Disc Sander - DIY Build for Free

Once again i was inspired to build something in my workshop after watching a Youtube video on Tested.  I've talked about Tested several times before, it's a website/Youtube channel, which focuses mainly on Adam Savage from Mythbusters.  My favorite video's are ones where Adam is building something in his shop.

Some of the other projects i've done in which i was partially inspired by those video's are:

Folding Tool Box - Nail Gun Case

 Link to build Video - http://youtu.be/weCN9YpEskY

Organize Parts Storage Stacking Cases 

Link to build Video - http://youtu.be/ctgp7JBPLXs

While Adam is building he sometimes talks about the tools he uses and why he likes them.  A couple of times he has mentioned how much he loves using his large disc sander.  In a recent video he did a tour of his shop and again talked about how useful the disc sander is for quickly removing excess wood after cutting on the bandsaw.

Back when he first talked about how useful it was i started thinking that maybe i could use one in my basement workshop.  I do have a really nice PorterCable 3" hand belt sander, but i rarely use it.  It does a great job, but it's heavy and not exactly a precision tool.  With a big disc sander i figured that i could leave it sitting on the work bench.

When i started looking at buying a disc sander i noticed a few things.  First is that they are pretty basic.  There's a motor, framework, platform and the spinning disc.  Second is that most of them are pretty small.  A lot of the stores were selling 6" or 8" bench top disc sanders.  The sander in Adam's shop was a big industrial sander with something like a 16" or 18" disc.  I think he said that it's a 2 horse power motor and can really do some damage if your fingers get in the way.  Third is that they were pretty expensive.  Even for the cheaply made ones like at Harbor Freight they wanted $120.  Here's a pretty basic one on ebay, it's close to $300.

So for all of those reasons i decided that i could just build my own 12" disc sander.  

Here's a video of everything i did from start to finish, in but there's a more detail write-up and pictures in this blog below

Disc Sander - Make DIY Build

 
http://youtu.be/v0whmYkAV7U

I decided to make the spinning disc 12" for a couple of reasons.  If i'm going to build my own disk sander i might as well make it big.  There's no point in building a small 6" or 8" sander if i could just go to the store and buy one.  I might as well build something that would cost $200 at the store.  I did want to keep it simple though.  Just a motor, frame, disc and surface.  Also it had to be lightweight and compact.  Something like this.

Another thing i thought about is that i had to be able to buy round sandpaper for it.  There were only a couple of places that sell sticky-back round sandpaper in sizes bigger than 12" and it isn't cheap.  Amazon had some 16" sandpaper for around $30 a piece.  But Harbor Freight had a 2-pack of 12" round 120-grit sandpaper for $6.  I really wanted 80-grit but 120 is all they sell.

The last reason why i decided to build a 12" disk sander is because of the power needed from the motor.  I've had an old 1/3 hp 1750rpm electric motor that came from the furnace blower at my parents old house.  Here's the specs.

The furnace motor is the one on the left, the one on the right is a really old motor that my grandpa gave me years ago.

After reading a lot of things online, i was worried that it might not be powerful enough. Those big 14" and 16" sanders use 1hp and bigger electric motors.

Obviously i wasn't going to go out and buy a motor, plus i had already installed a small on/off switch on the back years ago.

The 1750rpm was perfect, but many people said that 3/4 hp or a 1 horse power motor is really the right size.  I didn't want to go to the trouble of building the disc sander, just to have it bog down every time i tried sanding something.  But i thought "Eh it'll be fine" so i started building.  One of my goals, to make it as simple as possible, is always a lot harder than you'd think.  Looking back at the final product it looks like it should have taken 5 minutes to build, and yes if i had to build it again now it probably would take 5 minutes.  But there's always a lot of thought that goes into making something simple.  You have to strip away the unnecessary parts, getting down to just the basic core of the machine.

