The MachinistPost Blog

Structural bolt holes have defined sizes per AISC Table J3.3. Knowing the standard, oversized, and slotted hole dimensions — and which drill produces them — is fundamental to structural fabrication.

In a production cell, drill management is a systems problem. Establishing a change interval, tracking tool life, and calculating resharpening economics keeps the cell running predictably.

Blind holes don't give chips a way out, don't let coolant drain, and require active depth control. In thick plate, every one of these gets harder.

The gap in an interrupted cut is where drills break. The re-engagement impact — not the cutting itself — is the failure mode. Here is how to manage it.

H7 means reaming. H11 means careful drilling. Understanding ISO hole tolerances tells you which process your drawing actually requires.

Drilling plastics seems simple until the hole melts or the part cracks. Each engineering polymer has different heat tolerance, chip character, and geometry requirements.

Too much allowance and the reamer deflects. Too little and it rubs. The standard 0.010 to 0.015 inch rule is a starting point — here is how material and diameter shift the correct range.

Mill scale can hit 500 HBW on a 120 HBW steel. Understanding how scale and weld surface affect drill entry keeps your cobalt edges from wearing down before they reach base metal.

Understanding the manufacturing process — flute grinding, heat treatment, point grinding — explains why resharpening works and why grade differences matter.

Titanium work-hardens aggressively and generates heat that destroys cutting edges. With the right cobalt grade, geometry, and 15 to 30 SFM discipline, HSS handles it.

Every time a drill gets resharpened shorter, the web gets thicker. Understanding this changes how you specify resharpening and how you diagnose drilling problems.

TiN, TiAlN, black oxide — the coatings on your drill bits are more marketing than performance upgrade in most shop conditions. Here is what each coating actually does.

Most small shops run drills until they break. A 15-minute weekly audit prevents that — and tells you exactly when to resharpen before quality suffers.

Abrasion-resistant plate is some of the toughest drilling you will do with a twist drill. The right cobalt grade and geometry make a real difference.

Insert drills promise speed. HSS promises flexibility. The real comparison depends on volume, diameter, and what your shop actually runs.

Tapping is faster. Thread milling is more flexible. Knowing when to switch saves tools, time, and broken tap extractions.

Counterbores seat socket head cap screws. Countersinks seat flat-head fasteners. Understanding the geometry difference is the first step.

Most tapping failures start before the tap touches the part. Here is how to drill the hole so the tap has a chance.

How to plan a fixture plate that makes drilling faster and more accurate — hole spacing, edge distance, workholding rules.

When a simple bushing guide pays for itself in the first batch — and how to decide which type you need.

When a two-pass approach outperforms a single-drill cut — and how to size the pilot for maximum benefit.

Resharpening and reconditioning are not the same thing. The difference determines whether drills come back right.

Reaming only works if the drilled hole is close to right. Here is what the drill needs to deliver first.

The actual decision framework for peck drilling — when to peck, how deep, and when single-pass is better.