This is a Harbor Freight angle head grinder. It is not their least expensive, nor their most expensive grinder, but a mid-range choice that sells for around $35 US. It works well, but has a weakness. See the second photo. Note the red arrow. It indicates the location of a break in the plastic linkage from the electrical switch to the yellow switch button visible in the first photo. Once the plastic linkage breaks, the grinder is useless. In the second photo you can also see the steel linkage I made to replace the plastic linkage and restore function to my grinder. This Instructable will describe how I made and fitted the steel linkage. It will also provide an option for those who do not have access to a welder.
- Steel 1/16" (about 1.6mm) thick
- Steel 1/8" (about 3mm) thick
- Phillips screwdriver
- Small file
Step 1: Open the Grinder
Remove the single screw near where the power cord enters the case and slide the half of the case on the power cord end away from the motor. See the second photo. Remove the wheel guard. Then remove the four screws holding the metal head on the grinder. Two are encircled in red. Two are not visible, but their approximate location is indicated by the red arrows.
Step 2: The Switch
Note the text box in the photo. If you do not have access to a welder so you can make a steel linkage to replace the plastic linkage, you can mount a replacement toggle or twist switch on the bottom half of the case where you can find space. Connect to the two wires shown in the photo.
Step 3: Steel Linkage
I tried to replicate the broken plastic linkage as closely as possible with my replacement steel linkage, but there were limitations. The yellow switch button requires a square hole for a fitting. I drilled two holes and used a small file to make it rectangular. See the text boxes. Some improvising was needed. I also left an open door for myself so I could make small adjustment to the length of the linkage. After making and installing the steel linkage, I used some grinding to smooth the linkage so it releases as it should. Still, that is better after some usage. Lubrication with some paraffin rubbed on the steel helps, too.
See the second photo. A plastic linkage does not conduct electricity, so there is no danger it will short leads and terminals. But, a steel linkage is a different situation. I thinned the width of the steel linkage so it would not wear on the insulation for the wires and create an electrical short.
Step 4: Reassembly
When I made and installed my steel linkage, I had to remove the motor's armature. That meant the commutator had to come out of the brush assembly. Getting the commutator back between the two brushes is very difficult. I could hold one brush back out of the way, but finally removed the brush holder screws on the second brush and put the brush holder back in place afterward. See the second photo and the text box.
This angle head grinder need not be considered a cheap throw away item. I use it quite a lot. That would not be possible if I had not replaced the weak plastic linkage with a sturdy steel linkage. I use this grinder with a cut off wheel most of the time. I do not use it continuously for long periods. So, mine has plenty of time to cool. It will continue to serve me well for a long time.