Benchtop Disc Sander

by tomatoskins

80K61538

Intro: Benchtop Disc Sander

Disc sanders are extremely useful tools used for rough shaping wood. When I needed a dedicated sander that could take off a lot of material at once, I was less than impressed with what was available. After not finding any disc sanders with the size and power I wanted in my price range, I started thinking of other options. Looking at what others have made in the past, most did not include a tilting work surface. This was a great design challenge that turned out better than I could have hoped!

If you are looking for your own disc sander and not impressed with anything available for the price, a homemade disc sander may be for you.

STEP 1: Tools and Materials

This is a comprehensive list of tools and materials I used. Not everything is necessary, but I'm sure you will find them useful.

Tools:

Materials:

STEP 2: Motor Selection and Other Information

There are many motors out there that are suitable for a benchtop disc sander. However, free motors are the best motors. If you can find any motor second hand, that would be best for this project. You want to find a motor that is at least 1/2 HP (3/4 HP or 1HP would be best). The motor that I used, was from an old swamp cooler. It's rated at 3/4 HP with two speeds, 1725 RPM and 1140 RPM. Most 12 inch commercial disc sanders (that I looked at) are somewhere between 1600 and 1800 RPM making my motor perfect!

Make sure that you know what way your motor spins before making this project. Most motors are reversible, but not all. The motor I used runs clockwise (backwards from most, if not all disc sanders). I could have taken the time to see if my motor was reversible, but I didn't care. Just be sure to always use the 'downstroke' of the disc when in use to keep all your fingers where they should be. If your motor does not spin clockwise, you will want to move the dust collection port to the other side of the housing.

I have outlined the steps I took when making this sander, but your's will most likely be different as every motor mounts differently. I have added rough measurements to the end of each step to help with making your own sander.

STEP 3: Shape Disc

Using a piece of 3/4 inch melamine particle board, draw a circle the size of your sand paper. Cut the disc just larger than what was drawn using a bandsaw or jigsaw. Find the middle of the disc and mark screw locations to attach the disc to the hub. Cut shallow holes at the screw locations using a forstner bit to create a recess for the t-nuts. Attach the hub to the disc and cut off the extra length of bolt.

STEP 4: Test and Shape the Disc

Having never created a tool before, I was a bit weary of the stability of my simple design thus far. I clamped it to my workbench to do preliminary tests and to get ready to shape the disc. I made temporary supports out of scrap 2x6 I had laying around the shop.

Once I was sure nothing was going to explode, I shaped the edge of the disc using my sanding blocks stabilized by a temporary tool rest made from scrap wood.

STEP 5: Balance the Disc

Using a cut up aluminum can as shim stock and a dial indicator, balance the disc. This is important so your sander has complete contact with the work piece for the whole rotation. If the disc wobbles, you will have uneven wear on your sandpaper. With a lot of tinkering, I was able to get this disc to wobble less than 5 thou.

STEP 6: Create Motor Mounts

Using a compass, mark out the size of the motor to be held along with the mount to hold it. Pre-drill the screw holes before cutting the mount apart (this will ensure everything lines up correctly). I used a bandsaw to cut everything apart. Test fit the mounts.

two 10 x 8 inch squares to make both mounts.

STEP 7: Create the Bottom

Use a scrap piece of wood to line up the front of the sander to ensure clearance. Pre-drill and attach the bottom. Once you have verified the fit, disassemble and glue everything together.

10 x 10 inch square for the bottom.

STEP 8: Create and Attach the Sides

Use scrap pieces of wood to elevate the sander. This will ensure clearance of the disc above the workbench. Mark the locations of the bottom and motor mounts and decide where you want your screw locations. I secured each side with two screws in each motor mount and three in the bottom of the housing. Once everything is lined up successfully, glue the sides in place.

10 x 11 inch sides.

STEP 9: Create the Front Face

Find the location of the motor shaft and drill a large hole at it's location (I started with a pilot hole to ensure accuracy. This will allow the hub of the disc to be mounted from the front of this face. Mark, pre-drill, and secure the face using screws (DO NOT GLUE).

