DRILL PRESS MILLING ATTACHMENTS
In order to extract the maximum versatility from any machine tool, you need good, well designed accessories. The same holds true with a lathe, milling machine or in our case, our drill press doubling as a milling machine. Since a lot of our milling work will involve truing up raw stock by milling its surfaces to right angles and parallel to each other, we can jump directly to the flycutter. We will purposely skip the end mill for now. Flycutters can be purchased with 1/2" diameter shafts and are generally made of hardened steel. The main body is of varying diameter depending on their milling capacity and size tool they accept. Some people will prefer to make them from scratch but I feel that this is one of those items best purchased. You just can't improve too much on the basic unit by scratch building it. Besides they are so cheap to buy that I don't see the advantage. The front of the tool is sloped and slotted to take a regular high speed steel cutter or a right cutting carbide or HSS tool. The orientation of the cutting tip to the work surface is important and the tool bit must be the kind that cuts from left to right. It is inserted in the holding slot so the right cutting edge is facing the work and top of the tool is sideways. Because the tool is held at an angle to the work surface so only the front portion of the cutting edge touches the surface being milled. I prefer a high speed bit for all metals but steel and I like to grind front, side and top positive clearances on them, finishing them with a 1/23" nose radius for a smooth finish. The diameter or arc of the cut is controlled by the amount the tool extends beyond the edge of the fly cutter slot. The tool is used at a slow to medium speed and it is passed across the surface needing machining, removing metal evenly and over a large surface, making it the ideal tool for the initial surfacing of raw stock. It is usually held in a special arbor in the milling spindle but since the tool has its own shaft, it can be directly gripped by the drill chuck as with end mills. Because the typical drill press spindle is not designed for this type of work, the arc of the cut should be kept to no more than 1" to 2" in diameter. Chatter and other unwanted gremlins will be kept to a minimum with a smaller arc of rotation. Of course, the surfaces can be machined with just an end mill but many more passes will be needed to complete the job. I did recently see a 3/4" six flute end mill with a 1/2" shaft that would prove just perfect for surfacing jobs. If you are only machining. very narrow edges, you can perform that job with end mills. I like to square the rough cut edge on plate stock by side milling. Place the stock flush on the vise, griping it along the factory edge while using the Y advance to take light side cuts along the sawn edge until it is clean of all saw marks. The milled edge should now be square to the factory edge. Rotate and flip the work end for to finish cleaning up the opposite edge until it is milled to the final length needed. All that would be needed is to lightly run a fine cut file along the edges to remove any sharp spots or burrs.
A large portion of the milling required in model making will be fully handled by end milling, flycutting and drilling. The next operation is basically a sawing cut done with slitting or slotting saw blades for which a special arbor will have to be made or purchased. The slitting saw arbor that we first made for use on the lathe will not work in this case because as you might remember, it was threaded to the lathe spindle and its diameter is 1". Too big for most drill chucks. We will make one from scratch, just like the first one but with a 1/2" diameter shaft instead of a threaded bore. A portion of the stock will need to be reduced to 1/2" so it can be gripped in the chuck. The rest will consist of about a 1" long 3/4" diameter end with a 3/32" deep shoulder turned on the end to match the arbor hole of the saw blades used. A locking flange is turned with a matching recess that will overlap the arbor shoulder. The outer edge of the flange with hold the blade square around the arbor's rim. A cap screw holds everything together through a central threaded hole. This was discussed before and is basically the same information. The slitting saws are primarily used to create very narrow slots such as across the head of a specially made screw. These blades are available in a myriad of diameters, thicknesses and tooth configurations from just about any major tool and supply house. The workpiece is held in the cross vise and oriented to bring the surface requiring slotting to run horizontal to the blade. The blade is raised or lowered until it is at the correct level and the slot is cut against the rotation of the blade in several ever deeper passes. Advance the workpiece with the cross slide and bring it back to the original position before moving the work over for a deeper pass. Continue the process until you reach the final required depth. Slots are not the only cut that can be made with a slitting saw. Two cuts at right angles to each other will remove a corner to quickly create a step on an edge. These basic cuts will cover about 99% of all the milling work you will need to do unless you decide to get into milling your own gears. Gear cutting is a very specialized field where you need to study a bit of general gear tooth design by reading any of the many good books available on the subject. All of the theoretical mumbo jumbo is not that difficult to apply once you learn and understand it. Gears must have perfectly spaced teeth so you definitively need a dividing head and or a chuck with indexing plates. The gear cutters themselves are called involute gear cutters and look similar to saw blades only much more robust, with the side profile of the cutting teeth matching that of the spaces between the gear teeth they produce. The are classified by tooth pitch and numbers #1 to #8. The pitch indicates the number of teeth per inch of circumference of the finished gear it is designed to cut while the number designates the range of the number of teeth in a gear that it is designed to cut. A matching set of gears in a gear train will all need to be cut with the same cutter otherwise they will not mesh. They are not cheap so you have to be careful and know ahead of time what your requirements will be so you can acquire only the cutters you really need. They tend to have 1" diameter arbors and basically require a similar holder as with the slitting saw arbor but with a 1" bushing to take the larger cutter hole.