日本語

Printed from Kezuriba (kezuriba.net/en/threads/m2/)

M2×0.4

ISO metric coarse thread

Nominal diameter 2 mm, pitch 0.4 mm. Tap makers recommend slightly different drill sizes, so they are listed side by side.

Tap drill, rule of thumb (d − P)
1.60 mmMaker recommendations below
Minor diameter D1 range (6H)
1.567 – 1.679 mmKeep the hole inside this range[4][5][3]
Pitch diameter d2 (basic)
1.740 mmd2 = d − 0.649519P
M2 basic profile and dimensions (schematic)
external thread (bolt)major dia. d = 2pitch dia. d2 = 1.74minor dia. D1 = 1.5676H range 1.567–1.679 (tap drill target)P = 0.4H160°

Thread angle 60°. H1 (basic thread engagement) = 0.541266P = 0.217. 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
OSG1.6min. 1.57, 6H max. 1.67
previous edition recommended 1.63 (changed in the current edition)		[3]
Nachi (Nachi-Fujikoshi)1.6high-performance drill 1.65[5]
Yamawa1.65[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 d2
Pitch P0.4
Pitch diameter d2, D21.740
Basic minor diameter D1 (nut), d1 (bolt)1.567
Fundamental triangle height H = 0.866025P0.346
Basic engagement H1 = 0.541266P0.217

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)4Agrees in 2+ sources[10][11]
Hex bolt width across flats s (old JIS, annex)—Not confirmed
Hex nut width across flats s (ISO-based JIS, main body)4Agrees in 2+ sources[10][12][13]
Hex nut width across flats s (old JIS, annex)41 source (reference)[14]
Hex nut height m (style 1, max.)1.6Agrees in 2+ sources[12][13]
Socket head cap screw head diameter dk (max.)3.8Agrees in 2+ sources[15][16][17][18]
Socket head cap screw head height k (max.)2Agrees in 2+ sources[15][17][18]
Hex socket size s (hex key size)1.5Agrees in 2+ sources[15][16][17][18][10]
Hex socket depth t (min.)1Agrees in 2+ sources[15][16][17][18]

⊙Clearance holes and counterbores

ItemmmConfidence
Clearance hole d′ for socket head cap screws—Not confirmed
Counterbore diameter D′ for socket head cap screws—Not confirmed
Counterbore depth H″ (head sits below the surface)—Not confirmed
Counterbore depth H′ (head slightly proud)—Not confirmed
Clearance hole, class 1 (JIS B 1001)2.21 source (reference)[19]
Clearance hole, class 2 (JIS B 1001)2.41 source (reference)[19]
Clearance hole, class 3 (JIS B 1001)2.61 source (reference)[19]
Spotface diameter for hex bolts and nuts (JIS B 1001)71 source (reference)[19]

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.

📚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. jp.misumi-ec.com https://jp.misumi-ec.com/pdf/fa/2015/p1_2369.pdf
  13. fabory.com https://www.fabory.com/en-GB/p/01103020001
  14. static.nbk1560.com https://static.nbk1560.com/images/ja-JP/product/technical_data/rokkaku_nut_NBK/rokkaku_nut…
  15. jp.misumi-ec.com https://jp.misumi-ec.com/pdf/fa/2015/p1_2363.pdf
  16. tsurugacorp.co.jp https://www.tsurugacorp.co.jp/img/usr/pdf/A00000.pdf
  17. static.nbk1560.com https://static.nbk1560.com/images/ja-JP/product/technical_data/rokkaku_bolt_NBK/rokkaku_bo…
  18. mikipulley.co.jp https://www.mikipulley.co.jp/EN/Services/Tech_data/tech10.html
  19. static.nbk1560.com https://static.nbk1560.com/images/ja-JP/product/technical_data/boltana_zagurikei_NBK/bolta…