14 x 14 inch square.

STEP 10: Route Slot for Disc Attachment/Detachment

Using a core box router bit, route a slot deep enough to allow access to the set screw on the disc hub.

STEP 11: Create Top

Create a top for the sander housing. Using a dado stack or flat tooth saw blade, cut a rabbet on each side to allow the top to sit securely in place.

10 x 11 1/2 inch top.

STEP 12: Disc Guard

Using a circle cutting jig, cut a disc just larger than the the main disc. Remove the bottom right hand corner of the guard. This will allow for better dust collection.

14 x 14 inch square.

STEP 13: Align Guard to Enclosure

First attach the front of the enclosure followed by the disc. Using the disc, align the guard to the front and secure it in place with a few screws.

STEP 14: Shape Guard

What better way to test out the usefulness of the new sander than to use it to shape itself? Set up a temporary rest and shape the guard to match the front face.

STEP 15: Glue Together

My guard needed a little bit more thickness so I added a 1/4 inch plywood in between the face and the guard. Glue, clamp, and shape once dry as shown in the previous step.

STEP 16: Dust Collection

Dust collection on a disc sander is extremely important (this will also aid in keeping the motor cool). I routed out a large section of plywood to keep about 1/4 inch of clearance in front of the disc.The top of this board is placed at exactly half way up the disc. This will help out greatly later on when setting the height of the table.

14 x 7 inch dust collection cover.

STEP 17: Dust Collection Port

I created this dust collection port around the hose to my shop vac. It's shaped to only cover about half the front of the sander while having a 135 degree angle.

STEP 18: Attach Dust Collection Port

Trace the outside of the dust collection port onto the dust collection cover. Mark the interior perimeter and cut using a jigsaw or scroll saw. Glue in place and smooth out the edges using sandpaper to ensure smooth air flow.

STEP 19: Attach Dust Collection

Using three long machine screws and t-nuts, attach the dust collection to the disc sander. This will allow for simple removal of the dust collection for easier sandpaper changes.

STEP 20: Trunnions

Using the previously discarded scrap from the centers of the guard, cut in half to create the trunnions.

With a circle jig on the bandsaw, cut the exterior of each trunnion so they match. Cut 3/4 around the half circle in two locations to create a track about a 1/4 inch wide.

STEP 21: Fill Gap in Trunnions

Using the scraps from the previous step, fill the end of the gap created in the previous step. Using a round file or same diameter drill bit, round both ends of the track.

STEP 22: Trunnion Mounts

Using hardwood, make mounts that fit on each side of the sander. This will hold the trunnions created previously. Dress the edges with whatever router profile you like. Drill recesses in the back anywhere a screw head will prevent the mounts from resting flat against the housing. Drill four clearance holes in each mount and pre-drill the holes in the site of the sander housing. One hole is countersunk because the trunnions will ride directly against that face.

STEP 23: Trunnion Slides

Trace the track of the trunnions on a piece of hardwood and cut them out with a bandsaw. Using sanding blocks, shape them until they slide easily in the track of each trunnion.

STEP 24: Attach Slides

Use the index holes created from the circle cutting jig to index the trunnions on the top and middle of each side of the dust collection cover. This will be the point that the trunnions will rotate around even when the get cut down in a later step.

Glue the slides in place. After the slides are dry, mark the edges of the trunnions on the slides and cut just short of this mark. This will allow the knobs to hold the trunnions tight against the mounts and not apply any pressure on the slides.

STEP 25: Separable Table

Since the table will be permanently attached to the trunnions in a later step, it needs to be separable (this will allow easy replacement of the sandpaper.

To create a spline joint, cut the table in half. Using a flat tooth table saw blade cut matching dados to accept a 1/4 inch spline of MDF. Glue the spline on one side only so the table can be separated.

10 x 17 inch table.