I drew lots of different versions of how i thought it might look.  From different motor mounts, to a sheet metal dust screen, to a pivoting platform so that i could sand at different angles.  But i finally ended up on a very compact and basic design.

I knew that in order to keep it cheap and light-weight i would make the "frame" out of wood.  But before i began building i needed to decide on the disc itself.  My original plan was to use metal, aluminum specifically.  Steel would be too heavy, straining the motor every time it tried to start spinning.  Aluminum is not only light but it's a strong metal that can be shaped on a lathe.  Disc sanders you buy in the store use an aluminum disc, which varies in thickness.  For a big 16" disc sander like Adam's, the aluminum disc might be 3/4" thick.  It has to be rigid enough to not bend when pushing on the end away from the center.

I looked for about a month for a round piece of thick aluminum that i could use.  But not surprisingly it's not easy to find a 12" piece of 1/4" thick aluminum just lying around.  I concluded that the disc i would use would not be made out of aluminum.  So i decided to use wood.  I knew that i wanted to use something like plywood or particle board.  If i had used a solid piece of cut pine, it's possible that it would bend or bow because of the variance in its grain.  With wood that's been laminated together, the difference in the pieces and direction make sure to keep it from warping.  So i ended up using a piece of 3/4" melamine.

Melamine isn't cheap, a 4'x8' - 3/4" board cost around $38.  I've used melamine in the past as the work surface for my work benches.  It's a very sturdy, rigid board with a really great smooth white plastic coating on both sides.  I've used it on both my work benches and i also used it when i built the table top for Karrie's arts and crafts table.  Here's me cutting out the top many months ago. 

You can see the same piece of scrap wood in the picture above is the piece that i was using.  Also on the table were just some random scraps of wood that i thought would work.

To begin i started by cutting the melamine in a 12" circle.  I did this by drilling a small in a piece of plastic, then drilled another hole 6" away.

Then i drilled into the piece of melamine and left the drill bit sticking out of the wood.  It acted as the center fulcrum for drawing the circle.  The first hole i put through the drill bit and the second hole i used to draw the circle. 

Then i got out my jig saw and cut the 12" disc out.  The funny thing is that the perfect tool that i could have used to smooth out the cuts would have been a big disc sander.  It would have been nice to use the tool i'm building, to help me build the tool i'm building.  (that sounds like something out of a Dr Seuss book)

Then i came to the next, and probably the most critical step, figuring out how i would attach the 12" circle to the motor.  This was the part of the machine that had to be done right.  It not only had to be strong, but it also had to fit tightly to the motor shaft and the disc.  If it was wobbly or not at a perfect 90 degree angle the sander wouldn't work.  

The ideal thing to use would be a big pulley which fit the shaft of the motor.  Unfortunately the only things i had were a tiny 1" pulley, random metal bracket, and plastic sprocket.

One good thing about the pulley is that it fit tightly and had a bolt that locked to the flat part of the shaft.  To strengthen the critical point and expand the area where the twisting force would be applied, i decided to add a large metal washer.  The washer provided extra strength and also gave me a place to mount the 12" disc to the motor.

Next i drilled 4 holes through the metal washer, then marked and drilled 4 matching holes in the disc.  I figured that it would be easier to drill the holes in the washer before attaching it to the pulley.

To attach the washer to the pulley luckily i had just the right tool, my welder.  I bought a cheap 90 amp welder from Harbor Freight a few years ago and have used it on a few projects.  So far it's worked great for welding my mufflers and attaching wheels to metal tables.

So i went to the garage and started welding the washer to the pulley.  I didn't do what you would call a pretty job, but it was definitely strong.  I welded full beads around the front and back.

Here's a closeup of what the coupling looked like.  Not perfect but hopefully good enough. 

It was easy finding just the right bolts to use, now that i have my stacking cases.  Everything is so organized.

To make it nice and strong i used fairly large bolts to attach the two together. Here's about where i was at.

