The tangential tool holder project was based on an article in Home Shop Machinist; Jan/Feb 2009 (Vol. 28, #1) pg 12. My original write-up was quite sparse. First the dimensions of the tool holder were completed. A hole was drilled for the clamp. The center drill was used as an edge finder and then the table was moved into the workpiece the required distance plus half of the center drill diameter. The hole was drilled 0.660" deep with a #21 drill bit and threaded 10-32 for 0.50".
Significant difficulty with too little head room for both drilling procedures. Angle plate + vise raises work piece a minimum of 2 3/4" off the base, even with the vise hanging off the end of the angle plate.
A relief groove was cut with a 3/8" end mill from (0.629 - 0.25) to (0.629 + 0.25) and 0.379 to 0.879 to a depth of 0.050" in 0.010" passes. The cutter was touched against the edge and dialed in 0.379 + 0.375 = 0.754".
The tool holder clamp was begun next. Began with material different in size from the article: 1" instead of 5/8" wide. So the instructions were adjusted accordingly. Angled lines were drawn on the steel bar using the tool holder as a guide. A hacksaw was used to cut the first line. The workpiece was placed on the reference edge in vise, which was still on the 12° angle plate. Too much chatter was experienced with an end mill so the end was finished with a fly cutter. All sides were cleaned up and trimmed to the size of the holder.
The tool holder clamp was clamped above a piece of aluminum waste for drilling. Measuring in from the top 0.38" and across from the side 0.31" located the spindle for drilling. Drilled through with a 13/64" drill bit and counterbored 0.57" deep with a 3/8" end mill. Experienced a lot of chatter even with a lot of cutting fluid. A reasonable fit resulted. The clamp was flipped over to finish the inside cuts. At this point it was noticed that the bar was 1/4" not 3/16" as ordered. The fly cutter was used to narrow to 3/16" and then cut most of the piece up to a scribed line at 0.140". The end was furthered trimmed to 0.130" on the end.
The clamp was attached to the body of the cutter holder with a cutter blank in place. The resulting gap was measured with a thickness gauge at 0.045". The position of the bit was marked with a marker and a groove was cut to the line with a 1/4" end mill to a depth of 0.049". The part was touched up with a file and assembled for a nice tight grip on the bit blank.
The grinding jig was made next. The jig is designed to hold the bit blank 12° from level at an angle of 30°. A 1" X 1/2" X 2 7/8" aluminum block was cleaned up with a file. The angle table was angled at 30° aligned with the mill's y-axis and set to 12°. The center was marked and then a line was drawn with a marker 1/8" to the left of center. Repeated with a line to the right of center. Both lines were 60° relative to the edge. The area between the lines was milled out to a depth of 0.315" at the deep end of the groove.
Since the work is 0.265" longer than planned, the hole should be placed 0.875" + 0.265/2" = 1.008" from the left end. The workpiece was squared relative to the mill table, but still on the 12° angle plate. Center drilled, drilled with a #21 drill bit, and tapped with a 10-32 tap to the bottom of the 0.40" hole. This completed the guide block.
A clamp was then made for the grinding jig. Squared up one end of a brass bar to 0.25" X 0.50" X 1.49". Two holes need to be drilled and must be centered and 0.622" apart. This results in each hole being 0.434" in from the side. The brass bar was squared in the vise and drilled with a #9 drill bit (0.196") at 0.434" from the end and 0.25" in from back. The hole was counterbored with a 3/8" end mill. The clamp was advanced 0.622" and the process was repeated. It was a perfect fit with the blank in place! The clamp was polished with a file and plastic sheets(?).
The counterbore was 0.20" deep.
A blank tool bit was ground with the left wheel of the grinder after setting the rest to horizontal. Clearances looked fine after setting the bit to the appropriate height. A problem is that the tool blank is too long. The steel is too hard to cut with a hack saw. Will need to find a source of shorter bits. About 1 3/4" is the maximum length that will work, otherwise the bit hits the lathe bed! What a great project that was based on the level of detail in the article.
Communicated with the author via email (jost.mj@opengate.com.br). He used a chop saw to cut off his bits. I found diamond wheel saws for the Dremel and bought them. After clamping the bit in the mill vise it was cut off with a lot of cutting fluid. Excellent! Put the cut off 1/2" in the clamp and shaved off the front end to provide a bit of relief on facing operations. Did not need to trim the side. Used the new bit after sharpening on the grinding wheel and cut some alumininum. Very smooth!