STEP 26: Shape Table

Centering the table on the housing, measure what needs to be removed to allow for the clearance of the table. The table needs to reach back to the ends of the trunnions.

Using a tilting bandsaw, a 45 degree cut was made along the inside edge of the table this will allow for the table to be moved down to 45 degrees past square.

STEP 27: Cut Rabbet

Using the flat tooth blade on the table saw, cut a rabbet the size of the trunnions and half way through the table.

STEP 28: Knobs

I ended up make separate larger round knobs as I didn't like how these turned out, but the method is the same.

Cut a knob in any shape you like. Drill a hole through the center the size of the t-nut and tap the t-nut in place. If you find your t-nut is falling out often, you can use a small drop of epoxy to hold it in place after everything is painted.

STEP 29: Add Threads

This was changed to a regular bolt once the entire project was finished as the wood screws did not hold well enough. But the existing hole was used to epoxy the bolt in place after everything was painted.

STEP 30: Power Switch

I created a switch cover using MDF, but one can be purchased for much less time commitment.

Mark the location of the switch and cut it out using a jigsaw.

STEP 31: Electricity

Drill a hole in the side of the enclosure the size of your power cord. Do not tie a knot in the cord to use as a cord stay. This can cause shorts and other electrical problems down the road. This was only done as a temporary measure. A cord stay is shown in a later step.

Running the power inside, connect the common to the motor along with the ground, run the hot side to the switch and back to the motor.

Secure the switch in the side of the housing and verify everything works correctly.

STEP 32: Set Table Height

Set the table on the trunnions as is and mark the height on the disc. Remove the table and mark the center of the disc. Measure the distance between the center of the disc and the mark of the height of the table. Using a table saw, remove this much from the trunnions. Replace the trunnions back on the slides and the table. The table should now be the same height as the center of the disc.

STEP 33: Recut the Dust Collector Height

Mark the height of the bottom of the table and cut the dust collector cover to a 45 degree angle. This will allow the table to tilt down 45 degrees off of square. I had to change the height of the screws holding the dust collector in place. This wasn't a big deal and I was able to fill the holes in a later step before painting. Secure the table to the trunnions using screws (DO NOT GLUE YET).

STEP 34: Attach Steel

Use flat head screws to attach the steel to the wooden table. This will give a much more durable work surface as well as hold the two table halves together. Drill a 1/4 inch pilot hole through the steel. Clamp the steel in place and drill the clearance holes through the wood. Using a metal countersink bit, cut the hole in the metal wider until the flat head screw is flat with the surface. Secure on the other side of the table using t-nuts.

17 x 6 1/2 steel plate.

STEP 35: Cut Table

This was one of the most stressful steps as I needed to cut into the table to allow for clearance of the dust collection port while tilting the table down 45 degrees. I cut off little by little until I was able to measure 135 degrees from the disc face to the top of the table. From there, mark what to remove from the steel plate. Using an angle grinder and a small cut off wheel in a rotary tool, remove this section from the steel. Use hand files to smooth the rough cut edges.

STEP 36: Create Back

This disc sander was designed to have vents in the back utilizing the shopvac as the method to cool the motor. With the shopvac on, air will be drawn from the back the unit through these vents cooling the motor, around the disc collecting all sawdust created, then into the shopvac itself.

This simple design was created using a 3/8 inch drill bit and laid out with a protractor and compass.

11 1/2 x 11 1/2 inch square.

STEP 37: Attach Top and Back

The top and back are held in place using dowel pins along with center finders to drill accompanying holes. The top has two dowels in the front and two in the back. They have drastically different spacing to easily see what way it goes. The back is held in place using six total pins.

STEP 38: Fill Holes and Imperfections

Using wood filler, fill all holes and plywood defects. This will make for a much better painting result. Sand when dry.

STEP 39: Back Panel Latches

Use an 1/8 inch rod to hold the back in place. Bend them using vice grips and make these angled hooks.

