Turning Question

[Stanley Campbell]

I am fairly new to turning and I can not figure out what I am doing wrong, so I need some help. I have turned a few small lidded boxes (5), but all of a sudden I can't seem to get the blank to stay firm in the scroll chuck. I have the outside turned down round, made a dovetail spigot on one end, then put it in a scroll chuck with dovetail jaws. I start hollowing out the lid and I get a catch and the blank is all of a sudden wobbling. I have tightened the chuck as tight as I can get it but it doesn't help. this has happened twice, first on a piece of purpleheart and now on a piece of white ash. I thought the first one was because the purpleheart was so hard. My tools are new, only about a month old and I think still sharp.

My lathe is a jet mini lathe 14 inch.
Axminster Chuck
Axminster ODONNELL Dovetail Jaws
I am hollowing with a 3/8 inch Spindle gouge (Ray Key)


What am I doing wrong :confused:

Thanks
Stan

[Tom Hintz]

Stan,
Have faith my son! You probably are doing nothing wrong other than getting catches, a right of passage in turning and tools that might need a bit of honing. I use the best chisels I can buy, sharpened on a Tormek system but still touch up the honing frequently to get that "edge" feeling back. It's hard to describe but you can tell the difference, or learn to feel the difference with experience.
By the way, ash is by no means a soft wood! A catch in ash is going to put a bunch of force on the grip the chuck has on the piece.
The good news is that my best prescription for you and your problem is practice and developing your honing skills. I hereby command you to spend more time at the lathe making fun things. There are worse fates my friend.

[Tom Mullane]

I think the primary problem you are having comes in the statement "My tools are new, only about a month old and I think still sharp."
You need to sharpen your tools often, especially when working with hard exotics like purpleheart... if you are not sharpening your tools you can expect to get catches.
Do you have a good sharpening system... I use a slow speed 8" grinder and the Wolverine sharpening jig system... keeps my tools nice and sharp... it is not uncommon to resharpen a tool 6-7 times when doing a bowl (if not more often)...

[Andy London]

I would third what the others have said with respect to sharp tools, they go a long way to elinimating a catch as does your technique.

I will sharpen a gouge three times while turning a single bowl or mortar, it's onlu a touch up on the wolverine jig which takes seconds. You can tell with a little experience the moment...it's time...

[Bill Grumbine]

Stanley, let me echo all that has been said so far. Tool edge sharpness can be measured in minutes, not months. If you get an hour out of a sharp tool without resharpening, that is a very very long time. Even with sharp tools, a catch can remove the wood completely from the chuck. Introducing a wobble is almost a given.

There is nothing that you are experiencing that cannot be cured by practice and experience. Learning tool presentation goes a long way to reducing or even eliminating catches, and that makes the esperience that much mroe enjoyable. Catches do not ever go away forever though. I have been teaching turning for nine years now, and last Friday while showing a student a cut, I had a (gasp!) catch! :eek: I told him I did it on purpose so he could see what would happen, but I don't think he bought it. ;)

In fact, I think the same thing happened when Tom Mullane, who answered further up in this thread, was here? Is that right Tom? :D

Good luck with it.

Bill

[Richard Allen]

Sharpen your tools. I sharpen my tools every time I turn. Often my tools will need sharpening while I am turning. I plan my turning so that I can use a freshly sharp tool for the finial cuts.

That being said the are a couple of other things to check.

The diameter of the tennon should be such that the chuck, when closed tight on that tennon is very close to a circle. So look at your chuck jaws and find the position where the jaws form a circle. When the jaws are wide open the points of contact are the corners of the jaws. If the jaws are fully closed then just the middle of each jaw makes contact. For maximun grip you need to have as much of the jaw surface in contact with the wood as posible.

Make sure the sholder of the tennon come firmly in contact with the face of the jaws. This is to say that the tennon should not bottom out in the jaws and there should be a good bearing surface of the sholder to the face of the jaw.

It is better that the dovetail be to shallow than to deep. Idealy the entire jaw will make good contact with the wood. But contact with the top part of the jaw will provide more holding power than contact with the bottom part of the jaws. In fact contat with the bottom part of the jaw tens to eject the turning from th jaws.

Recap Sharp tools, Shape of tennon, Sholder as a bearing surface, Size of tennon = full circle of jaws.

[Tom Mullane]

Yes, Bill... but I was too much of a gentleman to mention it.. .LOL...
Just an aside.. if any of you ever get a chance to take lessons from Bill.. do not hesitate... I managed to rough turn a beautiful ambrosia maple bowl under his guidance and it actually came out the diameter we aimed for... I was expecting to turn that beautiful piece of maple into a finger bowl instead of a salad bowl.. LOL
Now I am waiting patiently for it the dry so I can finish it... but am practicing on lots of other wood so I don't louse it up...

[Stanley Campbell]

:rolleyes: Sharpen Tools? Now I guess I will have to learn that before I turn anymore.
Since it is unanamous...uh.. since everyone agrees I probably have dull tools. what does everyone think I should do. Get a sharpening system or learn to do it by hand?:confused:

Thanks

Stan

[Jim Becker]

Since it is unanamous...uh.. since everyone agrees I probably have dull tools. what does everyone think I should do. Get a sharpening system or learn to do it by hand?
Well...there are still some "traditionalists" that insist that sharpening freehand is the cat's meow, but even some of the most enduring pros are using jigs these days. Why? For consistancy. For the beginner, a sharpening system, such as the OneWay Wolverine combined with a 1725 rpm 8" grinder with white AO wheels will result in less frustration and less metal being uselessly removed from your tools. That's my opinion on this. Your mileage may vary... ;)

[Kent Cori]

I'm with Jim. Except for having a 6" grinder, I have the same system. It makes sharpening a gouge the matter of 30 seconds with very consistent results. I wouldn't go any other way.

[Dennis Peacock]

I agree....along with a lighter tool touch/presentation. Sharp turning tools makes all the difference in the world. I use a Tormek for most of my tool sharpening and it works very well. However, I also use a variable speed grinder with AO wheels to shaping and sharpening at times.

[Richard Allen]

A sharpening jig and grinder as Jim mentions is a great place to start. That 3/8" Ray Key spindle gouge needs to be sharpened by hand. So even though the jigs are a terrific tool and I wouldn't be without mine, you also need to sharpen by hand sometimes.

The keys to sharpening by hand are good light and magnification.

To sharpen a tool by hand take a black marker and "paint" the bevel. Lightly try to evenly remove the "paint". Repeat the process and inspect your sharpening with good light and magnification.

There is also a very good vedio on sharpeing availble from the AAW.

Good Luck

[Stanley Campbell]

Thanks Guys. I'll give it a try.


Stan