Miter Saw Laser Switch Mod

Miter Saw Laser Switch Mod

The Problem

So I got this miter saw from Harbor Freight Tools back around August or so of last year as part of our Stairs Remodel project. It has a laser feature where the saw projects a laser line onto your workpiece where the cut will be made. This is super handy and made cutting custom treads for our stairs much easier than it would have been without it, but there was one little problem I had to solve first. The laser only turns on when the saw blade is spinning. That’s right, you have to pull the trigger on the handle and start the saw blade to make the laser turn on. That means you have to keep one hand on the handle while you use the other hand to attempt to line up your workpiece under a spinning blade (there is a plastic cover that doesn’t retract until the blade is pulled down so I’m being a little dramatic, but still). If there’s any part of using a miter saw that could benefit from being able to have both hands available for it, it’s lining up and clamping down your workpiece. When I discovered this deficiency, I was at a point in the stairs project where I felt less than confident about the direction things were headed so I decided to take a break from carpentry and dig into something I actually know a little better: electronics!

The Plan

I decided that my ideal miter saw would have a switch on the side of the handle that I could flip to control the laser without needing to have the blade spinning. Looking at the photo above (which was taken before this little project began), there is no such switch. I had a few switches lying around but I wanted something with a higher current rating than my usual type of electronics hobbies (Arduinos and such). So I picked up one of these little guys from Amazon. I don’t have to do any math to know that a 20A rated switch is going to be plenty good enough because the wiring in my house is only rated for 15A!

The Procedure

The first step was undoing a bunch of screws and prying apart the case of the handle to get a peak inside.

Everything is hooked up to a single switch that is controlled by squeezing the handle. The black and white wires coming in from the right are the hot and neutral wires from the 120VAC source. The hot wire is interrupted by the handle switch and after the switch, the hot wire and also the neutral wire are branched off into two green wires that connect to a tiny pcb which has the power conversion circuit for the laser. The red and black wire going off to the right from the pcb carry a lower voltage and directly power the laser. The main thing I notice here is that the power conversion circuit on the PCB is tiny and probably not rated for prolonged usage (which may be part of the reason the saw was designed to power the laser only when the saw is on — this virtually guarantees that the laser will never be used for long periods of a time with no breaks). What this tells me is that if I go through with this procedure I should be careful not to leave the laser switch turned on for long periods of time or I may cause the power conversion circuit to overheat and cause damage. I decided to move forward anyway. My plan at this point was to branch off of the hot wire before it goes through the squeeze handle switch and run a separate branch of the circuit through my new switch to power the laser. I’m not going to go into all the details because you really shouldn’t try to replicate this unless you know what you’re doing anyway.

Cutting the Plastic

The next part was fun. I got to use my Dremel rotary tool to cut away part of the handle housing to make room for a new switch on the side of the handle. I didn’t really make any measurements, I just started cutting away and repeatedly checking if the switch would fit yet.

Wiring it up

Once there was room for the new switch, I could finish wiring everything up. I used a soldering iron and some heat shrink tubing. Ever since I got my Weller digital soldering station, electrical work has been so much more pleasant. It’s just nice to be able to set an exact temperature and know that the iron will respond quickly and maintain the correct temperature throughout the job. Makes for quick and easy soldering. And if you haven’t tried heat shrink tubing for insulating your electrical connections, it’s fun to use and much cleaner than electrical tape in the end. You’ll also need a heat gun if you want to go that route. You can find very inexpensive heat guns at Harbor Freight Tools.

The Finished Product

I really love the result, and taking a break for the stairs remodel to do some electrical work helped me keep my sanity. Also, being able to switch the laser on without the blade running so I could position workpieces with two hands really helped me keep my sanity. I wouldn’t necessarily recommend that you try to do this yourself, but I would say that if you’re going to buy a miter saw that is laser-guided, you should definitely look into whether the laser can be controlled independently of the blade before you buy. For me this was a feature I couldn’t live without so I was willing to put a little time into making it happen with an after-market custom mod. Sometimes you just have to make things work! It’s the Johnson way.

Comment below about a time when you made your project dreams work out in an unconventional way!

 

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