- Joined
- Jul 28, 2017
- Messages
- 2,522
I recently made a small face mill that uses a 3/16" diameter HSS rod for the cutter. The idea was to replace an indexable face mill with something that would handle interrupted cuts better (I always seem to chip the inserts). I like the concept of the tangential cutter because they're dead easy to sharpen. To simplify some of the machining steps I made the face mill in two parts -- the arbor and the holder for the cutter. I started with a 3/4" rod of HRS for the arbor and some 1.25" diameter 4140 for the holder. The photos below show a few steps in the process of making it, after I did the initial lathe work to turn the 3/4" rod down to 11/16" to fit my R8 collet and smoothed/faced the holder down to a .486" thick disk (there was no specific thickness target, it just ended up that thick).
This photo shows the holder in my angle vise. The vise is set to 12 degrees from horizontal, and I'm milling a flat preliiminary to drilling the 3/16" hole for my HSS rod.
The slot (machined in a previous step) is .1" deep and .5" wide, and matches a tang milled on the end of my arbor. With this approach the bolt that joins the two pieces doesn't have to resist the torque produced by the cutter when it's removing metal....and I can make different-sized holders as needed. To make it easy to accurately rotate the holder 90 degrees, before breaking down the previous setup I also milled two flats on the side of the holder. That gave me a nice secondary reference plane.
The photo below shows the holder and arbor assembled to make sure they fit OK. This photo actually predates the first one shown above. My old drafting ruler is there to provide a sense of scale. I was able to machine the slot and tang accurately enough to get a friction fit. 'Course, if I hadn't done so well I wouldn't have mentioned it .
Below shows the finished product, complete with a shortened hunk of HSS that's been ground to 30 degrees on the end. I wrote a spreadsheet to calculate the offset necessary to place the tip of the cutter so it is exactly tangential to the circle swept out by the tool, when the cutter is projecting .1" below the bottom face of the holder. I also used the same spreadsheet to determine where I needed to drill/tap the hole for the set screw.
After grinding the HSS I did notice a small burr on the end so I honed it with a 600 grit diamond file. That produced an edge that would easily shave my fingernail.
Below shows the result when I tried my face mill on a piece of 6061. I also tried it on some HRS with a .01" depth, full .75" wide cut and it worked just fine. No chatter, nice smooth surface. This was done on my Sieg SX2 mini mill, not the most powerful beast around, so I call it a success.
I was concerned that the cutting forces would push the cutter into the holder but that wasn't a problem. Not so far, anyway....
This photo shows the holder in my angle vise. The vise is set to 12 degrees from horizontal, and I'm milling a flat preliiminary to drilling the 3/16" hole for my HSS rod.
The slot (machined in a previous step) is .1" deep and .5" wide, and matches a tang milled on the end of my arbor. With this approach the bolt that joins the two pieces doesn't have to resist the torque produced by the cutter when it's removing metal....and I can make different-sized holders as needed. To make it easy to accurately rotate the holder 90 degrees, before breaking down the previous setup I also milled two flats on the side of the holder. That gave me a nice secondary reference plane.
The photo below shows the holder and arbor assembled to make sure they fit OK. This photo actually predates the first one shown above. My old drafting ruler is there to provide a sense of scale. I was able to machine the slot and tang accurately enough to get a friction fit. 'Course, if I hadn't done so well I wouldn't have mentioned it .
Below shows the finished product, complete with a shortened hunk of HSS that's been ground to 30 degrees on the end. I wrote a spreadsheet to calculate the offset necessary to place the tip of the cutter so it is exactly tangential to the circle swept out by the tool, when the cutter is projecting .1" below the bottom face of the holder. I also used the same spreadsheet to determine where I needed to drill/tap the hole for the set screw.
After grinding the HSS I did notice a small burr on the end so I honed it with a 600 grit diamond file. That produced an edge that would easily shave my fingernail.
Below shows the result when I tried my face mill on a piece of 6061. I also tried it on some HRS with a .01" depth, full .75" wide cut and it worked just fine. No chatter, nice smooth surface. This was done on my Sieg SX2 mini mill, not the most powerful beast around, so I call it a success.
I was concerned that the cutting forces would push the cutter into the holder but that wasn't a problem. Not so far, anyway....