To prepare blanks from the tree for turning I use a chainsaw, these things are very dangerous and if you disrepect them they will attempt to kill/maim you and to be honest they have a pretty good chance of being successful.
Before we go any further here are the safety warnings:
- I am not a qualified instructor for chainsaws and my methods may not be those recommended. This is how I prepare blanks and not a guide on chainsaw use.
- The chainsaw MUST be properly maintained and it MUST be sharp....again if you don't know how then get help.
- Always use safety equipment and follow the instructions provided with the chainsaw.
- If possible get someone experienced/qualified to do the chainsaw work for you.
- If you are working indoors then don't use a petrol chainsaw....you can clearly see here that the saw in use is an electric one - no fumes and it stops when you take your finger off the button.
So we start with a lump of tree, it is usual that these will come in a range of shapes and sizes but will almost always be in the form of a "log" which means that the endgrain will be exposed at either end and usually the bark will still be on.
Your local tree surgeon will mostly always have logs as its how they remove trees i.e. in bits as they are blinking hard to move in one piece! The timber you get is always going to be wet and usually muddy.
I always like to "square up" the log and by that I mean get the ends at right angles to the bark and get the log to a size where it is roughly as long as it is round, if your log is significantly longer than it is round you will just end up wasting timber.
Normally blanks for bowls are prepared from the sides of the logs, this means they have both side and end grain in them and this is what I have shown in the photos. The log is simply marked up using either a timber crayon or chalk with a cut line which is positioned to go through the pith if possible, this removal of the pith is important as it will reduce the splitting an cracking of the blanks when drying.
Just to repeat, this guide is for normally oriented bowls - not end grain or natural edge bowls.
So this step is shown here (the log underneath stops the saw contacting the floor):
Once cut we have two blanks!!
Next I use a large compass, the sort of thing used by teachers for work on blackboards...or at least it was when I went to school, as I understand things now they use intelligent whiteboards and all sorts of things. Mark out the largest circle you can, again use chalk or a timber crayon as the timber is most likely going to be pretty wet.
Its then just a case of removing the waste outside of the circle you have drawn to produce a shape with facets which is not round but has fewer edges to contend with, you are going to need to wedge the blank to stop it moving whilst cutting it - this is actually harder with smaller blanks. Usually I start with the cut face upwards to get the basic shape then flip the blank over to remove as much as possible with the chainsaw to end up with something I can mount on the lathe.
When it comes to mounting, especially for larger blanks I use a faceplate with coach screws - we don't want any large blanks making unplanned excursions across the workshop as those 70kg lumps of wood tend to smart when they hit you.
You really want to get these wet blanks processed as quickly as possible into bowls and then dry them as this will reduce the wastage through cracking and splitting.
Once again, if you don't know how to use a chainsaw then don't do it...get help!!
The rest of the pics are below.