Introduction: BIG Disk Sander: Build, Use and Tips

Picture of BIG Disk Sander: Build, Use and Tips

I've lost count of the times when I have been mid project and thought, what I really want now is a nice big fat disk sander. With them you can make precise angles in wood and metal. You can produce brilliant outer edge curves, and very accurate circles. You can quickly remove material and flatten off stock that's too small to be safely planed, or thicknessed. You can sharpen tools, tidy up rough edges, deburr and square up, and do extreme toenail manicure (just in case you're insane, I'm not really recommending that last one).

In short, a disk sander is an awesomely useful machine to have in the shop!

Like most of my instructables, this one is mainly made from reclaimed materials.

Where is the bill of materials and tools used?? For this 'able it didn't make so much sense. a) because I'm using lots of strange materials that I have fished out of skips, and b) because I was experimenting with tools and techniques quite a lot. And c) if you're planning to build one you're going to read this all through and get an idea of what you need anyway based on what you already have available, right? I'll give tips on what might be useful reclaimed sources along the way.

If you're still not convinced you neeeed a disk sander, fly on ahead to the various steps on 'Use' to give you ideas and tips on what cool things you could do with one.

What makes a good disk sander?

OK so lets say you're thinking of buying one - what would you be looking for?

I'd say you'd want: a very strong solid base, good quiet, smooth and vibration free running, along with a perfectly flat and accurate work table with a parallel mitre slot. A tilting table seems like it would be a nice feature - but not at the expense of solidity. Something user friendly and safe - safety is obviously important.

Personally I'd want it BIG too. 500mm (20") abrasive disks are about the biggest economically available here in the UK, so that seems a good size to aim for. Having a nice big disk doesn't just mean you can sand bigger stuff, it also means you have a bigger range of abrasive speeds. That is, you can vary the material removal rate by choosing how far out from the centre of the disk you present the workpiece: towards the outer edge will be exceptionally aggressive, with the abrasive moving many times faster than say half way out.

When we look at fulfilling all those requirements in a bought machine, the cost is over £1.5k - which is quite a bit (eeeek!) - so lets make one from some rubbish!

Step 1: Mounting the Motor

Picture of Mounting the Motor

I started with a 1kw single phase induction motor that I rescued from a broken floor scrubber/polisher we found in the skip. I was well pleased when I got it home, dried it out, and tested it. It went really well with very little vibration or noise, running at 1450rpm. At that speed, at the edge of a 20" disk, the abrasive will be travelling at roughly 38 meters per second - which is very fast!. But not too fast :D

This motor had a face mount, the design would have varied quite a bit if I was basing it round a foot mount motor.

I did some modification and used the housing/flange mount that came with the motor. To sit the motor horizontal I needed to support the rear end of the motor with something. For this, I glued two ply pieces together and routed a circle in them. Follow along with the notes on the photos for the whole story.

Step 2: Laminating a Work Table

Picture of Laminating a Work Table

A major part of the disk sander is a work table. Its basic function is to remain nice and solid at a set angle relative to the spinning disk. It is also usual, and extremely useful, to have a slot parallel to the disk. This is used for the mitre gauge (which is why it's often called a mitre slot) and other jigs and accessories.

I had some scrap aluminium sheet that we rescued from a skip (it was a backing to a really big black and white photo that presumably no one in the whole world liked). It was 2.5mm thick - not sturdy enough on its own, but...

Why not laminate some bits together, I thought. So I marked them up, and risked using the tablesaw with a non-ferrous metal cutting blade. I used a cast iron surface plate to try and achieve flatness while epoxy gluing three layers together.

I made the table big enough to overlap a 20" disk at either end.

Advantages of laminating:

The aluminium was free :)

I could fabricate a mitre slot along the length without a giant mill. To do this both the top layers are made up of two pieces, spaced out with some 1/2" parallels.

There will probably be some vibration damping of the table by virtue of the constrained layers of epoxy.

Disadvantages / what went wrong:

The epoxy was smelly, and squeezed out the edges of the joints. This wasn't a problem, apart from where it filled the mitre slot! Oh well I can deal with that later...

It's more complicated and takes time.

It is probably not as strong as a single beefy piece of aluminium because of the chance of de-lamination - so far it's held up well though. I put a few countersunk machine screws at strategic points, which puts the epoxy under compression. Meaning the only forces on it are likely to be shear forces - epoxy is very strong at resisting this kind of force.

Step 3: Table Relief Cut

Picture of Table Relief Cut

This is just a case of angling the table's 'disk-meeting edge' so that when you adjust it to 45 degrees, the table will not catch on the disk.

My little mill is too small to make this cut all in one go, so there was some clamp re-jigging about involved. Worked out ok in the end.

Note- if you don't have a mill, I think this step could be completed at the end on the sander itself. Once you have the abrasive running on the disk, with care it should be possible to lower the table into the disk, and let it cut the relief (I imagine).

Step 4: Table's Frame & Vibration

Picture of Table's Frame & Vibration

So to make the table super rigid and sturdy, I added an under-frame. The frame also gives me some bits strong enough to house the pivot fixings. It's scrap aluminium extrusion I cut to size on the mitre saw - a hacksaw would have worked, if you can cut superhumanly square (or you already have a disk sander, with which you could quickly square up the rough cut - ahh the tool maker's paradox).

