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Printed from Kezuriba (kezuriba.net/en/threads/m3/)

M3×0.5

ISO metric coarse thread

Nominal diameter 3 mm, pitch 0.5 mm. Tap makers recommend slightly different drill sizes, so they are listed side by side.

Tap drill, rule of thumb (d − P)
2.50 mmMaker recommendations below
Minor diameter D1 range (6H)
2.459 – 2.599 mmKeep the hole inside this range[4][5][3]
Pitch diameter d2 (basic)
2.675 mmd2 = d − 0.649519P
M3 basic profile and dimensions (schematic)
external thread (bolt)major dia. d = 3pitch dia. d2 = 2.675minor dia. D1 = 2.4596H range 2.459–2.599 (tap drill target)P = 0.5H160°

Thread angle 60°. H1 (basic thread engagement) = 0.541266P = 0.271. The pitch diameter is where the thread ridge and groove are equally wide. For cutting taps, pick a drill that lands inside the 6H tolerance of the minor diameter D1. Enlarged to show the shape; proportions are not to scale.

⌀Tap drill size for cutting taps (maker recommendations)

For internal thread class 6H. Values as given in each maker’s technical data (mm).

MakerRecommended drillNotesSource
OSG2.5min. 2.46, 6H max. 2.59
previous edition recommended 2.53 (changed in the current edition)		[3]
Nachi (Nachi-Fujikoshi)2.5high-performance drill 2.55[5]
Yamawa2.56[4]
Calculate tapping RPM for this size →

Forming (roll) tap drill sizes differ by maker and product line; see the Japanese page for the table.

⌇Basic dimensions

Nominal (major) diameter d3
Pitch P0.5
Pitch diameter d2, D22.675
Basic minor diameter D1 (nut), d1 (bolt)2.459
Fundamental triangle height H = 0.866025P0.433
Basic engagement H1 = 0.541266P0.271

Basic dimensions are theoretical values without tolerance. Try other pitches with the thread dimension calculator.

⬡Bolt and nut sizes

ItemmmConfidence
Hex bolt width across flats s (ISO-based JIS, main body)5.5Agrees in 2+ sources[10][11][12]
Hex bolt width across flats s (old JIS, annex)5.51 source (reference)[13]
Hex nut width across flats s (ISO-based JIS, main body)5.5Agrees in 2+ sources[10][14][15]
Hex nut width across flats s (old JIS, annex)5.51 source (reference)[16]
Hex nut height m (style 1, max.)2.4Agrees in 2+ sources[14][15]
Socket head cap screw head diameter dk (max.)5.5Agrees in 2+ sources[17][18][19][20][21]
Socket head cap screw head height k (max.)3Agrees in 2+ sources[17][19][20][21]
Hex socket size s (hex key size)2.5Agrees in 2+ sources[17][18][19][20][21][10]
Hex socket depth t (min.)1.3Agrees in 2+ sources[17][18][19][20][21]

⊙Clearance holes and counterbores

ItemmmConfidence
Clearance hole d′ for socket head cap screws3.4Agrees in 2+ sources[17][23]
Counterbore diameter D′ for socket head cap screws6.5Agrees in 2+ sources[17][23]
Counterbore depth H″ (head sits below the surface)3.3Agrees in 2+ sources[17][23]
Counterbore depth H′ (head slightly proud)2.7Agrees in 2+ sources[17][23]
Clearance hole, class 1 (JIS B 1001)3.21 source (reference)[22]
Clearance hole, class 2 (JIS B 1001)3.41 source (reference)[22]
Clearance hole, class 3 (JIS B 1001)3.61 source (reference)[22]
Spotface diameter for hex bolts and nuts (JIS B 1001)91 source (reference)[22]

Socket-head values are from the reference table of JIS B 1176; clearance-hole classes are from JIS B 1001. The two standards give different clearance holes for some sizes.

≋M3 fine threads

SizeD1 range (6H)Recommended drill (cutting tap)
M3×0.352.621 – 2.721OSG 2.65 / Nachi (Nachi-Fujikoshi) 2.65 / Yamawa 2.7

📚Sources

Most sources are Japanese technical documents from the tap and fastener makers.

  1. iwata-fa.jp https://www.iwata-fa.jp/contents/assets/pdf/technicaldata/2022_tec_other_13.pdf
  2. nbk1560.com https://www.nbk1560.com/images/ja-JP/product/technical_data/meternezi_NBK/meternezi_NBK_1.…
  3. osg.co.jp https://www.osg.co.jp/media_dl/technical/file/drill_hole_size.pdf
  4. yamawa.com https://www.yamawa.com/Portals/0/images/download/holesize/jp/technical-contents-15.pdf
  5. nachi-fujikoshi.co.jp https://www.nachi-fujikoshi.co.jp/dcms_media/other/2501-12.pdf
  6. osg.co.jp https://www.osg.co.jp/media_dl/technical/file/p_8.pdf
  7. yamawa.com https://www.yamawa.com/Portals/0/images/download/holesize/jp/technical-contents-16.pdf
  8. baer.tools https://baer.tools/en/blog/core-hole-dimensions-for-screw-taps-everything-you-need-to-know
  9. orist.jp https://www.orist.jp/technicalsheet/98015.PDF
  10. eg.aktio.co.jp https://www.eg.aktio.co.jp/wp-content/uploads/R3T_1-5_TONE_bolt_nimen.pdf
  11. jp.misumi-ec.com https://jp.misumi-ec.com/pdf/fa/2015/p1_2367.pdf
  12. mikipulley.co.jp https://www.mikipulley.co.jp/en/resources/standards-hex-bolt
  13. tsurugacorp.co.jp https://www.tsurugacorp.co.jp/img/usr/pdf/B00000.pdf
  14. jp.misumi-ec.com https://jp.misumi-ec.com/pdf/fa/2015/p1_2369.pdf
  15. fabory.com https://www.fabory.com/en-GB/p/01103030001
  16. static.nbk1560.com https://static.nbk1560.com/images/ja-JP/product/technical_data/rokkaku_nut_NBK/rokkaku_nut…
  17. jp.misumi-ec.com https://jp.misumi-ec.com/pdf/fa/2015/p1_2363.pdf
  18. tsurugacorp.co.jp https://www.tsurugacorp.co.jp/img/usr/pdf/A00000.pdf
  19. static.nbk1560.com https://static.nbk1560.com/images/ja-JP/product/technical_data/rokkaku_bolt_NBK/rokkaku_bo…
  20. mikipulley.co.jp https://www.mikipulley.co.jp/EN/Services/Tech_data/tech10.html
  21. farnell.com https://www.farnell.com/datasheets/11699.pdf
  22. static.nbk1560.com https://static.nbk1560.com/images/ja-JP/product/technical_data/boltana_zagurikei_NBK/bolta…
  23. nbk1560.com https://www.nbk1560.com/resources/other/article/technical-22-dimensions-of-holes-for-hexag…