Thursday, 29 March 2012

Chef's Knife (pt4) - 220 Grit

March Break put a slight crimp in the project and I missed a couple of weeks on the knife. Fortunately, in that time Chuck was able to finish the Master Grind. He's brought the metal down close to the center line we marked from last visit. It's starting to look like a knife now.

A close look at the edge shows we haven't hit the center lines, but we're close. The rest we'll take down during sharpening.
But before we can send the metal out for hardening we have to make it pretty. The metal right now is a mess of scratches, nicks and dings. 

We'll use some 220grit sand paper to start the effort. This is the Karate Kid "Wax On, Wax Off" phase of the project. Time for me to get all Zen about the process. There are no tools to make this easy ... only elbow grease.
This bench will be my church pew for the many more hours. It holds the blade at a comfortable working angle and supports the blade underneath so my pressure doesn't bend it. I can rotate the metal as needed relatively easily.
Assume the position. For the 220 grit I can do a forward/backward motion initially, but later as we get closer I have to switch to a single direction stroke. And this is only the 220 grit, we're going to be going all the way up to 800 grit ... I save the details of that little treat for later. It gets quite fussy. You can see some of the higher grits in the photo above.

Even putting the sandpaper on the blade and taking it off is an art. Any horizontal movement, angles or swirls of the sander will leave an ugly mark on the metal ... which means more work.

We aren't taking off a lot of metal with the 220, so it takes time to get take out all the little scratches from the belt sanders. 
After about an hour or more of steady work I think it's looking pretty good. I mark a couple of spots with a normal indelible ink marker (like a Sharpie) on the blade that need more work and hand it off the Chuck for inspection. He's relatively unimpressed and proceeds to mark up the blade like a mad man. You could never imagine how thick marker ink is. Feeling this ink on the smooth metal feels like Mount Everest. And the stuff gets deep into any remaining scratches, so you really have to work to make them go away.
After another hour or more I've got a nice pile of used paper. It doesn't take long for this stuff to lose its grit. You're constantly changing it and moving it around.
But the end result is beautiful. Blemish free. And it's only going to get better with the higher grits.

This is the part of the process I really have to get right. This is the part when I'm showing the knife to friends that I can say "I made that" ... any blemishes will immediately stand out.

And this was only one side of the blade. I still have to do the other side with the 2200 in the same manner as this side was. And the edges.
Fortunately, some of the mess will be hidden by the bolster, which I've indicated here.
 More karate practice next week ...

Wednesday, 14 March 2012

CNC Machine - Part 1

I've been working on a robot since I've been in High School. Several robots actually. My downfall has always been with the mechanical linkages between the motor and the wheel. My fabrication skills just aren't that great and I don't want to incur the hefty machinist fees that I have in the past. My solution to this has been to get a home CNC router to help me fabricate gears, brackets, mounts and whatever I need for the robot.

At the end of last year I picked up a ZenToolworks 12x12 kit. This is a well-priced, well designed kit that will give a basic CNC router capable of 12"x12"x5" of work area. Over the holidays I started on the fabrication of the machine itself. I won't go into the details of it here, since it's well documented on the Toolworks site.

The kit is a little daunting when it first arrives. The thing weighs a ton and has lots of little scary parts. There are your core PVC parts ...
And your nuts, bolts, couplers, lead screws, bushings, bearings and electronics ...
The tricky part is ensuring your bearings are installed flush with their holders. Also finicky is the tension on the backlash nuts.
In the end the basic device came together as expected.

But now the real work began ... mounting and hooking up the electronics. We have two power supplies (one for motors and one for the router), a stepper motor control board, a router speed control board, six limit switches that need to get mounted, an on/off switch, a speed control and an emergency stop. I didn't want to rush into a crappy wiring job to see how the assembly went only to find myself debugging a mess of wires. Instead I put off my excitement to mount all this stuff correctly.

I decided to mount everything on a piece of masonite so it could be mounted on the rear gantry.
I figured I'd mount the two power supplies outwardly to conserve space and help with the heat dissipation. I'm not sure yet if this is a good idea or not. But this is as far as I got for a while until I gather the needed spacers, connectors and wiring. 
Today I was able to get my 4-pin connectors on the X, Y & Z stepper motors. I also had to resolder a voltage regulator from the router speed controller board that was completely unattached to the PCB. Just a fluke that I spotted it before it fell out and had no idea which way it went back in.
As well as mount the emergency stop, speed control and on/off controls. Note, this is the what the view will be from the front of the machine. All the electronics will be hidden behind.
I also decided to bring the motor connectors to a terminal block rather than directly to the controller board. My fear was a renegade machine pulling the control board apart from the mounts. At least this way the wire should fail before the traces on the circuit board.
And finally here is how it looks from the back. Next I need to wire up the power, the limit switches and the controls. I may leave the router and limit switches for now so I can focus on basic control. 

Stay tuned ... more to come ...

Friday, 2 March 2012

Chef Knife - pt 3 - Master Cut ...

Short post this week. We started on the Master Cut (the primary cut to give an edge). I'll give more on this next week.

First we had to make some more decisions on the bolster style. After sketching out a design based on some sample knives Chuck sent me, we agreed on this look. However this required a change to the pin hole locations. Some quick math and adjustments got us ready. No biggie since the extra hole will be filled with epoxy.

Some other cleanup on some rough curves and the point and we were ready to get started on the master grind. First it needed some fresh tooling dye.
Using this marking tool, we found a spot that would give us about a 1/32" knife edge. 

And we set our marks for the grind. We'd have to bring the edges of the knife down to these marks on both sides.
Chuck did the Master Grind work. This is the most critical step and if we screwed up it's game over. I was happy to hand over the reins ... maybe next knife.

This step involves starting your Grind Edge on one side, moving it down and across the whole blade, but not losing the bottom curve or taking too much from the top side of the knife. For a chef's knife we want, essentially, a triangular cut from top to edge (vs. a curved cut in traditional knives).
Here's we are one-quarter done. Have to bring the other side down like the left side here and then do it all over again to get to the etch lines. The metal gets really hot doing this. 

In the next couple of weeks I'll show the final result of this cut.