To attach the under-frame I used the same low viscosity, slow set epoxy: having roughened up all glue surfaces with an angle grinder. Note: The user Amclaussen, was kind enough to mention test he had with epoxy bonding aluminium. You can see the discussion in the comments, but the gist of it is that rough grit sanding is better than grinding, when it comes to improving bond strength. If I was doing it again I would probably go carefully with angle grinder with flap disk - hand sanding aluminium makes my soul ache.

To help prevent vibration and add still more rigidity, I filled in the spaces created by the frame with a home brew epoxy granite mix, with steel wire reinforcing.

Step 5: Motor Housing: Rigidity and Damping

Picture of Motor Housing: Rigidity and Damping

I was coming on nicely with the table, so now I need to stiffen up the motor mount. I used a similar epoxy granite mixture, with steel wire reinforcing. I tamped the mixture down with a bit of scrap wood.

The mix is about 80% sand & small gravel : 20% out of date low viscosity epoxy.

I was quite pleased with the finish. It's a LOT stiffer, and vibration damping wise it just feels solid!

Step 6: ​Table Pivot Mounting

Picture of ​Table Pivot Mounting

Attaching the table to the motor housing time.

I scored an awesome find during a dusty loft clear-out, with this thick metal bar - it was a bit rusty, but it's only very surface, and I found two long lengths :)

So anyway, sorry about the gloating, back to business. The bar is cut (with the steampunk power hacksaw) and drilled to accept some M12 8.8 bolts that act as a pivot. Then I drilled and tapped it for some perpendicular M6 clamping bolts. This locks the big bolts tightly (eek, wordy - just see the photo - you'll get the idea).

Step 7: Welding Up the Pivot Points

Picture of Welding Up the Pivot Points

So after taking extra care to clamp, check squareness and dimensions, fiddle about, re-clamp, re-check squareness, and fiddle about some more, I tac-weld the pivot points in place.

For welding purposes, the steel bar is very thick so I ground bevels on the mating faces, which can be filed with weld fillet. This helps get a larger joining surface and stronger weld. I am using the welder on maximum power!

Once tacked in place we can mount the table, check it all fits (in my case it seems to!), before removing the table again and completing the weld.

You can expect it to warp a bit during the final welding, though you can minimise this by stitch-welding 1/2" sections. If it does warp, it's not too big a deal and can be adjusted out later...

Step 8: No Volt Release Switch

Picture of No Volt Release Switch

We are starting to get to the point where we are going to want to be testing this beast! It's never too early to add in a safe switch. I had this ready made no volt release switch (NVRS) hanging about from a box of random bits I picked up at an auction.

The NVRS basically prevents the tool from being powered up if power is cut and then restored. ie. It wont leap to life unexpectedly as you plug the socket in, or if the power comes on after a power cut.

If you dont have one you can make one from some easy to salvage components. Here's an instructable of a NVRS I made for a wood lathe.

WARNING: Mains electricity death! Please get help with wiring if you're in any way unsure (or prone to bouts of swaggering overconfidence).

Step 9: Casting the Hub & Trunnions Pt1

Picture of Casting the Hub & Trunnions Pt1

Like I said at the beginning, I was experimenting with lots of different techniques with this disk sander. I wanted to try casting the trunnions from scrap aluminium. Yep, before I go any further I should admit, I have no idea if they are technically called 'trunnions', but I don't know how else to describe them. Well whatever they are, you could make them from other materials, good quality plywood, for example, if the dimensions were suitably scaled-up.

Enough of the alternatives, here's my aluminium experiment:

I started by making the pattern from some shuttering ply, drawing out and cutting the shape on the bandsaw. I wanted two of them.

Next I chamfered the edges - this gives you a release angle - vertical edges would be impossible to remove from the casting sand.

I was in a bit of a rush, and the patterns could have been better, smoother, more identical, varnished etc. But I was hopeful they would do the job...

Step 10: Casting the Hub & Trunnions Pt2

Picture of Casting the Hub & Trunnions Pt2

Time to fire up the furnace!

I used a home made one in an old propane tank, using a blower from an old oil boiler.

Aluminium was melted (lots of info on the net on this if your interested in casting methods).

I poured into the mould for the trunnions, and the 'mould' for the hub: see pics...

There's soooo much information out there about aluminium casting that I'm not going to go into loads of detail here. An instructable search reveals some goodies, and I found the book "Metal Casting A Sand Casting Manual for the Small Foundry, Vol. 1" by Steve Chastain, 2004, really useful - it may well be at your local public library.

Step 11: Truing Up the Hub

Picture of Truing Up the Hub

So I would probably classify the frying pan mould experiment as a fail. The molten aluminium warped the pan so much that it created quite an odd shaped disk.

Still, I'm stubbornly pressing on with it and spent a LONG time on the metal lathe truing it up.

Step 12: Mounting the Hub

Picture of Mounting the Hub

Ok this was a bit of a time consuming fiasco. Mainly because of the frying pan incident!

In the end though, I got the hub on there (tightly!) - and its made from scrap aluminium I had collected and melted.

Exasperated satisfaction....

Step 13: The Disk on the Hub

Picture of The Disk on the Hub

I pondered the idea of casting a big aluminium disk to cover the whole 20", but it seemed ambitious, and I wouldn't be able to true it up on the lathe. In the end I had a free evening in which I really wanted to make progress on the sander. I started thinking about making the pattern for the casting and found a square of plywood that was about the right size.

