Tuesday, October 15, 2013

Milling around

 Looking at my labels I am surprised I don't have a label for "milling." But I do have a label for "Proxxon mill". The only mill I have, in fact. A mill holds the work still, and a cutter revolves. In a lathe it is the other way around. Both are very useful in my miniature machine shop. I have been milling (and turning) for quite a few days now, in fact is quite an obsession. My first attempts at milling have been documented. But now I want to cut flutes on the clamp bolts on my digital indicator stand.Ideally, in machinespeak, these would be knurled on the lathe. But I don't have a knurling wheel set.

 Instead, I took a  hint from Tom Lipton's oxtool videos and cut flutes instead. Very nice. I decided to use 8 flutes. This required making the fixture shown above. A square piece of aluminum. I scribed one line at 45 deg. By simply flipping the fixture around I can cut four flutes. Then I carefully align any one of the flutes I just cut. And I then, by flipping, cut four more flutes. My steampunk dial indicator stand is really beautiful now. And I can adjust it with my fingers. Should have a pic of it, but omitted to get one.

However, today I decided to make a fly cutter for the mill. I had a piece of very nice steel, taken from a defunct printer. It made the clamp bolts. Now I want to make a fly cutter out of the rest of it. A fly cutter is used to level out rough surfaces. I did some internet research. There is always myfordboy to the rescue. Another good reference is Dean. From these two references, I extracted the fact that a fly cutter must be angled to the work. I picked 45 deg per myfordboy. OK, I have this piece of 13mm (more or less) round bar, and I have to drill a 45 deg hole in it. How do I do this? I spent the entire morning working this out. I am no professional machinist! I finally cobbled up the setup shown below.

I held the round in the vise.  It is pure serendipity that the Taig milling vise (Imperial) fits the Proxxon mill (metric).  I propped it the round bar on a step block kindly provided by Proxxon. Thanks Proxxon! I packed things up with stray aluminum scrap and it all worked, a miracle because the mill is metric and the rest of it is all Imperial. But Aluminum has a bit of squish in it, so the thing was well held.

Next problem is to drill the hole. Were you to simply bear down with the drill, it would skitter all over the place. This is not wood, it is metal. So I had previously made a 2mm or so end mill out of a broken drill. Ground it to shape. I ran this end mill so it made a little step in the round bar. The step gives the drill something to bite into. So I went through with a small drill and then a 3.2 mm drill (0.125") which is a collet size I have -- standard Dremel size shank. I had very carefully drawn out the thing to scale, a very good idea.

Next step was to turn down the shank to something that would fit a 3.2 mm collet. Straightforward turning. Now I have to make a setsrew hole in the thing to hold the cutter bit. Not to mention grind the cutter bit itself! That's another day's post.

Now I have to figure out how to get a setscrew in there to hold the cutter bit down. Later.

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