Thanks for the input.It's hard to say. It depends on the distance the laser is from, and the amount of ambient light, on the work. Most such (Red) lasers are 635-650nm with a maximum output of 5mW or less. In your case it sounds like the laser will be close to the work, so unless you have a very bright light on the saw, you don't need a vey bright laser. The laser manufactures spec sheets should tell you the optimal focus range, line or dot width, etc to help you make a selection.
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Accu-Path Band saw laser
The Accu-Path band saw laser projects a laser line on to the band saw table to display the path of the band saw blade.www.accu-slice.com