STEP 40: Insert Hooks

Drill holes in each side of the back panel large enough for the hooks. I used a 9/64 inch drill bit.

STEP 41: Attach Latches

Use simple chest latches to hold the back in place. If your latches have a small tab at the top, remove it with a file. Hold the back firmly in place and mark your screw holes. To ensure that these latches hold tight, drill the pilot holes 1/16 of an inch 'tighter' than previously marked. Once each latch is in place, ensure they hold the back firmly in place.

STEP 42: Paint

Decide on what color scheme you like and paint. I opted for a blue/grey color scheme to match my table saw. Using primer first will give a more bold color while covering up most of the wood grain.

STEP 43: Cable Stay

There are many commercially available cable stays, but I couldn't find any that was not designed for an electrical box. Since I didn't want to include a box inside my sander I made my own cable stay that functions just the same as anything commercially available for free.

Using some pieces of scrap hardwood, fashon a clamp that will keep the power cord from being pulled from the motor. I used the spindle sander to carve out this small cove.

STEP 44: Add Washers to Trunnions

I had originally planned on using wooden washers between the knobs and trunnions, but I found the undesirable effect of it sticking well to the freshly painted surfaces. Using two or three fender washers allows the knobs to be tightened without anything sticking.

STEP 45: Attach Feet

This simple step will protect your paint job more than anything and will keep your sander in place while in use. Just screw them in place and forget about them.

STEP 46: Store the Tool

There is plenty of space inside the housing to store the t-handle hex wrench. If you are concerned about it causing troubles with the motor you can make a simple holder for it, but I didn't find this necessary.

STEP 47: Enjoy Your New Tool!

Now that your new disc sander is complete, enjoy it! Make something useful with it! I used this tool many times over the past year (when I got distracted by other projects before it was complete). It was extremely useful for these projects (clicking on these images will take you to those projects):

What projects have you made with your disc sander? Have your made your own sander? I want to see them in the comments!

28 Comments

mxx 6 years ago

A very thorough and well presented instructable for a very, very useful tool. Congratulations!

deuce1313 6 years ago

I am really impressed with what you were able to do with a few simple tools! This is definately a future build for me

sgsax 6 years ago

Really nice build and great detail in your plan here. This is on my list to do and I've been checking out several of these here and on YouTube. Yours is definitely one of the better ones I've seen. Thanks for sharing!

autotech1 6 years ago

For a first time attempt at building a tool, especially a power tool, you did a great job. If I can procure a 120 volt motor I will seriously consider building one for myself.

relbatto 6 years ago

really useful information, and the instruction is first rate. i may never build one but the method of adding a motor, cooling it and ability to collect dust would transfer easily to working with shaping and finishing minerals and gems, and if you think sanders for wood are expensive take a look at working with gems, indeed i am tempted to send you some minerals and see what happens! Hint ebay sells polishing diamond disks for <30$ for an entire set....evil minions are extra.

dietmarg6 11 months ago

WWas ist das für ein motor und wieviel umdrehen macht er

Radeks Workshop 4 years ago

I don't have a motor and need to buy one. Problem is that there are many types out there split phase, evaporative cooler etc. Do you know what type is the best for a sander?

Beagles 5 years ago

I took a different approach when I wanted a disc sander. I found a belt driven Homecraft sander and built a stand for it. I prefer a belt driven version as you can choose your own speed....most sanders rotate too fast and burn things.

Nice work on yours BTW.

eGadgetGuy 6 years ago

First I want to say Amazing Design! It seems you've thought of everything.

I am definitely going to make this. I may have to borrow some of the power tools I need. I do have a couple of comments/suggestions.

1. The table - wouldn't it be better to make the whole thing out of steel or aluminum?

2. The switch is not what I'd call safe. If you can get one that's more suited to power tools [EG: double insulated.] that would be better.

3. the cord relief. Real cord reliefs are very inexpensive and I think worth the pennies.

4. this is another safety concern. The motor "straps" don't seem strong enough to withstand any real incident. If, say, you jam the sander, the motor could fly off. I would use metal straps with long bolts to secure the motor.

