My previous entry set the stage for my approach to sanding, namely that is not an afterthought, rather an integral part of the woodworking process. I can remember the days when I enjoyed the building more than the finishing and simply got it over as quickly as possible. My results showed exactly that. I’m going to express a strong statement here: Sanding scratches are the mark of a poor craftsman.
This blog will teach and show you how to produce turned work that is free from those circular sanding scratches you see in most turners’ work.
The most typical sanding error seen in a woodturner’s work is the circular sanding marks that circumscribe the surface of a bowl. You’ve seen them. You’ve even created them, those marks that occur when you hold a piece of sandpaper against a spinning chunk of wood on the lathe. I hate them and am on a personal quest to rid them from the earth.
The first and best way to avoid these scratches is learn proper gouge technique. It is quite possible to turn both interior and exterior surfaces that really need little or no sanding, but that discussion is outside the scope of this blog entry.
Lets face it, sanding with the lathe turned on is great, it is fast, quick, and easy, except for those darned scratches. They occur quite simply from stationary (unmoving) sanding grit staying in contact with the rotating bowl surface. If you are sanding by hand with the bowl rotating, there are a few things you can do to improve your results.
1. Lathe speed low. Very low. This will prevent the stationary sanding grit from creating a long straight scratch pattern.
2. Hand speed high. Very high. Keep your hand constantly moving back and forth on the bowl surface, never ever ever letting it stand still for even a moment. This will also prevent long scratch patterns from forming.
3. After each grit with the lathe turned on, turn it off and lock the spindle. Use that same grit by hand again, going over the bowl with the grain orientation. Any sanding scratches will be removed.
In between grits, wipe the surface off with a tack cloth and/or compressed air. This will remove any grit that has come loose and keep it from rescratching the surface with the next higher grit.
Eventually you will want to power sand, with a drill mounted sanding pad and the lathe turned on. This is a great way to speed up the process but you can still wind up with the same poor results if you are not careful. In fact, it is easier to make mistakes and alter the form of your turning as you can sand with more gusto, removing more material with each pass. The same exact process applies as when doing the sanding by hand, low lathe speed, very high drill speed. Never let it stay in one spot for even a moment. When done, lock the spindle and go over it again with the powered drill, this time in the reverse direction (reverse the drill rotation). You’ll see your sanding improve immediately. Also, if your lathe is reversible, reverse the lathe rotation direction with each successive grit.
Employ critical observation in your sanding process. Take the piece off of the lathe (chucked up). Put it in a bright light, examine it in a very detailed manner. Move the light around, (incandescents, btw, fluorescents won’t show the problems well), wet the surface with mineral spirits. PUT ON YOUR READING GLASSES. Look for scratches, because I can tell you that in a competition/show the jury will. Wetting the surface with mineral spirits will give you an idea of how it will look with a finish on it, and often will show hidden defects that need more work. It is a very good method for detecting sanding scratches.
Consider raising the grain on your projects. I hate to do it too because it requires even more sanding and time, but it helps with the finishing process. After you get to 320 grit, wipe the surface down with water, then wait for it to dry. Go back to 220 grit and proceed from there.
What to sand with? There are many, many choices, and you’ll have to find one that works for you. I prefer the sanding discs made by Steve Worster. http://www.turningwood.com/
He also sells Abralon discs and Micro Mesh discs. Abralon is fantastic stuff for turners. It offers grits from 360-4000 grit and is wonderful for polishing the surface. Polish with Abralon and then finish with Watco oil – you’ll be amazed at the finish.
Micro Mesh – a cushioned abrasive used for polishing scratches out of windows, is also now available in discs for power sanding. I have only used the micro mesh paper, but with my next order will probably try some of the pads. For now I highly recommend Abralon pads for your powered sanding work at high grit.
Try some of my techniques – if you don’t like the results you can always go back to your old methods. And remember, sanding scratches are the mark of someone not concerned with quality. You won’t get to the top without putting in top level effort. You would be AMAZED at the amount of time the top level turners put into their work.
-- Just another woodworker