Machine Shop Trade Secrets. James Harvey
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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.
Adjust your cleaning procedure according to the type of material you are cutting. With aluminum or other soft, clean materials, you probably won’t damage anything by using air. With hard, gritty, or abrasive material, it makes sense to use a brush and paper towel to wipe the grit off the machine’s ways. If you use sandpaper or other abrasives in or around your machine, wipe the grit off with a paper towel or rag before moving the table. (See Fig. 1-18)
With that in mind, get yourself an air nozzle that puts out some volume so you can blow chips off quickly.
Figure 1–18 Wipe gritty material from the ways of machines to avoid wearing them out prematurly.
| Suggestions for Working Quickly | ||
| 1. | Turn man-time into machine time. | |
| 2. | Have lots of tools. | |
| 3. | Use dedicated tools. | |
| 4. | Make all your parts the same. | |
| 5. | In a milling machine, when practical, use a large enough cutter to cut across the entire surface of the part in one pass. | |
| 6. | Turn the shanks of your larger drill bits down to common collet sizes. | |
| 7. | Use stub drills. | |
| 8. | Use a speed chuck in a conventional milling machine. | |
| 9. | Use a slide fixture in a conventional mill to drill holes. | |
| 10. | Use chip color to determine speed, feed, and depth of cut in ferrous materials. | |
| 11. | Rough ugly. | |
| 12. | Work your way up to a heavy roughing cut. | |
| 13. | Avoid using a single flute fly cutter to rough with. | |
| 14. | Try to rough as close to final size as practical. | |
| 15. | Work your machine hard when roughing, but do it the right way. | |
| 16. | Place your hand on a milling machine table to gauge the pressure of a cut. | |
| 17. | Make parts with as few setups as possible. | |
| 18. | Use air mist to prolong the life of your cutter and increase stock removal rates. | |
| 19. | Go as fast as you dare in aluminum and other easily machined materials. | |
| 20. | Bore holes with a mill like you would with a lathe. | |
| 21. | Power tap blind holes that are drilled deep enough. | |
| 22. | Saw your raw stock about a tenth of an inch larger than finished size. | |
| 23. | Use a cold cut saw for cutting off bar stock. | |
| 24. | When running multiple parts do one operation at a time in a tool room lathe | |
| 25. | Change small lathe parts when using a collet closer without turning off the spindle. | |
| 26. | Stack parts when you can. | |
| 27. | Stack parts on edge for drilling and tapping. | |
| 28. | Consider buying pre-squared blocks for high quantity runs. | |
| 29. | Use an end mill in the lathe to rough out a flat bottom hole. | |
| 30. | Keep a box of loose drill bits handy. | |
| 31. | Keep a large assortment of T-nuts on hand. | |
| 32. | Avoid clearing your cutter to go back for another cut. | |
| 33. | Don’t bother removing a built-up edge on a lathe tool when roughing. | |
| 34. | Drill deep holes in a conventional lathe quickly by sliding the tailstock. | |
| 35. | Deburr rough edges with a small, angle-head die grinder. | |
| 36. | To save a little time, avoid turning off a conventional milling machine to change parts. | |
| 37. | Cut the diameter of a lathe part instead of the face to remove material quickly. | |
| 38. | Cut arcs by hand in a conventional milling machine by using a dowel pin as a center pivot. | |
| 39. | Cut spherical shapes with a conventional lathe. | |
| 40. | Use short, stubby end mills whenever possible. | |
| 41. | Use a hex cutter for deep arrow slots. | |
| 42. | Measure stock one time only to rough in a feature. | |
| 43. | Avoid tilting the head of a mill when possible. | |
| 44. | Take your drawing with you to the stock room. | |
| 45. | Use |