After cutting a circle out of it on the bandsaw, I started thinking that I could just as easily make the disk from the ply itself. Not quite as bling, but a lot easier and lighter.

Once I decided that, I used a top-bearing pattern bit with the router to cut a relief in the middle of the disk, so the hub and disk would fit...

Then I drilled 9 holes in both the disk and hub to fix it on. I made M5 threads in the aluminium hub, and counterbored the ply disk so the bolt heads were well below the surface.

Step 14: Truing Up the Ply Disk's Circumference

Picture of Truing Up the Ply Disk's Circumference

So the disk was only compass-line-freehand-bandsaw accurate and needed quite a bit of truing up.

The machine was borderline scary (in a bad way) when I first turned it on with the big unbalanced ply disk.

After truing it up with a lathe tool (that needed resharpening a lot!), it was much better.

Step 15: The Legs

Picture of The Legs

We need more stability before re-fitting the table. As it was, any heavy weight placed on the table would unbalance the whole assembly.

I had some bits of chainsaw milled ash left over from this lovely table I made which would make nice beefy legs (sorry for the blatant project plugs, cough, go like FE on facebook, cough, if you have read this far you will certainly enjoy it).

So yeah, I cut them so they were more alike on the bandsaw, flattened the bottoms on the jointer, and tidied up the surfaces with the thicknesser. Then I needed to cut some small relief grooves for the disk - I did that with good old handsaw and chisel.

To fix them on so they were exactly co-planer and flat I clamped them to the surface plate before screwing them up to the sides.

Step 16: Trunnion Clamps

Picture of Trunnion Clamps

So the trunnion clamps basically fix the angle of the table by clamping the trunnions in position.

I made them from threaded rod and two bits of scrap steel that sandwich the trunnion.

Step 17: Trunnion-table Interface Prep

Picture of Trunnion-table Interface Prep

I would call the aluminium trunnion castings rough and ready, but that would be an insult to the rough and ready genre. They should work though - with a little effort, that is.

Where they will bolt to the underside of the table needs to be nice and flat. I use the little mill to do this...

Step 18: Trunnion-table Interface

Picture of Trunnion-table Interface

With the angle and face of the trunnions sorted, we now need to work out exactly how and where they join the table.

I installed a bit of flat steel bar, which I milled flat where it meets the trunnion.Then drilled and tapped appropriately, so the trunnion could bolt on.

Step 19: Trunnion Mounting Strips

Picture of Trunnion Mounting Strips

I didn't really fill the space properly earlier, when I was epoxy-granite filling the table. So now was my chance to fill while embedding the flat bar in epoxy-granite.

Before I do that I bolt the steel strips on in just the right place, and mask their face.

Step 20: Mounting the Table

Picture of Mounting the Table

The moment of truth when it's time to bolt on the table!

It pleasingly fits together quite well, without any mega fettling.:D

Step 21: ​Tidying Up the Table Slot

Picture of ​Tidying Up the Table Slot

I think I mentioned already, when I laminated the table together, some of the epoxy squoze out and pooled in the mitre slot. At the time I thought, no problem, I'll be able to scrape that out later with an old chisel or something.

How wrong I was!

So began the mission to rout out the epoxy, and a very small amout of the aluminium to achieve the perfectly straight slot.

I ended up using the saw guide, clamped down, and the router with a 1/2" Pattern bit.

This was exceptionally nerve wracking! I had the potential of trashing the whole table by loosing control of the router (it's only a hand router) and munching up the world. Well that's how it felt... See pic notes for details.

Step 22: Mitre Gauge 1 of 3 - Making a Semi Circle

Picture of Mitre Gauge 1 of 3 - Making a Semi Circle

It may seem strange to be going straight to making the mitre gauge, but I wanted that before I put abrasives on and did a first test because it will be instrumental in making the ply disk absolutely flat.

The mitre gauge is made from an old car disk brake cut in half. Follow along with the picture notes.

Step 23: Mitre Gauge 2 of 3 - Making a Square Angle

Picture of Mitre Gauge 2 of 3 - Making a Square Angle

We need a piece of angle-iron to go on the front of the disk. I spent way too long cutting up and squaring a bit of old scrap. Again the pictures tell the story.

Step 24: Mitre Gauge 3 of 3 - Milling, Angle Arc & Assembly

Picture of Mitre Gauge 3 of 3 - Milling, Angle Arc & Assembly

So I basically fit the half-disk to the square angle, to form the base of a mitre gauge. I cut a strip of oak to sit in the table's slot.

Step 25: Truing Up the Disk

Picture of Truing Up the Disk

The plywood I used was a fairly old scrap. It was not flat and thus wibble-wobbled about horribly (technical term for bad run out).

Using a carbide insert lathe tool clamped to the mitre gauge I was able to slide it across the table, taking small cuts off the ply disk. This trued it up nicely.

This is why it was useful to make the mitre gauge before we even tested out the disk sander with an abrasive on yet.

After this I used a bit of sandpaper wrapped around a block to gently bring the surface, to super smooth, ready for the stick on abrasive disk .

