A bit of a background story, skip this if you are impatient
Background Story
To build a new workbench, I bought some salvaged wood from a 100 year old barn in Brazil. It was supposed to be Peruba Rosa, and maybe some Cumaru, the seller wasn't sure. I got 3×5 pieces for the legs, which turned out to be Peruba Rosa. Beautiful, and moderately easy to plane by hand and machine. For the top, I got 3×7 pieces, which are most likely Cumaru or some similar extremely dense wood.
The 3×7 pieces are just too big to maneuver over my jointer, and my jointer is a bit out of alignment on top of it (which is extremely difficult to fix, another story altogether). So I resorted to planing one face and one edge by hand; after that I can shove them through my planer.
So far so good… the only problem is, that this wood is extremely hard, and, to make matters worse, contains silica, which makes it seem like you are hand planing sandpaper. After about 5-10 minutes of hand planing, I need to resharpen my blade. I usually use water stones and a Richard Kell Honing Guide, but since my plane irons are a 2, 2-1/8 and 2-3/4 inch wide, it's a bit difficult to say the least. It's also quite slow, and if you have to do this every 30 minutes or so… tiring! So I looked for some other sharpening options…
DIY Worksharp Idea
As a sharpening alternative to stones and a honing jig, I came across the Worksharp WS3000 and liked the idea. But it isn't exactly cheap, especially if you want to add some diamond lap discs in order to grind and hone on the machine. So I figured maybe I can build my own
Before spending any money, I looked at what I had at hand, and put this simple crude disk sharpener together:
This is an old belt-driven turntable. I increased the speed somewhat (maybe to around 100 RPM) by putting a rubber wheel over the motor shaft. I glued some sandpaper onto Melamine disks, and drilled a hole into each disk to fit the shaft of the turntable.
I also wanted to "wet-grind", that's why there is a bunch of plastic protecting the tonearm parts etc.
To get into the same level as the spinning disk, I simply made a platform (that partially hugs the platter) with a couple of 2×6 pieces underneath, trimmed to elevate the platform slightly above the disk.
Lastly I put together a simple jig to hold the plane irons, similar to what you may have seen for the "scary sharp" system.
OK, long story short: It works. It actually works really well, except for one thing: The turntable motor has way to little torque. I can only apply a small amount of pressure before it stalls. Eventually I disconnected the motor and spun the turntable by hand-this gave me a faster speed and more torque.
I was surprised how easy it was to bring the edge back (until I got the "wire edge") with the 220 disk, and it also was quite quick to get a pretty sharp edge with the 1500 disk. Once the wire edge was removed, I was able to attack the Cumaru again for a while…
Please keep in mind this was only a crude experiment to check if this will work at all. Going from 220 to 1500 is certainly a bit of a big step… and there are probably dozens of other improvements I could make.
Here are some ideas I had:
What I am a bit confused about, is how to control a motor's speed. I have seen PWM controllers, that appear to work well. But then there are DC motors and AC motors, and I am not sure if both can be controlled with that.
A Variac can also be used to some extend, but from what I read, it may damage the motor.
If anyone can offer some insight to the use of motors and controlling their speed, or if you have any other ideas or suggestions, please let me hear from you!
P.S.: Of course I could just buy a Worksharp WS3000… but you know how it is… we like to build things ourselves, it's fun, and may even turn out better than the commercial option
Background Story
To build a new workbench, I bought some salvaged wood from a 100 year old barn in Brazil. It was supposed to be Peruba Rosa, and maybe some Cumaru, the seller wasn't sure. I got 3×5 pieces for the legs, which turned out to be Peruba Rosa. Beautiful, and moderately easy to plane by hand and machine. For the top, I got 3×7 pieces, which are most likely Cumaru or some similar extremely dense wood.
The 3×7 pieces are just too big to maneuver over my jointer, and my jointer is a bit out of alignment on top of it (which is extremely difficult to fix, another story altogether). So I resorted to planing one face and one edge by hand; after that I can shove them through my planer.
So far so good… the only problem is, that this wood is extremely hard, and, to make matters worse, contains silica, which makes it seem like you are hand planing sandpaper. After about 5-10 minutes of hand planing, I need to resharpen my blade. I usually use water stones and a Richard Kell Honing Guide, but since my plane irons are a 2, 2-1/8 and 2-3/4 inch wide, it's a bit difficult to say the least. It's also quite slow, and if you have to do this every 30 minutes or so… tiring! So I looked for some other sharpening options…
DIY Worksharp Idea
As a sharpening alternative to stones and a honing jig, I came across the Worksharp WS3000 and liked the idea. But it isn't exactly cheap, especially if you want to add some diamond lap discs in order to grind and hone on the machine. So I figured maybe I can build my own
Before spending any money, I looked at what I had at hand, and put this simple crude disk sharpener together:
This is an old belt-driven turntable. I increased the speed somewhat (maybe to around 100 RPM) by putting a rubber wheel over the motor shaft. I glued some sandpaper onto Melamine disks, and drilled a hole into each disk to fit the shaft of the turntable.
I also wanted to "wet-grind", that's why there is a bunch of plastic protecting the tonearm parts etc.
To get into the same level as the spinning disk, I simply made a platform (that partially hugs the platter) with a couple of 2×6 pieces underneath, trimmed to elevate the platform slightly above the disk.
Lastly I put together a simple jig to hold the plane irons, similar to what you may have seen for the "scary sharp" system.
OK, long story short: It works. It actually works really well, except for one thing: The turntable motor has way to little torque. I can only apply a small amount of pressure before it stalls. Eventually I disconnected the motor and spun the turntable by hand-this gave me a faster speed and more torque.
I was surprised how easy it was to bring the edge back (until I got the "wire edge") with the 220 disk, and it also was quite quick to get a pretty sharp edge with the 1500 disk. Once the wire edge was removed, I was able to attack the Cumaru again for a while…
Please keep in mind this was only a crude experiment to check if this will work at all. Going from 220 to 1500 is certainly a bit of a big step… and there are probably dozens of other improvements I could make.
Here are some ideas I had:
- Use a direct-drive turntable. These should have better torque, especially the DJ models. However, it is probably still far from strong enough.
- Use a pottery wheel. It comes with most of everything that's needed, a strong motor, nice platter to mount sanding disks, and is even meant to be used with water, so wet grinding wouldn't interfere with electronics etc. Problem is, pottery wheels are not cheap. Even a "kick wheel", which is basically driven by your foot kicking a large cement or cast iron wheel that's connected to the platter, is not cheap.
- Use a retired juicer (with a working motor…). This should be strong enough, but they spin too fast-one model I have seen spins at 3600 RPM.
- Find another slower spinning motor and connect a turntable platter, pottery wheel, or other balanced disk to it.
What I am a bit confused about, is how to control a motor's speed. I have seen PWM controllers, that appear to work well. But then there are DC motors and AC motors, and I am not sure if both can be controlled with that.
A Variac can also be used to some extend, but from what I read, it may damage the motor.
If anyone can offer some insight to the use of motors and controlling their speed, or if you have any other ideas or suggestions, please let me hear from you!
P.S.: Of course I could just buy a Worksharp WS3000… but you know how it is… we like to build things ourselves, it's fun, and may even turn out better than the commercial option