rough cutting stock to size, you usually have to remove the resultant burr to begin machining. You can remove those and other fairly large burrs by sanding them with a small sanding disk mounted in an angle-head die grinder.
The advantage of this method is that you can do the deburring at your machine between cuts instead of having to file or walk to a disk sander.
There are a few things you can do to minimize burrs and the effort it takes to remove them. One method you can use is to climb mill into material. The use of sharp cutters also minimizes burrs.
Figure 1–13 An angle-head die grinder can be used to remove heavy burrs quickly.
36.To save a little time, avoid turning off a conventional milling machine to change parts.
Common sense is needed here. If the setup is such that you can move the cutting tool beyond the part by at least a few inches, you can usually change parts safely without turning off the spindle. If you measure the part, file the part, or do any operation other than just changing or removing the part, then it is best to turn the spindle off.
Be especially careful around cutters that rotate close to another piece of solid tooling such as a vise. That situation is potentially more dangerous than having a cutter that is just rotating out in the open.
I know of two accidents that happened when machinists did not stay clear of a cutter rotating next to a solid piece of tooling. One machinist used a milling machine to cut screw slots in some small parts with a slitting saw. When he went to change a part, he got his fingers caught in the small opening between the rotating saw blade and the holding fixture. The blade sucked three of his fingers through the small opening. Fortunately, the opening was big enough that he didn’t completely chop off his fingers. The other incident happened in a surface grinder. The rotating grinding wheel was about 1/4" above the magnetic vise when the machinist used his hand to wipe some debris off the magnet. Four of his fingers were ground down as they passed through the opening between the wheel and magnet.
37.Cut the diameter of a lathe part instead of the face to remove material quickly.
If you have a lot of material to remove from the length of a lathe part, it is faster to remove material by taking cuts off the diameter rather than the face of the part.
38.Cut arcs by hand in a conventional milling machine by using a dowel pin as a center pivot. (see Fig. 1-14)
To cut an arc around the end of a part, use a dowel pin as a center pivot and rotate the part around by hand. Mount the dowel pin in your milling machine vise with a V-block. I’ve used this method several times with good results. Be careful. Begin by cutting the protruding corners of the part first so that the cutter does not suddenly jerk the bar and break the cutter.
Figure 1–14 An arc is being machined around the end of a small part by rotating the part on a dowel pin.
39.Cut spherical shapes with a conventional lathe. (See Fig. 1-15)
These tools are easy to set up and work well for quickly and consistently cutting spherical shapes conventionally.
Figure 1–15 These tools make cutting spherical-shapes a breeze with a conventional lathe. This tool was made by Holdridge Mfg. Co.
40.Use short, stubby end mills when possible. (See Fig. 1-16)
Short, stubby end mills don’t deflect as much as longer end mills; as a result, they last longer. End mills with flute lengths about one and a half times the diameter of the end mill, or less, don’t flex much, and can be pushed harder than longer end mills. It’s hard to beat a short, stubby corncob type rougher for removing material quickly.
Figure 1–16 Stubby end mills are rigid and should be used whenever possible.
41.Use a hex cutter for deep arrow slots.
If you have to use a small diameter end mill, be prepared to take your time. End mills under 1/8" in diameter simply can’t be pushed very hard. They’ll break if you do.
I’ve found that when it comes to milling with small diameter end mills, a six-sided single flute cutter can withstand more side pressure than a multi-flute helical end mill of the same diameter.
Hex cutters can be quickly made on a surface grinder or cutter grinder (see Fig. 1-17).
When making carbide cutters like this, it is best to lightly break the vertex of the hex on the opposite side of the cutting edge to reduce the tendency for the cutter to chip out. You can use either a diamond file or diamond grinder to break the edge, as shown in the right-hand photo.
Figure 1–17 Single flute hex cutters are easy to make and can withstand more side load than helical end mills. They work great for cutting O-ring grooves and other features requiring deep, narrow cuts.
42.Measure stock one time only to rough in a feature.
Some machinists waste time by re-measuring after every roughing cut. It’s not necessary. Measure stock carefully one time before you begin roughing to determine how much stock you need to remove, then don’t measure again until you are within finishing range. Either that or cut to a scribe line.
43.Avoid tilting the head of a mill when possible.
When cutting or drilling an angle in a part, either tilt the part or use an angle cutter to do the job. Using a mill with a tilted head is awkward. Furthermore, once you tilt the head, you’re obliged to tram it back in.
44.Take your drawing with you to the stock room.
When searching through stacks of material in the stock room, you don’t want to have to remember what you are looking for. It can be a little confusing at times, especially when you don’t have exactly the stock you need. Save yourself a trip. Take your drawing with you to the stock room.
45.Use a high volume air nozzle.
This subject can be controversial. In some shops, the rule is never to use air to blow chips off machines. Some believe cleaning with compressed air ruins the machine—the air stream forces small chips and debris between the table and ways of the machine, causing binding, scratching, and rapid wear on the ways.
Common sense is needed. If you do use air to blow off chips, don’t aim the air stream directly into the junction of the machine table and ways. Aim or blow the chips away from areas of the machine that may trap chips.
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