when stacking parts.
If you have to move a stack in order to do other machining operations, try to keep the parts clamped together so they move as one block. In other words, when you can, try to avoid moving the parts in relation to one another.
Figure–19 Stack milling is an effective way to save time. The tradeoff is that setups take more time and tolerances are usually more difficult to hold.
27.Stack parts on edge for drilling and tapping. (See Figure 1-10)
Drilling and tapping a stack of parts on edge can save you time. However, you have to be careful how you do it so that you don’t accumulate error.
Let’s say you have a stack of twenty 1/4" plates that need to be drilled and tapped in the center of their edges. After clamping the stack in the vise, you next have to measure the width of the stack. Then divide that measurement by 20 to get the distance you should move between holes.
Say your overall stack measures 4.94". The real distance between the centers of the plates is 4.94 divided by 20, or .247". That’s how far you would have to move each time to keep the holes centered in the plates. If you moved over .250" each time, your holes would become increasingly off center as you advanced.
Figure 1–10 A stack of parts is drilled and tapped on edge.
28.Consider buying pre-squared blocks for high quantity runs.
There are vendors that specialize in supplying material squared to size so that you don’t have to do the squaring. Having blocks prepared this way is a great way to get a job off to a fast start
29.Use an end mill in the lathe to rough out a flat bottom hole. (See Fig. 1-11)
Using an end mill in a conventional or CNC lathe allows you to rough out a flat bottom hole very close to depth with a square corner.
Any subsequent boring you do to complete the hole will take less cutting than if you used a standard drill bit to rough out the hole. You can hold an end mill in the tailstock chuck.
An end mill fed in with the tailstock will usually cut a hole a little larger than the end mill diameter; be careful that you don’t cut an oversize hole. An end mill used this way will cut with less pressure if you drill a pilot hole first. Use the “tan chip rule” for setting spindle speed.
Figure 1–11 An end mill is used in the tailstock to rough out a counter bore.
30.Keep a box of loose drill bits handy.
If you need to drill an approximate size hold—such as a pilot hole—there is nothing faster than just grabbing and using an approximate size drill from a box of loose bits.
Sample Catalogs for T-nuts
McMaster-Carr
Travers Tool Company
Rutland Tool & Supply
ENCO
31.Keep a large assortment of T-nuts on hand.
Angle plates, rotary tables, drill presses, and other machines and fixtures around the shop are going to have different T-nut slot sizes. Not having the right size T-nut for a piece of tooling can be frustrating when you want to keep a job moving. T-nuts are cheap. Open a catalog and buy yourself a large assortment of T-nuts to avoid getting hung up.
32.Avoid clearing your cutter to go back for another cut.
If you rough off material in steps in a conventional mill or lathe, don’t bother clearing the tool to return for the next cut. If the roughing tool rubs or grooves the part as it is returned to the starting point, so be it. This technique saves you from having to look at your dial settings all the time.
Don’t, however, take finishing cuts over a rough surface with swirls or grooves. Clear the tool when you are within finishing range so the tool cuts with even pressure over a consistent surface for finishing.
33.Don’t bother removing a built-up edge on a lathe tool when roughing.
Your cutting tools may accumulate a built-up edge when roughing. A built-up edge or BUE is a slight accumulation of material from the workpiece that adheres to the cutting edge of your tool.
A tool will still cut with a built-up edge, at least well enough to rough with.
To make smooth, precise finishing cuts, it is best to remove the built-up edge so that chips slide off the tool freely and the edge of the tool does the cutting instead of the built-up edge.
Removing it is often easier said than done. On carbide, if you attempt to just pick it off with a knife or something, you’ll likely pull off a bit of the carbide and ruin the cutting edge. If you attempt to stone or file it off, you may end up rolling the edge over, which is also no good.
You can remove a built-up edge by applying a liberal amount of cutting oil to the tool and then abruptly but intermittently hand feeding the tool into some stock. The build up edge will usually get pushed off by the resultant chip.
Figure 1–12 A deep hole can be drilled with a conventional lathe by sliding the tailstock.
34.Drill deep holes in a conventional lathe quickly by sliding the tailstock. (See Fig. 1-12)
Chip packing becomes an issue when drilling deep holes. The deeper you drill, the harder it is for chips to get out.
Instead of winding the drill bit in and out with the tailstock crank, you can manually push the tailstock in and out along the ways of the lathe.
When the drill bit packs, loosen the tailstock and pull it back to free the chips. Then push it back in until the drill bit bottoms. Re-tighten the tailstock and drill a little more using the crank. Repeat the process until you are to depth.
You’ll be surprised how fast you can drill a deep hole with a conventional lathe using this method.
Always begin drilling deep holes with a standard length drill to get the hole started straight.
Drill as deep as you can with a standard length drill before switching to a longer one.
35.Deburr rough edges with a small angle-head die grinder. (see Fig. 1-13)
Burrs and therefore the task of deburring are the unfortunate by-products of machining. There is no way to completely avoid throwing burrs when
