A CHUCK HELD MILLING SURFACER
This little tool can be chucked on a lathe three jaw chuck and used to prepare the surfaces of work held on the cross slide or vertical vice/slide. One inch wide passes can be taken without it being classified as a fly cutter. It can better be used on a vertical milling machine or the bench drill press/ cross vice modification previously discussed.
The tool couldn't be simpler to make and anyone with even the smallest of lathes can easily fabricate one of these. Take a 2" long piece of 1-1/2" diameter aluminum or steel rod, chuck, face off the end and begin to turn down the end to a diameter of 1/2" and a length of 1-1/4" to leave a 3/4" long 1-1/2" diameter head. Reverse chuck and face and turn the large end just enough to clean it. Chamfer all the edges and locate a position for the tool bit hole 1/2" from the center of the large end and drill and ream a 1/4" hole to a depth of 5/8". Drill two equally spaced set screw holes along the side and directly in line with the tool hole for a 10-32 thread. Make a cutter out of 1/4" drill rod by grinding a 3/16" long flat with about a 10o positive rake on one end. Grind the tip to a 1/16" radiused nose and follow with a thumb nail shape ground 10o bevel on the under side sort of like that on a wood turning gouge. Cut the tool to a total length of 1". Chuck and face the cut end of the cutter and put a slight chamfer on the end. The tool has to be heat hardened and tempered before the final honing of the edge is done and installed on the arbor. To properly orient the cutter, the arbor should be held so the large front end is facing directly at you and the tool hole is at a 12 o-clock position. Insert the cutter into the tool hole and turn the tool bit so the flat facet is facing the direction of rotation and aligned with a imaginary line from 12 to 6 o-clock. In other words, the flat is facing west / left / or toward the 9 o-clock side.
Place the tool in the drill or milling chuck and proceed to mill as if you were using an end mill. Because you are only cutting with a single point cutter you will have to slow the feed rate by a factor of three or four in order to produce a smooth finish on the work. Also because the tip of the cutter is radiused, it will tend to produce a much finer finish than that of a sharp pointed tool. Milling machines will use similar milling cutters that are essentially the same tool but with multiple cutting edges that must be set at exactly the same extension so they all touch the surface being milled. As with any milling operation on a small machine, minimal cuts must be taken for the best and smoothest finishes.
After having finished building and testing the first prototype, I decided to put a larger radius on the nose of the cutter which has effectively contributed to a much smoother finished cut. Although originally I conceived this cutter for use on the drill press or milling machine, I decided to test it on the lathe by chucking it to the spindle and machining a 3/4" wide edge of a raw chunk of aluminum clamped to the vertical milling vise / slide. I ran it about 850 rpm and it produced a beautiful finish which was actually quite a bit better than that produced on the drill press. Obviously, the spindle on my very cheap little bench top drill press seems to have a certain amount of vertical play probably coming from its cheap bearings that allows it to move ever so slightly up and down during the cut even after the quill is locked in position. The TAIG spindle is far more superior to that on the drill press, thus the much better surface finish. I noticed that the chips were coming off as fluffy wisps instead of the heavier little chips the drill press was producing. Although I have tightened the spindle lock and taken up any slack by snugging up the depth setting nuts, I still could not get the glassy finish I was getting on the TAIG. Having come to the realization that this particular drill press is unsuitable for milling operations demanding the best of finishes I have begun to shop around for an up grade. I have found a drill press of a larger capacity to allow a larger workpiece under the spindle and positive dialed depth control, much better and accurate than the usual threaded rod and locking nut affair. The spindle and its bearings are also heavy duty with absolutely no play. A machining X/Ycarriage that is bolted to the table to turn the drill press into an actual milling machine is also available. A vise would have to then be bolted and aligned to the milling bed carriages. In the long run it is a hack of a lot cheaper than a milling machine. The whole set up of drill press, machining cross carriage and a small machinist vice could be put together for $300, a bit better than the $450 to $900 without accessories for a dedicated milling machine.
The surfacing tool I have just built is a non adjustable first prototype, meaning that the machining path is constant at about 1" in width. It would not be any great problem to make one with a slightly large diameter face and drill out 3 tool bit holes at varying distances from center, at 12 - 4 - and 8 o-clock to give three progressively larger cutting paths of the bit. The tool bit could be installed in any of the three holes depending on the size machining path you require. At this point, I am perfectly satisfied with the first one so the other more "advanced" model can sit on the planing bench for a while.