Scrappy Lil’ Circular Saw

Like a lot of us, [Andrea] has a habit  of disassembling everything he runs into. He recently came across a fairly substantial motor he’d salvaged and envisioned its new life as a small circular saw.

[Andrea] bought new cutting discs, but the rest is salvage and scrap. He had already mounted the motor, pivot, belt, and gear to a wood block, so he added two more wood scraps for a base and a cutting surface. He screwed a metal L beam to one side of the surface block to keep the disc adjacent to the edge. A couple of washers keep the disc rotating freely. [Andrea] used a piece of hydraulic pipe and a cylindrical nut to attach the disc to the pivot. This assembly can be easily tightened by hand, so changing discs is a quick operation.

He kept the electrical as-is and mounted the box to the saw body. This 30W motor runs at ~600-1000RPM which isn’t fast enough to cut wood. Undeterred, [Andrea] plans to use it to cut steel bolts, copper circuit boards, and metal plates. If you need to cut through anything and everything, try this 700W DIY table saw.

22 thoughts on “Scrappy Lil’ Circular Saw

  1. Another project where the builder, in their haste to get working and up on the web, has scant regard for safety. Can’t these people think about a simple guard to a) protect fingers from the toothed belt and b) stop metal particles dropping into the motor’s cooling slots? And what about a proper earth for that mains-run motor?

    1. There was no earth coming in from the original mains cable, so that leads me to think the motor is isolated.

      In general I like power tools that have as few as possible safety features. You have to give the machine only one look and understand you have to treat it with respect. Bigger machines like lathes, milling machines or guillotines come with very scant safety features. Maybe just a lockout switch, emergency stop and emergency brake. It’s infinitely more valuable to operate a machine without safety features and you fully aware of the dangers of operating it than using a machine that protects you from yourself, and then you still make an accident and blame the manufacturer.


      The other day I saw a .gif on reddit about a dumbass that was using his sweater sleeve to clean/polish a ~100mm dia steel rod that was spinning in a lathe. I nearly crapped myself when he got swallowed by the machine. Luckily the cloth ripped and he only took one spin around the rod before someone was there to stop the machine…

      1. I still remember my coworker telling me about a machine he once worked with. One of the other workers got his hand jammed in the machine, but stopped it in time to avoid punching a hole all the way through the palm of his hand. Unfortunately, the machine had no way of being reversed at that point in the cycle, without disassembling the entire machine.

        I don’t know whether this actually happened, but I know he tended to clean the printing presses while they were running by dragging a rag along the rollers – in direct conflict with company policy. One time he called me in to the room to unplug the press – he’d climbed inside it and only by shocking himself did he realize it was still live.

      2. The lathe & mill we recently purchased did come with additional guards. A chuck guard that hinges over the top of the chuck so you cant leave the key in. The mill had a spindle guard. Both were removed even before power was connected.

        The spindle guard was especially useless as it gets in the way of working on jobs, often forcing you to use the quill when you shouldn’t be. The chuck cover was slightly yes useless as a chuck key could easily kill/mame however anyone who is a qualified tradesman should NEVER leave the key in and a spring attached to the key is enough to remind any apprentice/hobby user.

        Not surprisingly the guards were wired into the machine in such a way that they could be disconnected in less than a minute.

        Safety features are important on machines however there should be a push towards developing smart safety features like the “saw stop”

        1. Saw Stop is designed to protect the operator from accidents, not from his own stupidity. This is totally acceptable. You must be smart enough to realize that blade will destroy your hand if you are not careful. Saw stop will not prevent stupid accidents, just avoid serious injury!

          About the lathe chuck key… I’ve had one fly past me once in the university machine lab… Why cant the machines have a ‘soft start’ feature where it makes a full rotation at a really slow speed to make sure the key is not in the chuck. Maybe have something below the chuck where the key will catch on, but completely out of the way otherwise? Obviously it must be able to be disabled first…

      3. You are assuming that an electrical motor can’t get a short to the chassis. Grounding is always mandatory, only exeption is when there are no conductive surfaces at user reach.

      4. Even when completely aware and focused something can go amiss, and at that time having something to reduce the damage being present is welcome

        As for the project: it seems to rely on a lot of luck in having all the right parts. But I like the concept of having a small no-nonsense cutter.

  2. 30 Watts? That’s nothing! You’d be better off using a hacksaw.

    Don’t get me wrong that’s a pretty cute little gadget, but any cheap $30 Chinese angle grinder can do a better job, and most of them put out about 800 watts of power.

  3. to the few that think this is unsafe, it is, but only to you, the rest of us could use this without fear of an accident, imagine cutting a 1 inch square pcb in half, would you use this or the allegedly safe $30 angle grinder? I have many tools infinitely more dangerous looking than this, I show them respect! oh and RCDs no need for earth leads, they can break like any other wire.

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