Warning - to quote the Hackaday website "... Once these were cleaned up, a disk was mounted on the hub and trued up in the most unsafe manner possible." Which did make me chuckle - but there is some truth in that. This method works, but TO MAKE IT SAFER I recommend a MUCH beefier clamping system, and a way of being absolutely sure the back end of the tool cannot lift up, if the tool tip catches.

Step 26: Testing With Abrasive

Picture of Testing With Abrasive

I went ahead and stuck an abrasive disk on! I'm using the kind that have a peel off plastic backing. You can take them on and off by warming the glue with a heat gun. You can then put the plastic backing back on, so the abrasives can be re-used later.

It's turned on for the first time and makes some dust!

The dust extractor is bodged up temporarily so it sorta helps a bit..

Step 27: Balancing

Picture of Balancing

Now that we have flattened off the disk, its a good time to balance the whole thing. There is a good instructable on this, and I pretty much followed the same procedure. So check it out here.

The only real difference to my method was that I didn't use sugru. Instead I cut a small channel in the back outside edge of the disk, which blue tack would nestle in nicely. Once I had calculated the position and weight needed, I used some small screws to add the weight more permanently.

Step 28: Dust Extractor Hood

Picture of Dust Extractor Hood

So after the first test where I absolutely filled the workshop with airborne dust that settled on every exposed surface overnight night, I concluded we need some good dust extraction. I wasn't hooking up the dust sniper to this one as I figured that a large volume of airflow might be better than high static pressure.

To start off I made a shroud that will cover the bottom part of the disk. It was made from a scrap of 10mm engineered oak floorboard (very common in skips and usually worth picking up). This shroud simply slots into some notches I cut into the legs.

I then cut a 150mm (6") hole in the board to make a dust collector port. Onto this we add a little ring (more floorboard) that just snaps round and retains the hose... The ring was drawn with a compass, cut on the bandsaw, and smoothed off on, you guessed it, the new disk sander!

Step 29: Guarding

Picture of Guarding

Whenever you have fast and powerful spinning things, it is important to think safety. The first couple of times you are using it, it may not seem necessary, but years down the line, when you have forgotten the danger is there, or when your friend comes to visit...

So yeah, I strongly suggest guarding all the spinning bits that you don't need constant access to in order for the machine to work.

Scrap bicycle rims (from a 24" wheel) and some more floor board seemed to fit the bill nicely. See pic's notes for details.

Step 30: Metal Dust Collector

Picture of Metal Dust Collector

AKA magnets!

I used a little round scrap of plastic, I forget what it was from (it was in the round disks box along with all my hole-saw scraps), and glued some metal magnet backings from an old microwave to it. I fixed just the metal backings, so the magnets themselves can be removed and 'emptied'.

The magnets are wrapped in thin plastic bags, so 'emptying' is as simple as pulling the bag off with the metal dust inside.

As an aside - keep the iron filings for other projects - it's a cool additive to various concoctions...

Update & Warning: so turns out the plastic bags round the magnets to conveniently capture the dust wasn't such a good idea - they quickly caught on fire from the hot sparks. This is fun and exciting but smelly and potentially very dangerous. So yeah, bags not recommended, just clean the magnets off without them. It's not as easy but it's safe.

Step 31: Use 1: General Usage and Safety, Tilting Table & Sanding to a Line.

It's time to get this machine working! There are a bunch of 'Use' steps. Most of them have videos on different aspects of using a disk sander.First check out the intro video on this step - it goes over general use and some safety points.

The second video in this step is a discussion (with myself) about the benefits (or not) of having a tilting table.

A few points not mentioned in the videos:

As with most machines with spinning bits, eye protection is a must. A dust mask is also wise. A fast acting brake and kick emergency stop switch would be a useful addition to this project.

Step 32: Use 2: Precise Angles

See the video. You can make precise angles in small things that would be dangerous on a tablesaw or mitre saw, and you can quickly square up metal stock.

Step 33: Use 3: Exact Circle Sanding Jig

I made this from some more of the old engineered floorboard, and a few scraps of oak. Check out the photo's notes for build information.

As well as circles the jig is also very good at making arches - anything roundish really. See the video for an explanation of the circle making jig's use.

Step 34: Use 4: Small Parts - Zero Clearance

Picture of Use 4: Small Parts - Zero Clearance

So this is one of the best things about a disk sander - the ability to straighten up, square off and smooth small parts that won't fit on a table saw or planer.

To do it safely you really want to have the edge nearest the disk fully supported so the part doesn't up end and get stuck. To do this I have been using the circle cutting jig base which goes right up to the abrasive.

I'm torn as to whether, if building the machine again, I would make the table come right up to the disk. The advantage would be better support for the workpiece, but the disadvantage would be that the table would have to be taken right off to switch over abrasives - as it is I can get them on and off without doing that (though it's still a bit fiddly).

Step 35: Use 5: Tool Sharpening Jig

Picture of Use 5: Tool Sharpening Jig

The disk sander is really good at sharpening. Using a reasonably course grit, like 80, you can quickly take out big nicks, and renovate old chisels and planer blades. I have a wetstone grinder, but it isn't aggressive enough to remove nicks in a reasonable time frame - this works much better for that. You can go razor sharp all with the disk sander if you can be bothered to change grits on the disk. I haven't had the disk sander long enough to know what my process will be, but thus far I've hogged off material on the disk removing nicks and making them perfectly square, and then given a razor micro bevel on the wetstone - that worked well.

