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Doug Ayen

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new discs for pizza cutters [Oct. 12th, 2007|02:12 pm]
Doug Ayen
I haven't been completely idle over the gap in posting, I've been covering for several people at work who left the group, which has been a major time-suck, but also spending some time tooling up and getting ready for the next season of knife making.

Now that it's no longer regularly in the 90s, for a few days at least, I've gotten some work done. I bought a Lennox 3-5/8" carbide-tipped hole saw, and cut out two discs out of the damascus I made last spring. Even though the steel was pretty soft, it's still tool-steel (O1 and L6), and took a while to cut through. I used plenty of lube, took my time, and now have the disks.

A quick deburring (necessary, the edge burs are sharp enough to cut through a glove -- as the 1/4" long cut on my left thumb attests to) and polish of the edges, and I sat down with a loupe to examine the edges for defects.

As I had expected, based on an earlier examination of the billet, one has a "cold shut," a layer where the billet didn't quite weld up completely, but it looks pretty small (about half an inch long -- in the final product it'll be barely visible with a deep etch, and just look like a dark line on a light etch or polish). The other one looks ok. I'm also going to cut out one of stainless, and one out of straight L-6, mostly for practice before I start working on the damscus.

To grind in the bevels, I really can't freehand it -- I tried that last time, and didn't like the results. What I'm thinking of trying this time is to create a mandrel and brace system to give a bit more control to the process.

First, I'm going to take a C-clamp, and affix a 2" long by 1/4" ID sintered bronze bearing to the top of it. Welding won't work, obviously, so I'm thinking braze, or maybe even good-old JB-weld. Since I have a fairly ridgid work rest on the 3hp grinder, I can then clamp the assembly to the rest, leaving the bearing facing the contact wheel at about the right angle, and be able to adjust that angle by adjusting the work rest or by twisting the C-clamp a bit.

I can then use some 1/4" round, threaded for the last inch or so, fed through the bearing with the disk clamped between two nuts and lock-washers on the end to hold it steady. Put a crank handle on the rod, or just bend it 90 deg., and I now have a handle to control the rotation of the disc. This should let me do a controlled grind of the surfaces of the discs to a specific angle against the contact wheel, resulting in an even bevel.

As you might have guessed, the right tool for this job is actually a metal lathe. I don't have one, and it looks like one that meets my needs (able to work in tool steel, handle a billet up to 6" in diameter, cut a bevel, etc.) will cost at least a couple thousand, used. So, once I've made a few of these using bear skins and stone knives, I'm hoping to sell them off, and use the proceeds to tool up. The day job is taking care of mortgage, retirement, and day-to-day stuff, but I'm still making less than I was at UUNET, so my tool budget is rather slim. More on this later.


[User Picture]From: perspicuity
2007-10-12 08:03 pm (UTC)
the things you can do with computer controlled carving, or at least a good lathe:




in other news, "rotary pressure forging" or "friction forging" is making t he news in the magazines lately. interesting.

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[User Picture]From: scliff
2007-10-12 09:30 pm (UTC)
I don't know anything about metalworking, so this is probably insane (what use is the Internet except to provide a forum for the uninformed?), but here it is anyway:

Could you use a combination of a (presumably cheaper) wood lathe and an angle grinder? Spinning the billet would provide the consistency (on one side, at least), and the grinder might work the surface without loading the
lathe nearly as much as a cutting tool. I've seen video of similar combinations used in other contexts, but I can't remember exactly what they were (polishing/finishing?)
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[User Picture]From: blackanvil
2007-10-13 12:37 am (UTC)
Well, in theory, yes, in practice, it's probably pretty dangerous.

Also, as per my last post, my wood lathe died a while back, and I haven't replaced it yet.

That said, if you did get a wood lathe with a slow-enough turning speed and a collett that could hold the piece, you could use the angle grinder -- but you'd still need some way to arrange to hold the grinder steady -- and angle grinders, even the small ones, are hard to keep ahold in a set posiion for any length of time.

Last time, I chucked the disc into the milling machine, and made a sort of impromptu lathe that way, after discovering how hard it is to make a perfect circle by hand. Sadly, the milling machine is now defunct, as one of the gears in the head went, and I haven't fixed it yet (and may not, I was never happy with it -- under powered and too much slop, and the table binds on the y-axis).

A lathe would give me the accuracy that I'm looking for, plus I could use it for knife furniture, handle fluting, and so on -- and it's the right tool for the job.

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