ALL suggestion appreciated

[Norris Randall]

Trying to get red cedar bowl completed. Seem no matter how light my touch the knots are grabbing. Already flew out of nova chuck, so trying to holding in place with center pressure. Thank you one and all for suggestions. cedar start.jpg

[John Beaver]

Sharp tools, high speed, light cuts, square tenon, ride the bevel.

Most of the time when a piece comes out of a chuck it is because the tenon is not made properly - however cedar is a soft wood, so it could pull out if you get a catch.
Turn the speed up and take light cuts with the bevel rubbing and it should work.

[John Keeton]

John’s suggestions are good ones. However, given the form you are attempting and the interior shape, with the center post, it is virtually impossible to ride the bevel. Is it possible you are cutting from the bottom outward toward the rim? That would nearly guarantee a catch.

[Norris Randall]

Thank you John AND John, I have been slowest RPM and plan to remove the center post. The center post was my attempt to helping the chuck hold . I'll check sharpness and increase speed. oldtimercp.gif

[John K Jordan]

Trying to get red cedar bowl completed. Seem no matter how light my touch the knots are grabbing. Already flew out of nova chuck, so trying to holding in place with center pressure. Thank you one and all for suggestions.

This is a little hard to diagnose without more information. Maybe describe a bit more - the type of tool you are using, the type of cut. Are you holding with a tenon or recess, straight or dovetailed? Are the jaw faces properly seated firmly against a clean, flat surface (e.g. a tenon not bottomed out in the jaws)? The bowl in that picture looks fairly large. What is the diameter of the tenon/recess and the bowl? Which chuck jaws are you using? It doesn't matter as much with cedar, but is the wood wet or dry?

By "knots are grabbing" do you mean hitting the knot forces the tool further into the wood for a massive catch? (A good catch can throw anything out of the chuck.) A knot itself should not be a problem.

Do you have another turner near you who can watch and perhaps spot some issue? For example, some people hollow a bowl like that with scrapers which can dig in violently if deflected by something such as a know, especially if the scraper is used in some ways.

A piece is forced out of the chuck by side forces, of course, compounded the further the catch is from the mounting point. Light bevel-riding cuts with sharp tools can certainly eliminate catches. However, the side walls on that vessel look almost vertical - it's sometimes difficult to get the tools in the right position to ride the bevel. One thing I've done it this case to reduce the wall thickness (depending on the wood) is to use a scraper and push straight in, removing just a little with the corner of the scraper with each pass. This crude cut makes a very rough wall which can smoothed up with a different tool, for me often a Hunter tool for a piece with vertical walls or a partially closed form (with opening a bit smaller than the widest place inside.) The scraper-push method is the only cut I know that would work with the tailstock support you show. The Hunter tool can be used as an extremely sharp scraper on the inside walls to clean up roughness. BTW, the round flat-top carbide scraping cutters could be a problem in this situation.

Another big issue with some tools and methods is a a long overhang of the tool from the tool rest. A "grabby" spot can cause the tool to suddenly move in disastrous ways. One help for this is to use a tool rest the fits inside the piece for support closer to the wall. I have a couple of curved Robust rests that fit inside the piece and sometimes use a "box" rest for that. Sometimes you can angle a long standard rest to fit one end fairly deep into the piece.

Since a bevel-riding cut when you are standing in front of the lathe would require pushing the tool handle way over across the bed a little trick I've used which might not be as hard as it might seem is to put the lathe in reverse and make the cut "backwards" on the far side of the piece. (Requires a reversing lathe, of course, as well as locking the chuck to the spindle.) I do agree with Sir Keeton that the center support would make working on this difficult or impossible.

I've turned a number of ERC bowls. One other possibility is cedar is so soft it might not take much for the wood to deform and pull from the chuck jaws. I nearly always use a recess, fairly deep for a larger bowl. With either a tenon or recess the larger the diameter the better it resists side forces. I have reinforced a soft tenon with CA glue which hardens the wood a bit but only on the surface - a catch would still pull it out.

For a soft wood, gluing on a waste block made from a harder wood might help it resist minor side forces, the largest diameter possible for the piece and available jaws. I usually use something like red oak.

That's all I can think of at the moment.

Again, having another turner see your methods might help a lot. If that's not possible, perhaps a few more photos would help, maybe showing the holding method, the tool you are using, and a shot with it held as when you are cutting - with the lathe off!

JKJ

[Fred Belknap]

All of the above is excellent advise. My solution to a bowl like that would be to use a Negative rake Scraper with a lot of weight. Like maybe 3/8" at least. A bur from the grinder works great for very light cuts and the negative rake will keep the tool from catching. Try grinding a negative rake on the top side of a scraper, the angle should be around 25 degrees or around about that.

[Glenn C Roberts]

Don't want to steal the thread, but this may help the OP (and me!): Does the OP have the piece end grain to the tail stock? When he refers to the knots it would seem that they would be on the outside of the bowl. And is the sapwood on the outside? If that is the case, then is the proper cutting direction from the inside (bottom) to the rim because it may be an "end grain" bowl? Or have I got it backwards?

[daryl moses]

Red Cedar is so soft that it is sometimes hard to work with. The knots are a lot harder than the surrounding wood which can cause a "catch" if you are cutting too aggressively. Red Cedar takes a sharp tool and a very light touch.