I made a jig to help get the angles spot on. It works with the circle cutting jig base (see photos). I don't have video of this one, but there is a random axe sharpening one...

Important note: It is quite possible to overheat the cutting edge of chisels (especially at the outer edge of a 20" abrasive disk!), so don't overdo it. I tend to have a container of water nearby that I periodically dunk the chisel into to cool it off (that can be done without un-clamping it from the sharpening jig. It's also a good idea to move the chisel back and forth, to evenly wear the abrasive disk...

If you do 'blue' the edge, you can simply remove that section of metal, by further (and more careful) grinding, but it takes a while. Not that I've ever needed to do that when I started woodworking, of course. Certainly not.

Step 36: Signing Off

Picture of Signing Off

I hope some of this was helpful to you. The project was quite a fun one for me, as I was experimenting with unusual materials (aluminium casting and epoxy granite), and as always, it was a learning experience. It hasn't been finished long, but I reckon this is going to be a very useful addition to the shop. But...

I did just want to mention that I have been doing woodworking some time, and have gotten by ok without a disk sander until now... So yeah, the more tools at your disposal the better - they do open up new possibilities. I guess the moral of the story is, you don't need fancy tools to be creative, but they help ;)

most of the time...

Anyway, if you liked this or found it useful please go like the Flowering Elbow page on facebook, where I post my latest experiments.


bongodrummer (author)2015-04-08

Hey everyone! It won! Totally thrilled to bits! Thanks so much everyone who voted and commented, and the judges who took the time to look it over! The prize looks like it will be really very useful, :)

RonaldR (author)2017-01-09

WHAT A GREAT HOME BUILD , But I don’t have to skills or equipment
to do the metal work so the one I
am building has 2 x12’ Discs and
all my work is with plywood & MDF

1 hp Bench Grinder 1,000
x 400mm base, Centre Block to raise the grinder

Left and Right blocks for
tables. Table 400mm x 400mm made from three pieces of Board the 20mm
MDF has a Triangle routed 4mm deep 305 bottom
on side facing sander the triangle
is to the centre of the
board 25.4mm hole drilled inside top of
triangle with a 25mm pvc pipe glued

The bottom board which is also top of block is 400mm w 300
deep has a 25mm w slot that is 90mm long and each side slot
for the fastening bolt on each side also allows table to be slid back to
change discs . on top has 12mm MDF 400x
400 glued to top and lid for
the routed dust port #1

Then the bottom of the sanding
wheel is boxed in base slot across directly under sanding disc with PVC conduit
glued I place then a slot routed across top opening conduit the area below
table is boxed in with front and back sides angled and starting near the edge
of conduit (blocked off one end and connector for vacuum cleaner.

The wheels are made from
2x 350mm Sq pieces of ply glued and screwed together hole drilled in centre and then wheel created by cutting circle
using table saw .

One wheel had 40 grit disc and the
other has 180grit

Don’t have photos ready as have only
cut all the pieces waiting for new brad gun to arrive to assemble (brads hold
in place while glue sets saves having to have a lot of expensive clamps)

Also making mounting frame for
hand belt sander so can be used as a fixed vertical and horizontal belt
sander and still easily removed to use
as hand power tool.

Building most of woodworking
machinery in my work shop thanks to the inspiration and guidance by all these
wonderful people in INSTRUCTABLES & YOUTUBE

bongodrummer (author)RonaldR2017-01-10

Hi Ronald. Sounds like you have your hands full. Looking forward to seeing a photo of it when you have it all glued up. Having 2 discs will really be useful. I have wanted to have 40 or 60 grit for quick stock removal a number of times, but am usually set up with 80 as a kinda compromise between surface finish and removal rate. I could change the disc, but who wants to bother with that when they are mid project!?

yacer.ahmidi (author)2016-06-24

this was awesome
i am surely making this *-*

Thanks :)

Bill WW (author)2015-12-31

Great work, Bongodrummer! Yet another recognition on Instructables!

I have not yet read all 36 steps, but will; there seems much good info here. I got caught up on your chisel sharpening jig. Nicely done. I believe a disk sander for sharpening is underutilized. I made a couple of jigs for my little 150 mm sander, photos attached. The first is for chisel sharpening; magnets hold the blade in position. The other is for conventional grind woodturning gouges.

bongodrummer (author)Bill WW2016-01-03

Hi Bill.Those look like some very useful jigs! Interesting idea with the magnets to simplify the holding method. Out of curiosity, what grit paper do you use for sharpening?

Bill WW (author)bongodrummer2016-01-03

The grit I was using in these two photos was 320. But it depends on the condition of the chisel; maybe start with 120 grit in some cases, then end up with 400 grit.
Woodworking chisels are not made from high speed steel, so we need to take care not to overheat the blade, which is easy to do with any powered sharpener.
Thanks for your interest!

bricabracwizard (author)2015-08-02

I don't know if this has been asked of you and I couldn't find the info, maybe I skipped over it while drooling over your did you balance the disk? I know you cut a groove etc..but how do you find out where to put the weights?

Hi Bricabracwizard, Check out step 27 on balancing...

