Thread: Blackwood Platter Incident

Originally Posted by NeilS

....leaves one wondering why all those top woodworkers included our acacias in their commissions when they were working on the fit-out for our new national parliament...

Acacia's are dense timbers just like politicians............also stops the drone as its a good sound insulator keeps it all in the House.

Originally Posted by wheelinround

Acacia's are dense timbers just like politicians............also stops the drone as its a good sound insulator keeps it all in the House.

.....

Originally Posted by HSS

Anyhow, visually it seemed fine and I didn't even think what I'd done would be a problem. I remounted the platter on the lathe and began facing it to get rid of the bow. To do this I was using the carriage rather than doing it by hand (because I can! also, you can take very controlled, light passes and it ends up dead straight).

Loverly big lathe you've got there! What do you mean "Using the carrage"? Is it a metal lathe?

tells a similar story involving an escaped platter. Only his made it out the door and across the highway! Has us in stitches.

Originally Posted by tea lady

What do you mean "Using the carrage"? Is it a metal lathe?

Checkout the 2nd photo

Originally Posted by sjm

Checkout the 2nd photo

Oh I see! Can wind it across the face like a metal lathe. Does that mean you use a scraper? Puts the work under alot more pressure than a bowl gouge in cutting mode. Although I guess if its gonna let go its gonna let go.

Good escape! Luck, higher power, clean living. Doesn't matter, no one hurt.

What is the name of the lovely lathe? I can't make it out.

Originally Posted by Paul39

What is the name of the lovely lathe? I can't make it out.

It's a Wadkin Paul

Thanks, for all the replies, sorry about not getting back to it for a while. As far as speed goes, I find it's a pay off between reduced vibration and a good finish. Having said that, I didn't consider the speed too great for the task. I was aiming for a good finish off the tool to reduce the amount of sanding I'd have to do since blackwood is reasonably soft and the soft grain is chewed out by the sand paper.

Yes the lathe has a carriage like a metal lathe. It moves in both directions and rotates to any angle in between as well. It's a very handy feature and I use it all the time in conjunction with the tailstock that can be wound off-centre for doing tapers etc. It's far quicker than trying to do straights by hand (cheating I know). Anyhow, although scrapers do impose a greater force on the wood, I find this is negated by the control that you gain from using the carriage (with scrapers of course). You can take very light cuts and there is no chance of the tool inadvertently digging in and ruining your day. In the case of this platter it was a failure in the mount, rather than a failure in the turning process. I believe it still would have sheared off the mount at a slower speed, It just might not have gone off with such a bang. a platter moving at 400 rpm is going to hurt more or less the same amount as a platter moving at 700 rpm.

There's another point I noticed whilst turning the edge of this platter prior to the incident. I was using a gouge on the edge of the platter to reduce friction and get a clean cut (no chatter). However, long splinters were coming off the side grain as it came around(reducing my diameter considerably with every splinter). I changed to using a 4mm wide round nose scraper bit in the carriage and the problem was solved; no more splinters.

Don't want to be a nuisance but I disagree with what appears to be your feeling about the speed not being significant. The RPM should only be used to determine the surface speed of a rotating disc. A disc of 25mm at 700 rpm will have a surface speed of approx. 200FPM. A disc of 300mm at a speed of 700rpm will have a surface speed of nearly 3000 FPM. Quick mental calc. so don't take them as exact. This means the stresses in the disc at the edge are quite considerable and in the case of soft wood (maybe with flaws) the stresses will overcome the adhesion factor and we get "explosions". A slight amount of excess pressure or slight catch can add to the problem. ON the 300 mm disc. when a piece leaves the surface for other locations it is travelling at the 3000 FPM mentioned above. This is a respectable muzzle velocity for many weapons.

It is very good to know that no one was hurt. There was a report a year or two ago that a turner on Ontario Canada was killed in a incident where a workpiece aperantly exploded and a piece struck him in the neck. Never could get the full details but it was a newspaper article.

"Long splinters coming off the side grain."
"The wood will show you."

Originally Posted by HSS

Yes the lathe has a carriage like a metal lathe. It moves in both directions and rotates to any angle in between as well. It's a very handy feature and I use it all the time in conjunction with the tailstock that can be wound off-centre for doing tapers etc.

I think is crying now! I'm crying now!