Portable 2in1-disc-drum-sander

instructables
Portable 2in1 Disc & Drum Sander
by diyperspective
#woodworking #electronics #mechanics #design
In this instructable - full in depth build of the Portable 2in1 Disc & Drum Sander. It has integrated 12V 7Ah lead
acid battery and is powered with the model 895 12-24V DC motor. If I need more power or I have a lot of sanding
to do, I can easily plug an external 12-24V power supply. Sander has two dust ports, one for the disc and one for
the drum.
This project focuses on portability and convenience for very small workspaces. If you look for a powerful sander,
you should look elsewhere. Realistic power while using the sander is ~30W @12V and ~100W @24V. But despite
being low on power, it works like it should, only the sanding takes longer.
So again, this tool is more for the occasional woodworker with a tiny workspace.
FREE SketchUp 3D model - http://bit.ly/PortableSander3D
Provided Amazon links are affiliates.
Main Tools:
12V drill: https://amzn.to/2U5QQmL
20V drill https://amzn.to/2MY3GRt
Jigsaw https://amzn.to/2rg4uXx
Router https://amzn.to/2DVXXZC
Rotary tool https://amzn.to/2MWaP4H
Multimeter https://amzn.to/2MTl4Xs
Tachometer https://amzn.to/2MtYmWW
Clamps https://amzn.to/2YKWmRS
Speed square https://amzn.to/2Ee6lDh
Hole-saw set https://amzn.to/2pcizay
Spade bit set https://amzn.to/2J8iPP3
Combination square https://amzn.to/2oLYnwv
Fretsaw https://amzn.to/33LcvVr
Basic chisel set https://amzn.to/32xld9G
Flexible drill extension https://amzn.to/2oZthBl
Small drill chuck https://amzn.to/32y7yix
Portable 2in1 Disc & Drum Sander: Page 1

Main Components & Materials:
895 motor low-speed https://amzn.to/2BuIxsA
Bracket for the motor https://amzn.to/2VZhuiG
12V 7Ah sealed lead acid battery https://amzn.to/2W1lfUL
8mm x 300mm shaft https://amzn.to/2P19ufG
Bearings with holders https://amzn.to/31p91q4
20T 5B pulley https://amzn.to/2J1tjPV
60T 8B pulley https://amzn.to/2VXHyec
Timing belts https://amzn.to/35QXSld
ON-OFF-ON switch https://amzn.to/2quO6Fn
Dust cap https://amzn.to/2oLYhVD
Terminal block https://amzn.to/2MuDLle
Spade crimp terminals https://amzn.to/2VY2jq5
Power connectors https://amzn.to/2VWyFBo
Power plug https://amzn.to/2VZfkjd
Fuses https://amzn.to/2p1O0oj
Optional 10A motor speed controller https://amzn.to/2N3DW6h
150mm/6inch sanding disc https://amzn.to/2VZpJeC
Sandpaper roll https://amzn.to/31BliIh
Threaded e-nut M4 size https://amzn.to/2MwI7s7
Cold-weld compound https://amzn.to/35O9Yvv
Other Things:
Bolts, screws, washers, wires, heat shrink tube, right angle fastener, hinges, lock,
You can follow me:
YouTube: https://www.youtube.com/diyperspective
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https://youtu.be/E_bmdZH6N5s
Step 1: Preview
Few photos of the build. If you want all the dimensions you can download the free SketchUp 3D model of this build
- http://bit.ly/PortableSander3D

Step 2:
Previously I cut my project pieces one at a time,
immediately tested if it fits the others, and did another
cut. But it takes way too long. So this time I tried to
cut everything in one go. Meaning that I need to
measure and cut very precisely. But is that realistic
on the jigsaw table like mine? Well yes, later I needed
to trim just a few pieces. It was much faster this way.
With all the parts cut from a 12mm thick plywood, I
placed main frame parts and made more cuts.

Step 3:
I glued parts one by one. It is time-consuming, but it’s
easy to get perfect results.
With only one side glued, I made the hole for the dust
port. The design of it is simple. As my vacuum
connector’s outer diameter is 35mm there will be
three pieces (including hole in the side) of the
plywood with 35mm holes. And the last one will be
with 25mm as this is the inner diameter of the
connector. It will also act as a stop block for the max
depth.

Step 4:
To make the 150mm and 100mm discs for the sander, I used a router. This can be done with a jigsaw, but later
you will need to do a lot more of sanding, to get a perfectly round circle.
You can see how the back of the disc should look like. 150mm and 100mm discs glued together, 8mm hole drilled
not all the way through, in the end a 2mm hole, four holes and two groves in the 100mm disc.

