Tapping guides
The charts tell you which drill. These explain why, and what to do when the standard answer is not the right one: how percent of thread works, where the formulas come from, how to tap material that fights back, and how to get a broken tap out of a part you care about. 10 articles, each with worked examples from the same data the charts use.
- Cut Taps vs. Form Taps: Drill Sizes, Materials, Pros and Cons Cutting taps vs. thread forming (roll) taps: why form taps need a bigger drill, which materials they suit, and when each one is the better pick. Published
- How Deep to Drill a Blind Hole for Tapping Work out tap drill depth for blind holes: thread depth plus tap chamfer plus clearance. Plug vs. bottoming taps, drill point length and chip control. Published
- How to Remove a Broken Tap (and Stop Breaking Them) Why taps break, how to prevent it, and how to remove one: extractors, carbide, EDM, alum for steel taps in aluminum, and when to re-drill instead. Published
- Metric vs Imperial Threads: How to Read and Tell Them Apart Read M8 x 1.25 and 5/16-18 callouts, see why M6 and 1/4-20 are not interchangeable, and identify an unknown thread with a pitch gauge and calipers. Published
- Percent of Thread Explained: Why Tap Drill Charts Use 75% What percent of thread means, why charts target about 75%, how strength and tapping torque trade off, and how to pick a drill for your material. Published
- Tap Drill Formula Explained, With Worked Examples How to calculate tap drill size for inch, metric and form taps, check percent of thread, and pick the nearest real drill. Worked 1/4-20 and M8 examples. Published
- Tapping Aluminum: Drill Sizes, Form Taps, Lube and Galling How to tap aluminum cleanly: 6061 vs. cast alloys, why the 75% chart drill works, when to use form taps, which lubricant to pick, and when to use inserts. Published
- Tapping Plastic: Drill Sizes, Inserts and Better Options How to tap acrylic, polycarbonate, nylon, Delrin, ABS and 3D prints: drill sizes, tap tips, heat-set and threaded inserts, and thread-forming screws. Published
- Tapping Stainless Steel: Drill Size, Speed, Lube and Tap Choice How to tap stainless steel without breaking taps: pick a 60-65% thread drill, beat work hardening, run slow, use real tapping oil and the right tap. Published
- UNC vs UNF Threads: Differences, Strength and Tap Drills Coarse vs fine thread explained: when to use UNF or UNEF, how strength compares, and side-by-side tap drills for 1/4-20 vs 1/4-28, #10-24 vs #10-32. Published
Topics covered
Every subject these articles touch, with the number of guides covering each.
- form taps 3
- inch threads 2
- metric threads 2
- percent of thread 2
- spiral flute tap 2
- tapping tips 2
- 3D printing
- 6061
- acrylic
- aluminum
- blind holes
- bottoming tap
- broken tap
- broken taps
- cast aluminum
- chip evacuation
- coarse thread
- cutting taps
- Delrin
- drill depth
- EDM
- fine thread
- galling
- heat-set inserts
- imperial threads
- materials
- pitch gauge
- plug tap
- roll taps
- spiral point tap
- stainless steel
- tap drill basics
- tap drill formula
- tap drill size
- tap extractor
- tap selection
- tapping plastic
- tapping problems
- tapping torque
- thread identification
- thread inserts
- thread repair
- thread strength
- UNC
- UNC vs UNF
- UNEF
- work hardening
Charts
- UNC tap drill chart The default inch series: 1/4-20, 5/16-18, 3/8-16.
- UNF tap drill chart More threads per inch: 1/4-28, 10-32, 1/2-20.
- UNEF tap drill chart Thin walls and fine adjustment: 1/4-32, 5/16-32.
- Metric coarse tap drill chart M1 to M64, the standard pitch for each diameter.
- Metric fine tap drill chart M8 x 1, M10 x 1.25 and the rest of the fine pitches.
- NPT pipe tap drill chart Tapered pipe threads, 1/16 to 2 in, with and without a reamer.
- Form tap drill chart The larger holes a roll tap needs, every size.
- Clearance hole chart The through hole for the bolt, close to loose.