I worked on a pizza cutter wheel for a clients cutter last week. It was a good week last week and I was very productive in the short amount of time I had to get things done. I was going to use a cast wheel that I had made previously, but the scale just wasn't correct, so I decided to machine a new one. I figured that I might as well document the process so I can show what goes into one of these since they require multiple machining operations. I started by cutting out the center hole, surrounding holes, and roughing contour on the Tormach with a large endmill and then moved to the finishing operation (using a small end mill) to create the final contour of the teeth. Then I created a mandrel so I could mount the gear blank on the lathe. From there the turning began with a series of different shaped toolbits to arrive at the final shape. The final wheel is a great match to the the scale of the handle.
7 comments:
Cool... thanks for sharing!
I know very little about metal processes, so it's neat to see this.
glad you liked it!
I noticed that you've got your custom tool mounted upside down - is this so that you have a better view of where you're cutting (keeping chips out of the way), or is there some sort of machinist voodoo going on?
ah, the "custom toolbit" was ground from some leftover HSS that a student had left behind. I think it had some severe top relief to begin with so I left it that way rather than grind it all the way back and start over with shaping the tool.
The tip was the only part of the bit that I was cutting with, so I just left it the way it was and then made sure to set the height of the tool based on the tip and not farther back on the tool bit. After looking at the pics it does look really strange.
My biggest concern with cutting with a thin pointed tool like this, is to make sure it doesn't get snagged deep inside the area I'm trying to get in behind to carve away. I'm always afraid it's going to hang up and rip the delicate parts of the piece I'm turning to shreds.
The type of turning I'm doing here is not your typical machining to spec for sure. A true machinist would probably die if they saw me make this kind of thing and the way in which I do it. I tend to "carve" intuitively when I use this method. This is my favorite way to make something with the lathe though. I probably would make more work if I made stuff more like this rather than modeling stuff.
I guess I just don't over-think or over-plan things if I'm making something like this "in the moment". I think that's why I can build tools more quickly than the pieces I usually make.
Ah, okay - taking a closer look I see that it is conventionally mounted but just looks like an upward hook at that angle.
I wonder if it would be possible to build some sort of special tool holder for the lathe that would provide the needed rigidity, but could be moved (and even rotated a little) 'freehand' without having to turn cranks - something that feels less like an etch-a-sketch and more like wood turning...
yeah, I've always wonder that too. When I looked at the old watchmakers who would use gravers with a woodturners toolrest to make small parts for watches I was reminded of that.
http://www.youtube.com/watch?v=k0VXYBc6PPQ
http://www.youtube.com/watch?v=M6svZzTBIeM
Okay, bunch of comments...
1) Yes, just like being able to use a watchmaker's lathe! I actually made a set of gravers in the horology class last fall - I'll have to bring them by to show you sometime (parting tools get freaky thin).
2) This was one of the linked videos after watching those (and now I want to sign up for another semester of clock repair at MATC) - I love seeing this kind of stuff: http://www.youtube.com/watch?NR=1&v=IUBQN1JfY80&feature=endscreen
3) After a lot of pondering, I think a 'freehand' system for doing work the size of your pizza cutters (and even larger) is entirely feasible! I'm envisioning a system that uses a tool mounted on an air bearing levitated platform, but that also uses an electromagnet to keep the platform firmly stuck in the X-Y plane with no tipping. Furthermore, with a bit of sensor feedback, you could have the system abruptly kill airflow to the bearing surface so that it sticks hard in place in case the system detects that the tool has 'grabbed' and is pulling into the workpiece (if you have aggressive rake angles). Alternatively, you could probably do something similar with a joystick and a hydraulic tracer unit, but you'd lose all the 'feel' of making a cut. While entirely workable, it just wouldn't be the same.
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