Step 5:
I deliberately cut the 150mm disc in a bigger piece, that later I could use it for the bottom of the disc. I also routed
the edges of the pieces for the wires from the battery to go through.
Step 6:
These parts won’t be disassembled in the future, so gluing makes perfect sense, as you can precisely place and
adjust it how you need it. Back and top support parts will be permanent too. All these glued parts is the key to the
perfect alignment of other parts.
I made the hole in the top part for the 60T pulley and the 200mm length belt to go through.

Step 7:
Other parts here are two bearings integrated into the holders, 300mm long and 8mm thick shaft, 20T pulley, motor
holder with bolts and the model 895 12-24V DC motor.
This is the “low-speed” variant, which means that you will get 3000RPM at 12V instead of 6000RPM on the “high-
speed” variant. Max voltage for the motor is 24V and at this voltage, you will get ~7000RPM.

Step 8:
To make the drum, I cut 7 pieces of ~40mm diameter with a hole saw bit. For this, you better have good bits to
avoid the struggle. When I had all the pieces, I stacked them on the shaft. I used a spare short one, but you can
easily use the main one. Even when drilled with an 8mm drill bit, they fit snugly onto the shaft. I sanded it until I get
a nice and round surface.

Step 9:
To finish the drum, I cut one smaller piece and drilled a hole into the side. When glued on top of the drum, it will be
a spot for the threaded e-nut. Just make sure to drill big enough hole and clamp the parts while threading in, that
the nut wouldn’t split the plywood. With a small bolt in, now I can tighten the drum to the shaft.
Step 10:
Only one thing is missing – the sandpaper. To secure it to the drum, I just made a groove. The sandpaper goes
inside and wraps around the drum. And the end of the sandpaper, I just glued with a double side tape. Very simple
and effective. Only one condition – you need to start wrapping sandpaper in the opposite direction that the drum
spins.

Step 11:
On the end where the disc will be, I roughen the shaft as much as I could with 60-grit sandpaper. Then with a
rotary tool, I cut out small grooves vertically and horizontally. The rougher it looks the better it will bond to a “cold
weld” type bonding compound.
Step 12:
This type of compound has a very bad and strong
smell, so better do this in a well-ventilated area. You
can see that the routed circle is for that the compound
wouldn’t spread too much. It should cover the 8mm
hole and a little bit around it. Without that smaller hole
in the end, you won’t be able to push in the shaft, as
the compound is very viscous. It also usually has a
very short set time, so I had to set everything square
quickly.
I finished securing the shaft to the disc with four extra
screws and washers. Just try not to drill into holes,
which were previously made in the disc.

Step 13:
I started making holes in the parts, where the shaft with the drum comes out. Three holes of 62mm, bottom one of
10mm and top one of 50mm. Then, I rounded inside edges of the top part for the best airflow.

Step 14:
I made similar dust port like before and glued the parts. When glue completely dried up, I made a hole that directly
goes into the 62mm hole where the drum will be. Inside edges should be sanded as round as possible, again to
minimize restriction of the airflow. And then, that part just glues to the back cover.

Step 15:
To mount the shaft, I marked and drilled pilot holes for the bearing holders and secured the parts, which won’t be
disassembled later. After securing the bearings, don’t forget to tighten all the screws on them, and on the big
pulley.

Step 16:
When mounting a motor, it is important that the shaft
of it will be parallel with the 8mm shaft. It will give
even tension across all the width of the belt, which
will minimize the wear of it. As the bracket has wide
holes for the screws, you will still be able to adjust it
slightly with a trial and error method, after you drill the
pilot holes.
Also, it’s a good idea to grind a flat spot on the
motor’s shaft for the pulley, as here the motor
transfers full force to it. The belt should be neither
loose, neither too tight. In the last photo is an
example of how it looks when the motor is instantly
powered with 12V. Not much play, but also not too
tight.

Step 17:
Next, I really wanted to finish the disc, so I added extension wires for the motor, put on the belt and clamped the
top. I powered the motor with the 12V battery and sanded edges with a chisel to get a perfect balance and reduce
all vibrations.
I applied few coats of hard varnish, as I will be using sanding pads with a sticky back, rather than with a Velcro
hook and loop system. It will give more consistent sanding results.

