditional grind on your bowl gouge. I've found it to be capable of cuts your Ellsworth/side ground gouge isn't......particularly when the transition is very pronounced, such as when the walls of the bowl are inward slanting.

-----odie-----

 

[Dean Center]

This might be a good excuse to get together with a club mentor. Perhaps she could see something about your technique that you haven't been able to.

 

[Bill Boehme]

I have been turning for awhile but still have trouble on the inside of the bowl on turning onto the transition and across the bottom. I use a side ground bowl gouge with a 60 degree bevel and the heel is relieved.
I know this is end grain but I was hoping someone could give me some pointers to help control the tool when making the transition.
Thanks

You didn't say exactly what kind of trouble you are having. Is it with getting catches or with having a smooth flowing curve that matches the external shape? Catches happen when you lose bevel contact which can be the result of cutting below center or rolling the flute too far "open" (pointing upwards so that the left edge digs into the wood). Getting a smooth flowing curve that follows the exterior curve is a much tougher problem because you can't really see the inside shape like you can see the exterior. That is a problem that still bugs me. I think that the cause mainly happens if I use my arms rather than my body to guide the gouge. The best way to "see" the interior curve is with your fingers.

If the problem is tear out then the tool is probably dull and it is being pushed harder to make it cut.