Otherwise, great work.

tomatoskins 6 years ago

Thanks for your interest!

It would definitely be stronger
if you made the entire thing of metal, but I didn't have means to use metal.
Use what you got!

I can see where you are coming
from. The switch is grounded and the only exterior metal parts that could
conduct electricity (in the whole tool) are the two screws holding the cover in
place. It's running on the same power that the rest of the light switches in my
house are using and I've never been shocked there. But you're right, it can be
safer.

You can purchase premade cord
reliefs, but they provide no extra benefit than what this free version does (in
my opinion) unless they are used as part of an electrical box.

I completely agree that the use
of metal for the straps would make it more secure. However, I didn't have any
available and I've been using this sander (in an unfinished state) for over a
year and have not had any troubles. If I ever do, I'll be sure to update this
instructable.

Beagles 5 years ago

Metal motor straps are easy to come by.....watch for that metal banding that comes on crates. Double over the ends and attach with screws. I keep a supply of them in various widths, on hand for multiple uses, including mounting odd ball motors.

NexGen FS 6 years ago

ok, I might have been a little hard on you. But I can not envision the importance of proper strain relief. The purpose of the clamp is two-fold:

1 is to protect the wire abrading the wood. 2 is to hold the wire in place. hope I'm preaching to the choir.

I have retired now aside I held a master electrical license, ex-AF Crew Chief, and BSEE/Aerospace/Computer Science Engineer.

I'm glad you never got shocked I took a summer class in electronics before my freshmen HS year and Got Nailed by an Oscilloscope' HV that jumped to a control knob. (held in with Allen Screw and metal shaft) That SOB put me on the ground. I have been shocked many times since 1963/4. and will always go the extra mile for safety.

FYI 120vac makes you release. 220vac and it grabs you and does not let go!

espdp2 5 years ago

I was always told the opposite regarding voltage, but I'm sure that you have the experience to know. I've only been buzzed by 120 running through my finger which slipped to the inside of a plug I was inserting into the wall.

corradini 5 years ago

VERY nice, professional engineering work here, in particular on the centering & balancing - kudos. For 3 things: (a) centering the disc by attaching it and then sanding it centered (vs. cutting a disc and 'finding the center'); (b) knowing to balance it, and (c) using a dial indicator to get good balance. Shoutout for using can stock, and anyone who's read Zen/Motorcycle Maintenance will get a chuckle.

Question might be: how can someone who doesn't have a dial indicator balance it? There might be at least a rough way to do it with, say, a zig-zag bent length of sharpened coat-hanger, kind of like how you test a drill press table for level, as a touch probe instead of the dial indicator...

TravisNTexas 6 years ago

Just an excellent design and an amazing write up! Very well done, and thanks.

CXYyuppie 6 years ago

WOW! I don't know what else to say. I'm a fan. Now I'm looking at all of your Instructables. Keep them coming.

MoP1 6 years ago

I'm going to stare at your tool wall and drool for a bit, if you don't mind. :)

MatH2 6 years ago

$75 Bucks at Harbor Freight, and even has a belt sander on it...

JidisS 6 years ago

I've had what's probably the Craftsman equivalent to that for years and finally moved up to the larger Craftsman 9"/48" combo (bought used), but I can definitely appreciate a DIY version of the disc part. In addition to skimpy motors (which are also constantly powering the belt half), the table parts of those low end units aren't exactly the most robust things on earth. I had a more solid DIY version for my smaller one, but it was non-tilting. The 6" diameter also became a bit of a limitation and the aluminum platter itself wasn't perfectly flat and could flex as well. I'd imagine the HF is even a step or two down from that. The HF belt pulleys are molded plastic from what I remember.

Take Care

tomatoskins 6 years ago

The difference between the two is night and day. $75 for a 4 inch sander that I'll throw away in 6 months, or build your own exactly how you like? The choice is clear to me. :)

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