As a mental exercise I wanted to write up a plan to machine a simple part.
It
wasn't the idea to have someone else do the mill work, I just wanted to see
if I
could do the operations in my head and write it out accurately and
functionally.
Here is the first draft. After reading through it I see a number of small
problems, bad practices, better ways of using the DRO's features and better
ways
of communicating. So, that got me to thinking about how to plan machining
operations and provide the right numbers from the drawing to a spreadsheet
or
such, trying to minimize the "Art" in machining. To actually do this part,
I
would just pin up a drawing on the mill and make chips without too much
thought.
For this simple part, no big deal, and the chance of screwing it up is
minimal.
However, as parts get more complicated, the chance or screwing it up or
wasting a
bunch of time increases. It seems to me that a good plan is a good idea. I
have
no idea how to do this planning and I'm wondering if there are resources
available. I think I also want to roll good planning into the drawings
trying to
imagine tool paths, DRO readings and order of operations. So, it seems I
not
only need to re-learn over how to machine stuff, I need to re-learn how to
draw
stuff. This little exercise has been very revealing.

Here's a pix of the part in the dropbox: http://www.metalworking.com/dropbox/ob_cutter_arm.jpg

0. Prepare rectangular blank. 1. Bandsaw the upper left corner leaving .01" to .02" 2. With the left corner of the Kirt vise indexed to X=0, Y=0,(memory "0") on the DRO, support the blank on parallels with the sawed corner up and left even with the indexed vise corner. 3. With a 3/4" end mill, finish machine the blank's corner. A. Clean-up enough of the bottom of the notch to measure the thickness. B. Mill the bottom of the slot to the finished dimension to the right until the DRO reads .625" thus the cut will be 1". Mill the Y axis to remove the radius left by the end mill. 4. Clamp the blank face-up on parallels with the notch to the left rear. 5. Move the table to: X=.750", Y=.-1.4982" and drill using a small starter drill. Change bit to .250" and drill until the flutes are a bit deeper than .250" set DRO to zero on upper left corner of the pocket. 6. With a 1/2" end mill, mill out the carbide pocket. A. With the DRO at Y=0 and the mill off the blank to the left, move the table to the left until the DRO reads X=.480" cutting to .125" deep. Move the table to the right off the blank. Move the table back to Y=-.250 and repeat cutting .250" on the y until Y=-.480". Repeat until depth = .250" B. Using a 1/4" end mill, clean up the sides of the pocket to X=.625 and Y-.625". 7. Zero the DRO back to home position and move table to the bore at X=1.866" Y=-.6875" 8. With a small center drill, start the hole. Drill through with 1/4", 1/2", 5/8", and 11/16". 9. Bore to .749" with adjustable boring head and small boring bar.

Tooling: End mills: 3/4", 1/2", 1/4" Small and medium-large Starter drills (Combined drill-countersink) Boring head with small boring bar. Parallels Micrometer or caliper Bore gauge for 3/4" BFH

Here's a pix of the part in the dropbox: http://www.metalworking.com/dropbox/ob_cutter_arm.jpg

0. Prepare rectangular blank. 1. Bandsaw the upper left corner leaving .01" to .02" 2. With the left corner of the Kirt vise indexed to X=0, Y=0,(memory "0") on the DRO, support the blank on parallels with the sawed corner up and left even with the indexed vise corner. 3. With a 3/4" end mill, finish machine the blank's corner. A. Clean-up enough of the bottom of the notch to measure the thickness. B. Mill the bottom of the slot to the finished dimension to the right until the DRO reads .625" thus the cut will be 1". Mill the Y axis to remove the radius left by the end mill. 4. Clamp the blank face-up on parallels with the notch to the left rear. 5. Move the table to: X=.750", Y=.-1.4982" and drill using a small starter drill. Change bit to .250" and drill until the flutes are a bit deeper than .250" set DRO to zero on upper left corner of the pocket. 6. With a 1/2" end mill, mill out the carbide pocket. A. With the DRO at Y=0 and the mill off the blank to the left, move the table to the left until the DRO reads X=.480" cutting to .125" deep. Move the table to the right off the blank. Move the table back to Y=-.250 and repeat cutting .250" on the y until Y=-.480". Repeat until depth = .250" B. Using a 1/4" end mill, clean up the sides of the pocket to X=.625 and Y-.625". 7. Zero the DRO back to home position and move table to the bore at X=1.866" Y=-.6875" 8. With a small center drill, start the hole. Drill through with 1/4", 1/2", 5/8", and 11/16". 9. Bore to .749" with adjustable boring head and small boring bar.

Tooling: End mills: 3/4", 1/2", 1/4" Small and medium-large Starter drills (Combined drill-countersink) Boring head with small boring bar. Parallels Micrometer or caliper Bore gauge for 3/4" BFH