Interesting, or not, observation.

[syncopator]

These are made from 3/8"square brass.

When handling one of them I noticed that it behaved like a tuning fork when struck.

When I tried the others there was once which didn't produce the effect. It was quite dead.
Examination revealed that the holes through the fork ends were full of a mixture of swarf and cutting fluid.

Once this was removed it sounded like the others.

I find it quite amazing that contamination in the holes was sufficient to completely damp any oscillation.

Attachments:

[isc]

Just like wrapping some rosin cored solder around a boring bar to stop it chattering. It does'nt take much to de-tune a piece of metal does it. isc

[steam4ian]

G'day isc

Thanks for the tip.

Resonance is a funny thing. I changed to a larger chuck on my lttle lathe and now it chatters, nothing else has changed just increased mass on the end of the spindle. I will now have to work out some kind of damper.

Regards
Ian

[isc]

The other end of the mandrel from the chuck will have a thread on it, if you can find a reasonably large lump of steel you could bore and screw cut it to rebalance the mandrel. Some large lathes have a chuck on this end to grip long bar stock. I don't know how big/small your lathe is, but a small Chinese one a bit of steel 3-5" dia(75-120mm) x1"(25mm) should be OK. On the mandrel there is 2 nuts locking the gear on the shaft, One of these could come of to be replaced by the new flywheel/balance wheel. Worth a try if you have the metal and time. If your lathe has taper bearings it might be worth adjusting these. isc

[steam4ian]

G'day again isc

Thanks for that.

I already have part of the device. I bought a large diameter plastic trolley wheel and mounted it on an adapted 3/4" expanding bolt. I use this for hand turning the chuck for short threads. Some people use a handle but I had visions of being cracked by a whirling handle if I forgot to disconnect it.

I could pick up a crankshaft damper from a wrecker and mount that on the same type of expanding bolt. That would both add the mass and a viscous element for damping.

Regards
Ian

[isc]

Your idea sounds good. Yep I agree with you about crank handles in lathe mandrels, I'm afraid that I stick the chuck key in the chuck and pull it over with that ( I'v got 8" chucks), and a 1326 belt head lathe so it is a distance around to the end of the mandrel. isc (another Ian)