Thread: Unwanted spiral when spindle turning

To far from the work with the tool rest overhang of skew/gouge Macca or height of tool rest

Mind some times the chatter looks great as an effect on work

Might be rubbing the bevel a little toooooooooo hard. (not that I'm an expert. ) Sharpen chisel a bit more often so you don't want to push so hard?

Thanks for the quick replies.
I have been fooling around with the lathe setup. As you know it is set on angle to allow me to turn from the chair.
I have changed the angle at which it is set and this has probably effected the tool rest height.
The tools are nice and sharp. The gouge at about 40 degrees. How does that sound.

Macca

G'Day Macca,

You may also need to look at supporting the piece if it long and especially if it is thin. You can get the piece wobbling, thus it needs support from your spare hand, tricky to do, but it does help or get a three point steady for it, such as:
http://www.woodfast.com.au/index.php?p=1_5
Scroll to the bottom of the page.

Cheers, Steve

Scroll to the bottom of the page he says ...
Struth , I had trouble gettin' past the big lump of wood at the top

G'day Macca

Had the same problem recently. Had me buggered for a while until I realised I had not locked the shaft in the tailstock after re tensioning the live centre. The tailstock shaft has a little bit of play in it and this caused the spindle to jump up and down while I was trying to get a nice finish off the skew. Had a beautiful spiral happening for a while though.

Cheers
Shorty

Overtightening the tail stock has the same effect. Tends to bend the timber instead of just holding it.

Originally Posted by

Overtightening the tail stock has the same effect. Tends to bend the timber instead of just holding it.

Same phenomenon as column buckling. The bow, however slight, whips about to create chatter.

Joe

Originally Posted by joe greiner

Same phenomenon as column buckling. The bow, however slight, whips about to create chatter.

Joe

Yessum.

I had the same problem using the skew, and asked Richard Raffan at the WWW Show. His advice was that the bevel probably was not rubbing the whole time, so adjust angle slightly and it was all fixed. This assumes of course that there is no play/misalignment in the centres.

I spent a couple of hours yesterday in the shed and did the following.

Checked the bevel angle on the gouge I was using, and found it to be >45 degrees,so I reground it to more like 35-40. Slack?????

I then checked the positioning of the toolrest. It may have been a little higher than it should have been. And maybe at times further away from job than should be. Lazy????

Checked for correct lathe speed. Belt change but not difficult. Lazy?????

I then attacked the same piece of old dry Jarrah with great care and found I could once more get a nice finish off the tool.

After turning for about 9 years I must have got a little complacent. It does not hurt to go back to basics now and then.

Thanks for all the help

Macca

Originally Posted by joe greiner

Same phenomenon as column buckling. The bow, however slight, whips about to create chatter.

Joe

So by way of diagnosing, if this was the case the spiralling would be worse in the centre?

And if you were only getting it heading in one direction and not the other (my problem) then it's a bevel rubbing/cutting angle issue?

Edit: Macca, yeah, my bevels shrink over time too. Must be the elves playing in the shed at night.

Originally Posted by macca2

.....After turning for about 9 years I must have got a little complacent. It does not hurt to go back to basics now and then.

It's amazing how easily bad habits creep into all facets of our lives. It not a bad thing to take a stop and take a good look at yourself occasionally.

As etc said:

Usually that spiraling comes from the piece getting into a resonant vibration. Usually with spindles too long or too thin. Compounded by poorly sharpened tools, and setup, (overhang, and particularly too tight tailstock.

Other than the obvious regarding setup and tools, the following are possible solutions:

Change lathe speed (up or down). This might get you away from the resonance.

Take lighter cuts with sharp tools

Use a steady in the middle of the piece. This could be a 3-point type, but could be as simple as a "bird mouth" cut in a piece of timber, clamped in place behind the spindle, and lubricated by soap or wax.

For long thin spindles, like headboard sides, or standard lamps, split the piece into (several) shorter spindles, at detail points, (like the groove next to a bead), and turn a dowell on one side and a recess on the next piece, and glue join.

For smaller and thin spindles, (eg conductors' baton), it helps to turn with your left hand as a steady. Instead of the normal overhand or underhand grip on the tool shaft, loosely grasp the spinning spindle with the fingers of the left hand over the top, and down the back. Support and control the gouge/skew using the left thumb, close to the cutting point. By doing this carefully, you supply some support close to the cutting point, and also help to dampen out the vibrations. It also helps to keep your hand warm!

HTH