Ed Garrett
08-13-2007, 7:15 PM
I’ve found a couple of tricks for making better and easier sled cuts for odd angles or on odd shaped pieces of wood.
I’ve lately been making architectural models from 1/4” oak plywood. One model consisted of over 100 little pieces, all of which had to be pretty accurately cut in order to fit tightly. I wasn’t initially satisfied with the accuracy of conventional sled cuts. I was drawing the geometry directly on the boards, but at odd angles I couldn’t quite get the saw blade lined up with the pencil lines.
Cross Hair Sled: The solution was to install a dental floss cross hair on the sled. It was surprisingly easy to engineer and calibrate:
Clamp two scraps of wood on the inside face of both sled fences.
With the blade about 2mm higher that the objective, cut a kerf through the clamped scraps.
Run dental floss through the upper left (as you face the saw blade) corner of the kerf and tie it off on the outside faces of the fence.
Lower the saw blade 1mm so the teeth won’t hit the string
Slide the piece you want to cut under the string. There will be 1mm clearance between the wood and the string.
The string defines the exact left edge of where the saw blade will cut.With a little practice I was cutting thin pencil lines in half on the first try. However, this technique limits you to a specific thickness of wood, which gave me the idea to use a laser.
Laser Sled: I have a cheap laser level for use with mounting shelves, pictures, etc.
With a little effort I was able to make bracket for it which allowed me to clamp it to my sled fence directly above the kerf of the sled.
Calibrating it was similar to calibrating the dental floss.
First I set my laser level to “lock mode” so it was no longer trying to find level.
I clamped two pieces of scrap at either end of the sled and cut through them.
Then I adjusted the laser bracket clamps until the left edge of the laser beam just touched the left edge of the kerf on the scraps.
This time remove the scraps.
The beam will “wrap” itself over boards of variable thickness or irregular upper surface shape.
The saw teeth become red sparkles when you turn it on.
For eye and finger safety while making the cut, I intentionally focused on the cutting target about two inches in front of the bladeThe laser also worked well, but surprisingly, the dental floss cross hair system was more precise because the contrast between the edge of the laser beam and pencil marks was more difficult to discern. Also, certain segments of the laser beam’s trace are slightly fuzzy with this particular laser level, probably due to low cost plastic optics.
Both methods are now part of my repertoire. Under the right circumstances it’s worth the few minutes it takes to set it up. All this has me thinking a laser could be applied to a high end commercial sled made by companies such as Incra or Kreg who specialize in aftermarket precision.
Tilting Laser: While using the two techniques listed above, I regretted that I couldn’t also cut laser guided bevels on the table saw. A laser could easily be mounted on an appropriate splitter. For example, the stock splitter on the Powermatic PM2000 TS would be a perfect platform for a laser device because the splitter extends completely over the blade. From a few inches above the front edge of the blade the laser could be directed downward onto the lumber and yet not into the operator’s eyes. Can you imagine making laser guided bevel and miter cuts on your table saw???
Sincerely,
Ed Garrett
Tallahassee
P.S.: On the Pics: The cross hair photos are a simulation using thick string because my camera wouldn't pick up the fine dental floss (and no I wasn't going to cut the black sheet of steel. The camera also didn't pick up the laser beam well, so I had to dim the lights.
I’ve lately been making architectural models from 1/4” oak plywood. One model consisted of over 100 little pieces, all of which had to be pretty accurately cut in order to fit tightly. I wasn’t initially satisfied with the accuracy of conventional sled cuts. I was drawing the geometry directly on the boards, but at odd angles I couldn’t quite get the saw blade lined up with the pencil lines.
Cross Hair Sled: The solution was to install a dental floss cross hair on the sled. It was surprisingly easy to engineer and calibrate:
Clamp two scraps of wood on the inside face of both sled fences.
With the blade about 2mm higher that the objective, cut a kerf through the clamped scraps.
Run dental floss through the upper left (as you face the saw blade) corner of the kerf and tie it off on the outside faces of the fence.
Lower the saw blade 1mm so the teeth won’t hit the string
Slide the piece you want to cut under the string. There will be 1mm clearance between the wood and the string.
The string defines the exact left edge of where the saw blade will cut.With a little practice I was cutting thin pencil lines in half on the first try. However, this technique limits you to a specific thickness of wood, which gave me the idea to use a laser.
Laser Sled: I have a cheap laser level for use with mounting shelves, pictures, etc.
With a little effort I was able to make bracket for it which allowed me to clamp it to my sled fence directly above the kerf of the sled.
Calibrating it was similar to calibrating the dental floss.
First I set my laser level to “lock mode” so it was no longer trying to find level.
I clamped two pieces of scrap at either end of the sled and cut through them.
Then I adjusted the laser bracket clamps until the left edge of the laser beam just touched the left edge of the kerf on the scraps.
This time remove the scraps.
The beam will “wrap” itself over boards of variable thickness or irregular upper surface shape.
The saw teeth become red sparkles when you turn it on.
For eye and finger safety while making the cut, I intentionally focused on the cutting target about two inches in front of the bladeThe laser also worked well, but surprisingly, the dental floss cross hair system was more precise because the contrast between the edge of the laser beam and pencil marks was more difficult to discern. Also, certain segments of the laser beam’s trace are slightly fuzzy with this particular laser level, probably due to low cost plastic optics.
Both methods are now part of my repertoire. Under the right circumstances it’s worth the few minutes it takes to set it up. All this has me thinking a laser could be applied to a high end commercial sled made by companies such as Incra or Kreg who specialize in aftermarket precision.
Tilting Laser: While using the two techniques listed above, I regretted that I couldn’t also cut laser guided bevels on the table saw. A laser could easily be mounted on an appropriate splitter. For example, the stock splitter on the Powermatic PM2000 TS would be a perfect platform for a laser device because the splitter extends completely over the blade. From a few inches above the front edge of the blade the laser could be directed downward onto the lumber and yet not into the operator’s eyes. Can you imagine making laser guided bevel and miter cuts on your table saw???
Sincerely,
Ed Garrett
Tallahassee
P.S.: On the Pics: The cross hair photos are a simulation using thick string because my camera wouldn't pick up the fine dental floss (and no I wasn't going to cut the black sheet of steel. The camera also didn't pick up the laser beam well, so I had to dim the lights.