Mark 42 (author)bricabracwizard2016-01-02

I've balance ceiling fans by trial and error.
Basically, you glue a weight on, and move it around noting whether each new position is improving the smoothness. Eventually you find the best position for the weight. Then you just experiment with how much weight gives the smoothest running. You usually have to iterate between adjusting position and adjusting the mass a couple of times.
It's not as hard as you'd think.
Also, google the words "balance disk sander" - there are probably better ways.
You could put a shaft through the disk and lay the shaft on two rails made of angle iron (the rails need to be leveled) to get a static balance.

jimluschen (author)2015-04-06

Nice job, I need one of these! I did have a chuckle at this:

"Next I chamfered the edges - this gives you a release angle - vertical edges would be impossible to remove from the casting sand."

Adding draft to ensure release from the sand, you are a funny guy!

bongodrummer (author)jimluschen2015-04-07

My dear fellow! I'm not too sure what you mean? Have you spotted a blunder, that even now, I am ignorant of??? Maybe I should have said green sand? What else? What's so funny!?!?

Mark 42 (author)bongodrummer2016-01-02

Sand casting is a one shot process - you just break the mold apart after the casting becomes solid.

bongodrummer (author)Mark 422016-01-03

True but it was the original wooden pattern that I needed to get out of the sand, without damaging the mould. That's what I was chamfering - the wooden part.

rolandcontreras (author)2016-01-01

Very professional project. The stability seems excellent. Congratulations!!

ETERNUR (author)2015-12-31

Wow. I am absolutely amazed with the amount of repurposed materials that have been used in this Instructable. Talk about upcycling!

Kwdavis (author)2015-04-07

Thanks for sharing. I learn something ingenious from most of these projects. I'm currently making a CNC machine that will take 4x8 sheet goods...and fold up in half (like a ping pong table) and work for 4x4... Its figuring out the issues and working some solution thats the fun in it...Thanks again.

bongodrummer (author)Kwdavis2015-04-08

Thanks Kwdavis. Foldable CNC sounds like a cool project!

rwinscot (author)2015-04-06

Fantastic job - abrasive and gritty... yet, delicious!

Mmm... trunnions!

bongodrummer (author)rwinscot2015-04-07

Thanks Rwinscot! trunntastic!

BrettHacks (author)2015-03-30

Beautiful build! I can not imagine the hours you put into this project. I am intrigued with the "epoxy granite" Could you share the product you used? I don't imagine it machines very well with the rock aggregate, but it seems ideal for a structural reinforcement. Thanks!

bongodrummer (author)BrettHacks2015-03-30

Thanks Brett, your instincts on epoxy granite are spot on - it doesn't machine at all well, and cannot be threaded. To make threads you have to strategically place nuts in the mold before casting.

On the plus side it is very good at vibrational damping - roughly 10 times better than cast iron, and 30 times better than steel...

I can't remember the epoxy name off the top of my head (will look next time I'm at the shop), but I can tell you it was about a month out of date, and therefore very cheap (but still worked well - possibly slightly slower cure time).

When choosing the epoxy - it wants to be low viscosity (the lower the better), slow cure is good, because it gives you more time to tamp/vibrate everything into place in your mold. Also, you always want zero solvent epoxy, which will not then shrink upon cure.

amclaussen (author)bongodrummer2015-04-01

Thanks for an incredibly ambitious tool build bongodrummer! congrats.

About Epoxy: I've found that most epoxies last a very looooong time and still work impressively fine. I have used some more than 20 year old ones without ANY discernible degradation! About yout use of an angle grinder to roughen up the aluminum for a better adhesión of the epoxy: I have done this kind of roughening, and the very best results are (as tested in a simple but effective home test) by using very coarse NEW wetordry sandpaper with a high pressure applied and in a cross hatch pattern, so as to produce "V" shaped grooves to provide good anchoring...

But using an angle grinder only roughens a fraction of the entire Surface, therefore lessening the anchoring. (or at least I humbly suggest you to improve your excellent instructable on this minor point).

On general comments, I have found that I tend to use about 90% of the time the belt and only 10% the disc on my quite smallish bench sander (which worked OK for the first couple of years, and then started to play foul by failing miserably to maintain the proper belt alignment...) So, when I read your instructable, I wondered about a large Disc AND belt sander...

Regards, Amclaussen.

bongodrummer (author)amclaussen2015-04-02

Hi Amclaussen. Cool, actual science style tests on the epoxy subject! Will mention you point in the instructable. I did start by hand sanding, and got impatient - the angle grinder seemed to work so much quicker ;)

Did you try power sanding, with a belt sander or an angle grinder with flap disks in your tests? I imagine an angle grinder with a flap disk would work quite well. The main problem with all the power methods, as is see it, is that you risk inadvertently un-flattening the piece.

In terms of which is used most on belt&disk combos, I agree it tends to be the belt, but I think that's because the disks are a bit of an afterthought on those machines. They are usually small, as is the table, which rarely has a mitre slot.

In terms of making a large belt and disk sander, I like the idea, but I think it may become a bit unmanageable. I can just about move the disk sander about at the moment - a Belt and disk would definitely be a BIG static machine. The main advantage is obviously the shared motor... but that's a sorta disadvantage too because it uses more energy - why drive that big belt when not in use?

amclaussen (author)bongodrummer2015-04-02

Hi bongodrummer! Before anything, just seeing all your capabilities and tools makes me a little jealous, I must admit! I build a lot of things, but admitedly, I've never learned to weld, much less to cast aluminum, both abilities that I have a need for several projects.

