I finished up the Peerless power hacksaw. At the end of the last post, I had it running but the electrical wiring wasn’t completed. There’s a limit switch in the saw that is supposed to turn the saw off when it finishes cutting. Its a single pole, single throw, normally closed switch. At the end of the cut the upper lever gets released and swings back pressing on the switch. This opens the switch and turns the machine off. I chose to use a contactor with a control circuit that makes use of the limit switch. A contactor is an electrical switch. When current is passed through the coil of the contactor, it generates a magnetic field that pulls the contactor closed. When closed, it allows voltage to pass through another circuit. In my use the contactor will pass 240V single phase to the motor.
I have a contactor and enclosure that I picked up an estate sale auction for cheap. It has a 120V coil and is rated to take the two hot wires for 240V. The contactor is the white block in the picture below. The black wire goes to the limit switch.
On the side of the machine is the limit switch. The bronze arm is in the “off” position in the picture and the end of it is over the wheel that opens the circuit. To turn the machine on the top of the lever is moved forward, moving the bottom of it off of the switch. The small steel rod to the right of the lever jams against the flat piece behind it to hold the lever in the run position against the spring force. Well, it’s supposed to but it slips at the time the picture was taken.
Below is the finished wiring. Voltage from the wall comes into the left side of the contactor. It goes out the right side and up to the motor when the contactor is closed. I connected one end of my control circuit to the black hot wire then through the limit switch, an on off switch, the coil, and finally to the neutral wire. By connecting it to the neutral wire, I can get the 120V I need.
At the other end of the power cord is the plug. Here’s how it is wired up. Once the wires are securely in place, this section recesses into the rest of the plug. I use a locking connector but a regular one would be fine. At this point I double checked my circuit, hooked it up, and turned on both switches. Nothing happened. I checked and checked but still couldn’t figure out what was wrong. I talked to my dad who suggested checking the electrical panel because I’d gotten some weird hot to neutral voltages from the wall. Once I had the face off the panel I saw that whoever had wired my receptacle didn’t bother to hook up the neutral wire. Once I hooked it up the saw ran as expected. I still don’t understand how I got significant voltage readings between the hot lines and neutral.
With the saw running I decided to address the rod that is supposed to keep the lever shown above in the run position. I decided to build up the end of the rod with my new MIG welder and then machine it down on the lathe. Here’s how it looked after I got done building it up the first time. Ugly.
But after turning it down, I have a nice edge to catch the rod and hold it in place. There’s a lot of wear where the rod catches on the machine ( I think, but its possible it is supposed to look worn) and I may have to address it later.
When checking the control circuit with my DMM I proved that the limit switch worked by pushing it open with my finger. Once I had everything hooked up and running I found out that the pad on the end of the lever didn’t press the switch in far enough to open the switch. Not a problem though. I turned a piece of brass down on the lathe and then soldered it to the end of the lever. Problem fixed.
Here’s how all the electrical stuff looks buttoned up. The only thing that can be seen is my on/off switch. I liked the idea of having another switch other than the limit switch to turn the machine on and off.
How’s it work you ask? Well, I took some videos to show you. In this video, I’m cutting through some 1.25″ diameter mild steel. I’m using the slowest saw speed and moderate to heavy downfeed pressure.
Here is it cutting through some 3/4″ brass. I changed the saw to the middle speed and have it set on moderate downfeed pressure.
I’m sure modern saws cut a little faster but I think my saw does well. It certainly makes quick work of the brass. If I decide to run coolant on the saw, I may try cutting the steel at the middle speed.
I shimmed the blade a little bit and think I’ve got it cutting pretty straight. Ignoring the bit left over where the brass broke off, I’d say its pretty flat.
I turned the saw on with the gear box in the high speed position and the saw tried to roll away. I’m not sure what I’d use that speed on though. Now to find some bigger stuff to try cutting!