Tuesday, April 26, 2011

Sanding A Sculptured Rocker or Daddy Aren't We There Yet?














"If you are a fine woodworker, do you have to like sanding?" I had a student ask me this salient question yesterday. He was building a Krenov style table at my woodworking school and hand sanding the gentle curves of the table's legs. The answer for me is this - I do not like sanding "Sam I am"! I do love the results of my efforts.

Final sanding of a rocker is a marathon not a sprint! Sanding a rocker takes a lot more time than the initial roughing out. I can build a rocker in a couple of days. Sanding is something different. I use to do it by hand then I found some time savings from using an angle type drill with a 2" disk and an interface pad. The drill was a good one but did not last under the punishment. The disk would also fly off the interface pad with just a little speed. Then I moved to a pneumatic sander with another 2 inch random orbit pattern. Speed was hard to control and there was no dust pick-up except my nose and a dust-pan.

Because of all of the variations in surfaces and the problems with sanding the seat contours and under the arms, I can't use a 5" random orbit power sander because they it's too big, bulky and just plain too hard to work with on this project.

It takes some true grit to remove the rasp marks and scratches made by 24 grit paper on my Festool angle grinder. First sanding with my new Festool RO-90 at about 40 to 60 grit is still in the realm of shaping, you must work out all the highs and lows in a surface or discrepancies in a hard or soft line and reconcile one part or side to the other for the sake of symmetry. I consider myself still shaping until I get to 100 grit. Just establishing a consistent scratch pattern is the next order of business. The Festool Rotex Sander is just the best tool I have found for removing rasp and grinder scratches and preparing the first consistent scratch pattern to most of the chair's parts.

As for scraping I do continue to scrape all the way up to 100 grit in the shaping mode. After establishing the overall shape. I usually will lightly scrape the entire piece.


How long is the journey and how many stops do we have to make? How fast can we do it? Sanding a rocking chair is more about quality than quantity. You have to sand with each grit until you have:
  1. Established a consistent scratch pattern all over the piece or area.
  2. Removed all deviations or exceptions to the the surface you are preparing.
  3. Softened all hard or knife edged lines to the touch.
You must utilize all the grits once you start. (24, 40, 60, 80, 100, 120, 150, 180, 220, 320, 400, Then the 3M pads (red, gray, white) taking it to 1000 grit (if you are sanding a ring porous wood like walnut). Do not skip around. It's important to know what grit with which to start and when to stop. I start with the most effective grit that accomplishes the above. It also has to be the highest grit (by number that will do the job). You can't effectively sand a project like this with 24 grit scratches all over it with 100 grit paper! So you must start aggressively with at least 40 or 60 grit paper by hand or with power. I usually use the higher grits like 180 + to provide softening.

Well daddy are we gonna walk (sanding by hand) all the way or ride in a car (use a power sander)? Their are some places on the rocker where you really need to sand by hand. Such as the front leg to set at joints because of the inside radii. You can get a feel for the wood and its smoothness, how much pressure is necessary and just get intimately acquainted where the paper meets the rocker.

The Festool R-90 Rotex Sander helps me sand on the go fast side. It uses a 3" disk and an (accessory) interface sponge pad so that it does a great job of making constant contact with the contoured surfaces without removing the lines that I have worker so hard to make. The detail that remains is very crisp. After roughing out the chair and shaping it with a collection of rasps both powered and unpowered, I can start with 40 grit hook and loop paper and work my way up the schedule. This saves time and produces outstanding results. The sander is easy to hold and move around the chair. I like to sand as much as possible before I start gluing up the chair. I finish by gluing, fairing in the parts and sanding the transitions. Like most Festool products, dust extraction is easy and excellent. It works in two disk modes. Rotex is fast and aggressive, the other random orbit. After 40 grit I seldom use the Rotex mode. They also have a red and gray 3M pad equivalent that makes burnishing very easy.

Then I go over everything with a white 3M pad by hand. It looks like I have a very slight coat of finish on at this time and it will tell me what I missed. Yes the blemishes just jump out. Then only back up as much as is necessary grit wise to remove the alien inhabitants (I'm not sure I know what I am talking about).

Sanding stars, flap wheels, inflated sanding domes, drums and such can all be used to move the sanding down the road.

Now, does A fine woodworker like to sand? The answer is .............. NO!!!!!!!!






2 comments:

nantuckettiechic said...

I do children's rockers and totally get the "are we there yet?' part of sanding. Then...seven finish coats with a final sanding after coat 3. Patience is a virtue worthy of cultivation. Love your work.

Pezdad said...

What are the "red and gray 3M pad equivalent that makes burnishing very easy"? I have the RO-90 and would like to know.