On your idea of power sanding: I'd say Nope...

As you can clearly see, almost any power sander (unless it is so small as a palm sander!) passes the sandpaper so many times that the grooves cut by the grain are very close to each other, thus the final effect is that the sander polishes more than creating more distinct grooves (separated from each other). I did many tests because I was helping some friends to assemble an Ultralight aircraft, and the wings needed to be joined at the center through a "joiner" made from an aluminum alloy, and it needed to be joined with an epoxy to the spar box securely. Researching on the subject, I found a lot of knowledge, as there are quite a few methods to properly join aluminum with epoxy type adhesives. One thing is clear: polished aluminum oxidizes in air and forms a smooth passive aluminum oxide barrier that prevents further corrosion but has a very low surface energy that limits adhesion a lot. By sanding, one removes the oxide layer and produces what is known as an "Anchoring Profile", which is best when it reaches several thousands of an inch deep. Therefore, I perfomed many tests at home, to be able to really be sure the sanding action produced the strongest joint. It was achieved with No. 60 wet-or-dry sandpaper, followed by acetone cleaning. the epoxy was a professional grade from "West System". Even when West recommends 80 -grit sandpaper, I found that 60 produces better gripping surfaces when I used new sandpaper sheets and applied strong vertical load, so that the grooves looked like fine thread on a fine thread small screw like an "0-80" but in a crossed pattern. The secret was to do a few straight line strokes, cleaning the paper after each,so as not to clog or re-deposit the sanded paticles again on the roughened surface. Before sanding, a first acetone cleaning is needed to avoid sanding the contaminants into the surface. After many flights, the aluminum wing spar joiner epoxy jouint has not loosened not even the slightest bit. And my test samples broke the hard wood well before the epoxy was remotely close to fail.

I'll keep an eye on your future Instructables, congratulations again. Amclaussen, Mexico City.

M2aestro (author)amclaussen2015-04-05

Check with the manufacturer of the epoxy, and also check many manufacturers. We used to use (20-30 years ago) several types, depending on whether or not we needed high peel strength, could use heat curing of the epoxy, needed moisture resistance, needed it to be hard on the surface (some are silica-filled, for example), were merely bonding or actually casting, and whether-or-not the metal surface was already treated with something that made good adhesion difficult. An example of that would be black oxide coated steels or aluminum that have an oil or acetate sealing material.

bongodrummer (author)amclaussen2015-04-02

LOL, don't be jealous you can pick up a decent mig welder for very little, and I knocked up the gas bottle furnace in an afternoon for a very low cost (learning about the green sand mixing and casting, not so quick - still lots to do there).

Anyway, to your point on epoxy. First thanks for the detailed info- plane making = very exciting! I didn't mention it in the instructable but I also used acetone to clean the surface and lots of vacuuming with a brush as I went. So yeah , I should recommend that too.

Did you actually test with a grinder, because you get very defined groves and a fully shiny surface? The other thing that occurred to me was power wire brushing - any tests?

One thing to consider is that you get very different results with different sanders - random orbit= a surface as you described, more polished. But a belt sander on the other hand, with a fresh 40 grit on slow speed will leave very distinct grooves. A belt sander also has the advantage that a high powered vacuum can be connected so you're not rubbing in removed aluminium particles/don't need to clean the paper so often.

So are you sensing my reluctance to join you and say nope to power sanding?

Last thing, the epoxy I used was very similar to west systems, which is a touch more expensive per liter (and in my case WAY more expensive because I never did see a WS out-of-date-bargain).


M2aestro (author)bongodrummer2015-04-05

I recall when 20 or more years ago the so-called epoxy granite hit the market, and may folk made their own machine bases from the stuff. Something to remember is that despite the fact that it contains rock chips or aggregate, the material that binds all of the sand and rock chips together is still resin, and tends to be a resin that permits abrasive materials to embed easily. This makes it harder to clean, too. To clean it, that is, remove abrasive materials from the surface, a technique I used on this and on semi-steel bases, as well, was to take a hard paper (I usually used hard drafting paper, in the day), wet it with kerosene or another solvent that was not too hazardous, place a flat steel block on the opposite side of that hard paper, and pull the abrasive materials out of the surface of the plate into the paper, which could be discarded after getting loaded with abrasives. You can make very flat slide surfaces of so-called cast granite with epoxy grades that are loaded with graphite in addition to the stone materials, but I cannot vouch for the claim that that graphite would protect your other hardware from the abrasive characteristics of your stone - sand fillers. You apply a release coating, just as in casting other precision surfaces with resin, to a reference surface, build your form that gets place on that precision surface to contain your composite materials, and just pour it on. Try to get a maximum amount of stone materials in it if you want to minimize the coefficient of expansion, for the casting resin would have a much thermal coefficient of expansion than would steel or aluminum structural members.

bongodrummer (author)BrettHacks2015-04-02

@BrettHacks - I was 'Gurit Ampreg20' Resin and slow hardner. Looking at the packet now I can see it was actually about a year out of date.

BrettHacks (author)bongodrummer2015-04-02

Thanks! Now I just need a project to try it on.

BeachsideHank (author)2015-03-31

In keeping with the spirit of spend little or no money, keep an eye out at boot sales, etc. for a cheap pair of used boater's shoes, the kind with crepe rubber soles, they make serviceable disk cleaners that will greatly extend abrasive life.

