Walk through enough job shops and you'll see the same selection errors repeated across facilities of every size. Some of them are small inefficiencies. Others cost real money in broken tooling, out-of-tolerance holes, and cycle time that's twice what it should be. None of them require expensive fixes — just a better decision framework at the time of purchase and setup.
Here are the five that show up most often.
Running Jobber-Length Drills on Everything
Jobber-length drills are the default. They're what's in the bin, what's in the catalog at the front, and what most machinists reach for without thinking. For general work in moderate depths, they're fine. But they're not the right tool for short, rigid holes or for drilling into difficult materials where deflection is the enemy.
Screw machine (stub) length drills are shorter and significantly more rigid. In applications where hole depth is less than 3x diameter, they run faster, break less often, and hold tighter tolerances than jobber drills doing the same job. The additional rigidity reduces the tendency to walk on entry, makes them more forgiving in interrupted cuts, and lets you run higher feeds without the lateral deflection that causes oversize holes.
The fix: keep a set of screw machine drills in common sizes and default to them for any hole where the jobber length is more than you need. The speed and accuracy improvement is immediate and measurable.
Using HSS in Stainless Without Cobalt
Standard HSS handles stainless — technically. It will make a hole. What it won't do is last, and the failure mode is fast and expensive: built-up edge forms on the cutting lips, the bit stops cutting and starts rubbing, heat builds rapidly, and the drill hardens the surface of the hole it's supposed to be opening up. Work hardening in austenitic stainless is severe enough that a dull drill can harden the bore enough to make re-entry with another dull drill nearly impossible.
Cobalt HSS (M35 or M42) handles the heat much better. The cobalt content raises the material's hot hardness — the ability to maintain a sharp edge at elevated temperatures — which is exactly what stainless drilling requires. The cost premium over standard HSS is real, but it's recovered quickly in fewer broken bits and longer tool life. If your shop runs any meaningful volume of stainless, cobalt is standard issue, not a premium option.
Ignoring Point Geometry for the Material
The 118-degree standard point is not universal. It's a reasonable default for mild steel in general-purpose applications, but it's the wrong choice for a number of common materials shops encounter regularly.
Hard materials (alloy steel, hardened steel, stainless) drill better with a 135-degree point — the flatter geometry distributes load, is more self-centering on entry, and is less prone to edge chipping at the point. Softer materials like aluminum, copper, and plastics benefit from a sharper (lower-angle) point and higher helix. Sheet metal requires a special flat-bottomed or modified point to prevent breakthrough deformation. Drilling into hardened steel with a 118-degree standard bit on a manual machine is a good way to break drills — not because the operator did something wrong, but because the tool selection was wrong from the start.
Check the point geometry specification before setting up any job in material that isn't mild steel. The few minutes it takes to confirm the right bit are worth it.
Not Specifying Split Point for Production Work
Split point drills cost more and are more complex to resharpen. So shops default to standard-ground bits and pay for it in a different way: pilot holes for anything over 1/2" because the standard point can't start accurately under production feeds, wandering entry that forces slower approach speeds and a pecking cycle to get on location, and higher thrust requirements that load up small-diameter spindles and cause premature bearing wear.
For production programs running more than a few hundred holes in any size above 3/16", split point geometry pays for itself. The self-centering entry eliminates the need for a pilot or a spotting operation in most setups, the reduced thrust allows higher feeds and faster cycles, and the bit runs truer over its service life. The higher regrind complexity is a real cost — but it's a manageable one if you're sending bits to a competent service shop rather than trying to restore split point geometry on a bench grinder.
Buying Cheap and Replacing Instead of Buying Good and Resharpening
The economy drill bit is a real product category. It exists for a reason — for one-off jobs in easy materials where you don't care about consistency and you just need a hole. But when shops apply the economy-and-replace logic to production tooling, the math stops working.
A quality HSS bit from a reputable manufacturer can be resharpened multiple times before it reaches the end of its useful life. The regrind cost is a fraction of replacement cost, and a properly resharpened bit performs the same as a new one. A cheap bit often can't be meaningfully resharpened — the geometry was imprecise from the start, the steel won't hold an edge through multiple cycles, and the value of the bit is entirely in that first set of uses before it gets thrown away.
The total cost of ownership calculation favors quality tooling with a regrind program over cheap tooling with replacement, in almost every production application. The upfront cost is higher. The 12-month cost is lower.
None of these are obscure or technical. They're common decisions that happen every week in every shop — bit selection, material compatibility, point geometry, production geometry, buy-vs-resharpen. Getting them right consistently is a cost-of-running-the-shop issue, not an advanced machining topic.