Sunday, February 13, 2011

Punky wood

 Alviti asked me the other day in the comments about punky wood.  It wasn't my intention for this post to focus on punky wood but things took a turn for the worse on this piece.

This is African Sumac I picked up back on June 1st 2010 -

There didn't appear to be any major issues on this blank from the outside.
The blank was chainsawed round and a faceplate attached.  I had to do just a bit of trimming to get it to clear the bed of the lathe, final clearance was under 1/16".

Well balanced and safely spinning at 294 RPMs.   This may not sound very fast but at nearly 20" diameter the outer surface is spinning at about 17 MPH.

Here the outside has been roughed and the blank is read to be flipped so I can access the inside.  I didn't think the bark inclusion in the middle of this photo was going to be a problem, it turns out I was wrong, very wrong.
Now the blank has been flipped and is held in a chuck.  The outer edge of the top face of the blank has started to be trued up so I can start coring.  I use my live center with a 60 degree cone on it to support the other end of the blank during coring.

 I skipped the photos of the coring process and went straight to the blank after the inside has been turned true and the walls to a consistent thickness.  The finished diameter of this piece is just under 18 1/2".  Following this step the core that was removed is threaded back onto the lathe, the outside of the core is cut true.

The core was then mounted on the chuck and the center of this piece was cored out.  Near the bottom of the piece the coring went fast and easy and the piece broke free earlier than expected.  Removing the core revealed the problem.  The inside of this piece was too far gone, rotted from the inside out.

A closer view of the decay.  This is extremely punky wood, all structural integrity is gone, the wood can be pulled apart by hand with minimal effort.

The inside of the core cleaned up decent enough, there are some areas that will need to be strenghtened and/or filled but most of the wood is solid.  The medium brown areas are lightly spalted and slightly punky but nowhere near as bad as the rest of the piece.  This ended up at 14" diameter.

Here's the bottom of the piece that was cored from the inside of the blank above.  I put it back on the late hoping that I could turn away the punky wood and get back to good solid wood but that wasn't going to happen.  This piece ended up in the recycling bin just after this photo was taken.  A famous turner once said "Life is too short to turn crappy wood".  I tend to agree.

1 comment:

  1. Thanks for the post! I'm fairly sure I'll encounter some soon as I get more adventurous with my woodturning (and start to raid my brothers piles and piles of tree surgery offcuts...).
    I bet it was disheartening but at least you chose how it came off the lathe - if it had been worse it could have made the decision for you!