Before i went any further i figured that i should probably test to see if the motor can spin the disc fast enough.  So with one hand i held the motor to the table and with the other hand i turned it on.  Lets just say that there was plenty of power.  And that it's not easy to hold down a motor spinning a 12" piece of wood at 1750 rpm.  It almost vibrated off the workbench while i was holding it.  But it passed my un-scientific power test and i decided that it was plenty powerful enough, i could continue.

Next it was time to start building the frame to hold the motor and attach the platform.  To hold everything together i decided to use a scrap piece of 1x12.  I think it used to be part of a shelf board in one of the closets in the house.  It seemed pretty simple to me, just 4 boards and a platform on top for the surface to rest the wood on while i was sanding. 

With everything basically set, i was ready to glue it together.  I didn't have a good clamp for the 3 boards in the back so i used my 50lb anvil.  It worked well.

Then i had to make the motor mount.  For the 12" disc to clear the table i had to raise the center point at least 6" up.  The distance from the center of the motor to the bottom was around 3" so that meant that i had to raise it up at least another 3".  Back before i started building i came up with some fancy designs using bent sheet metal for the motor base.  What i ended up using was 3 pieces of a 2x6 pine board.  The wood was strong, light and provided me with a more than adequate base to attach the motor.

The last piece was the platform.  This is where i would rest/brace whatever i was sanding perpendicular to the disc.  I originally thought about having the platform pivot so that i could sand an angle between 90 and 45 degrees.  But i figured that i don't ever need to be that precise, if i needed to sand an angle i could just lift the piece and eyeball whatever angle i needed.  Plus a pivoting platform would not be as strong as something that i fixed in place.  So i just glued and screwed two 2x4's and two 2x3's to the base.  On top of those i attached the melamine platform.

Again i decided to use melamine because it's strong and great to work with.  Plus the scrap piece was large enough for what i needed.  So i attached the motor and disc to the completed frame and test it again.  Almost everything worked perfectly.

The motor was solid and the platform was fine, but the disc had a small wobble.  It must have been when i welded the washer to the pulley.  I assumed that the washer was flat, but it must have been slightly bent.  Something that isn't noticeable on a 3" spinning piece of metal, but that gets magnified 4x on a 12" piece of spinning wood.  I tried using small shims and adjusting the bolts, but that didn't work.  Eventually i got the disc wobble/fluctuation to go away by brute force.  With the motor locked in place i forcibly twisted the disc until i was able to bend the washer back to a simi-flat shape.  There was still a small wobble, noticeable when you spin it with your hand, but at full speed you can't tell.  

The last few steps were markings and paint.  I used a sharpie to mark the center of the platform and different angles to the disc.  It's important, for a counter-clockwise spinning disc sander, that you don't use the right side of the disc.  If you do the thing you're holding will go shooting from your hands, since the disc is spinning upwards.  You want to use the left side where the disc is rotating downward to the platform.

Another angle of what it looked like.

And here it is from the back.  Super simple.

For paint i did what i always do, use whatever color paint i already have.  I used up all the old red paint with the welder cart, miter saw, and tool box.

Wood Tool Box

Welder Cart

Miter Saw Stand

For the last project i did:
Organize Parts Storage Stacking Cases

I used some old lime green paint that was left in the basement when we bought it.  There was still plenty left so i decided to use that again.


I made sure i taped off the top melamine surface with masking tape, then applied 2 coats of the green paint.  After those dried i applied 2 coats of polyurethane.  And the sander was done.

I'm super happy with the 12" disc sander i built.  It ended up being everything i had hoped.  It's small, light weight, easy to move and cheap to build.  Basically the only thing i had to buy was the sandpaper.  So really i only spent $6 for the whole thing.  A lot better than $280.

It does a great job of sanding wood, even with the 120 grit sandpaper it can remove a lot of material in a couple seconds.  Once again i have a tool that i can't imagine having to get by without.