Bolt holes look simple until the parts reach assembly. On the drawing, the bolt diameter is known, the hole is there, and the joint seems straightforward. In production, the hole can still be wrong for the job. The bolt may not pass through easily. A stack of parts may refuse to line up. Painted parts …
Many seating problems start around the hole, not in the hole. A bolt head, washer, or nut may be the correct size, yet still fail to sit flat because the surrounding surface is rough, curved, or locally distorted. This is common on castings, weldments, forgings, and angled faces where the fastener seat cannot be trusted …
Thread engagement looks simple on a drawing. A thread callout is added, a depth is assigned, and the hole appears finished. In real machining work, that is often where trouble starts. A threaded hole can be deeper than it needs to be, harder to machine than it should be, and still not give better joint …
Chamfers are easy to overlook because they look small on a drawing. A corner is broken, a hole mouth is beveled, and the edge looks cleaner, so the feature often feels less important than hole position, flatness, or thread depth. On real CNC parts, that small feature can affect assembly far more than many …
Blind holes often look simple on a drawing. A diameter is specified, a depth is added, and the feature seems complete. In real machining, that is where many problems begin. A blind hole is not just a hole that stops before breaking through the part. It is a hole with a bottom condition, and that …
A slot usually looks harmless on a drawing. Two walls, one width, one depth, one length. On the machine, that same feature can turn into the part of the job that drives tool wear, slows cycle time, and creates the most inspection risk. Standard slot milling is common enough, but long narrow slots are a …
Counterbore and countersink are both common hole features in CNC machining, but they are not interchangeable. Both are used to prepare a hole for a fastener head, and that is where many drawings stop. On real machined parts, the choice affects much more than appearance. It affects how the screw head is supported, whether the …
Flatness problems in CNC machining usually do not show up as obvious dimensional errors. A part can pass checks for length, width, thickness, and hole location, then still rock on a base plate, leak across a sealing face, or sit unevenly during assembly. When that happens, people often go back to the dimensional report first. …
Sharp internal corners look clean in CAD. In real CNC machining, they are usually one of the first features that gets reviewed before a part is quoted or programmed. That is not because the machine cannot hold size. It is because standard milling tools are round, and round tools leave radius in inside corners.
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A hole and a shaft can look perfectly correct on a drawing and still turn into a bad assembly on the shop floor. One shaft stops halfway into the bore. Another part presses together, but the housing flares at the entrance. A third assembly works in raw machining and then becomes impossible after anodizing. That …
