Milling 101

Host Gene Niegoff

November 22, 2003

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Meeting began at 9:10 as we allowed extra time for some those with a longer commute. While we waited Merlin showed us his portable air compressor made from a Cadillac air suspension pump. It was nicely tucked into small piece of luggage and looked to be very handy indeed. Thanks Merlin! Everyone did a great job on carpooling and participating in the meeting, Which was a good thing as this was our largest meeting yet with 25 members/guests attending. They were in no particular order; Neil and David Butterfield, Glen and Jeff Lynch, Bob Harbour, Robert Riesman, Neil Peters, Merlin Darlton, Richard Bennet, Russ Stillman, Jerry Hine, Bob Sanders, Doug Wilson, John Clayton, Ron Watkins, John Cannon, Robert Stewart, Robert Gallagher, Doug Wilson, Scott Brown, Lance Greathouse, Dale Schmidt from Queen Creek, Owen Jeffers from Prescott, Tom Jenner and Roger Mathewson both came down from Havasu and last but not least Bob Hanson came over from Wilcox. That's what I would call a "driving commitment" towards education!
Picture of members attending
Gene began with a discussion of the tooling that is used on a vertical milling machine. Our target audience is that of the home shop machinist and Gene did a very good job of displaying the full run of tools as evidenced by the following picture.
Table o' tools
A milling vice, a stud and nut set, and some end mills will get you started but how are you going to hold those end mills. With a chuck right ? Wrong! A drill chuck (Jacobs/keyed or Albright/keyless) is great for downward pressure but has limited lateral stability. A collet would be better and can also get the job done but the proper way would be to use an end mill holder. Why? Because an end mill holder will retain the end mills by applying pressure on the "Weldon Flat" or that handy little flat spot on the side of you end mill. This handy little flat was actually patented by (you guessed the Weldon company) and allows for better torque to be applied to the end mill. While there are many sizes and descriptions of end mills we covered 2,4 and multi flute and shell end mills. The 2 flute are good for roughing, 4's for finishing cuts and multi flutes have many uses but come in really handy for facing.
Gene has been in the biz for a while and has accumulated quite a collection. You might not need all of these starting out but eventually you will find a use for all of them. Each tool was held up or passed around needed to describe it and what is used for. One particular mystery was the edge finder. After aligning all the pieces of the tool and setting your rpm to around 400 you bring the mounted work piece into the tool until it is knocked of axis. Now you can set your zero and begin whatever operation had in mind. Below is a picture of Gene demonstrating its use on a drill press.
Gene at drill press
As Gene went about identifying and describing each of the tools he also advised us to be on the look out for yard/estate sales and online auctions. Here is a tool he was very proud of and indexable face mill procured for a song and a shipping fee on one of those auctions. These can make facing much easier than a fly cutter as mentioned earlier. The nice thing with this one is many shells can be placed on the end the shaft. Since the shaft is smaller this can be used on smaller home shop equipment like the Ronfu's you see in many home shops. Below is a picture of the face mill.
Indexable Shell End Mill ? / Face mill
It was stated that milling is a very versital and often abused practice. Climb vs Conventional milling was covered and aided by a drawing that I have failed to replicate here. Basically if the tool is turning clockwise and you are feeding the piece into the cutter the chips should be peeled up and away from movement of the work and not along with it. Think of it like your cars back traveling over a rock while driving forward, if this rings a bell turn off your machine cause your climb milling. It was strongly recommended that on a manual machine that climb milling is not practical. If any backlash is present bad things will happen like breaking end mills and nasty metal noises coming from your valuable machinery. It was also noted that if you can feel a pulse in the feed handle of your machine this is a bad thing as well. Here are some of the formulas that we covered;
CS = is Cutting Speed and is always in surface feet per minute.
RPM = 4xCS / Diameter of the tool
Feed rate is dependant on the HP of the motor and the number of teeth or flutes on your tool. You will want to remove no more than 2-10 thousandths per tooth per revolution. When working with steel 1 HP is equal to 1 cubic inch of steel per minute and for aluminum it is .28 HP dependant on coolant. Coolant can be used on most materials EXCEPT cast iron, when working with cast iron use air. If in doubt about speeds and feeds, error on the side of feed rate not RPM or you will defeat rule #1 which is cutting speed. It was noted that if your surface is bad or you are doing a finish cut that you should double your rpm and cut your feed rate in half. It was clarified that chip load is the thickness of material being removed by a single tooth or flute.
At this point we stopped for a quick break and some doughnuts. Some of the group took this opportunity to ogle the table O' tools and ask Gene more questions. Here Neil Butterfield and Neil Peters wait to ask our esteemed instructor more questions.
The Neil's getting ready to ask Gene more questions
After the break Gene covered the parts of the mill, it was stated that the z axis is always the rotating portion of the machine or the spindle. The quill is that nifty little thing that goes up and down in the spindle when you pull the handle. Inside the quill you have a drawbar and fixture for holding your tooling. This could be a chuck or collet but preferable an end mill holder if using end mills. Below is a picture of Gene changing out the tooling and showing us the drawbar.
Gene and quill / drawbar
The X and Y axis are always on the table. This type of mill is a bench top mill so the table is fixed, with a knee mill you can raise or lower the table to facilitate changing tools of checking parts.
We then engaged in a discussion about the CNC SIG and the progress that they have made on the project.

CNC SIG