Nice job too, by the way.

Top tip thanks! Will keep a look out for that, as I have just about used up the off-cut of a proper one a friend gave me... Anyone know exactly what that stuff is made from?

VeeMer (author)bongodrummer2015-04-01

For cleaning the disc, I use old silicon sealer after it has gone off in the tube. Simply remove it from the outer plastic & voila. Works well for me.

bongodrummer (author)VeeMer2015-04-01

oooo, interesting idea.

sWillyPs (author)bongodrummer2015-03-31

Gum rubber or natural rubber... if you want to buy one, look at

bongodrummer (author)sWillyPs2015-03-31

Cool thanks for the info... Now I feel like I should do some editing. I'm sure in one of the videos I call it "a plastic-stick-like-thing"...

ShawnC3 (author)2015-04-01

What about using a flywheel from a discarded spin bike. They're already balanced and flat and the extra mass would help prevent the motor from slowing under a heavy load. In addition, the ones I've picked up had heavy duty bearings, a nice chain or belt drive and plenty of square steel tubing that could be reused.

bongodrummer (author)ShawnC32015-04-01

Hay Shawn, I had the same though when I was just starting, and I was sure I would see one somewhere, being thrown or even at a garage sale or something. But nay, nothing turned up... Ill still keep a look out for one now of course, they sound really useful!

ShamWerks (author)2015-03-31

Great instructable, thanks!

MichaelG9 (author)2015-03-31

So, having access to a machine shop is not something that would be considered excessive? Anyone with a machine shop would not only have a disc sander, but one that was attached to their belt sander.

If everyone had a machine shop it would be great, but I thought these "instructables" were a resource for those of us who do not have access to a full blown machine shop!

I have a MIG welder, drill press, a band saw, a home made router table, and a table saw and an assortment of hand tools. I would consider a lot of these common to most home shops out there, but not all of it.

I need to make a 6 inch wide belt sander with a disc on it and have to build it without a machine shop.

sWillyPs (author)MichaelG92015-03-31

Every instructable has some tool that somebody doesn't have acsess to or doesn't know how to use... 3D printer, welder, soldering iron, whatever.

ShamWerks (author)sWillyPs2015-03-31

Agreed. A while ago someone asked me how to shorten a screw. I told him to to put it in a vise and cut it with a hacksaw. He told me "Whaaat?? I don't have a full workshop like yours, just tell me how to cut the bloody screw!".

So for some, a vise and a hacksaw are a complete machine shop... Different instructables for different makers! ;-)

bongodrummer (author)MichaelG92015-03-31

Hi Michael, you raise an interesting point, and you remind me that I still need to make a router table!

I wonder at what point a regular shop becomes a machine shop? I never really though of my shop as a machine shop (and trust me it doesn't come close to a 'fully blown' machine shop). But maybe it is part way there now. It only really has a decent lathe and a small hobby mill. Even with those, there were many things I couldn't do that I wanted to (eg. surface grind flat the table and machine a perfectly parallel t-slot, turn a 20" metal disk, roll sheet metal into a circular form for a guard, effortlessly cut a disk break in half, etc). In some ways the fun is in finding ways round those limitations... I actual made the little gas bottle furnace specifically to cast parts for this disk sander – that was one of my wacky work arounds – a long cut. But I learned a lot.

One way of doing it would be to pay some one to make those parts, nothing wrong with that. I didn't make the threaded rod or high tensile bolts I used... Most people don't. But then most people don't make expensive tools either. So I guess it's a trade off.

Where am I going with this? When I look at instructables where makers are using awesome cool 3d printers, lasers and waterjet cutters, and CNC mills, I'm not thinking “grrr they shouldn't be on instructables, the flashy gits” - well ok, sometimes a little jealous bit of me is thinking that. But mainly I'm just excited by the possibilities and the little things they did that I could nick and fit into this project or that. Or how I could combine a cutting edge technique of theirs with some old school method and come up with something completely new. So yeah, take what you can, leave the rest. Get thrilled to learn about lasers n jazz, even if you don't have access to them right now...

Anyway, good luck with your 6” belt and disk sander. Have you seen this one? pretty cool.

MichaelG9 (author)bongodrummer2015-03-31

A belt sander is next on my tool list as I'm killing my hands sanding and filing for hours that I could do in a few minutes with the right equipment. I wish I had a lathe and milling machine but never had the space, time, oppportunity, and the money all at the same time.

pudtiny (author)2015-03-31

nice work, and like you I like enjoy the conversion of junk into useful things.

jose romildoL (author)2015-03-31

muito bom parabens

MissionSRX (author)2015-03-31

Awesome! Last month I posted my 15" sander/lathe mod and thought that was overkill... now, not so much.

Nicely done.

ChemicalBurn (author)2015-03-31

Wow, you have skill. Good instructable as well.

Random_Canadian (author)2015-03-31

At first I was disappointed that I missed the deadline for the tool contest... then I saw this... Honestly, there is kill then there is overkill! You awesomely covered all aspects of making your own tools. Casting and machining, your home shop is to die for... If this is a contest entry you definitely have my vote!

About This Instructable




Bio: BongoDrummer is co-founder and member of Flowering Elbow. He loves to learn about, invent, and make things, particularly from waste materials.
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