As I mentioned in the first blog entry in this series, I will mostly focus my attention on end grain natural edge woodturning. In this blog entry I will explain how I prepare the wood for lathe work and how I mount it on the lathe. These blog entries reflect mostly my experience and preferences for woodturning. Hopefully you can draw inspiration form this but ultimately you have to find your own way.
1. Stock Selection
The first step in woodturning is, obviously, selecting a piece of wood that you will turn. I prefer to keep the wood in large pieces since in this way only the ends will go bad (crack) but I still have a lot of good wood. Here is my wood pile, to get an idea:
While painting the end grain of logs with some wood sealer helps (I use paraffin wax softened in paint thinner) the logs will crack anyway—it will just take longer,
Since you very much have to adapt to the type of wood when turning end-grain pieces, I usually prepare several raw pieces that I turn within few days (before they go bad). I keep a variety of woods in my pile so that I can pick something I feel like turning (as opposed to whatever I have). This time I selected the lower part of a camphor tree (about 1 foot off the ground). This piece is interesting since it has two main branches of roughly the same size. The idea is to select a 3” piece and try to turn a large (almost 16”) platter and from the rest to make a some small wood bowls.
The ends of the two branches are bad for at least 8” so I have to throw them (i.e. recycle them). Here is a picture taken my by 5 (almost 6) years old photographer (my son).
While cutting the log I try to think what I will make out of it. Since I will mount the wood on the lathe using a faceplate (more about this latter), I have to leave about 1”-1 1/2” extra wood at the base. To true up the top, I leave at least an extra 1/2”. That means I cut the piece about 2” taller than the intended dimension of the turning. When you cut the wood with the chainsaw (the best method but a decent hand saw would do as well) I try to select the interesting part for the rim. I decide which part is the top and which part is the bottom as well.
For natural edge end grain turning, the wood preparation consist only in cutting the log across. The only concern is to keep the angle close to 90% and the two sides reasonably parallel (helps latter).
2. Mounting the raw wood on the lathe
Once I cut the log in sections, I select one that I turn and get ready to mount it on the lathe for initial turning. I first put the wood on the workbench and try to select a reasonable center for the piece. I like to do the initial turning between centers. My main motivation is the fact that my lathe cannot go below 600rpm in speed and, as I explain below, I can make even large pieces behave at 600rpm when I turn between the centers but I would get disastrous results If I mount the piece initially using a faceplate.
Why do initial turning between centers?
When I started woodturning, I was installing a faceplate on the blank as the first step in turning a log. While you can reasonably center the faceplate on the blank to get decent bowls as a result, I had two main problems with this method:
1. The cross cut had to be truly orthogonal on the piece otherwise piece would rotate around a slanted axis (violent shaking of the lathe immediately results if the wood is spinning at 600rpm)
2. No matte how careful I was with getting the crosscut and center the faceplate on the log, unless the wood was almost round, I still got enough vibration to scare me (had the piece fly from the lathe a couple of times). The process of getting a good position of the faceplate and cutting the log took a good 1/2 of an hour or more (takes the fun out of woodturning).
At some point it just struck me: I should mount the piece between centers initially instead of faceplate. Now, this might be even a bigger disaster than faceplate mounting since the spur is less likely to keep a piece of wood from flying than 4-8 screws you can put in a face plate. For this to work, something else is crucial: spend a couple of minutes to center the piece between centers so there is almost no vibration. It is not the geometrical center that matters but having the rotation axis go through (or close by) the gravity center of the piece. To do this, I apply the following procedure:
1. I guess an initial center of the piece and make a small puncture on the top of the piece.
2. I put the tip of the spur in the marked point and guesstimate where the tailstock has to go. I do not tighten the tailstock all the way and have the piece suspended between the two tips but without the teeth of the spur bitting into the wood. In this way, the piece is free to rotate without much resistance (the motor has enough friction so the piece would nor rotate if the spur goes all the way in).
3. I rotate the piece around and let it free. If the piece takes less than 3 seconds to go from the highest spot to the lowest spot, I move either the spur or the tailstock. One of these points has to move lower when the wood is in the lowest energy spot. I decide which one to move in order to make the face towards the spur be as orthogonal on the rotation axis as possible.
4. If the piece is centered. I tighten the tailstock and let the lathe run for 1-2 seconds. If it looks like the rotation is almost vibration free, I move to start turning.
Here is a picture with the piece balanced between centers:
Now the piece is ready to do the initial turning. What I do during rough turning is to give the piece a rough form and to prepare it for the mounting on the lathe that will allow me to turn the outside and the inside.
3. Faceplate Turning
In order to finish the turning of the piece, the wood needs to be attached to the head of the lathe securely. While initially the tailstock acan be used, eventually the tailstock needs to be removed.
There are two methods to mount the piece on the headstock alone: faceplates and chucks. Chucks are all the rage for the last 10 years. They are very versatile, come with all kinds of accessories, etc. I prefer to use a faceplate for the following reasons:
1. A good faceplate is 30$ while a decent chuck is 200$ (without accessories)
2. The faceplate grabs the wood with 4-8 screws while the chuck mechanically holds the wood. I feel a lot more secure with a faceplate, especially for larger pieces. I explain below how to install well a faceplate, as easily as a chuck.
The main disadvantage of a faceplate is the fact that 1” of the wood is wasted. Since the wood I use is free, this is a non-issue.
Mounting the rough turned piece on the faceplate
In order to mount the faceplate on the piece, i true up the bottom of the piece (I make a small concavity on the bottom so the faceplate touches on a ring). I leave a spigot that fits snugly inside the whole in the faceplate. To get the size right, I keep a wrench of the exact size next to the lathe and measure while I turn. To install a chuck you have to do something similar. If the spigot is too tall, i cut it with a coping saw.
Here are some pictures with the spigot formed:
and here one with the faceplate install on top of the spigot:
To mount the faceplate, I use 1” sheet metal screws (they grab the wood really well and they do not need predrilled wholes—they will not split the wood). To install the screws, I use a corded drill. Putting in the screws goes as fast as installing a chuck. With a little care, when installed on the lathe, the rough turned piece will be almost true:
When turning, you have to remember that the screws go into the wood for about 3/4”. Once turned, the remaining wood on the faceplate can be used a a friction chuck so the bottom of the piece can be turned as well:
To recenter the piece when reversing it, I use a piece of metal that I keep fixed and gauge the difference between the closest and furthest away points (without the lathe turning, of course). Once I get within 1/32” I start turning the piece.
In the next blog entry in the series, I’ll talk about actual turning by describing tools and how to use them (with pictures, of course).
You can see some of the things described in this blog entry in the video in my other blog entry:
Thanks for looking,
-- -- Alin Dobra, Gainesville, Florida