Once I have the 3 lamination blanks cut to width I thickness sand the strips to reach the final dimension. I have tried using my planer, but when the strips get this thin it is easy to end up with damage. I set my ShopSmith up as a disc sander and use a thicknessing jig. I first showed the use of this in a previous blog. There was some interest in a more detailed description so here it is.
Here is the setup.
Basically it is a 3 1/2 inch tall bullnosed block clamped to the fence. The block is set up closer to the edge of the table than the desired final thickness of the strip. In this case I want strips 0.175” thick so the block is set about 1/8” from the edge of the table. The disc is initially positioned from the block at the current strip thickness (just over 0.2 inches in this case). I take advantage of the quill advance capability of the ShopSmith and move the disc closer to the block after each pass.
The construction of the block is pretty staright forward. I cut a bevel on each end of a 2×4 leaving about 1/4” flat on the end. I then cut the beveled end off making sure I had enough length to accomodate the clamp I will be using. Make sure the cut is square. Then mount the beveled piece to a cross piece. The final step is to true up the edge. I clamped the block to the fence and set it up hanging over the table. I then advanced the disc against the block. This way I have the functional edge of the block exactly parallel to the disc.
Once this was done I marked the top side (see top two photos). If I were to flip this over, I might get tapered width strips (that would be bad).
A final set up element is to mount a dust collection hose underneath the table next to the disc. I don’t always do this, but this project has a lot of strips to sand. In no time, I had my shop coated with fine mahogany powder. The hose does a good job of collecting most of the dust. I took this shot while sanding a strip. You can see some of the dust in the picture.
Finally, here are a few operating tips.
1. Do not let your fingers touch the disc! Use long strips – they should extend 3 or 4 inches past each side of the disc to give you good finger access.
2. Set the block up to contact the disc on its downward motion. Setting block close to center can result in the strip being pushed back at you.
3. Feed the strip in until there is only 3 or 4 inches of strip left, then pull the strip out on the exit side.
4. Allow about 3 inches on each end as waste. The strips can taper a bit as you start the strip or pull it out.
5. Keep the strip feeding in as straight as possible. Letting it bump against the disc any where but at the block can result in gouges.
6. The exception to #5 is if you are sanding very thin strips. Then the strip can fall between the table and the disc – in fact there may be no table exposed past the block. In this case rest the strip on the table, bend it into the gap and bend it back onto the table once you can reach it safely. I have managed to sand strips as thin as 0.02”
7. Use light passes. I take off about 0.005 each time. You can force a bigger cut, but I worry about deflections and not getting a consistent strip.
8. One time past the disc will not remove all the material. I have made as many as 5 passes without changing the spacing.
9. You can control how much is removed in a pass by how quickly you feed the strip. This gets easier on the 2nd or 3rd pass at the same gap between the fence and disc.
I have been using this method for several years. I am able to set my strip thickness to within 0.004” (+/- 0.002”).
If you have a conventional disc sander, you could shim the block closer after each pass – or get fancy and build an adjustable version.
The next entry will cover glueing up some curved parts. As always, comments are welcome.
Current time log:
Cutting rough stock: 2 hrs
Cutting legs to width and thickness: 4 hrs 20 min
Cutting thin stock for seat back laminations: 3 hrs 35 min
Prepping laminations: 3 hrs 20 min
Glue up Laminations: 1 hr 35 min
Trim Laminated Parts: 15 min
Total so far: 15 hrs 5 min
-- Steve - Impatience is Expensive