# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/Dcph4C4ACmp
- **Gondola URL:** https://gondola.cc/posts/69727796-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/1bfd6c2341.jpg
- **Posted:** 2026-08-30T03:19:21.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

A slot is the hardest simple feature in machining. A hole has a drill. A face has a facemill. A slot has a cutter buried on both flanks at once, and most of the rules of good milling collapse the moment full radial engagement begins.

Run an endmill the same width as the slot and it is engaged across 180 degrees of arc. Several things go wrong together:

- One wall is climb milled and the other conventional, so deflection flips direction mid-cut
- Chips have nowhere to escape and are recut, which is the fastest way to chip a carbide edge
- Heat stays in the cut instead of leaving with the swarf
- Radial load bends the tool, producing tapered walls and a slot that measures narrow at the bottom

The workaround is to stop slotting. Rough with a cutter around 70 per cent of the finished width using trochoidal or peel passes, keeping radial engagement low and arc of contact short, then take a light finishing pass on each flank to correct for deflection. Enter by helix or ramp, never by plunging, because the tool centre has zero surface speed and simply rubs.

Then there is the corner problem. A rotating cutter cannot produce an internal sharp corner; it leaves a radius equal to its own. If a square tab has to seat in that slot, the part will not sit down. The fixes are dogbone or T-bone reliefs cut past the corner, or wire EDM, which leaves a corner radius of roughly the wire radius plus the spark gap, often under 0.15 mm.

Alignment cutouts exploit the geometry rather than fight it. Pair one round hole with one slot and the hole fixes position while the slot kills rotation yet still allows expansion along its length. Two round holes over-constrain the assembly, and any thermal or tolerance mismatch turns into stress instead of movement.

A hole tells a part where to be. A slot tells it where it is allowed to go.

#stemantics #machining #precisionengineering #manufacturing #cnc

## Stats

- **Views:** 8,404
- **Likes:** 54
- **Shares:** 0
- **Comments:** 3

## Tags

machining, cnc, manufacturing, stemantics, precisionengineering

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