How good/bad/useful are laser pointers for Zeroing?

[paul_z]

With two lasers, you don't have to use an offset. One laser produces the x line and the other produces the y line. Geometrically speaking, one laser fan beam is in the x=0 plane and the other is in the y=0 plane. The intersection of the beams is x=0, y=0 for all z values.
You can't do this with a single crosshair laser because it would have to be located where the router/spindle is or canted at an angle. If it is canted, then it would work for only one height below the carriage. That's why most crosshair users make sure the beam is vertical and they compute an offset.
BTW an easy way to compute the offset is to peck the spoil board with a v bit, and set x and y to zero. Make sure that the crosshair is dead on vertical. Then move the carriage so the crosshair is dead center over the peck point. The offset is the current x,y. The offset does not vary with z.
Paul Z

[geneb]

How wide is the beam?

g.

[paul_z]

The crosshair pattern is about 12" wide when the laser is 12" away. Beam width at this distance seems to be about 0.015".

The beam is very intense at 12" and easily seen on wood with the shop lights on (my shop lights are very bright). If anything, the laser is too bright for accurate alignment (which is easily corrected by using a resistor in series).

The line lasers have the same angle and beam width.

(I bought a few of each about two years ago and I can't find where I put the spares!)

Paul Z

[Coleman Becker]

it has been there for about 6 months and i have only had to change the battery. i dont know exactly what the tolerances is but it is a lot better than a v-bit in the spindle eying your offset

[dhunt]

it has been there for about 6 months and i have only had to change the battery.

Speaking of battery life, I just noticed that we installed our laser July 24th. 2011
-and we're still using the first set of CopperTop AA batteries, nearly a year later
with no obvious signs of battery failure.


Around that same time we also installed a small Genius keypad on a 10+ ft. USB cable
for easier finding our X/Y zero point
and together with the laser, this combo has made it a lot easier!
.

[paul_z]

If you use a crosshair laser, mount it on the router/spindle holder and make sure it points straight down. If it is not vertical on both directions, you will get different results as the Z axis goes up and down. Using the Z travel is a good way to verify that the laser is pointing straight down.

Using a V bit, cut a very slight dent in your spoil board or a piece of scrap. Then zero the x and y axis. Move the router/spindle until the cross hairs are directly over the dent. Write down the x and y values. This is the offset between the router/spindle and the crosshairs. Use these offsets when zeroing x,y using the crosshair laser.

A better approach would be to use two line lasers. They are mounted the carriage on an angle so they shine right under the bit. One line will be adjusted to be parallel to the X axis and the other to the Y axis. This takes some time but the result is a "dead on" crosshair that doesn't require an offset.

In either case, add a variable resistor in series with the laser(s). The dot from a good laser pointer is perceived to be much larger than it really is. This is due to saturation of the cones in the retina of your eye. You can reduce/eliminate the saturation effect by reducing the intensity of the beam.

I have used both of these methods and have reverted to using my edge finder from SDA Manufacturing the few times that I need an accurate zero. (The crosshair is a big wow factor if you have visitors.)

Paul Z