Collated from newsgroup postings.
The unfortunate result of torn endgrain on a gouge-finished bowl can be described as a "Weetbix Finish". The predominant subject for discussion in turning circles is torn endgrain. The hardest lesson to teach is how to get a good finish on your work. The average novice turner believes that the secret to good finish is sandpaper and magic potions. This I am afraid this is a fallacy.
Let's have a look at what it takes to beat the Weetbix finish. When it comes to getting a good finish the best thing you can do to start off with is to leave the sand paper in the cupboard for a while and try to understand why your piece looks like it does. It is my belief that the biggest causes of bad finish are rules, tools, skills and technique, bowl shapes and angle of grain, moisture content and wood types, so lets have a look at these individually.
Although the purest will tell you that there are no rules to turning there are a couple of rules we should follow very religiously. These are:
- Rule 1 - Rub the Bevel,
- Rule 2 - Sharp tools are Paramount.
- Rule 3 - Speed Kills,
- Rule 4 - Cut in the Right Direction.
Rub the Bevel. If the bevel of the gouge does not stay in contact with the wood being cut the tool is being used as a scraper and it leaves a very bad finish.
Sharp tools are Paramount. This one is very straightforward. When it comes to your final pass with the gouge, insure your cutting tip is sharp. Many professionals have a gouge they use solely for doing their finishing cuts with. If you don't have a chosen finishing gouge, give the tool a quick lick on the grinder before you do the last cut.
Speed Kills - Here I am referring to the speed of travel of the tool as it shapes the bowl. Let's call it assent rate. If the tool travels to fast up the wood, you don't give the bevel time to do its work and tear out the wood instead of cutting it. Please don't confuse this with bowl rpm; the speed of the bowl revolving is not what we are after. It is the time it takes for you to cut from the foot of the bowl to the rim. The advice is, on your last pass; slow your assent rate right down, for the best finish.
Cut in the Right Direction. Believe it or not there is a right and a wrong direction to cut wood. Face work - You should always cut from the smallest diameter to the largest on the outside of a bowl, call it uphill if you like. On the inside you should cut down hill from the largest diameter to the smallest. This might help explain why when we make a bowl we start with the outside first, because it helps us attain a better finish off the gouge.
Spindle Work- Cutting rules for spindle work are exactly opposite to face work Here you should cut from the largest diameter to the smallest or down hill.
When it comes to tools rule 2 is a biggie. Sharp tools cut wood blunt tools butcher wood. For the beginner tool sharpening is more important than anything else. There is no short cut to sharpening. The novice is best advised to invest in a sharpening jig. The Teknatool sharpening centre is as good as any and there are plenty of people around who can show you how to drive one. The other thing with tools is quality. High-speed steel will keep its edge much longer than carbon steel. If you are not keen on sharpening get yourself into better quality steel. But remember even high-speed steel still needs sharpening, just less often.
Skills are something that is gained with practice. There is only one way to gain tools skills and that is to cut wood. All my beginners want to make something with the first piece of wood they put on the lathe. My advice is to make shavings and use the whole bowl to practice with. If you are having problems with your finishing cut, you have the whole bowl to practice with. While you are shaping the outside get the feel of how this particular piece of wood performs in the finishing cut while you are still shaping it. If you are experiencing problems in attaining a decent finish off the tool, I can thoroughly recommend putting pieces of wood on the lathe and wasting them away to nothing all in the name of skills. Until you can master the gouge its probably best not to make your projects to complicated. Technique is another matter. In time you will probably come up with a technique that works okay. My advice is to get someone to show you how to do it. If there is someone in the area offering classes, go to the professionals. It will take a lot less time for you to learn the techniques and possible years off the time in becoming proficient.
Often the shape of the bowl can be the problem with the finish. Have you noticed that it is very hard to sand the end of a piece of 4x2 to make it look good? This is because the straws that carried the trees nutrients are exposed like the end of a pipe and fall inwards on them selves when cut at right angles. Now take your average bowl, if it has perpendicular sides the whole of the side of the bowl has right angle cut endgrain on it on either side of the bowl. Not great for finishing. If we have sloping sides, say at 45deg we can eleviate the right angle endgrain problem and make finishing much easier. So the advice here is stay away from flat-sided bowls when we are learning the business.
Moisture content is a problem that is cropping up more and more as we strive to recycle the timbers that are pulled out of old houses and the like. For wood to cut easy it needs a certain amount of moisture in it. To confirm this try a piece of green wood, it cuts like cheese. Now imagine a piece of wood that has sat in the ceiling of an old house for a hundred years, it has very little moisture in it at all. Instead of pieces being cut from wood like this it tends to break off, this is due it being brittle because it is dry and hard. There is no real answer to old dry wood other than patience. You might like to try turning at one speed slower and keeping the assent rate slow. Rule 2, as in sharp tools is really important as well.
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