Mike and His 300 Rockwell C Object
July 31st, 2009Diamond is #2 Now
I quit trying to mill the strange object Mike brought me. It appears to be hardened, so it does not like being machined. I dug out a 3 1/2″ 12L14 disk someone sent me, and I mounted it in my vise and ran a fly cutter over it. Big difference. It cuts like butter.
Here’s a photo. The cut is around 2.5″ wide. I made three passes. The last one is 0.003″ deep. You can see marks from both “sides” of the fly cutter (same side on different parts of the rotation), but the trailing “side” left the most obvious marks. I am hoping this is acceptable. I am not eager to tram the mill again.
I haven’t found good information on fly cutter tool grinding yet. I found a diagram of a design on a CNC forum, but it had no relief on the bottom of the cutter, which surely has to be a mistake. I ground this new one with relief but no radius. I assume a radius would give a better finish.
I ordered some square T6 whatever bars. If I’m careful, I should be able to slice them in nice pieces with the dry saw and WD40. That will give me plenty of mill fodder for a while.
I still don’t understand why people say you should get a lathe before a mill, and that a lathe is more useful than a mill. The lathe is swell, but it’s harder to understand, and you can’t make straight cuts without a milling attachment. The mill is very straightforward, and you can do all sorts of things with it. I guess the traditional wisdom will make sense to me eventually.
More
I divided the RPMs by about 8 (115), changed the workholding method, and ran it through again. This time the finish is much better. I believe the feed was around 3″ per minute.
The disk is wider than the cutter, so I had to run it through twice. You can see a small part and a big part, with a dividing line. The small part is the last part I ran under the cutter. For some reason, it’s a tiny bit higher than the rest of the disk. No idea why. I locked the spindle this time, but I didn’t lock the gibs in the z-direction. Is that the problem?
July 31st, 2009 at 6:03 PM
Trust me on this: use carbide on steel. the day will come when you need to break that rule, but for now its a good rule.
also, use a face shield when you can. and keep a fire extinguisher handy. Nice looking cut. When the time comes i’ll get you some diamond cutters.
July 31st, 2009 at 6:24 PM
Right now I have no way to grind carbide tooling. I suppose I can make some kind of 12L14 holder for a triangular carbide insert and cram it in the fly cutter.
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The cobalt HSS I used for this cut sliced very nicely, although I have been informed that the RPMs (1000) were too high by a factor of around 8.
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I’m concerned because I stuck this thing on two parallels to get it up high in the vise, and when I tightened the vise, I couldn’t keep the parallels from getting loose under the work. I hope I am not going to have a problem with the jaws rising.
July 31st, 2009 at 7:09 PM
tighten the part then use a chunk of brass to tap the part down to the parallels.
Use small presharpened lathe tools in the flycutter, dont grind. best to use an inserted flycutter.
July 31st, 2009 at 7:19 PM
Any word on your sister yet?
July 31st, 2009 at 7:27 PM
No word from my sister.
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Her dog is here. Last night he serenaded me several times. “BYOOOOOOOOOOOO, cluck cluck cluck, BYOOOOOOOOO”
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Tonight I may let him sleep in the beer cooler.
July 31st, 2009 at 7:39 PM
the step in the par means the head is out of tram.
July 31st, 2009 at 7:42 PM
Steve, this is so cool to see how you are totally becoming a tool Nerd.
Hope your sister is ok. Will send up a prayer for her.
August 2nd, 2009 at 9:43 PM
Wow.
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I leave for two weeks to go feed my aviation-habit at aviation mecca (http://www.airventure.org) and return to find you milling and fly-cutting! Cool!
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Will you be starting your Stone-Crab-Claw-Cracker soon?
August 2nd, 2009 at 9:51 PM
Oh…and read the previous post, so I’m praying…
August 3rd, 2009 at 8:53 AM
>The lathe is swell, but it’s harder to understand
> and you can’t make straight cuts without
> a milling attachment.
You can cut square blocks on the lathe without a milling attachement. You’ll either need a 4 jaw chuck or a faceplate to hold them in place. Here’s some I did last year using some faceplate dogs
I’ve not seen anything on flycutter grinding either, other than that CNC article so I’d be interested too.
Time will tell if you find the milling machine harder to use that the lathe.
August 3rd, 2009 at 11:33 AM
Re the dog: Were the birds listening?