You pull the trigger on your miter saw, but nothin’ happens. The motor doesn’t hum, and the blade doesn’t spin. You look down at the tool and wonder in frustration what’s wrong with it.
It’s an inconvenence; particularly if you’re on a deadline, or you need to get that deck done before the rain begins. Everyone think the saw’s dead. The circuit boards is fried.
The motor fail inside. But that’s not normaly the case. Usually it’s just mechanical and much easier than most folks think.
Bosch miter saws are solid tool. Generally speaking, they holds up pretty well. If one goes wonky, it’s usually not some horrible defect.
You can fix it in five minutes, either because of a small part failure or simply a user error. The beginning is always the end: When something go wrong with a machine, start with the obvious. Walk yourself through common points of failure before calling for a part or tearing it apart.
Not only does this keep your project on schedule and save you money, but it will teach you how the machine work, making you more efficient (and safe) operator over time.
How To Troubleshoot A Non Starting Bosch Miter Saw
Check Your Power Supply
First, the power supply. Duh.
But realy, this has got to be the first check. Is the cord securely inserted? Plug something else in (a lamp, for instance) and see if the outlet is working.
Many of the Bosch tools require higher amps then some other tools; a poor quality extension cord will lead to voltage drop which can keep motor from turning on. Try plugging right into the wall if possible. Occasionally the plug where the cord connects at the end are corroded or not secure.
A poor connection kills current before it even makes its way to the saw.
Inspect Safety Interlocks and Blade Guard
These are safety interlocks. These days, there is all kinds of safety interlocks built into miter saws, such as those made by Bosch.
Chief among them is a blade guard. Is it retracting smoothly? Does it seem to stick in place at times?
Then the safety switch won’t activate. So the motor won’t come on. Spritz some silicone spray or other light oil onto the guard mechanism and work it back and forth manually to see if it’s free to open and close.
A sticky blade guard is one of the most frequent causes of a “non-starting” miter saw; it’s an easy remedy and can save your bacon many times. Inspect the pivot spring on the blade guard. The pivot spring of the blade guard should be inspected.
A broken or disconnected pivot spring will cause the guard to not close properly. The saw sees this as a safety issue, it won’t start. Examine the area where the guard pivots.
There’s a little metal spring there. That’s the pivot spring. If you need one, you can order replacement part from Bosch.
It is not hard to replace and is very inexpensive. Don’t skip this one. Running your saw without an interlock in place are a bad idea.
Replace Worn Carbon Brushes
If your saw has a brushed motor, inspect the carbon brushes. Carbon brushes found in older Boschs is consumable items. Over time they will became worn.
Once they become too small (less than 1/4″), they won’t make good contact with armature. This results in the loss of an electrical connection to the armature, and the motor fail to spin. Usually, there is some grinding noise and sometimes even sparks coming from within the motor housing prior to it totally dying.
Remove the brush caps on each side of the motor and pull out the brushes and measure them. Replace them if they are less than 1/4″ long. Doing this routine maintenance extend the life of tool considerably.
Check for a Bound or Seized Blade
Examine the blade. Sometimes just a seized or bound blade will keep a saw from starting. The blade could of been caught on an unseen obstacle while cutting out a nail, for example.
Take off the blade and see if there is something sticking to it, or any damaged area on the blade. Then make sure the arbor nut is snug. A loose blade can start to wobble and bind up against the fence or the guard.
This creates resistance that the motor cannot overcome. Reinstall the blade clean and tight. Next check that your riving knife lines up properly in kerf of the blade because it can cause some binding too.
Test or Replace the Trigger Switch
My last thought is to switch. The trigger switch has an internal component that eventually fails over time. You’ll notice this if there’s a click but no power.
In this case, the contacts on the switch is either burnt or worn out. This happens more frequent in pro settings where switches get abused more. It’s a modest repair job to change the switch.
You have to remove motor housing and handle, too. It is not something for the faint of heart when it comes to electrics. Unless you’re up to tinkering yourself, haul it into your local shop.
Bosch authorized dealers can do it and they will have correct parts and skills. Avoid all this by keeping your saw tuned up and clean. Precision tools does not like dust and debris.
Regularly clean the table and fence and blow out the vents. A clean saw last longer and runs better. Step-by-step troubleshooting turns what could of been a disaster into a mere hiccup.
The next time you make that cut it’ll be accurate and smooth.