Mini circular bench saw from scrap [UPDATED]

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Picture of mini circular bench saw from scrap [UPDATED]
Try to salvage little electric motors from scrap, because you can usually find a way to reuse them. I don't remember where this motor comes from, I've got it many years ago when I used to dismount everything I bumped into, anyway when I found it the other day I immediately pictured a small bench saw to cut metal. Not wood, because motor has a belt and a ratio so that the gear turns at a speed of about 600-1000 RPM which is good for metal, bricks, stones but wood needs very fast speed. To cut these materials you can use a disc grinder, so I bought a pair of discs to apply to my motor.
[UPDATE] I also can apply a disk of sand-paper if needed. To check speed of the disk see last step.
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Step 1: Motor and pulley

Picture of motor and pulley
I already put together motor, pivot, belt and gear with a wood block when I was a boy, so I left that mounted. The pivot is a very sturdy steel beam and at that time I drilled an hole in the wood and I wedged the pivot into it. The gear has not bearings but uses a metal bushing to rotate around the pivot. The mechanism you see around the little gear on the motor pivot is meant to release the rotation when motor stops, anyway I don't need this feature.
The motor has 30W power, and with this gear the final disc has a very strong cutting force.

Step 2: Finding a fastening

To attach and change easily the discs on the gear I needed a simple and effective way. After some research I retrieved a piece of hydraulic pipe and a cylindrical nut. Since the pipe's external diameter is almost equal to the disc hole measure, and the pipe fits very good on the gear's steel pivot, that solution works perfectly. I only had to glue with two-components adhesive the pipe on the pivot, adding a plastic ring where discs will be pushed by the cylindrical nut. This nut is very easy to tight by hand, and changing the disc will be fast.
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Hi bro how u come up with this idea
andrea biffi (author)  bradley1marler1 month ago

only thinking about a way to use that motor... always save stuff from scrap! ;-)

andrea biffi (author) 2 months ago

thanks guys :)

veelicious2 months ago

I am impressed with your creative thinking. Great photo and instructions. I hope you win its awesome.

legamin3 months ago

very eloquent. More sophisticated than what is offered at the discount tool shops and I'm sure better power and reliability. Thank you for sharing! It's something I can use.

gunnyboy4 months ago
Cool idea! I made a mini-bandsaw like device. I'd appreciate it if you told me what you thought.
T-BONE34 months ago
It works
mcshawnboy5 months ago

I like what you've done, but I don't know if I'll get around to it. I voted for you & hope you do well! :)

andrea biffi (author)  mcshawnboy4 months ago

LOL, thanks!

thinkpadt304 months ago

Andrea, you're my hero! Your 'ibles are super! I really admire your creativity and your determination to follow through with your ideas. Most people would think of an idea, but see all the obstacles, and never finish it. I have a motor that I have been trying to use to make a small sanding table using a 1" sanding belt. I've run into trouble at every turn, though, from attaching the pulley to the shaft to figuring out how to change the belts. A new sanding table is only $45, but I should only have about half that into my DIY one, and I'll have the satisfaction of making it myself. I don't when, or if, I'll ever finish it, but your inspiration will help me to finish it.

andrea biffi (author)  thinkpadt304 months ago

Satisfaction is priceless, keep trying and good luck! ;-)

Ryan Hebron4 months ago

i think it looks great and is a verry good idea

iamtojo4 months ago

Speaking from experience: DO NOT CANTILEVER A BLADE Unless you are a professional and have done all the engineering calculations to prove it is safe. If the shaft gets bent even the tiniest bit, the eccentricity will cause the spinning of the balde to bend it even more. This will lead to catastrophic failure and shards of the blade flying every direction, usually with practically no warning. I generally agree with others that you need to add more safety to this concept.

Would use a solid board instead of particle board for the top surface. The real board will be much stonger and will last longer, especially if it gets wet.

Also, for mounting the disc runner, they make wall-mounting hardware that is designed to let you screw and unscrew several times without damage. This may be beneficial so that you don't end up having to replace the whole top because the screws wont hold securely anymore.

andrea biffi (author)  iamtojo4 months ago

The shaft in this case is an iron bar 20 cm long, no way it could bend. Then the blade is very slow, but your concern is right for very fast blades.

1164684 months ago

amazing. this is why i keep all the motors i find.

santibarraza5 months ago
jadm11045 months ago
maybe a mini band saw next? get idea. all table saws are dangerous if youre not paying attention so i dont see a huge issue with this one

very nice:)

profpat5 months ago

nice and very simple!

Junophor5 months ago

Hello andrea biffi

This is really a great idea and solves a small problem of mine!

Thanks for sharing it;-)))))

Yours Aeon Junophor

andrea biffi (author)  Junophor5 months ago

I'm glad of that :-)

ppatchen5 months ago

I agree with wkearney99. This is a very dangerous device. It's worth a couple of dollars to keep your fingers.

andrea biffi (author)  ppatchen5 months ago

Of course, always better to pay attention to safety, I don't believe it is so dangerous as it appears but anyway a protection is needed.