Step 18:
Finally, it is wiring time. I made the hole for the 3-position switch. It is important that it could handle at least 10A.
The design of the circuit is pretty simple here.
When the switch is at the first position, the motor is powered from the internal 12V sealed lead-acid battery. When
the switch is at the OFF position, the battery and the power supply are disconnected. When the switch is at the
second position, the motor is powered from the external power supply.
Circuit connection:
First, the battery charge port’s positive and negative wires connects directly to the battery, it is just
an extension of the wires for easy access.
Next negative wires from the battery, external power supply, and the motor connects together.
The positive wire from the motor goes to the middle connector of the switch, and positive wires of
the battery and the power supply to the outside contacts.
Also, it would be a great idea to add a 10A fuse from the outgoing positive wire from the battery for
safety in case of a short circuit.
Where I could, I added crimp terminals and heat-shrink tubing for the insulation.

Step 19:
Finally, I secured the top with four screws in each corner. Then, the hinges and the lock to the door. It’s nice to
have quick and easy access to all wiring and charging port when needed.
You additionally can grind a flat spot at the end, to add even more grip, if the drum slips from the shaft.

Step 20:
Now, not much left to do. I just need to secure the
backside with four screws, add the drum and tighten
it, add the top cover to neatly hide bearings and the
shaft, and finally add the battery cover.
Make sure that the battery is not fully sealed
inside the box and there are some gaps, as sealed
lead acid batteries can produce hydrogen gasses
(which isn't toxic, but is flammable) when you charge
them.
I also put on a dust-proof cap to the switch, as it
should be. And now, how I like to say it, the build is
complete.

Step 21:
The only thing that I additionally made, was this abomination. It’s a cable, that plugs into the socket for charging
the internal battery. But it additionally has soldered 6A fuse and different length contacts. Safety over looks, right?

Step 22:
While you read this instructable, I bet you had a
question, “how the hell he will sand with the drum
without tipping the whole thing?” So, as the battery
weights almost the same as a whole construction, it
gives a lot of mass to the bottom and prevents it from
tipping. But of course, you should clamp it while
sanding. I clamp it to my jigsaw table’s rip fence. And
when I am super lazy, I just sand while it lies on the
table.
Sanding with the drum takes some time, but not too
long, considering this is hard plywood and I need to
remove relatively a lot of material.

Step 23:
Meanwhile sanding with the disc is a lot faster. But
what’s the most impressive, is that all of this works
from the 12V battery.
For a lot of sanding more quickly, I just need to plug
the external power supply. But I think, I should talk
more about that. At 12V, starting the motor from a
standstill, there isn’t too much starting current and
force to be worried about fast wear of the belt and the
bearings. But at 24V there will be way more forces
and especially high starting current (my
measurements aren't fully realistic, as multimeters
usually shows value with some delay. Realistic
start/inrush current without power supply limits should
be around the value as the motor's stall current - last
picture).

1. Max measured starting current @12V 1. Max measured starting current @24V
1. General DC motor inrush current. Source:
https://blog.arduino.cc/2012/06/15/quick-tutorial-current-sensing-for-dc-
motors/
Step 24:
So to eliminate that, you can use a motor speed
controller like in the first and the second photo.
Every time you start a motor, you rotate the
potentiometer until you reach the desired speed.
Personally, I just like to do this trick – I start the motor
with an internal 12V battery and then switch to a
higher voltage like 24V from a power supply.
If anyone knows a very simple DC motor soft start
circuit, please post it in the comments. I would
appreciate that.
1 1
1

Step 25:
Realistic power while using the sander is ~30W
@12V and ~100W @24V.
If you will be running the sander at 24V, make sure to
make some sort of cooling for the motor. I just added
4000 RPM 12V 60x60x25 fan with the LM2596 buck
converter. The fan wires goes to the converter, and
wires from the converter goes on the motor's positive
and negative contacts. The module will reduce the
voltage for the fan to ~12V even if the motor will be
powered with 24V.
Overall, I call this project a huge success! It allows
me to sand outside and inside curves with one tool,
much faster and way more precisely than I ever could
do it before.
For a tiny workspace like mine, it is a very convenient
tool!

Step 26: END
I hope this instructable / video was useful and informative.
If you liked it, you can support me by liking this Instructable / YouTube video and subscribing for more future
content. Feel free to leave any questions about this build. Thank you, for reading / watching! Till next time! :)
You can follow me:
YouTube: https://www.youtube.com/diyperspective
Instagram: https://www.instagram.com/diyperspective
Twitter: https://twitter.com/diyperspective
Facebook: https://www.facebook.com/diyperspective

This is awesome! Thanks for sharing :)
Thanks :)
Great job! Your pictures and instructions are just perfect. I'm sure many readers could use a small
sander like this!
Thanks, I am happy that you liked it :)

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