Regats5 months ago

This saw would be VERY DANGEROUS unless securely affixed to a base where it won't slip or vibrate. The base, as pictured, will not keep the saw from moving around. At least make the base larger so it can be securely clamped to a table at at least two points.

andrea biffi (author)  Regats5 months ago
Motor is pretty slow, so the saw doesn't vibrate and the four rubber feet are enough to keep it still, since the wood base is very heavy (for its dimensions)

Actually I am rather tired of the screaming saws and ferocious cutting speeds of modern saws.

I am making a set of ULTRA LOW SPEED automatic saws, that rotate at like 60 - 120 RPM....

The rational is that a saw can cut timber far faster than I can drill screw, glue and paint all the pieces that come out of it.

And going deaf at 2200 RPM annoys me.

andrea biffi (author)  Wroger-Wroger5 months ago

modern saws also drink a lot of energy! this only asks 30W of power...

s555 months ago
dhilmes5 months ago
I love it for some of the stuff I do it would be handy
ibwebb5 months ago

This is a great instructable and you have some great pics to help out as well. This is one of those things that when I was going through it an wanted to smack my head .. one of those ' I cannot believe I didn't think of this' moments. This gives me a lot of ideas (and a lot of motors that I wish I would have kept now too lol). You got my vote here!

andrea biffi (author)  ibwebb5 months ago

thanks :-)

karti5 months ago

I voted!

agis685 months ago

awoseme job.....maybe some precaution details are missing but as idea is fantastic

thnx and voted

Looks like a death trap. Sorry but as clever it is, it's would be as scarey has hell to use.

wkearney995 months ago

Y'know, maybe in some post-apocalyptic world you'd need to do this... but given how phenomenally inexpensive a real table saw is... why bother? Why open the HORRENDOUS risks associated with a contraption like this? How a blade spins is not something to be careless about. How it's secured, both on the arbor and within the frame are IMPORTANT and should not be half-arsed like this.

Yes, it's a clever bit of repurposing, but it's a BAD IDEA.

andrea biffi (author)  wkearney995 months ago

One of the purposes of this making is to have a blade less and less dangerous than a commercial table saw. This motor is very slow and the disc cuts with abrasive force, not cutting material with blade's teeth, so you can't cut your finger neither putting it over the disc.

Carmelite5 months ago

You might want to check out Matthias Wandel's video series on converting a circular saw into a table saw. It might give you some ideas on how to add additional functionality to your saw!

andrea biffi (author)  Carmelite5 months ago

Mathias Wandel is already one of my greater inspirers! His projects are terrific!

dmadam5 months ago

Thanks you just gave me an idea for my old well pump motor. The pump casing cracked but the motor is a powerful one. Using your idea I plan on making a bench grinder/cutter for metal.

Wroger-Wroger5 months ago

Yeah the GRIPPING of the cutting disk MUST be done in a specific way.

It has to be down between TWO FLAT metal flanges, as wide as the metal strip on the disk.

And each side of the disk MUST be covered with a THICK cardboard disk, to allow a hard crunchy disk, to be held softly, between two metal plates.

You MUST design exactly like the manufacturers do, with these sorts of devices.

Complete with STEEL guards etc., in the area that the disk pieces will fly out and hit you.

The edge speed of the disk is around 300 - 340 kilometers per hour.

Most of the manufacturers are total douches when it comes to "How to mount a cutting wheel" - their information is at best terrible.

This company has a really great PDF and the Videos are excellent.

I have stuck all of them in here because they are good, short, to the point and if you pay attention - along with the manufacturers instructions - you will do the job correctly.

How to mount an Abrasive Wheel.

How to mount a cut off wheel in an Abrasive (chop) Saw

How to mount Bench Grinding Wheels.

You MUST study and copy the designs of the commercial manufacturers with this device.

Because when things go wrong, like an improperly mounted disk shatters, it happens SO fast - there is no time to go, "Ohhhhh NO!" - because it's already happened....

Chunks of disk coming at you at 300Kmh+ from 40cm away.... no time.

There is the vacant spinning shaft where the disk once was, some dust and all, and the bits have gone into you or through you.

This is a guy who made a bench grinder - but there apparently was a speed mismatch between the wheel, and the motor, or the wheel may have been cracked - whatever; and he ran it without a guard...

Many years ago I was shown an industrial safety video where they mounted wheels and had a dummy stand in front of them, and then they fired a bullet from a large calibre rifle into the sides of the wheels to make them explode...

We are talking 12" and 24" pedastle grinder wheels - the answer is "No hope".

And here are some young fellows making CD's explode....

The speed here is much higher, but CD's shatter into sharp fragments while cutting wheels tend to stay in large fast coming at you - edge on - chunks.. and they are way thicker and harder and reinforced with glass fibre matting etc....

So while there is some differences, the effect is similar - but the exploding cutting and grinding wheels are worse.

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